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/* $RCSfile: regcomp.h,v $$Revision: 4.1 $$Date: 92/08/07 18:26:31 $
*
* $Log: regcomp.h,v $
* Revision 4.1 92/08/07 18:26:31 lwall
*
* Revision 4.0.1.1 91/06/07 11:49:40 lwall
* patch4: no change
*
* Revision 4.0 91/03/20 01:39:09 lwall
* 4.0 baseline.
*
*/
/*
* The "internal use only" fields in regexp.h are present to pass info from
* compile to execute that permits the execute phase to run lots faster on
* simple cases. They are:
*
* regstart sv that must begin a match; Nullch if none obvious
* reganch is the match anchored (at beginning-of-line only)?
* regmust string (pointer into program) that match must include, or NULL
* [regmust changed to SV* for bminstr()--law]
* regmlen length of regmust string
* [regmlen not used currently]
*
* Regstart and reganch permit very fast decisions on suitable starting points
* for a match, cutting down the work a lot. Regmust permits fast rejection
* of lines that cannot possibly match. The regmust tests are costly enough
* that regcomp() supplies a regmust 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). Regmlen is
* supplied because the test in regexec() needs it and regcomp() is computing
* it anyway.
* [regmust is now supplied always. The tests that use regmust have a
* heuristic that disables the test if it usually matches.]
*
* [In fact, we now use regmust in many cases to locate where the search
* starts in the string, so if regback is >= 0, the regmust search is never
* wasted effort. The regback variable says how many characters back from
* where regmust matched is the earliest possible start of the match.
* For instance, /[a-z].foo/ has a regmust of 'foo' and a regback of 2.]
*/
/*
* Structure for regexp "program". This is essentially a linear encoding
* of a nondeterministic finite-state machine (aka syntax charts or
* "railroad normal form" in parsing technology). Each node is an opcode
* plus a "next" pointer, possibly plus an operand. "Next" pointers of
* all nodes except BRANCH implement concatenation; a "next" pointer with
* a BRANCH on both ends of it is connecting two alternatives. (Here we
* have one of the subtle syntax dependencies: an individual BRANCH (as
* opposed to a collection of them) is never concatenated with anything
* because of operator precedence.) The operand of some types of node is
* a literal string; for others, it is a node leading into a sub-FSM. In
* particular, the operand of a BRANCH node is the first node of the branch.
* (NB this is *not* a tree structure: the tail of the branch connects
* to the thing following the set of BRANCHes.) The opcodes are:
*/
/* definition number opnd? meaning */
#define END 0 /* no End of program. */
#define BOL 1 /* no Match "" at beginning of line. */
#define EOL 2 /* no Match "" at end of line. */
#define ANY 3 /* no Match any one character. */
#define ANYOF 4 /* sv Match character in (or not in) this class. */
#define CURLY 5 /* sv Match this simple thing {n,m} times. */
#define BRANCH 6 /* node Match this alternative, or the next... */
#define BACK 7 /* no Match "", "next" ptr points backward. */
#define EXACTLY 8 /* sv Match this string (preceded by length). */
#define NOTHING 9 /* no Match empty string. */
#define STAR 10 /* node Match this (simple) thing 0 or more times. */
#define PLUS 11 /* node Match this (simple) thing 1 or more times. */
#define ALNUM 12 /* no Match any alphanumeric character */
#define NALNUM 13 /* no Match any non-alphanumeric character */
#define BOUND 14 /* no Match "" at any word boundary */
#define NBOUND 15 /* no Match "" at any word non-boundary */
#define SPACE 16 /* no Match any whitespace character */
#define NSPACE 17 /* no Match any non-whitespace character */
#define DIGIT 18 /* no Match any numeric character */
#define NDIGIT 19 /* no Match any non-numeric character */
#define REF 20 /* num Match some already matched string */
#define OPEN 21 /* num Mark this point in input as start of #n. */
#define CLOSE 22 /* num Analogous to OPEN. */
/*
* Opcode notes:
*
* BRANCH The set of branches constituting a single choice are hooked
* together with their "next" pointers, since precedence prevents
* anything being concatenated to any individual branch. The
* "next" pointer of the last BRANCH in a choice points to the
* thing following the whole choice. This is also where the
* final "next" pointer of each individual branch points; each
* branch starts with the operand node of a BRANCH node.
*
* BACK Normal "next" pointers all implicitly point forward; BACK
* exists to make loop structures possible.
*
* STAR,PLUS '?', and complex '*' and '+', are implemented as circular
* BRANCH structures using BACK. Simple cases (one character
* per match) are implemented with STAR and PLUS for speed
* and to minimize recursive plunges.
*
* OPEN,CLOSE ...are numbered at compile time.
*/
#ifndef DOINIT
extern char regarglen[];
#else
char regarglen[] = {0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,2,2};
#endif
/* The following have no fixed length. */
#ifndef DOINIT
extern char varies[];
#else
char varies[] = {BRANCH,BACK,STAR,PLUS,CURLY,REF,0};
#endif
/* The following always have a length of 1. */
#ifndef DOINIT
extern char simple[];
#else
char simple[] = {ANY,ANYOF,ALNUM,NALNUM,SPACE,NSPACE,DIGIT,NDIGIT,0};
#endif
EXT char regdummy;
/*
* A node is one char of opcode followed by two chars of "next" pointer.
* "Next" pointers are stored as two 8-bit pieces, high order first. The
* value is a positive offset from the opcode of the node containing it.
* An operand, if any, simply follows the node. (Note that much of the
* code generation knows about this implicit relationship.)
*
* Using two bytes for the "next" pointer is vast overkill for most things,
* but allows patterns to get big without disasters.
*
* [If REGALIGN is defined, the "next" pointer is always aligned on an even
* boundary, and reads the offset directly as a short. Also, there is no
* special test to reverse the sign of BACK pointers since the offset is
* stored negative.]
*/
#ifndef gould
#ifndef cray
#ifndef eta10
#define REGALIGN
#endif
#endif
#endif
#define OP(p) (*(p))
#ifndef lint
#ifdef REGALIGN
#define NEXT(p) (*(short*)(p+1))
#define ARG1(p) (*(unsigned short*)(p+3))
#define ARG2(p) (*(unsigned short*)(p+5))
#else
#define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
#define ARG1(p) (((*((p)+3)&0377)<<8) + (*((p)+4)&0377))
#define ARG2(p) (((*((p)+5)&0377)<<8) + (*((p)+6)&0377))
#endif
#else /* lint */
#define NEXT(p) 0
#endif /* lint */
#define OPERAND(p) ((p) + 3)
#ifdef REGALIGN
#define NEXTOPER(p) ((p) + 4)
#else
#define NEXTOPER(p) ((p) + 3)
#endif
#define MAGIC 0234
/*
* Utility definitions.
*/
#ifndef lint
#ifndef CHARBITS
#define UCHARAT(p) ((int)*(unsigned char *)(p))
#else
#define UCHARAT(p) ((int)*(p)&CHARBITS)
#endif
#else /* lint */
#define UCHARAT(p) regdummy
#endif /* lint */
#define FAIL(m) fatal("/%s/: %s",regprecomp,m)
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