1 /* $RCSfile: regcomp.h,v $$Revision: 4.0.1.1 $$Date: 91/06/07 11:49:40 $
4 * Revision 4.0.1.1 91/06/07 11:49:40 lwall
7 * Revision 4.0 91/03/20 01:39:09 lwall
13 * The "internal use only" fields in regexp.h are present to pass info from
14 * compile to execute that permits the execute phase to run lots faster on
15 * simple cases. They are:
17 * regstart str that must begin a match; Nullch if none obvious
18 * reganch is the match anchored (at beginning-of-line only)?
19 * regmust string (pointer into program) that match must include, or NULL
20 * [regmust changed to STR* for bminstr()--law]
21 * regmlen length of regmust string
22 * [regmlen not used currently]
24 * Regstart and reganch permit very fast decisions on suitable starting points
25 * for a match, cutting down the work a lot. Regmust permits fast rejection
26 * of lines that cannot possibly match. The regmust tests are costly enough
27 * that regcomp() supplies a regmust only if the r.e. contains something
28 * potentially expensive (at present, the only such thing detected is * or +
29 * at the start of the r.e., which can involve a lot of backup). Regmlen is
30 * supplied because the test in regexec() needs it and regcomp() is computing
32 * [regmust is now supplied always. The tests that use regmust have a
33 * heuristic that disables the test if it usually matches.]
35 * [In fact, we now use regmust in many cases to locate where the search
36 * starts in the string, so if regback is >= 0, the regmust search is never
37 * wasted effort. The regback variable says how many characters back from
38 * where regmust matched is the earliest possible start of the match.
39 * For instance, /[a-z].foo/ has a regmust of 'foo' and a regback of 2.]
43 * Structure for regexp "program". This is essentially a linear encoding
44 * of a nondeterministic finite-state machine (aka syntax charts or
45 * "railroad normal form" in parsing technology). Each node is an opcode
46 * plus a "next" pointer, possibly plus an operand. "Next" pointers of
47 * all nodes except BRANCH implement concatenation; a "next" pointer with
48 * a BRANCH on both ends of it is connecting two alternatives. (Here we
49 * have one of the subtle syntax dependencies: an individual BRANCH (as
50 * opposed to a collection of them) is never concatenated with anything
51 * because of operator precedence.) The operand of some types of node is
52 * a literal string; for others, it is a node leading into a sub-FSM. In
53 * particular, the operand of a BRANCH node is the first node of the branch.
54 * (NB this is *not* a tree structure: the tail of the branch connects
55 * to the thing following the set of BRANCHes.) The opcodes are:
58 /* definition number opnd? meaning */
59 #define END 0 /* no End of program. */
60 #define BOL 1 /* no Match "" at beginning of line. */
61 #define EOL 2 /* no Match "" at end of line. */
62 #define ANY 3 /* no Match any one character. */
63 #define ANYOF 4 /* str Match character in (or not in) this class. */
64 #define CURLY 5 /* str Match this simple thing {n,m} times. */
65 #define BRANCH 6 /* node Match this alternative, or the next... */
66 #define BACK 7 /* no Match "", "next" ptr points backward. */
67 #define EXACTLY 8 /* str Match this string (preceded by length). */
68 #define NOTHING 9 /* no Match empty string. */
69 #define STAR 10 /* node Match this (simple) thing 0 or more times. */
70 #define PLUS 11 /* node Match this (simple) thing 1 or more times. */
71 #define ALNUM 12 /* no Match any alphanumeric character */
72 #define NALNUM 13 /* no Match any non-alphanumeric character */
73 #define BOUND 14 /* no Match "" at any word boundary */
74 #define NBOUND 15 /* no Match "" at any word non-boundary */
75 #define SPACE 16 /* no Match any whitespace character */
76 #define NSPACE 17 /* no Match any non-whitespace character */
77 #define DIGIT 18 /* no Match any numeric character */
78 #define NDIGIT 19 /* no Match any non-numeric character */
79 #define REF 20 /* num Match some already matched string */
80 #define OPEN 21 /* num Mark this point in input as start of #n. */
81 #define CLOSE 22 /* num Analogous to OPEN. */
86 * BRANCH The set of branches constituting a single choice are hooked
87 * together with their "next" pointers, since precedence prevents
88 * anything being concatenated to any individual branch. The
89 * "next" pointer of the last BRANCH in a choice points to the
90 * thing following the whole choice. This is also where the
91 * final "next" pointer of each individual branch points; each
92 * branch starts with the operand node of a BRANCH node.
94 * BACK Normal "next" pointers all implicitly point forward; BACK
95 * exists to make loop structures possible.
97 * STAR,PLUS '?', and complex '*' and '+', are implemented as circular
98 * BRANCH structures using BACK. Simple cases (one character
99 * per match) are implemented with STAR and PLUS for speed
100 * and to minimize recursive plunges.
102 * OPEN,CLOSE ...are numbered at compile time.
106 extern char regarglen[];
108 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};
111 /* The following have no fixed length. */
113 extern char varies[];
115 char varies[] = {BRANCH,BACK,STAR,PLUS,CURLY,REF,0};
118 /* The following always have a length of 1. */
120 extern char simple[];
122 char simple[] = {ANY,ANYOF,ALNUM,NALNUM,SPACE,NSPACE,DIGIT,NDIGIT,0};
128 * A node is one char of opcode followed by two chars of "next" pointer.
129 * "Next" pointers are stored as two 8-bit pieces, high order first. The
130 * value is a positive offset from the opcode of the node containing it.
131 * An operand, if any, simply follows the node. (Note that much of the
132 * code generation knows about this implicit relationship.)
134 * Using two bytes for the "next" pointer is vast overkill for most things,
135 * but allows patterns to get big without disasters.
137 * [If REGALIGN is defined, the "next" pointer is always aligned on an even
138 * boundary, and reads the offset directly as a short. Also, there is no
139 * special test to reverse the sign of BACK pointers since the offset is
155 #define NEXT(p) (*(short*)(p+1))
156 #define ARG1(p) (*(unsigned short*)(p+3))
157 #define ARG2(p) (*(unsigned short*)(p+5))
159 #define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
160 #define ARG1(p) (((*((p)+3)&0377)<<8) + (*((p)+4)&0377))
161 #define ARG2(p) (((*((p)+5)&0377)<<8) + (*((p)+6)&0377))
167 #define OPERAND(p) ((p) + 3)
170 #define NEXTOPER(p) ((p) + 4)
172 #define NEXTOPER(p) ((p) + 3)
178 * Utility definitions.
182 #define UCHARAT(p) ((int)*(unsigned char *)(p))
184 #define UCHARAT(p) ((int)*(p)&CHARBITS)
187 #define UCHARAT(p) regdummy
190 #define FAIL(m) fatal("/%s/: %s",regprecomp,m)