path: root/doc/gperf.info

This is gperf.info, produced by makeinfo version 4.13 from gperf.texi.

INFO-DIR-SECTION Programming Tools
START-INFO-DIR-ENTRY
* Gperf: (gperf).                Perfect Hash Function Generator.
END-INFO-DIR-ENTRY

   This file documents the features of the GNU Perfect Hash Function
Generator 3.0.4.

   Copyright (C) 1989-2009 Free Software Foundation, Inc.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the section entitled "GNU General Public License" is included
exactly as in the original, and provided that the entire resulting
derived work is distributed under the terms of a permission notice
identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the section entitled "GNU General Public License"
and this permission notice may be included in translations approved by
the Free Software Foundation instead of in the original English.


File: gperf.info,  Node: Top,  Next: Copying,  Prev: (dir),  Up: (dir)

Introduction
************

   This manual documents the GNU `gperf' perfect hash function generator
utility, focusing on its features and how to use them, and how to report
bugs.

* Menu:

* Copying::                     GNU General Public License says how you can
                                copy and share `gperf'.
* Contributors::                People who have contributed to `gperf'.
* Motivation::                  The purpose of `gperf'.
* Search Structures::           Static search structures and GNU `gperf'
* Description::                 High-level discussion of how GPERF functions.
* Options::                     A description of options to the program.
* Bugs::                        Known bugs and limitations with GPERF.
* Projects::                    Things still left to do.
* Bibliography::                Material Referenced in this Report.

* Concept Index::


High-Level Description of GNU `gperf'

* Input Format::                Input Format to `gperf'
* Output Format::               Output Format for Generated C Code with `gperf'
* Binary Strings::              Use of NUL bytes
* Output Copyright::            The Copyright of the Output.

Input Format to `gperf'

* Declarations::                Declarations.
* Keywords::                    Format for Keyword Entries.
* Functions::                   Including Additional C Functions.
* Controls for GNU indent::     Where to place directives for GNU `indent'.

Declarations

* User-supplied Struct::        Specifying keywords with attributes.
* Gperf Declarations::          Embedding command line options in the input.
* C Code Inclusion::            Including C declarations and definitions.

Invoking `gperf'

* Input Details::               Options that affect Interpretation of the Input File
* Output Language::             Specifying the Language for the Output Code
* Output Details::              Fine tuning Details in the Output Code
* Algorithmic Details::         Changing the Algorithms employed by `gperf'
* Verbosity::                   Informative Output


File: gperf.info,  Node: Copying,  Next: Contributors,  Prev: Top,  Up: Top

GNU GENERAL PUBLIC LICENSE
**************************

                        Version 3, 29 June 2007

     Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/'

     Everyone is permitted to copy and distribute verbatim copies of this
     license document, but changing it is not allowed.

Preamble
========

   The GNU General Public License is a free, copyleft license for
software and other kinds of works.

   The licenses for most software and other practical works are designed
to take away your freedom to share and change the works.  By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains
free software for all its users.  We, the Free Software Foundation, use
the GNU General Public License for most of our software; it applies
also to any other work released this way by its authors.  You can apply
it to your programs, too.

   When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.

   To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights.  Therefore, you
have certain responsibilities if you distribute copies of the software,
or if you modify it: responsibilities to respect the freedom of others.

   For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received.  You must make sure that they, too, receive
or can get the source code.  And you must show them these terms so they
know their rights.

   Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.

   For the developers' and authors' protection, the GPL clearly explains
that there is no warranty for this free software.  For both users' and
authors' sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.

   Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the
manufacturer can do so.  This is fundamentally incompatible with the
aim of protecting users' freedom to change the software.  The
systematic pattern of such abuse occurs in the area of products for
individuals to use, which is precisely where it is most unacceptable.
Therefore, we have designed this version of the GPL to prohibit the
practice for those products.  If such problems arise substantially in
other domains, we stand ready to extend this provision to those domains
in future versions of the GPL, as needed to protect the freedom of
users.

   Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
software on general-purpose computers, but in those that do, we wish to
avoid the special danger that patents applied to a free program could
make it effectively proprietary.  To prevent this, the GPL assures that
patents cannot be used to render the program non-free.

   The precise terms and conditions for copying, distribution and
modification follow.

TERMS AND CONDITIONS
====================

  0. Definitions.

     "This License" refers to version 3 of the GNU General Public
     License.

     "Copyright" also means copyright-like laws that apply to other
     kinds of works, such as semiconductor masks.

     "The Program" refers to any copyrightable work licensed under this
     License.  Each licensee is addressed as "you".  "Licensees" and
     "recipients" may be individuals or organizations.

     To "modify" a work means to copy from or adapt all or part of the
     work in a fashion requiring copyright permission, other than the
     making of an exact copy.  The resulting work is called a "modified
     version" of the earlier work or a work "based on" the earlier work.

     A "covered work" means either the unmodified Program or a work
     based on the Program.

     To "propagate" a work means to do anything with it that, without
     permission, would make you directly or secondarily liable for
     infringement under applicable copyright law, except executing it
     on a computer or modifying a private copy.  Propagation includes
     copying, distribution (with or without modification), making
     available to the public, and in some countries other activities as
     well.

     To "convey" a work means any kind of propagation that enables other
     parties to make or receive copies.  Mere interaction with a user
     through a computer network, with no transfer of a copy, is not
     conveying.

     An interactive user interface displays "Appropriate Legal Notices"
     to the extent that it includes a convenient and prominently visible
     feature that (1) displays an appropriate copyright notice, and (2)
     tells the user that there is no warranty for the work (except to
     the extent that warranties are provided), that licensees may
     convey the work under this License, and how to view a copy of this
     License.  If the interface presents a list of user commands or
     options, such as a menu, a prominent item in the list meets this
     criterion.

  1. Source Code.

     The "source code" for a work means the preferred form of the work
     for making modifications to it.  "Object code" means any
     non-source form of a work.

     A "Standard Interface" means an interface that either is an
     official standard defined by a recognized standards body, or, in
     the case of interfaces specified for a particular programming
     language, one that is widely used among developers working in that
     language.

     The "System Libraries" of an executable work include anything,
     other than the work as a whole, that (a) is included in the normal
     form of packaging a Major Component, but which is not part of that
     Major Component, and (b) serves only to enable use of the work
     with that Major Component, or to implement a Standard Interface
     for which an implementation is available to the public in source
     code form.  A "Major Component", in this context, means a major
     essential component (kernel, window system, and so on) of the
     specific operating system (if any) on which the executable work
     runs, or a compiler used to produce the work, or an object code
     interpreter used to run it.

     The "Corresponding Source" for a work in object code form means all
     the source code needed to generate, install, and (for an executable
     work) run the object code and to modify the work, including
     scripts to control those activities.  However, it does not include
     the work's System Libraries, or general-purpose tools or generally
     available free programs which are used unmodified in performing
     those activities but which are not part of the work.  For example,
     Corresponding Source includes interface definition files
     associated with source files for the work, and the source code for
     shared libraries and dynamically linked subprograms that the work
     is specifically designed to require, such as by intimate data
     communication or control flow between those subprograms and other
     parts of the work.

     The Corresponding Source need not include anything that users can
     regenerate automatically from other parts of the Corresponding
     Source.

     The Corresponding Source for a work in source code form is that
     same work.

  2. Basic Permissions.

     All rights granted under this License are granted for the term of
     copyright on the Program, and are irrevocable provided the stated
     conditions are met.  This License explicitly affirms your unlimited
     permission to run the unmodified Program.  The output from running
     a covered work is covered by this License only if the output,
     given its content, constitutes a covered work.  This License
     acknowledges your rights of fair use or other equivalent, as
     provided by copyright law.

     You may make, run and propagate covered works that you do not
     convey, without conditions so long as your license otherwise
     remains in force.  You may convey covered works to others for the
     sole purpose of having them make modifications exclusively for
     you, or provide you with facilities for running those works,
     provided that you comply with the terms of this License in
     conveying all material for which you do not control copyright.
     Those thus making or running the covered works for you must do so
     exclusively on your behalf, under your direction and control, on
     terms that prohibit them from making any copies of your
     copyrighted material outside their relationship with you.

     Conveying under any other circumstances is permitted solely under
     the conditions stated below.  Sublicensing is not allowed; section
     10 makes it unnecessary.

  3. Protecting Users' Legal Rights From Anti-Circumvention Law.

     No covered work shall be deemed part of an effective technological
     measure under any applicable law fulfilling obligations under
     article 11 of the WIPO copyright treaty adopted on 20 December
     1996, or similar laws prohibiting or restricting circumvention of
     such measures.

     When you convey a covered work, you waive any legal power to forbid
     circumvention of technological measures to the extent such
     circumvention is effected by exercising rights under this License
     with respect to the covered work, and you disclaim any intention
     to limit operation or modification of the work as a means of
     enforcing, against the work's users, your or third parties' legal
     rights to forbid circumvention of technological measures.

  4. Conveying Verbatim Copies.

     You may convey verbatim copies of the Program's source code as you
     receive it, in any medium, provided that you conspicuously and
     appropriately publish on each copy an appropriate copyright notice;
     keep intact all notices stating that this License and any
     non-permissive terms added in accord with section 7 apply to the
     code; keep intact all notices of the absence of any warranty; and
     give all recipients a copy of this License along with the Program.

     You may charge any price or no price for each copy that you convey,
     and you may offer support or warranty protection for a fee.

  5. Conveying Modified Source Versions.

     You may convey a work based on the Program, or the modifications to
     produce it from the Program, in the form of source code under the
     terms of section 4, provided that you also meet all of these
     conditions:

       a. The work must carry prominent notices stating that you
          modified it, and giving a relevant date.

       b. The work must carry prominent notices stating that it is
          released under this License and any conditions added under
          section 7.  This requirement modifies the requirement in
          section 4 to "keep intact all notices".

       c. You must license the entire work, as a whole, under this
          License to anyone who comes into possession of a copy.  This
          License will therefore apply, along with any applicable
          section 7 additional terms, to the whole of the work, and all
          its parts, regardless of how they are packaged.  This License
          gives no permission to license the work in any other way, but
          it does not invalidate such permission if you have separately
          received it.

       d. If the work has interactive user interfaces, each must display
          Appropriate Legal Notices; however, if the Program has
          interactive interfaces that do not display Appropriate Legal
          Notices, your work need not make them do so.

     A compilation of a covered work with other separate and independent
     works, which are not by their nature extensions of the covered
     work, and which are not combined with it such as to form a larger
     program, in or on a volume of a storage or distribution medium, is
     called an "aggregate" if the compilation and its resulting
     copyright are not used to limit the access or legal rights of the
     compilation's users beyond what the individual works permit.
     Inclusion of a covered work in an aggregate does not cause this
     License to apply to the other parts of the aggregate.

  6. Conveying Non-Source Forms.

     You may convey a covered work in object code form under the terms
     of sections 4 and 5, provided that you also convey the
     machine-readable Corresponding Source under the terms of this
     License, in one of these ways:

       a. Convey the object code in, or embodied in, a physical product
          (including a physical distribution medium), accompanied by the
          Corresponding Source fixed on a durable physical medium
          customarily used for software interchange.

       b. Convey the object code in, or embodied in, a physical product
          (including a physical distribution medium), accompanied by a
          written offer, valid for at least three years and valid for
          as long as you offer spare parts or customer support for that
          product model, to give anyone who possesses the object code
          either (1) a copy of the Corresponding Source for all the
          software in the product that is covered by this License, on a
          durable physical medium customarily used for software
          interchange, for a price no more than your reasonable cost of
          physically performing this conveying of source, or (2) access
          to copy the Corresponding Source from a network server at no
          charge.

       c. Convey individual copies of the object code with a copy of
          the written offer to provide the Corresponding Source.  This
          alternative is allowed only occasionally and noncommercially,
          and only if you received the object code with such an offer,
          in accord with subsection 6b.

       d. Convey the object code by offering access from a designated
          place (gratis or for a charge), and offer equivalent access
          to the Corresponding Source in the same way through the same
          place at no further charge.  You need not require recipients
          to copy the Corresponding Source along with the object code.
          If the place to copy the object code is a network server, the
          Corresponding Source may be on a different server (operated
          by you or a third party) that supports equivalent copying
          facilities, provided you maintain clear directions next to
          the object code saying where to find the Corresponding Source.
          Regardless of what server hosts the Corresponding Source, you
          remain obligated to ensure that it is available for as long
          as needed to satisfy these requirements.

       e. Convey the object code using peer-to-peer transmission,
          provided you inform other peers where the object code and
          Corresponding Source of the work are being offered to the
          general public at no charge under subsection 6d.


     A separable portion of the object code, whose source code is
     excluded from the Corresponding Source as a System Library, need
     not be included in conveying the object code work.

     A "User Product" is either (1) a "consumer product", which means
     any tangible personal property which is normally used for personal,
     family, or household purposes, or (2) anything designed or sold for
     incorporation into a dwelling.  In determining whether a product
     is a consumer product, doubtful cases shall be resolved in favor of
     coverage.  For a particular product received by a particular user,
     "normally used" refers to a typical or common use of that class of
     product, regardless of the status of the particular user or of the
     way in which the particular user actually uses, or expects or is
     expected to use, the product.  A product is a consumer product
     regardless of whether the product has substantial commercial,
     industrial or non-consumer uses, unless such uses represent the
     only significant mode of use of the product.

     "Installation Information" for a User Product means any methods,
     procedures, authorization keys, or other information required to
     install and execute modified versions of a covered work in that
     User Product from a modified version of its Corresponding Source.
     The information must suffice to ensure that the continued
     functioning of the modified object code is in no case prevented or
     interfered with solely because modification has been made.

     If you convey an object code work under this section in, or with,
     or specifically for use in, a User Product, and the conveying
     occurs as part of a transaction in which the right of possession
     and use of the User Product is transferred to the recipient in
     perpetuity or for a fixed term (regardless of how the transaction
     is characterized), the Corresponding Source conveyed under this
     section must be accompanied by the Installation Information.  But
     this requirement does not apply if neither you nor any third party
     retains the ability to install modified object code on the User
     Product (for example, the work has been installed in ROM).

     The requirement to provide Installation Information does not
     include a requirement to continue to provide support service,
     warranty, or updates for a work that has been modified or
     installed by the recipient, or for the User Product in which it
     has been modified or installed.  Access to a network may be denied
     when the modification itself materially and adversely affects the
     operation of the network or violates the rules and protocols for
     communication across the network.

     Corresponding Source conveyed, and Installation Information
     provided, in accord with this section must be in a format that is
     publicly documented (and with an implementation available to the
     public in source code form), and must require no special password
     or key for unpacking, reading or copying.

  7. Additional Terms.

     "Additional permissions" are terms that supplement the terms of
     this License by making exceptions from one or more of its
     conditions.  Additional permissions that are applicable to the
     entire Program shall be treated as though they were included in
     this License, to the extent that they are valid under applicable
     law.  If additional permissions apply only to part of the Program,
     that part may be used separately under those permissions, but the
     entire Program remains governed by this License without regard to
     the additional permissions.

     When you convey a copy of a covered work, you may at your option
     remove any additional permissions from that copy, or from any part
     of it.  (Additional permissions may be written to require their own
     removal in certain cases when you modify the work.)  You may place
     additional permissions on material, added by you to a covered work,
     for which you have or can give appropriate copyright permission.

     Notwithstanding any other provision of this License, for material
     you add to a covered work, you may (if authorized by the copyright
     holders of that material) supplement the terms of this License
     with terms:

       a. Disclaiming warranty or limiting liability differently from
          the terms of sections 15 and 16 of this License; or

       b. Requiring preservation of specified reasonable legal notices
          or author attributions in that material or in the Appropriate
          Legal Notices displayed by works containing it; or

       c. Prohibiting misrepresentation of the origin of that material,
          or requiring that modified versions of such material be
          marked in reasonable ways as different from the original
          version; or

       d. Limiting the use for publicity purposes of names of licensors
          or authors of the material; or

       e. Declining to grant rights under trademark law for use of some
          trade names, trademarks, or service marks; or

       f. Requiring indemnification of licensors and authors of that
          material by anyone who conveys the material (or modified
          versions of it) with contractual assumptions of liability to
          the recipient, for any liability that these contractual
          assumptions directly impose on those licensors and authors.

     All other non-permissive additional terms are considered "further
     restrictions" within the meaning of section 10.  If the Program as
     you received it, or any part of it, contains a notice stating that
     it is governed by this License along with a term that is a further
     restriction, you may remove that term.  If a license document
     contains a further restriction but permits relicensing or
     conveying under this License, you may add to a covered work
     material governed by the terms of that license document, provided
     that the further restriction does not survive such relicensing or
     conveying.

     If you add terms to a covered work in accord with this section, you
     must place, in the relevant source files, a statement of the
     additional terms that apply to those files, or a notice indicating
     where to find the applicable terms.

     Additional terms, permissive or non-permissive, may be stated in
     the form of a separately written license, or stated as exceptions;
     the above requirements apply either way.

  8. Termination.

     You may not propagate or modify a covered work except as expressly
     provided under this License.  Any attempt otherwise to propagate or
     modify it is void, and will automatically terminate your rights
     under this License (including any patent licenses granted under
     the third paragraph of section 11).

     However, if you cease all violation of this License, then your
     license from a particular copyright holder is reinstated (a)
     provisionally, unless and until the copyright holder explicitly
     and finally terminates your license, and (b) permanently, if the
     copyright holder fails to notify you of the violation by some
     reasonable means prior to 60 days after the cessation.

     Moreover, your license from a particular copyright holder is
     reinstated permanently if the copyright holder notifies you of the
     violation by some reasonable means, this is the first time you have
     received notice of violation of this License (for any work) from
     that copyright holder, and you cure the violation prior to 30 days
     after your receipt of the notice.

     Termination of your rights under this section does not terminate
     the licenses of parties who have received copies or rights from
     you under this License.  If your rights have been terminated and
     not permanently reinstated, you do not qualify to receive new
     licenses for the same material under section 10.

  9. Acceptance Not Required for Having Copies.

     You are not required to accept this License in order to receive or
     run a copy of the Program.  Ancillary propagation of a covered work
     occurring solely as a consequence of using peer-to-peer
     transmission to receive a copy likewise does not require
     acceptance.  However, nothing other than this License grants you
     permission to propagate or modify any covered work.  These actions
     infringe copyright if you do not accept this License.  Therefore,
     by modifying or propagating a covered work, you indicate your
     acceptance of this License to do so.

 10. Automatic Licensing of Downstream Recipients.

     Each time you convey a covered work, the recipient automatically
     receives a license from the original licensors, to run, modify and
     propagate that work, subject to this License.  You are not
     responsible for enforcing compliance by third parties with this
     License.

     An "entity transaction" is a transaction transferring control of an
     organization, or substantially all assets of one, or subdividing an
     organization, or merging organizations.  If propagation of a
     covered work results from an entity transaction, each party to that
     transaction who receives a copy of the work also receives whatever
     licenses to the work the party's predecessor in interest had or
     could give under the previous paragraph, plus a right to
     possession of the Corresponding Source of the work from the
     predecessor in interest, if the predecessor has it or can get it
     with reasonable efforts.

     You may not impose any further restrictions on the exercise of the
     rights granted or affirmed under this License.  For example, you
     may not impose a license fee, royalty, or other charge for
     exercise of rights granted under this License, and you may not
     initiate litigation (including a cross-claim or counterclaim in a
     lawsuit) alleging that any patent claim is infringed by making,
     using, selling, offering for sale, or importing the Program or any
     portion of it.

 11. Patents.

     A "contributor" is a copyright holder who authorizes use under this
     License of the Program or a work on which the Program is based.
     The work thus licensed is called the contributor's "contributor
     version".

     A contributor's "essential patent claims" are all patent claims
     owned or controlled by the contributor, whether already acquired or
     hereafter acquired, that would be infringed by some manner,
     permitted by this License, of making, using, or selling its
     contributor version, but do not include claims that would be
     infringed only as a consequence of further modification of the
     contributor version.  For purposes of this definition, "control"
     includes the right to grant patent sublicenses in a manner
     consistent with the requirements of this License.

     Each contributor grants you a non-exclusive, worldwide,
     royalty-free patent license under the contributor's essential
     patent claims, to make, use, sell, offer for sale, import and
     otherwise run, modify and propagate the contents of its
     contributor version.

     In the following three paragraphs, a "patent license" is any
     express agreement or commitment, however denominated, not to
     enforce a patent (such as an express permission to practice a
     patent or covenant not to sue for patent infringement).  To
     "grant" such a patent license to a party means to make such an
     agreement or commitment not to enforce a patent against the party.

     If you convey a covered work, knowingly relying on a patent
     license, and the Corresponding Source of the work is not available
     for anyone to copy, free of charge and under the terms of this
     License, through a publicly available network server or other
     readily accessible means, then you must either (1) cause the
     Corresponding Source to be so available, or (2) arrange to deprive
     yourself of the benefit of the patent license for this particular
     work, or (3) arrange, in a manner consistent with the requirements
     of this License, to extend the patent license to downstream
     recipients.  "Knowingly relying" means you have actual knowledge
     that, but for the patent license, your conveying the covered work
     in a country, or your recipient's use of the covered work in a
     country, would infringe one or more identifiable patents in that
     country that you have reason to believe are valid.

     If, pursuant to or in connection with a single transaction or
     arrangement, you convey, or propagate by procuring conveyance of, a
     covered work, and grant a patent license to some of the parties
     receiving the covered work authorizing them to use, propagate,
     modify or convey a specific copy of the covered work, then the
     patent license you grant is automatically extended to all
     recipients of the covered work and works based on it.

     A patent license is "discriminatory" if it does not include within
     the scope of its coverage, prohibits the exercise of, or is
     conditioned on the non-exercise of one or more of the rights that
     are specifically granted under this License.  You may not convey a
     covered work if you are a party to an arrangement with a third
     party that is in the business of distributing software, under
     which you make payment to the third party based on the extent of
     your activity of conveying the work, and under which the third
     party grants, to any of the parties who would receive the covered
     work from you, a discriminatory patent license (a) in connection
     with copies of the covered work conveyed by you (or copies made
     from those copies), or (b) primarily for and in connection with
     specific products or compilations that contain the covered work,
     unless you entered into that arrangement, or that patent license
     was granted, prior to 28 March 2007.

     Nothing in this License shall be construed as excluding or limiting
     any implied license or other defenses to infringement that may
     otherwise be available to you under applicable patent law.

 12. No Surrender of Others' Freedom.

     If conditions are imposed on you (whether by court order,
     agreement or otherwise) that contradict the conditions of this
     License, they do not excuse you from the conditions of this
     License.  If you cannot convey a covered work so as to satisfy
     simultaneously your obligations under this License and any other
     pertinent obligations, then as a consequence you may not convey it
     at all.  For example, if you agree to terms that obligate you to
     collect a royalty for further conveying from those to whom you
     convey the Program, the only way you could satisfy both those
     terms and this License would be to refrain entirely from conveying
     the Program.

 13. Use with the GNU Affero General Public License.

     Notwithstanding any other provision of this License, you have
     permission to link or combine any covered work with a work licensed
     under version 3 of the GNU Affero General Public License into a
     single combined work, and to convey the resulting work.  The terms
     of this License will continue to apply to the part which is the
     covered work, but the special requirements of the GNU Affero
     General Public License, section 13, concerning interaction through
     a network will apply to the combination as such.

 14. Revised Versions of this License.

     The Free Software Foundation may publish revised and/or new
     versions of the GNU General Public License from time to time.
     Such new versions will be similar in spirit to the present
     version, but may differ in detail to address new problems or
     concerns.

     Each version is given a distinguishing version number.  If the
     Program specifies that a certain numbered version of the GNU
     General Public License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that numbered version or of any later version published by the
     Free Software Foundation.  If the Program does not specify a
     version number of the GNU General Public License, you may choose
     any version ever published by the Free Software Foundation.

     If the Program specifies that a proxy can decide which future
     versions of the GNU General Public License can be used, that
     proxy's public statement of acceptance of a version permanently
     authorizes you to choose that version for the Program.

     Later license versions may give you additional or different
     permissions.  However, no additional obligations are imposed on any
     author or copyright holder as a result of your choosing to follow a
     later version.

 15. Disclaimer of Warranty.

     THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
     APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE
     COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
     WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE
     RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
     SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
     NECESSARY SERVICING, REPAIR OR CORRECTION.

 16. Limitation of Liability.

     IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
     AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
     FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
     CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
     THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
     BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
     PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
     PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
     THE POSSIBILITY OF SUCH DAMAGES.

 17. Interpretation of Sections 15 and 16.

     If the disclaimer of warranty and limitation of liability provided
     above cannot be given local legal effect according to their terms,
     reviewing courts shall apply local law that most closely
     approximates an absolute waiver of all civil liability in
     connection with the Program, unless a warranty or assumption of
     liability accompanies a copy of the Program in return for a fee.


END OF TERMS AND CONDITIONS
===========================

How to Apply These Terms to Your New Programs
=============================================

   If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.

   To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.

     ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
     Copyright (C) YEAR NAME OF AUTHOR

     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 3 of the License, or (at
     your option) any later version.

     This program is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with this program.  If not, see `http://www.gnu.org/licenses/'.

   Also add information on how to contact you by electronic and paper
mail.

   If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:

     PROGRAM Copyright (C) YEAR NAME OF AUTHOR
     This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
     This is free software, and you are welcome to redistribute it
     under certain conditions; type `show c' for details.

   The hypothetical commands `show w' and `show c' should show the
appropriate parts of the General Public License.  Of course, your
program's commands might be different; for a GUI interface, you would
use an "about box".

   You should also get your employer (if you work as a programmer) or
school, if any, to sign a "copyright disclaimer" for the program, if
necessary.  For more information on this, and how to apply and follow
the GNU GPL, see `http://www.gnu.org/licenses/'.

   The GNU General Public License does not permit incorporating your
program into proprietary programs.  If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library.  If this is what you want to do, use the
GNU Lesser General Public License instead of this License.  But first,
please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.


File: gperf.info,  Node: Contributors,  Next: Motivation,  Prev: Copying,  Up: Top

Contributors to GNU `gperf' Utility
***********************************

   * The GNU `gperf' perfect hash function generator utility was
     written in GNU C++ by Douglas C. Schmidt.  The general idea for
     the perfect hash function generator was inspired by Keith Bostic's
     algorithm written in C, and distributed to net.sources around
     1984.  The current program is a heavily modified, enhanced, and
     extended implementation of Keith's basic idea, created at the
     University of California, Irvine.  Bugs, patches, and suggestions
     should be reported to `<bug-gnu-gperf@gnu.org>'.

   * Special thanks is extended to Michael Tiemann and Doug Lea, for
     providing a useful compiler, and for giving me a forum to exhibit
     my creation.

     In addition, Adam de Boor and Nels Olson provided many tips and
     insights that greatly helped improve the quality and functionality
     of `gperf'.

   * Bruno Haible enhanced and optimized the search algorithm.  He also
     rewrote the input routines and the output routines for better
     reliability, and added a testsuite.


File: gperf.info,  Node: Motivation,  Next: Search Structures,  Prev: Contributors,  Up: Top

1 Introduction
**************

   `gperf' is a perfect hash function generator written in C++.  It
transforms an N element user-specified keyword set W into a perfect
hash function F.  F uniquely maps keywords in W onto the range 0..K,
where K >= N-1.  If K = N-1 then F is a _minimal_ perfect hash function.
`gperf' generates a 0..K element static lookup table and a pair of C
functions.  These functions determine whether a given character string
S occurs in W, using at most one probe into the lookup table.

   `gperf' currently generates the reserved keyword recognizer for
lexical analyzers in several production and research compilers and
language processing tools, including GNU C, GNU C++, GNU Java, GNU
Pascal, GNU Modula 3, and GNU indent.  Complete C++ source code for
`gperf' is available from `http://ftp.gnu.org/pub/gnu/gperf/'.  A paper
describing `gperf''s design and implementation in greater detail is
available in the Second USENIX C++ Conference proceedings or from
`http://www.cs.wustl.edu/~schmidt/resume.html'.


File: gperf.info,  Node: Search Structures,  Next: Description,  Prev: Motivation,  Up: Top

2 Static search structures and GNU `gperf'
******************************************

   A "static search structure" is an Abstract Data Type with certain
fundamental operations, e.g., _initialize_, _insert_, and _retrieve_.
Conceptually, all insertions occur before any retrievals.  In practice,
`gperf' generates a _static_ array containing search set keywords and
any associated attributes specified by the user.  Thus, there is
essentially no execution-time cost for the insertions.  It is a useful
data structure for representing _static search sets_.  Static search
sets occur frequently in software system applications.  Typical static
search sets include compiler reserved words, assembler instruction
opcodes, and built-in shell interpreter commands.  Search set members,
called "keywords", are inserted into the structure only once, usually
during program initialization, and are not generally modified at
run-time.

   Numerous static search structure implementations exist, e.g.,
arrays, linked lists, binary search trees, digital search tries, and
hash tables.  Different approaches offer trade-offs between space
utilization and search time efficiency.  For example, an N element
sorted array is space efficient, though the average-case time
complexity for retrieval operations using binary search is proportional
to log N.  Conversely, hash table implementations often locate a table
entry in constant time, but typically impose additional memory overhead
and exhibit poor worst case performance.

   _Minimal perfect hash functions_ provide an optimal solution for a
particular class of static search sets.  A minimal perfect hash
function is defined by two properties:

   * It allows keyword recognition in a static search set using at most
     _one_ probe into the hash table.  This represents the "perfect"
     property.

   * The actual memory allocated to store the keywords is precisely
     large enough for the keyword set, and _no larger_.  This is the
     "minimal" property.

   For most applications it is far easier to generate _perfect_ hash
functions than _minimal perfect_ hash functions.  Moreover, non-minimal
perfect hash functions frequently execute faster than minimal ones in
practice.  This phenomena occurs since searching a sparse keyword table
increases the probability of locating a "null" entry, thereby reducing
string comparisons.  `gperf''s default behavior generates
_near-minimal_ perfect hash functions for keyword sets.  However,
`gperf' provides many options that permit user control over the degree
of minimality and perfection.

   Static search sets often exhibit relative stability over time.  For
example, Ada's 63 reserved words have remained constant for nearly a
decade.  It is therefore frequently worthwhile to expend concerted
effort building an optimal search structure _once_, if it subsequently
receives heavy use multiple times.  `gperf' removes the drudgery
associated with constructing time- and space-efficient search
structures by hand.  It has proven a useful and practical tool for
serious programming projects.  Output from `gperf' is currently used in
several production and research compilers, including GNU C, GNU C++,
GNU Java, GNU Pascal, and GNU Modula 3.  The latter two compilers are
not yet part of the official GNU distribution.  Each compiler utilizes
`gperf' to automatically generate static search structures that
efficiently identify their respective reserved keywords.


File: gperf.info,  Node: Description,  Next: Options,  Prev: Search Structures,  Up: Top

3 High-Level Description of GNU `gperf'
***************************************

* Menu:

* Input Format::                Input Format to `gperf'
* Output Format::               Output Format for Generated C Code with `gperf'
* Binary Strings::              Use of NUL bytes
* Output Copyright::            The Copyright of the Output.

   The perfect hash function generator `gperf' reads a set of
"keywords" from an input file (or from the standard input by default).
It attempts to derive a perfect hashing function that recognizes a
member of the "static keyword set" with at most a single probe into the
lookup table.  If `gperf' succeeds in generating such a function it
produces a pair of C source code routines that perform hashing and
table lookup recognition.  All generated C code is directed to the
standard output.  Command-line options described below allow you to
modify the input and output format to `gperf'.

   By default, `gperf' attempts to produce time-efficient code, with
less emphasis on efficient space utilization.  However, several options
exist that permit trading-off execution time for storage space and vice
versa.  In particular, expanding the generated table size produces a
sparse search structure, generally yielding faster searches.
Conversely, you can direct `gperf' to utilize a C `switch' statement
scheme that minimizes data space storage size.  Furthermore, using a C
`switch' may actually speed up the keyword retrieval time somewhat.
Actual results depend on your C compiler, of course.

   In general, `gperf' assigns values to the bytes it is using for
hashing until some set of values gives each keyword a unique value.  A
helpful heuristic is that the larger the hash value range, the easier
it is for `gperf' to find and generate a perfect hash function.
Experimentation is the key to getting the most from `gperf'.


File: gperf.info,  Node: Input Format,  Next: Output Format,  Prev: Description,  Up: Description

3.1 Input Format to `gperf'
===========================

   You can control the input file format by varying certain command-line
arguments, in particular the `-t' option.  The input's appearance is
similar to GNU utilities `flex' and `bison' (or UNIX utilities `lex'
and `yacc').  Here's an outline of the general format:

     declarations
     %%
     keywords
     %%
     functions

   _Unlike_ `flex' or `bison', the declarations section and the
functions section are optional.  The following sections describe the
input format for each section.

* Menu:

* Declarations::                Declarations.
* Keywords::                    Format for Keyword Entries.
* Functions::                   Including Additional C Functions.
* Controls for GNU indent::     Where to place directives for GNU `indent'.

   It is possible to omit the declaration section entirely, if the `-t'
option is not given.  In this case the input file begins directly with
the first keyword line, e.g.:

     january
     february
     march
     april
     ...


File: gperf.info,  Node: Declarations,  Next: Keywords,  Prev: Input Format,  Up: Input Format

3.1.1 Declarations
------------------

   The keyword input file optionally contains a section for including
arbitrary C declarations and definitions, `gperf' declarations that act
like command-line options, as well as for providing a user-supplied
`struct'.

* Menu:

* User-supplied Struct::        Specifying keywords with attributes.
* Gperf Declarations::          Embedding command line options in the input.
* C Code Inclusion::            Including C declarations and definitions.


File: gperf.info,  Node: User-supplied Struct,  Next: Gperf Declarations,  Prev: Declarations,  Up: Declarations

3.1.1.1 User-supplied `struct'
..............................

   If the `-t' option (or, equivalently, the `%struct-type' declaration)
_is_ enabled, you _must_ provide a C `struct' as the last component in
the declaration section from the input file.  The first field in this
struct must be of type `char *' or `const char *' if the `-P' option is
not given, or of type `int' if the option `-P' (or, equivalently, the
`%pic' declaration) is enabled.  This first field must be called
`name', although it is possible to modify its name with the `-K' option
(or, equivalently, the `%define slot-name' declaration) described below.

   Here is a simple example, using months of the year and their
attributes as input:

     struct month { char *name; int number; int days; int leap_days; };
     %%
     january,   1, 31, 31
     february,  2, 28, 29
     march,     3, 31, 31
     april,     4, 30, 30
     may,       5, 31, 31
     june,      6, 30, 30
     july,      7, 31, 31
     august,    8, 31, 31
     september, 9, 30, 30
     october,  10, 31, 31
     november, 11, 30, 30
     december, 12, 31, 31

   Separating the `struct' declaration from the list of keywords and
other fields are a pair of consecutive percent signs, `%%', appearing
left justified in the first column, as in the UNIX utility `lex'.

   If the `struct' has already been declared in an include file, it can
be mentioned in an abbreviated form, like this:

     struct month;
     %%
     january,   1, 31, 31
     ...


File: gperf.info,  Node: Gperf Declarations,  Next: C Code Inclusion,  Prev: User-supplied Struct,  Up: Declarations

3.1.1.2 Gperf Declarations
..........................

   The declaration section can contain `gperf' declarations.  They
influence the way `gperf' works, like command line options do.  In
fact, every such declaration is equivalent to a command line option.
There are three forms of declarations:

  1. Declarations without argument, like `%compare-lengths'.

  2. Declarations with an argument, like `%switch=COUNT'.

  3. Declarations of names of entities in the output file, like
     `%define lookup-function-name NAME'.

   When a declaration is given both in the input file and as a command
line option, the command-line option's value prevails.

   The following `gperf' declarations are available.

`%delimiters=DELIMITER-LIST'
     Allows you to provide a string containing delimiters used to
     separate keywords from their attributes.  The default is ",".  This
     option is essential if you want to use keywords that have embedded
     commas or newlines.

`%struct-type'
     Allows you to include a `struct' type declaration for generated
     code; see above for an example.

`%ignore-case'
     Consider upper and lower case ASCII characters as equivalent.  The
     string comparison will use a case insignificant character
     comparison.  Note that locale dependent case mappings are ignored.

`%language=LANGUAGE-NAME'
     Instructs `gperf' to generate code in the language specified by the
     option's argument.  Languages handled are currently:

    `KR-C'
          Old-style K&R C.  This language is understood by old-style C
          compilers and ANSI C compilers, but ANSI C compilers may flag
          warnings (or even errors) because of lacking `const'.

    `C'
          Common C.  This language is understood by ANSI C compilers,
          and also by old-style C compilers, provided that you `#define
          const' to empty for compilers which don't know about this
          keyword.

    `ANSI-C'
          ANSI C.  This language is understood by ANSI C (C89, ISO C90)
          compilers, ISO C99 compilers, and C++ compilers.

    `C++'
          C++.  This language is understood by C++ compilers.

     The default is C.

`%define slot-name NAME'
     This declaration is only useful when option `-t' (or,
     equivalently, the `%struct-type' declaration) has been given.  By
     default, the program assumes the structure component identifier for
     the keyword is `name'.  This option allows an arbitrary choice of
     identifier for this component, although it still must occur as the
     first field in your supplied `struct'.

`%define initializer-suffix INITIALIZERS'
     This declaration is only useful when option `-t' (or,
     equivalently, the `%struct-type' declaration) has been given.  It
     permits to specify initializers for the structure members following
     SLOT-NAME in empty hash table entries.  The list of initializers
     should start with a comma.  By default, the emitted code will
     zero-initialize structure members following SLOT-NAME.

`%define hash-function-name NAME'
     Allows you to specify the name for the generated hash function.
     Default name is `hash'.  This option permits the use of two hash
     tables in the same file.

`%define lookup-function-name NAME'
     Allows you to specify the name for the generated lookup function.
     Default name is `in_word_set'.  This option permits multiple
     generated hash functions to be used in the same application.

`%define class-name NAME'
     This option is only useful when option `-L C++' (or, equivalently,
     the `%language=C++' declaration) has been given.  It allows you to
     specify the name of generated C++ class.  Default name is
     `Perfect_Hash'.

`%7bit'
     This option specifies that all strings that will be passed as
     arguments to the generated hash function and the generated lookup
     function will solely consist of 7-bit ASCII characters (bytes in
     the range 0..127).  (Note that the ANSI C functions `isalnum' and
     `isgraph' do _not_ guarantee that a byte is in this range.  Only
     an explicit test like `c >= 'A' && c <= 'Z'' guarantees this.)

`%compare-lengths'
     Compare keyword lengths before trying a string comparison.  This
     option is mandatory for binary comparisons (*note Binary
     Strings::).  It also might cut down on the number of string
     comparisons made during the lookup, since keywords with different
     lengths are never compared via `strcmp'.  However, using
     `%compare-lengths' might greatly increase the size of the
     generated C code if the lookup table range is large (which implies
     that the switch option `-S' or `%switch' is not enabled), since
     the length table contains as many elements as there are entries in
     the lookup table.

`%compare-strncmp'
     Generates C code that uses the `strncmp' function to perform
     string comparisons.  The default action is to use `strcmp'.

`%readonly-tables'
     Makes the contents of all generated lookup tables constant, i.e.,
     "readonly".  Many compilers can generate more efficient code for
     this by putting the tables in readonly memory.

`%enum'
     Define constant values using an enum local to the lookup function
     rather than with #defines.  This also means that different lookup
     functions can reside in the same file.  Thanks to James Clark
     `<jjc@ai.mit.edu>'.

`%includes'
     Include the necessary system include file, `<string.h>', at the
     beginning of the code.  By default, this is not done; the user must
     include this header file himself to allow compilation of the code.

`%global-table'
     Generate the static table of keywords as a static global variable,
     rather than hiding it inside of the lookup function (which is the
     default behavior).

`%pic'
     Optimize the generated table for inclusion in shared libraries.
     This reduces the startup time of programs using a shared library
     containing the generated code.  If the `%struct-type' declaration
     (or, equivalently, the option `-t') is also given, the first field
     of the user-defined struct must be of type `int', not `char *',
     because it will contain offsets into the string pool instead of
     actual strings.  To convert such an offset to a string, you can
     use the expression `stringpool + O', where O is the offset.  The
     string pool name can be changed through the `%define
     string-pool-name' declaration.

`%define string-pool-name NAME'
     Allows you to specify the name of the generated string pool
     created by the declaration `%pic' (or, equivalently, the option
     `-P').  The default name is `stringpool'.  This declaration
     permits the use of two hash tables in the same file, with `%pic'
     and even when the `%global-table' declaration (or, equivalently,
     the option `-G') is given.

`%null-strings'
     Use NULL strings instead of empty strings for empty keyword table
     entries.  This reduces the startup time of programs using a shared
     library containing the generated code (but not as much as the
     declaration `%pic'), at the expense of one more test-and-branch
     instruction at run time.

`%define word-array-name NAME'
     Allows you to specify the name for the generated array containing
     the hash table.  Default name is `wordlist'.  This option permits
     the use of two hash tables in the same file, even when the option
     `-G' (or, equivalently, the `%global-table' declaration) is given.

`%define length-table-name NAME'
     Allows you to specify the name for the generated array containing
     the length table.  Default name is `lengthtable'.  This option
     permits the use of two length tables in the same file, even when
     the option `-G' (or, equivalently, the `%global-table'
     declaration) is given.

`%switch=COUNT'
     Causes the generated C code to use a `switch' statement scheme,
     rather than an array lookup table.  This can lead to a reduction
     in both time and space requirements for some input files.  The
     argument to this option determines how many `switch' statements
     are generated.  A value of 1 generates 1 `switch' containing all
     the elements, a value of 2 generates 2 tables with 1/2 the
     elements in each `switch', etc.  This is useful since many C
     compilers cannot correctly generate code for large `switch'
     statements.  This option was inspired in part by Keith Bostic's
     original C program.

`%omit-struct-type'
     Prevents the transfer of the type declaration to the output file.
     Use this option if the type is already defined elsewhere.


File: gperf.info,  Node: C Code Inclusion,  Prev: Gperf Declarations,  Up: Declarations

3.1.1.3 C Code Inclusion
........................

   Using a syntax similar to GNU utilities `flex' and `bison', it is
possible to directly include C source text and comments verbatim into
the generated output file.  This is accomplished by enclosing the region
inside left-justified surrounding `%{', `%}' pairs.  Here is an input
fragment based on the previous example that illustrates this feature:

     %{
     #include <assert.h>
     /* This section of code is inserted directly into the output. */
     int return_month_days (struct month *months, int is_leap_year);
     %}
     struct month { char *name; int number; int days; int leap_days; };
     %%
     january,   1, 31, 31
     february,  2, 28, 29
     march,     3, 31, 31
     ...


File: gperf.info,  Node: Keywords,  Next: Functions,  Prev: Declarations,  Up: Input Format

3.1.2 Format for Keyword Entries
--------------------------------

   The second input file format section contains lines of keywords and
any associated attributes you might supply.  A line beginning with `#'
in the first column is considered a comment.  Everything following the
`#' is ignored, up to and including the following newline.  A line
beginning with `%' in the first column is an option declaration and
must not occur within the keywords section.

   The first field of each non-comment line is always the keyword
itself.  It can be given in two ways: as a simple name, i.e., without
surrounding string quotation marks, or as a string enclosed in
double-quotes, in C syntax, possibly with backslash escapes like `\"'
or `\234' or `\xa8'.  In either case, it must start right at the
beginning of the line, without leading whitespace.  In this context, a
"field" is considered to extend up to, but not include, the first
blank, comma, or newline.  Here is a simple example taken from a
partial list of C reserved words:

     # These are a few C reserved words, see the c.gperf file
     # for a complete list of ANSI C reserved words.
     unsigned
     sizeof
     switch
     signed
     if
     default
     for
     while
     return

   Note that unlike `flex' or `bison' the first `%%' marker may be
elided if the declaration section is empty.

   Additional fields may optionally follow the leading keyword.  Fields
should be separated by commas, and terminate at the end of line.  What
these fields mean is entirely up to you; they are used to initialize the
elements of the user-defined `struct' provided by you in the
declaration section.  If the `-t' option (or, equivalently, the
`%struct-type' declaration) is _not_ enabled these fields are simply
ignored.  All previous examples except the last one contain keyword
attributes.


File: gperf.info,  Node: Functions,  Next: Controls for GNU indent,  Prev: Keywords,  Up: Input Format

3.1.3 Including Additional C Functions
--------------------------------------

   The optional third section also corresponds closely with conventions
found in `flex' and `bison'.  All text in this section, starting at the
final `%%' and extending to the end of the input file, is included
verbatim into the generated output file.  Naturally, it is your
responsibility to ensure that the code contained in this section is
valid C.


File: gperf.info,  Node: Controls for GNU indent,  Prev: Functions,  Up: Input Format

3.1.4 Where to place directives for GNU `indent'.
-------------------------------------------------

   If you want to invoke GNU `indent' on a `gperf' input file, you will
see that GNU `indent' doesn't understand the `%%', `%{' and `%}'
directives that control `gperf''s interpretation of the input file.
Therefore you have to insert some directives for GNU `indent'.  More
precisely, assuming the most general input file structure

     declarations part 1
     %{
     verbatim code
     %}
     declarations part 2
     %%
     keywords
     %%
     functions

you would insert `*INDENT-OFF*' and `*INDENT-ON*' comments as follows:

     /* *INDENT-OFF* */
     declarations part 1
     %{
     /* *INDENT-ON* */
     verbatim code
     /* *INDENT-OFF* */
     %}
     declarations part 2
     %%
     keywords
     %%
     /* *INDENT-ON* */
     functions


File: gperf.info,  Node: Output Format,  Next: Binary Strings,  Prev: Input Format,  Up: Description

3.2 Output Format for Generated C Code with `gperf'
===================================================

   Several options control how the generated C code appears on the
standard output.  Two C functions are generated.  They are called
`hash' and `in_word_set', although you may modify their names with a
command-line option.  Both functions require two arguments, a string,
`char *' STR, and a length parameter, `int' LEN.  Their default
function prototypes are as follows:

 -- Function: unsigned int hash (const char * STR, unsigned int LEN)
     By default, the generated `hash' function returns an integer value
     created by adding LEN to several user-specified STR byte positions
     indexed into an "associated values" table stored in a local static
     array.  The associated values table is constructed internally by
     `gperf' and later output as a static local C array called
     `hash_table'.  The relevant selected positions (i.e. indices into
     STR) are specified via the `-k' option when running `gperf', as
     detailed in the _Options_ section below (*note Options::).

 -- Function:  in_word_set (const char * STR, unsigned int LEN)
     If STR is in the keyword set, returns a pointer to that keyword.
     More exactly, if the option `-t' (or, equivalently, the
     `%struct-type' declaration) was given, it returns a pointer to the
     matching keyword's structure.  Otherwise it returns `NULL'.

   If the option `-c' (or, equivalently, the `%compare-strncmp'
declaration) is not used, STR must be a NUL terminated string of
exactly length LEN.  If `-c' (or, equivalently, the `%compare-strncmp'
declaration) is used, STR must simply be an array of LEN bytes and does
not need to be NUL terminated.

   The code generated for these two functions is affected by the
following options:

`-t'
`--struct-type'
     Make use of the user-defined `struct'.

`-S TOTAL-SWITCH-STATEMENTS'
`--switch=TOTAL-SWITCH-STATEMENTS'
     Generate 1 or more C `switch' statement rather than use a large,
     (and potentially sparse) static array.  Although the exact time and
     space savings of this approach vary according to your C compiler's
     degree of optimization, this method often results in smaller and
     faster code.

   If the `-t' and `-S' options (or, equivalently, the `%struct-type'
and `%switch' declarations) are omitted, the default action is to
generate a `char *' array containing the keywords, together with
additional empty strings used for padding the array.  By experimenting
with the various input and output options, and timing the resulting C
code, you can determine the best option choices for different keyword
set characteristics.


File: gperf.info,  Node: Binary Strings,  Next: Output Copyright,  Prev: Output Format,  Up: Description

3.3 Use of NUL bytes
====================

   By default, the code generated by `gperf' operates on zero
terminated strings, the usual representation of strings in C.  This
means that the keywords in the input file must not contain NUL bytes,
and the STR argument passed to `hash' or `in_word_set' must be NUL
terminated and have exactly length LEN.

   If option `-c' (or, equivalently, the `%compare-strncmp'
declaration) is used, then the STR argument does not need to be NUL
terminated.  The code generated by `gperf' will only access the first
LEN, not LEN+1, bytes starting at STR.  However, the keywords in the
input file still must not contain NUL bytes.

   If option `-l' (or, equivalently, the `%compare-lengths'
declaration) is used, then the hash table performs binary comparison.
The keywords in the input file may contain NUL bytes, written in string
syntax as `\000' or `\x00', and the code generated by `gperf' will
treat NUL like any other byte.  Also, in this case the `-c' option (or,
equivalently, the `%compare-strncmp' declaration) is ignored.


File: gperf.info,  Node: Output Copyright,  Prev: Binary Strings,  Up: Description

3.4 The Copyright of the Output
===============================

   `gperf' is under GPL, but that does not cause the output produced by
`gperf' to be under GPL.  The reason is that the output contains only
small pieces of text that come directly from `gperf''s source code -
only about 7 lines long, too small for being significant -, and
therefore the output is not a "work based on `gperf'" (in the sense of
the GPL version 3).

   On the other hand, the output produced by `gperf' contains
essentially all of the input file.  Therefore the output is a
"derivative work" of the input (in the sense of U.S. copyright law);
and its copyright status depends on the copyright of the input.  For
most software licenses, the result is that the the output is under the
same license, with the same copyright holder, as the input that was
passed to `gperf'.


File: gperf.info,  Node: Options,  Next: Bugs,  Prev: Description,  Up: Top

4 Invoking `gperf'
******************

   There are _many_ options to `gperf'.  They were added to make the
program more convenient for use with real applications.  "On-line" help
is readily available via the `--help' option.  Here is the complete
list of options.

* Menu:

* Output File::                 Specifying the Location of the Output File
* Input Details::               Options that affect Interpretation of the Input File
* Output Language::             Specifying the Language for the Output Code
* Output Details::              Fine tuning Details in the Output Code
* Algorithmic Details::         Changing the Algorithms employed by `gperf'
* Verbosity::                   Informative Output


File: gperf.info,  Node: Output File,  Next: Input Details,  Prev: Options,  Up: Options

4.1 Specifying the Location of the Output File
==============================================

`--output-file=FILE'
     Allows you to specify the name of the file to which the output is
     written to.

   The results are written to standard output if no output file is
specified or if it is `-'.


File: gperf.info,  Node: Input Details,  Next: Output Language,  Prev: Output File,  Up: Options

4.2 Options that affect Interpretation of the Input File
========================================================

   These options are also available as declarations in the input file
(*note Gperf Declarations::).

`-e KEYWORD-DELIMITER-LIST'
`--delimiters=KEYWORD-DELIMITER-LIST'
     Allows you to provide a string containing delimiters used to
     separate keywords from their attributes.  The default is ",".  This
     option is essential if you want to use keywords that have embedded
     commas or newlines.  One useful trick is to use -e'TAB', where TAB
     is the literal tab character.

`-t'
`--struct-type'
     Allows you to include a `struct' type declaration for generated
     code.  Any text before a pair of consecutive `%%' is considered
     part of the type declaration.  Keywords and additional fields may
     follow this, one group of fields per line.  A set of examples for
     generating perfect hash tables and functions for Ada, C, C++,
     Pascal, Modula 2, Modula 3 and JavaScript reserved words are
     distributed with this release.

`--ignore-case'
     Consider upper and lower case ASCII characters as equivalent.  The
     string comparison will use a case insignificant character
     comparison.  Note that locale dependent case mappings are ignored.
     This option is therefore not suitable if a properly
     internationalized or locale aware case mapping should be used.
     (For example, in a Turkish locale, the upper case equivalent of
     the lowercase ASCII letter `i' is the non-ASCII character `capital
     i with dot above'.)  For this case, it is better to apply an
     uppercase or lowercase conversion on the string before passing it
     to the `gperf' generated function.


File: gperf.info,  Node: Output Language,  Next: Output Details,  Prev: Input Details,  Up: Options

4.3 Options to specify the Language for the Output Code
=======================================================

   These options are also available as declarations in the input file
(*note Gperf Declarations::).

`-L GENERATED-LANGUAGE-NAME'
`--language=GENERATED-LANGUAGE-NAME'
     Instructs `gperf' to generate code in the language specified by the
     option's argument.  Languages handled are currently:

    `KR-C'
          Old-style K&R C.  This language is understood by old-style C
          compilers and ANSI C compilers, but ANSI C compilers may flag
          warnings (or even errors) because of lacking `const'.

    `C'
          Common C.  This language is understood by ANSI C compilers,
          and also by old-style C compilers, provided that you `#define
          const' to empty for compilers which don't know about this
          keyword.

    `ANSI-C'
          ANSI C.  This language is understood by ANSI C compilers and
          C++ compilers.

    `C++'
          C++.  This language is understood by C++ compilers.

     The default is C.

`-a'
     This option is supported for compatibility with previous releases
     of `gperf'.  It does not do anything.

`-g'
     This option is supported for compatibility with previous releases
     of `gperf'.  It does not do anything.


File: gperf.info,  Node: Output Details,  Next: Algorithmic Details,  Prev: Output Language,  Up: Options

4.4 Options for fine tuning Details in the Output Code
======================================================

   Most of these options are also available as declarations in the
input file (*note Gperf Declarations::).

`-K SLOT-NAME'
`--slot-name=SLOT-NAME'
     This option is only useful when option `-t' (or, equivalently, the
     `%struct-type' declaration) has been given.  By default, the
     program assumes the structure component identifier for the keyword
     is `name'.  This option allows an arbitrary choice of identifier
     for this component, although it still must occur as the first
     field in your supplied `struct'.

`-F INITIALIZERS'
`--initializer-suffix=INITIALIZERS'
     This option is only useful when option `-t' (or, equivalently, the
     `%struct-type' declaration) has been given.  It permits to specify
     initializers for the structure members following SLOT-NAME in
     empty hash table entries.  The list of initializers should start
     with a comma.  By default, the emitted code will zero-initialize
     structure members following SLOT-NAME.

`-H HASH-FUNCTION-NAME'
`--hash-function-name=HASH-FUNCTION-NAME'
     Allows you to specify the name for the generated hash function.
     Default name is `hash'.  This option permits the use of two hash
     tables in the same file.

`-N LOOKUP-FUNCTION-NAME'
`--lookup-function-name=LOOKUP-FUNCTION-NAME'
     Allows you to specify the name for the generated lookup function.
     Default name is `in_word_set'.  This option permits multiple
     generated hash functions to be used in the same application.

`-Z CLASS-NAME'
`--class-name=CLASS-NAME'
     This option is only useful when option `-L C++' (or, equivalently,
     the `%language=C++' declaration) has been given.  It allows you to
     specify the name of generated C++ class.  Default name is
     `Perfect_Hash'.

`-7'
`--seven-bit'
     This option specifies that all strings that will be passed as
     arguments to the generated hash function and the generated lookup
     function will solely consist of 7-bit ASCII characters (bytes in
     the range 0..127).  (Note that the ANSI C functions `isalnum' and
     `isgraph' do _not_ guarantee that a byte is in this range.  Only
     an explicit test like `c >= 'A' && c <= 'Z'' guarantees this.)
     This was the default in versions of `gperf' earlier than 2.7; now
     the default is to support 8-bit and multibyte characters.

`-l'
`--compare-lengths'
     Compare keyword lengths before trying a string comparison.  This
     option is mandatory for binary comparisons (*note Binary
     Strings::).  It also might cut down on the number of string
     comparisons made during the lookup, since keywords with different
     lengths are never compared via `strcmp'.  However, using `-l'
     might greatly increase the size of the generated C code if the
     lookup table range is large (which implies that the switch option
     `-S' or `%switch' is not enabled), since the length table contains
     as many elements as there are entries in the lookup table.

`-c'
`--compare-strncmp'
     Generates C code that uses the `strncmp' function to perform
     string comparisons.  The default action is to use `strcmp'.

`-C'
`--readonly-tables'
     Makes the contents of all generated lookup tables constant, i.e.,
     "readonly".  Many compilers can generate more efficient code for
     this by putting the tables in readonly memory.

`-E'
`--enum'
     Define constant values using an enum local to the lookup function
     rather than with #defines.  This also means that different lookup
     functions can reside in the same file.  Thanks to James Clark
     `<jjc@ai.mit.edu>'.

`-I'
`--includes'
     Include the necessary system include file, `<string.h>', at the
     beginning of the code.  By default, this is not done; the user must
     include this header file himself to allow compilation of the code.

`-G'
`--global-table'
     Generate the static table of keywords as a static global variable,
     rather than hiding it inside of the lookup function (which is the
     default behavior).

`-P'
`--pic'
     Optimize the generated table for inclusion in shared libraries.
     This reduces the startup time of programs using a shared library
     containing the generated code.  If the option `-t' (or,
     equivalently, the `%struct-type' declaration) is also given, the
     first field of the user-defined struct must be of type `int', not
     `char *', because it will contain offsets into the string pool
     instead of actual strings.  To convert such an offset to a string,
     you can use the expression `stringpool + O', where O is the
     offset.  The string pool name can be changed through the option
     `--string-pool-name'.

`-Q STRING-POOL-NAME'
`--string-pool-name=STRING-POOL-NAME'
     Allows you to specify the name of the generated string pool
     created by option `-P'.  The default name is `stringpool'.  This
     option permits the use of two hash tables in the same file, with
     `-P' and even when the option `-G' (or, equivalently, the
     `%global-table' declaration) is given.

`--null-strings'
     Use NULL strings instead of empty strings for empty keyword table
     entries.  This reduces the startup time of programs using a shared
     library containing the generated code (but not as much as option
     `-P'), at the expense of one more test-and-branch instruction at
     run time.

`-W HASH-TABLE-ARRAY-NAME'
`--word-array-name=HASH-TABLE-ARRAY-NAME'
     Allows you to specify the name for the generated array containing
     the hash table.  Default name is `wordlist'.  This option permits
     the use of two hash tables in the same file, even when the option
     `-G' (or, equivalently, the `%global-table' declaration) is given.

`--length-table-name=LENGTH-TABLE-ARRAY-NAME'
     Allows you to specify the name for the generated array containing
     the length table.  Default name is `lengthtable'.  This option
     permits the use of two length tables in the same file, even when
     the option `-G' (or, equivalently, the `%global-table'
     declaration) is given.

`-S TOTAL-SWITCH-STATEMENTS'
`--switch=TOTAL-SWITCH-STATEMENTS'
     Causes the generated C code to use a `switch' statement scheme,
     rather than an array lookup table.  This can lead to a reduction
     in both time and space requirements for some input files.  The
     argument to this option determines how many `switch' statements
     are generated.  A value of 1 generates 1 `switch' containing all
     the elements, a value of 2 generates 2 tables with 1/2 the
     elements in each `switch', etc.  This is useful since many C
     compilers cannot correctly generate code for large `switch'
     statements.  This option was inspired in part by Keith Bostic's
     original C program.

`-T'
`--omit-struct-type'
     Prevents the transfer of the type declaration to the output file.
     Use this option if the type is already defined elsewhere.

`-p'
     This option is supported for compatibility with previous releases
     of `gperf'.  It does not do anything.


File: gperf.info,  Node: Algorithmic Details,  Next: Verbosity,  Prev: Output Details,  Up: Options

4.5 Options for changing the Algorithms employed by `gperf'
===========================================================

`-k SELECTED-BYTE-POSITIONS'
`--key-positions=SELECTED-BYTE-POSITIONS'
     Allows selection of the byte positions used in the keywords' hash
     function.  The allowable choices range between 1-255, inclusive.
     The positions are separated by commas, e.g., `-k 9,4,13,14';
     ranges may be used, e.g., `-k 2-7'; and positions may occur in any
     order.  Furthermore, the wildcard '*' causes the generated hash
     function to consider *all* byte positions in each keyword, whereas
     '$' instructs the hash function to use the "final byte" of a
     keyword (this is the only way to use a byte position greater than
     255, incidentally).

     For instance, the option `-k 1,2,4,6-10,'$'' generates a hash
     function that considers positions 1,2,4,6,7,8,9,10, plus the last
     byte in each keyword (which may be at a different position for each
     keyword, obviously).  Keywords with length less than the indicated
     byte positions work properly, since selected byte positions
     exceeding the keyword length are simply not referenced in the hash
     function.

     This option is not normally needed since version 2.8 of `gperf';
     the default byte positions are computed depending on the keyword
     set, through a search that minimizes the number of byte positions.

`-D'
`--duplicates'
     Handle keywords whose selected byte sets hash to duplicate values.
     Duplicate hash values can occur if a set of keywords has the same
     names, but possesses different attributes, or if the selected byte
     positions are not well chosen.  With the -D option `gperf' treats
     all these keywords as part of an equivalence class and generates a
     perfect hash function with multiple comparisons for duplicate
     keywords.  It is up to you to completely disambiguate the keywords
     by modifying the generated C code.  However, `gperf' helps you out
     by organizing the output.

     Using this option usually means that the generated hash function
     is no longer perfect.  On the other hand, it permits `gperf' to
     work on keyword sets that it otherwise could not handle.

`-m ITERATIONS'
`--multiple-iterations=ITERATIONS'
     Perform multiple choices of the `-i' and `-j' values, and choose
     the best results.  This increases the running time by a factor of
     ITERATIONS but does a good job minimizing the generated table size.

`-i INITIAL-VALUE'
`--initial-asso=INITIAL-VALUE'
     Provides an initial VALUE for the associate values array.  Default
     is 0.  Increasing the initial value helps inflate the final table
     size, possibly leading to more time efficient keyword lookups.
     Note that this option is not particularly useful when `-S' (or,
     equivalently, `%switch') is used.  Also, `-i' is overridden when
     the `-r' option is used.

`-j JUMP-VALUE'
`--jump=JUMP-VALUE'
     Affects the "jump value", i.e., how far to advance the associated
     byte value upon collisions.  JUMP-VALUE is rounded up to an odd
     number, the default is 5.  If the JUMP-VALUE is 0 `gperf' jumps by
     random amounts.

`-n'
`--no-strlen'
     Instructs the generator not to include the length of a keyword when
     computing its hash value.  This may save a few assembly
     instructions in the generated lookup table.

`-r'
`--random'
     Utilizes randomness to initialize the associated values table.
     This frequently generates solutions faster than using deterministic
     initialization (which starts all associated values at 0).
     Furthermore, using the randomization option generally increases
     the size of the table.

`-s SIZE-MULTIPLE'
`--size-multiple=SIZE-MULTIPLE'
     Affects the size of the generated hash table.  The numeric
     argument for this option indicates "how many times larger or
     smaller" the maximum associated value range should be, in
     relationship to the number of keywords.  It can be written as an
     integer, a floating-point number or a fraction.  For example, a
     value of 3 means "allow the maximum associated value to be about 3
     times larger than the number of input keywords".  Conversely, a
     value of 1/3 means "allow the maximum associated value to be about
     3 times smaller than the number of input keywords".  Values
     smaller than 1 are useful for limiting the overall size of the
     generated hash table, though the option `-m' is better at this
     purpose.

     If `generate switch' option `-S' (or, equivalently, `%switch') is
     _not_ enabled, the maximum associated value influences the static
     array table size, and a larger table should decrease the time
     required for an unsuccessful search, at the expense of extra table
     space.

     The default value is 1, thus the default maximum associated value
     about the same size as the number of keywords (for efficiency, the
     maximum associated value is always rounded up to a power of 2).
     The actual table size may vary somewhat, since this technique is
     essentially a heuristic.


File: gperf.info,  Node: Verbosity,  Prev: Algorithmic Details,  Up: Options

4.6 Informative Output
======================

`-h'
`--help'
     Prints a short summary on the meaning of each program option.
     Aborts further program execution.

`-v'
`--version'
     Prints out the current version number.

`-d'
`--debug'
     Enables the debugging option.  This produces verbose diagnostics to
     "standard error" when `gperf' is executing.  It is useful both for
     maintaining the program and for determining whether a given set of
     options is actually speeding up the search for a solution.  Some
     useful information is dumped at the end of the program when the
     `-d' option is enabled.


File: gperf.info,  Node: Bugs,  Next: Projects,  Prev: Options,  Up: Top

5 Known Bugs and Limitations with `gperf'
*****************************************

   The following are some limitations with the current release of
`gperf':

   * The `gperf' utility is tuned to execute quickly, and works quickly
     for small to medium size data sets (around 1000 keywords).  It is
     extremely useful for maintaining perfect hash functions for
     compiler keyword sets.  Several recent enhancements now enable
     `gperf' to work efficiently on much larger keyword sets (over
     15,000 keywords).  When processing large keyword sets it helps
     greatly to have over 8 megs of RAM.

   * The size of the generate static keyword array can get _extremely_
     large if the input keyword file is large or if the keywords are
     quite similar.  This tends to slow down the compilation of the
     generated C code, and _greatly_ inflates the object code size.  If
     this situation occurs, consider using the `-S' option to reduce
     data size, potentially increasing keyword recognition time a
     negligible amount.  Since many C compilers cannot correctly
     generate code for large switch statements it is important to
     qualify the -S option with an appropriate numerical argument that
     controls the number of switch statements generated.

   * The maximum number of selected byte positions has an arbitrary
     limit of 255.  This restriction should be removed, and if anyone
     considers this a problem write me and let me know so I can remove
     the constraint.


File: gperf.info,  Node: Projects,  Next: Bibliography,  Prev: Bugs,  Up: Top

6 Things Still Left to Do
*************************

   It should be "relatively" easy to replace the current perfect hash
function algorithm with a more exhaustive approach; the perfect hash
module is essential independent from other program modules.  Additional
worthwhile improvements include:

   * Another useful extension involves modifying the program to generate
     "minimal" perfect hash functions (under certain circumstances, the
     current version can be rather extravagant in the generated table
     size).  This is mostly of theoretical interest, since a sparse
     table often produces faster lookups, and use of the `-S' `switch'
     option can minimize the data size, at the expense of slightly
     longer lookups (note that the gcc compiler generally produces good
     code for `switch' statements, reducing the need for more complex
     schemes).

   * In addition to improving the algorithm, it would also be useful to
     generate an Ada package as the code output, in addition to the
     current C and C++ routines.


File: gperf.info,  Node: Bibliography,  Next: Concept Index,  Prev: Projects,  Up: Top

7 Bibliography
**************

[1] Chang, C.C.: A Scheme for Constructing Ordered Minimal Perfect
Hashing Functions Information Sciences 39(1986), 187-195.

[2] Cichelli, Richard J. Author's Response to "On Cichelli's Minimal
Perfect Hash Functions Method" Communications of the ACM, 23,
12(December 1980), 729.

[3] Cichelli, Richard J. Minimal Perfect Hash Functions Made Simple
Communications of the ACM, 23, 1(January 1980), 17-19.

[4] Cook, C. R. and Oldehoeft, R.R. A Letter Oriented Minimal Perfect
Hashing Function SIGPLAN Notices, 17, 9(September 1982), 18-27.

[5] Cormack, G. V. and Horspool, R. N. S. and Kaiserwerth, M.
Practical Perfect Hashing Computer Journal, 28, 1(January 1985), 54-58.

[6] Jaeschke, G. Reciprocal Hashing: A Method for Generating Minimal
Perfect Hashing Functions Communications of the ACM, 24, 12(December
1981), 829-833.

[7] Jaeschke, G. and Osterburg, G. On Cichelli's Minimal Perfect Hash
Functions Method Communications of the ACM, 23, 12(December 1980),
728-729.

[8] Sager, Thomas J. A Polynomial Time Generator for Minimal Perfect
Hash Functions Communications of the ACM, 28, 5(December 1985), 523-532

[9] Schmidt, Douglas C. GPERF: A Perfect Hash Function Generator Second
USENIX C++ Conference Proceedings, April 1990.

[10] Schmidt, Douglas C. GPERF: A Perfect Hash Function Generator C++
Report, SIGS 10 10 (November/December 1998).

[11] Sebesta, R.W. and Taylor, M.A. Minimal Perfect Hash Functions for
Reserved Word Lists  SIGPLAN Notices, 20, 12(September 1985), 47-53.

[12] Sprugnoli, R. Perfect Hashing Functions: A Single Probe Retrieving
Method for Static Sets Communications of the ACM, 20 11(November 1977),
841-850.

[13] Stallman, Richard M. Using and Porting GNU CC Free Software
Foundation, 1988.

[14] Stroustrup, Bjarne The C++ Programming Language. Addison-Wesley,
1986.

[15] Tiemann, Michael D. User's Guide to GNU C++ Free Software
Foundation, 1989.


File: gperf.info,  Node: Concept Index,  Prev: Bibliography,  Up: Top

Concept Index
*************