------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- S Y S T E M . R E G P A T --
-- --
-- S p e c --
-- --
-- Copyright (C) 1986 by University of Toronto. --
-- Copyright (C) 1996-2007, AdaCore --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT 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 distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package implements roughly the same set of regular expressions as
-- are available in the Perl or Python programming languages.
-- This is an extension of the original V7 style regular expression library
-- written in C by Henry Spencer. Apart from the translation to Ada, the
-- interface has been considerably changed to use the Ada String type
-- instead of C-style nul-terminated strings.
-- Note: this package is in the System hierarchy so that it can be directly
-- be used by other predefined packages. User access to this package is via
-- a renaming of this package in GNAT.Regpat (file g-regpat.ads).
package System.Regpat is
pragma Preelaborate;
-- The grammar is the following:
-- regexp ::= expr
-- ::= ^ expr -- anchor at the beginning of string
-- ::= expr $ -- anchor at the end of string
-- expr ::= term
-- ::= term | term -- alternation (term or term ...)
-- term ::= item
-- ::= item item ... -- concatenation (item then item)
-- item ::= elmt -- match elmt
-- ::= elmt * -- zero or more elmt's
-- ::= elmt + -- one or more elmt's
-- ::= elmt ? -- matches elmt or nothing
-- ::= elmt *? -- zero or more times, minimum number
-- ::= elmt +? -- one or more times, minimum number
-- ::= elmt ?? -- zero or one time, minimum number
-- ::= elmt { num } -- matches elmt exactly num times
-- ::= elmt { num , } -- matches elmt at least num times
-- ::= elmt { num , num2 } -- matches between num and num2 times
-- ::= elmt { num }? -- matches elmt exactly num times
-- ::= elmt { num , }? -- matches elmt at least num times
-- non-greedy version
-- ::= elmt { num , num2 }? -- matches between num and num2 times
-- non-greedy version
-- elmt ::= nchr -- matches given character
-- ::= [range range ...] -- matches any character listed
-- ::= [^ range range ...] -- matches any character not listed
-- ::= . -- matches any single character
-- -- except newlines
-- ::= ( expr ) -- parens used for grouping
-- ::= \ num -- reference to num-th parenthesis
-- range ::= char - char -- matches chars in given range
-- ::= nchr
-- ::= [: posix :] -- any character in the POSIX range
-- ::= [:^ posix :] -- not in the POSIX range
-- posix ::= alnum -- alphanumeric characters
-- ::= alpha -- alphabetic characters
-- ::= ascii -- ascii characters (0 .. 127)
-- ::= cntrl -- control chars (0..31, 127..159)
-- ::= digit -- digits ('0' .. '9')
-- ::= graph -- graphic chars (32..126, 160..255)
-- ::= lower -- lower case characters
-- ::= print -- printable characters (32..127)
-- -- and whitespaces (9 .. 13)
-- ::= punct -- printable, except alphanumeric
-- ::= space -- space characters
-- ::= upper -- upper case characters
-- ::= word -- alphanumeric characters
-- ::= xdigit -- hexadecimal chars (0..9, a..f)
-- char ::= any character, including special characters
-- ASCII.NUL is not supported.
-- nchr ::= any character except \()[].*+?^ or \char to match char
-- \n means a newline (ASCII.LF)
-- \t means a tab (ASCII.HT)
-- \r means a return (ASCII.CR)
-- \b matches the empty string at the beginning or end of a
-- word. A word is defined as a set of alphanumerical
-- characters (see \w below).
-- \B matches the empty string only when *not* at the
-- beginning or end of a word.
-- \d matches any digit character ([0-9])
-- \D matches any non digit character ([^0-9])
-- \s matches any white space character. This is equivalent
-- to [ \t\n\r\f\v] (tab, form-feed, vertical-tab,...
-- \S matches any non-white space character.
-- \w matches any alphanumeric character or underscore.
-- This include accented letters, as defined in the
-- package Ada.Characters.Handling.
-- \W matches any non-alphanumeric character.
-- \A match the empty string only at the beginning of the
-- string, whatever flags are used for Compile (the
-- behavior of ^ can change, see Regexp_Flags below).
-- \G match the empty string only at the end of the
-- string, whatever flags are used for Compile (the
-- behavior of $ can change, see Regexp_Flags below).
-- ... ::= is used to indication repetition (one or more terms)
-- Embedded newlines are not matched by the ^ operator.
-- It is possible to retrieve the substring matched a parenthesis
-- expression. Although the depth of parenthesis is not limited in the
-- regexp, only the first 9 substrings can be retrieved.
-- The highest value possible for the arguments to the curly operator ({})
-- are given by the constant Max_Curly_Repeat below.
-- The operators '*', '+', '?' and '{}' always match the longest possible
-- substring. They all have a non-greedy version (with an extra ? after the
-- operator), which matches the shortest possible substring.
-- For instance:
-- regexp="<.*>" string="title
" matches="title
"
-- regexp="<.*?>" string="title
" matches=""
--
-- '{' and '}' are only considered as special characters if they appear
-- in a substring that looks exactly like '{n}', '{n,m}' or '{n,}', where
-- n and m are digits. No space is allowed. In other contexts, the curly
-- braces will simply be treated as normal characters.
-- Compiling Regular Expressions
-- =============================
-- To use this package, you first need to compile the regular expression
-- (a string) into a byte-code program, in a Pattern_Matcher structure.
-- This first step checks that the regexp is valid, and optimizes the
-- matching algorithms of the second step.
-- Two versions of the Compile subprogram are given: one in which this
-- package will compute itself the best possible size to allocate for the
-- byte code; the other where you must allocate enough memory yourself. An
-- exception is raised if there is not enough memory.
-- declare
-- Regexp : String := "a|b";
-- Matcher : Pattern_Matcher := Compile (Regexp);
-- -- The size for matcher is automatically allocated
-- Matcher2 : Pattern_Matcher (1000);
-- -- Some space is allocated directly.
-- begin
-- Compile (Matcher2, Regexp);
-- ...
-- end;
-- Note that the second version is significantly faster, since with the
-- first version the regular expression has in fact to be compiled twice
-- (first to compute the size, then to generate the byte code).
-- Note also that you cannot use the function version of Compile if you
-- specify the size of the Pattern_Matcher, since the discriminants will
-- most probably be different and you will get a Constraint_Error
-- Matching Strings
-- ================
-- Once the regular expression has been compiled, you can use it as often
-- as needed to match strings.
-- Several versions of the Match subprogram are provided, with different
-- parameters and return results.
-- See the description under each of these subprograms
-- Here is a short example showing how to get the substring matched by
-- the first parenthesis pair.
-- declare
-- Matches : Match_Array (0 .. 1);
-- Regexp : String := "a(b|c)d";
-- Str : String := "gacdg";
-- begin
-- Match (Compile (Regexp), Str, Matches);
-- return Str (Matches (1).First .. Matches (1).Last);
-- -- returns 'c'
-- end;
-- Finding all occurrences
-- =======================
-- Finding all the occurrences of a regular expression in a string cannot
-- be done by simply passing a slice of the string. This wouldn't work for
-- anchored regular expressions (the ones starting with "^" or ending with
-- "$").
-- Instead, you need to use the last parameter to Match (Data_First), as in
-- the following loop:
-- declare
-- Str : String :=
-- "-- first line" & ASCII.LF & "-- second line";
-- Matches : Match_Array (0 .. 0);
-- Regexp : Pattern_Matcher := Compile ("^--", Multiple_Lines);
-- Current : Natural := Str'First;
-- begin
-- loop
-- Match (Regexp, Str, Matches, Current);
-- exit when Matches (0) = No_Match;
--
-- -- Process the match at position Matches (0).First
--
-- Current := Matches (0).Last + 1;
-- end loop;
-- end;
-- String Substitution
-- ===================
-- No subprogram is currently provided for string substitution.
-- However, this is easy to simulate with the parenthesis groups, as
-- shown below.
-- This example swaps the first two words of the string:
-- declare
-- Regexp : String := "([a-z]+) +([a-z]+)";
-- Str : String := " first second third ";
-- Matches : Match_Array (0 .. 2);
-- begin
-- Match (Compile (Regexp), Str, Matches);
-- return Str (Str'First .. Matches (1).First - 1)
-- & Str (Matches (2).First .. Matches (2).Last)
-- & " "
-- & Str (Matches (1).First .. Matches (1).Last)
-- & Str (Matches (2).Last + 1 .. Str'Last);
-- -- returns " second first third "
-- end;
---------------
-- Constants --
---------------
Expression_Error : exception;
-- This exception is raised when trying to compile an invalid regular
-- expression. All subprograms taking an expression as parameter may raise
-- Expression_Error.
Max_Paren_Count : constant := 255;
-- Maximum number of parenthesis in a regular expression. This is limited
-- by the size of a Character, as found in the byte-compiled version of
-- regular expressions.
Max_Curly_Repeat : constant := 32767;
-- Maximum number of repetition for the curly operator. The digits in the
-- {n}, {n,} and {n,m } operators cannot be higher than this constant,
-- since they have to fit on two characters in the byte-compiled version of
-- regular expressions.
Max_Program_Size : constant := 2**15 - 1;
-- Maximum size that can be allocated for a program
type Program_Size is range 0 .. Max_Program_Size;
for Program_Size'Size use 16;
-- Number of bytes allocated for the byte-compiled version of a regular
-- expression. The size required depends on the complexity of the regular
-- expression in a complex manner that is undocumented (other than in the
-- body of the Compile procedure). Normally the size is automatically set
-- and the programmer need not be concerned about it. There are two
-- exceptions to this. First in the calls to Match, it is possible to
-- specify a non-zero size that is known to be large enough. This can
-- slightly increase the efficiency by avoiding a copy. Second, in the case
-- of calling compile, it is possible using the procedural form of Compile
-- to use a single Pattern_Matcher variable for several different
-- expressions by setting its size sufficiently large.
Auto_Size : constant := 0;
-- Used in calls to Match to indicate that the Size should be set to
-- a value appropriate to the expression being used automatically.
type Regexp_Flags is mod 256;
for Regexp_Flags'Size use 8;
-- Flags that can be given at compile time to specify default
-- properties for the regular expression.
No_Flags : constant Regexp_Flags;
Case_Insensitive : constant Regexp_Flags;
-- The automaton is optimized so that the matching is done in a case
-- insensitive manner (upper case characters and lower case characters
-- are all treated the same way).
Single_Line : constant Regexp_Flags;
-- Treat the Data we are matching as a single line. This means that
-- ^ and $ will ignore \n (unless Multiple_Lines is also specified),
-- and that '.' will match \n.
Multiple_Lines : constant Regexp_Flags;
-- Treat the Data as multiple lines. This means that ^ and $ will also
-- match on internal newlines (ASCII.LF), in addition to the beginning
-- and end of the string.
--
-- This can be combined with Single_Line.
-----------------
-- Match_Array --
-----------------
subtype Match_Count is Natural range 0 .. Max_Paren_Count;
type Match_Location is record
First : Natural := 0;
Last : Natural := 0;
end record;
type Match_Array is array (Match_Count range <>) of Match_Location;
-- Used for regular expressions that can contain parenthesized
-- subexpressions. Certain Match subprograms below produce Matches of type
-- Match_Array. Each component of Matches is set to the subrange of the
-- matches substring, or to No_Match if no match. Matches (N) is for the
-- N'th parenthesized subexpressions; Matches (0) is for the whole
-- expression.
--
-- For instance, if your regular expression is: "a((b*)c+)(d+)", then
-- 12 3
-- Matches (0) is for "a((b*)c+)(d+)" (the entire expression)
-- Matches (1) is for "(b*)c+"
-- Matches (2) is for "c+"
-- Matches (3) is for "d+"
--
-- The number of parenthesis groups that can be retrieved is limited only
-- by Max_Paren_Count.
--
-- Normally, the bounds of the Matches actual parameter will be
-- 0 .. Paren_Count (Regexp), to get all the matches. However, it is fine
-- if Matches is shorter than that on either end; missing components will
-- be ignored. Thus, in the above example, you could use 2 .. 2 if all you
-- care about it the second parenthesis pair "b*". Likewise, if
-- Matches'Last > Paren_Count (Regexp), the extra components will be set to
-- No_Match.
No_Match : constant Match_Location := (First => 0, Last => 0);
-- The No_Match constant is (0, 0) to differentiate between matching a null
-- string at position 1, which uses (1, 0) and no match at all.
---------------------------------
-- Pattern_Matcher Compilation --
---------------------------------
-- The subprograms here are used to precompile regular expressions for use
-- in subsequent Match calls. Precompilation improves efficiency if the
-- same regular expression is to be used in more than one Match call.
type Pattern_Matcher (Size : Program_Size) is private;
-- Type used to represent a regular expression compiled into byte code
Never_Match : constant Pattern_Matcher;
-- A regular expression that never matches anything
function Compile
(Expression : String;
Flags : Regexp_Flags := No_Flags) return Pattern_Matcher;
-- Compile a regular expression into internal code
--
-- Raises Expression_Error if Expression is not a legal regular expression
--
-- The appropriate size is calculated automatically to correspond to the
-- provided expression. This is the normal default method of compilation.
-- Note that it is generally not possible to assign the result of two
-- different calls to this Compile function to the same Pattern_Matcher
-- variable, since the sizes will differ.
--
-- Flags is the default value to use to set properties for Expression
-- (e.g. case sensitivity,...).
procedure Compile
(Matcher : out Pattern_Matcher;
Expression : String;
Final_Code_Size : out Program_Size;
Flags : Regexp_Flags := No_Flags);
-- Compile a regular expression into into internal code
-- This procedure is significantly faster than the Compile function since
-- it avoids the extra step of precomputing the required size.
--
-- However, it requires the user to provide a Pattern_Matcher variable
-- whose size is preset to a large enough value. One advantage of this
-- approach, in addition to the improved efficiency, is that the same
-- Pattern_Matcher variable can be used to hold the compiled code for
-- several different regular expressions by setting a size that is large
-- enough to accomodate all possibilities.
--
-- In this version of the procedure call, the actual required code size is
-- returned. Also if Matcher.Size is zero on entry, then the resulting code
-- is not stored. A call with Matcher.Size set to Auto_Size can thus be
-- used to determine the space required for compiling the given regular
-- expression.
--
-- This function raises Storage_Error if Matcher is too small to hold
-- the resulting code (i.e. Matcher.Size has too small a value).
--
-- Expression_Error is raised if the string Expression does not contain
-- a valid regular expression.
--
-- Flags is the default value to use to set properties for Expression (case
-- sensitivity,...).
procedure Compile
(Matcher : out Pattern_Matcher;
Expression : String;
Flags : Regexp_Flags := No_Flags);
-- Same procedure as above, expect it does not return the final
-- program size, and Matcher.Size cannot be Auto_Size.
function Paren_Count (Regexp : Pattern_Matcher) return Match_Count;
pragma Inline (Paren_Count);
-- Return the number of parenthesis pairs in Regexp.
--
-- This is the maximum index that will be filled if a Match_Array is
-- used as an argument to Match.
--
-- Thus, if you want to be sure to get all the parenthesis, you should
-- do something like:
--
-- declare
-- Regexp : Pattern_Matcher := Compile ("a(b*)(c+)");
-- Matched : Match_Array (0 .. Paren_Count (Regexp));
-- begin
-- Match (Regexp, "a string", Matched);
-- end;
-------------
-- Quoting --
-------------
function Quote (Str : String) return String;
-- Return a version of Str so that every special character is quoted.
-- The resulting string can be used in a regular expression to match
-- exactly Str, whatever character was present in Str.
--------------
-- Matching --
--------------
-- The Match subprograms are given a regular expression in string
-- form, and perform the corresponding match. The following parameters
-- are present in all forms of the Match call.
-- Expression contains the regular expression to be matched as a string
-- Data contains the string to be matched
-- Data_First is the lower bound for the match, i.e. Data (Data_First)
-- will be the first character to be examined. If Data_First is set to
-- the special value of -1 (the default), then the first character to
-- be examined is Data (Data_First). However, the regular expression
-- character ^ (start of string) still refers to the first character
-- of the full string (Data (Data'First)), which is why there is a
-- separate mechanism for specifying Data_First.
-- Data_Last is the upper bound for the match, i.e. Data (Data_Last)
-- will be the last character to be examined. If Data_Last is set to
-- the special value of Positive'Last (the default), then the last
-- character to be examined is Data (Data_Last). However, the regular
-- expression character $ (end of string) still refers to the last
-- character of the full string (Data (Data'Last)), which is why there
-- is a separate mechanism for specifying Data_Last.
-- Note: the use of Data_First and Data_Last is not equivalent to
-- simply passing a slice as Expression because of the handling of
-- regular expression characters ^ and $.
-- Size is the size allocated for the compiled byte code. Normally
-- this is defaulted to Auto_Size which means that the appropriate
-- size is allocated automatically. It is possible to specify an
-- explicit size, which must be sufficiently large. This slightly
-- increases the efficiency by avoiding the extra step of computing
-- the appropriate size.
-- The following exceptions can be raised in calls to Match
--
-- Storage_Error is raised if a non-zero value is given for Size
-- and it is too small to hold the compiled byte code.
--
-- Expression_Error is raised if the given expression is not a legal
-- regular expression.
procedure Match
(Expression : String;
Data : String;
Matches : out Match_Array;
Size : Program_Size := Auto_Size;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last);
-- This version returns the result of the match stored in Match_Array;
-- see comments under Match_Array above for details.
function Match
(Expression : String;
Data : String;
Size : Program_Size := Auto_Size;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last) return Natural;
-- This version returns the position where Data matches, or if there is
-- no match, then the value Data'First - 1.
function Match
(Expression : String;
Data : String;
Size : Program_Size := Auto_Size;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last) return Boolean;
-- This version returns True if the match succeeds, False otherwise
------------------------------------------------
-- Matching a Pre-Compiled Regular Expression --
------------------------------------------------
-- The following functions are significantly faster if you need to reuse
-- the same regular expression multiple times, since you only have to
-- compile it once. For these functions you must first compile the
-- expression with a call to Compile as previously described.
-- The parameters Data, Data_First and Data_Last are as described
-- in the previous section.
function Match
(Self : Pattern_Matcher;
Data : String;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last) return Natural;
-- Match Data using the given pattern matcher. Returns the position
-- where Data matches, or (Data'First - 1) if there is no match.
function Match
(Self : Pattern_Matcher;
Data : String;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last) return Boolean;
-- Return True if Data matches using the given pattern matcher
pragma Inline (Match);
-- All except the last one below
procedure Match
(Self : Pattern_Matcher;
Data : String;
Matches : out Match_Array;
Data_First : Integer := -1;
Data_Last : Positive := Positive'Last);
-- Match Data using the given pattern matcher and store result in Matches;
-- see comments under Match_Array above for details.
-----------
-- Debug --
-----------
procedure Dump (Self : Pattern_Matcher);
-- Dump the compiled version of the regular expression matched by Self
--------------------------
-- Private Declarations --
--------------------------
private
subtype Pointer is Program_Size;
-- The Pointer type is used to point into Program_Data
-- Note that the pointer type is not necessarily 2 bytes
-- although it is stored in the program using 2 bytes
type Program_Data is array (Pointer range <>) of Character;
Program_First : constant := 1;
-- The "internal use only" fields in regexp are present to pass info from
-- compile to execute that permits the execute phase to run lots faster on
-- simple cases. They are:
-- First character that must begin a match or ASCII.Nul
-- Anchored true iff match must start at beginning of line
-- Must_Have pointer to string that match must include or null
-- Must_Have_Length length of Must_Have string
-- First and Anchored permit very fast decisions on suitable starting
-- points for a match, cutting down the work a lot. Must_Have permits fast
-- rejection of lines that cannot possibly match.
-- The Must_Have tests are costly enough that Optimize supplies a Must_Have
-- only if the r.e. contains something potentially expensive (at present,
-- the only such thing detected is * or at the start of the r.e., which can
-- involve a lot of backup). The length is supplied because the test in
-- Execute needs it and Optimize is computing it anyway.
-- The initialization is meant to fail-safe in case the user of this
-- package tries to use an uninitialized matcher. This takes advantage
-- of the knowledge that ASCII.Nul translates to the end-of-program (EOP)
-- instruction code of the state machine.
No_Flags : constant Regexp_Flags := 0;
Case_Insensitive : constant Regexp_Flags := 1;
Single_Line : constant Regexp_Flags := 2;
Multiple_Lines : constant Regexp_Flags := 4;
type Pattern_Matcher (Size : Pointer) is record
First : Character := ASCII.NUL; -- internal use only
Anchored : Boolean := False; -- internal use only
Must_Have : Pointer := 0; -- internal use only
Must_Have_Length : Natural := 0; -- internal use only
Paren_Count : Natural := 0; -- # paren groups
Flags : Regexp_Flags := No_Flags;
Program : Program_Data (Program_First .. Size) :=
(others => ASCII.NUL);
end record;
Never_Match : constant Pattern_Matcher :=
(0, ASCII.NUL, False, 0, 0, 0, No_Flags, (others => ASCII.NUL));
end System.Regpat;