dfa: new option for anchored searches

This follows up on a suggestion by Norihiro Tanaka (Bug#24262).
* src/dfa.c (struct regex_syntax): New member 'anchor'.
(char_context): Use it.
(dfasyntax): Change signature to specify it, along with the old
FOLD and EOL args, as a single DFAOPTS arg.  All uses changed.
* src/dfa.h (DFA_ANCHOR, DFA_CASE_FOLD, DFA_EOL_NUL): New constants
for dfasyntax new last arg.

4 files changed, 31 insertions, 10 deletions

diff --git a/src/dfa.c b/src/dfa.c
index 4cbaa75c..ff3721c1 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -335,6 +335,10 @@ struct regex_syntax
   /* Flag for case-folding letters into sets.  */
   bool case_fold;
 
+  /* True if ^ and $ match only the start and end of data, and do not match
+     end-of-line within data.  */
+  bool anchor;
+
   /* End-of-line byte in data.  */
   unsigned char eolbyte;
 
@@ -754,7 +758,7 @@ unibyte_word_constituent (struct dfa const *dfa, unsigned char c)
 static int
 char_context (struct dfa const *dfa, unsigned char c)
 {
-  if (c == dfa->syntax.eolbyte)
+  if (c == dfa->syntax.eolbyte && !dfa->syntax.anchor)
     return CTX_NEWLINE;
   if (unibyte_word_constituent (dfa, c))
     return CTX_LETTER;
@@ -3987,7 +3991,7 @@ dfaalloc (void)
 /* Initialize DFA.  */
 void
 dfasyntax (struct dfa *dfa, struct localeinfo const *linfo,
-           reg_syntax_t bits, bool fold, unsigned char eol)
+           reg_syntax_t bits, int dfaopts)
 {
   int i;
   memset (dfa, 0, offsetof (struct dfa, dfaexec));
@@ -4000,9 +4004,10 @@ dfasyntax (struct dfa *dfa, struct localeinfo const *linfo,
   dfa->canychar = -1;
   dfa->lex.cur_mb_len = 1;
   dfa->syntax.syntax_bits_set = true;
+  dfa->syntax.case_fold = (dfaopts & DFA_CASE_FOLD) != 0;
+  dfa->syntax.anchor = (dfaopts & DFA_ANCHOR) != 0;
+  dfa->syntax.eolbyte = dfaopts & DFA_EOL_NUL ? '\0' : '\n';
   dfa->syntax.syntax_bits = bits;
-  dfa->syntax.case_fold = fold;
-  dfa->syntax.eolbyte = eol;
 
   for (i = CHAR_MIN; i <= CHAR_MAX; ++i)
     {
diff --git a/src/dfa.h b/src/dfa.h
index 31baf7a1..b8c44cc2 100644
--- a/src/dfa.h
+++ b/src/dfa.h
@@ -46,15 +46,29 @@ struct dfa;
    calling dfafree() on it. */
 extern struct dfa *dfaalloc (void) _GL_ATTRIBUTE_MALLOC;
 
+/* DFA options that can be ORed together, for dfasyntax's 4th arg.  */
+enum
+  {
+    /* ^ and $ match only the start and end of data, and do not match
+       end-of-line within data.  This is always false for grep, but
+       possibly true for other apps.  */
+    DFA_ANCHOR = 1 << 0,
+
+    /* Ignore case while matching.  */
+    DFA_CASE_FOLD = 1 << 1,
+
+    /* '\0' in data is end-of-line, instead of the traditional '\n'.  */
+    DFA_EOL_NUL = 1 << 2
+  };
+
 /* Initialize or reinitialize a DFA.  This must be called before
    any of the routines below.  The arguments are:
    1. The DFA to operate on.
    2. Information about the current locale.
-   3. The syntax bits described earlier in this file.
-   4. The case-folding flag.
-   5. The line terminator.  */
+   3. Syntax bits described in regex.h.
+   4. Additional DFA options described above.  */
 extern void dfasyntax (struct dfa *, struct localeinfo const *,
-                       reg_syntax_t, bool, unsigned char);
+                       reg_syntax_t, int);
 
 /* Build and return the struct dfamust from the given struct dfa. */
 extern struct dfamust *dfamust (struct dfa const *);
diff --git a/src/dfasearch.c b/src/dfasearch.c
index 0838e1fe..96be58f2 100644
--- a/src/dfasearch.c
+++ b/src/dfasearch.c
@@ -123,7 +123,9 @@ GEAcompile (char const *pattern, size_t size, reg_syntax_t syntax_bits)
   if (match_icase)
     syntax_bits |= RE_ICASE;
   re_set_syntax (syntax_bits);
-  dfasyntax (dfa, &localeinfo, syntax_bits, match_icase, eolbyte);
+  int dfaopts = ((match_icase ? DFA_CASE_FOLD : 0)
+                 | (eolbyte ? 0 : DFA_EOL_NUL));
+  dfasyntax (dfa, &localeinfo, syntax_bits, dfaopts);
 
   /* For GNU regex, pass the patterns separately to detect errors like
      "[\nallo\n]\n", where the patterns are "[", "allo" and "]", and
diff --git a/tests/dfa-match-aux.c b/tests/dfa-match-aux.c
index e001b7de..070089c0 100644
--- a/tests/dfa-match-aux.c
+++ b/tests/dfa-match-aux.c
@@ -58,7 +58,7 @@ main (int argc, char **argv)
   init_localeinfo (&localeinfo);
 
   dfa = dfaalloc ();
-  dfasyntax (dfa, &localeinfo, RE_SYNTAX_GREP | RE_NO_EMPTY_RANGES, 0, '\n');
+  dfasyntax (dfa, &localeinfo, RE_SYNTAX_GREP | RE_NO_EMPTY_RANGES, 0);
   dfacomp (argv[1], strlen (argv[1]), dfa, 0);
 
   beg = argv[2];