awk: don't append bogus data after NUL in sub(); shrink

also renamed variables to more sensible names

function                                             old     new   delta
mk_re_node                                            56      49      -7
awk_sub                                              601     591     -10

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 68 insertions, 50 deletions

diff --git a/editors/awk.c b/editors/awk.c
index 30c6b88ef..3ba1a422d 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -1134,15 +1134,13 @@ static node *new_node(uint32_t info)
         return n;
 }
 
-static node *mk_re_node(const char *s, node *n, regex_t *re)
+static void mk_re_node(const char *s, node *n, regex_t *re)
 {
         n->info = OC_REGEXP;
         n->l.re = re;
         n->r.ire = re + 1;
         xregcomp(re, s, REG_EXTENDED);
         xregcomp(re + 1, s, REG_EXTENDED | REG_ICASE);
-
-        return n;
 }
 
 static node *condition(void)
@@ -1541,7 +1539,10 @@ static regex_t *as_regex(node *op, regex_t *preg)
         return preg;
 }
 
-/* gradually increasing buffer */
+/* gradually increasing buffer.
+ * note that we reallocate even if n == old_size,
+ * and thus there is at least one extra allocated byte.
+ */
 static char* qrealloc(char *b, int n, int *size)
 {
         if (!b || n >= *size) {
@@ -1983,83 +1984,100 @@ static char *awk_printf(node *n)
         return b;
 }
 
-/* common substitution routine
- * replace (nm) substring of (src) that match (n) with (repl), store
- * result into (dest), return number of substitutions. If nm=0, replace
- * all matches. If src or dst is NULL, use $0. If ex=TRUE, enable
- * subexpression matching (\1-\9)
+/* Common substitution routine.
+ * Replace (nm)'th substring of (src) that matches (rn) with (repl),
+ * store result into (dest), return number of substitutions.
+ * If nm = 0, replace all matches.
+ * If src or dst is NULL, use $0.
+ * If subexp != 0, enable subexpression matching (\1-\9).
  */
-static int awk_sub(node *rn, const char *repl, int nm, var *src, var *dest, int ex)
+static int awk_sub(node *rn, const char *repl, int nm, var *src, var *dest, int subexp)
 {
-        char *ds = NULL;
-        const char *s;
+        char *resbuf;
         const char *sp;
-        int c, i, j, di, rl, so, eo, nbs, n, dssize;
+        int match_no, residx, replen, resbufsize;
+        int regexec_flags;
         regmatch_t pmatch[10];
-        regex_t sreg, *re;
+        regex_t sreg, *regex;
+
+        resbuf = NULL;
+        residx = 0;
+        match_no = 0;
+        regexec_flags = 0;
+        regex = as_regex(rn, &sreg);
+        sp = getvar_s(src ? src : intvar[F0]);
+        replen = strlen(repl);
+        while (regexec(regex, sp, 10, pmatch, regexec_flags) == 0) {
+                int so = pmatch[0].rm_so;
+                int eo = pmatch[0].rm_eo;
+
+                //bb_error_msg("match %u: [%u,%u] '%s'%p", match_no+1, so, eo, sp,sp);
+                resbuf = qrealloc(resbuf, residx + eo + replen, &resbufsize);
+                memcpy(resbuf + residx, sp, eo);
+                residx += eo;
+                if (++match_no >= nm) {
+                        const char *s;
+                        int nbs;
 
-        re = as_regex(rn, &sreg);
-        if (!src)
-                src = intvar[F0];
-        if (!dest)
-                dest = intvar[F0];
-
-        i = di = 0;
-        sp = getvar_s(src);
-        rl = strlen(repl);
-        while (regexec(re, sp, 10, pmatch, sp==getvar_s(src) ? 0 : REG_NOTBOL) == 0) {
-                so = pmatch[0].rm_so;
-                eo = pmatch[0].rm_eo;
-
-                ds = qrealloc(ds, di + eo + rl, &dssize);
-                memcpy(ds + di, sp, eo);
-                di += eo;
-                if (++i >= nm) {
                         /* replace */
-                        di -= (eo - so);
+                        residx -= (eo - so);
                         nbs = 0;
                         for (s = repl; *s; s++) {
-                                ds[di++] = c = *s;
+                                char c = resbuf[residx++] = *s;
                                 if (c == '\\') {
                                         nbs++;
                                         continue;
                                 }
-                                if (c == '&' || (ex && c >= '0' && c <= '9')) {
-                                        di -= ((nbs + 3) >> 1);
+                                if (c == '&' || (subexp && c >= '0' && c <= '9')) {
+                                        int j;
+                                        residx -= ((nbs + 3) >> 1);
                                         j = 0;
                                         if (c != '&') {
                                                 j = c - '0';
                                                 nbs++;
                                         }
                                         if (nbs % 2) {
-                                                ds[di++] = c;
+                                                resbuf[residx++] = c;
                                         } else {
-                                                n = pmatch[j].rm_eo - pmatch[j].rm_so;
-                                                ds = qrealloc(ds, di + rl + n, &dssize);
-                                                memcpy(ds + di, sp + pmatch[j].rm_so, n);
-                                                di += n;
+                                                int n = pmatch[j].rm_eo - pmatch[j].rm_so;
+                                                resbuf = qrealloc(resbuf, residx + replen + n, &resbufsize);
+                                                memcpy(resbuf + residx, sp + pmatch[j].rm_so, n);
+                                                residx += n;
                                         }
                                 }
                                 nbs = 0;
                         }
                 }
 
+                regexec_flags = REG_NOTBOL;
                 sp += eo;
-                if (i == nm)
+                if (match_no == nm)
                         break;
                 if (eo == so) {
-                        ds[di] = *sp++;
-                        if (!ds[di++])
-                                break;
+                        /* Empty match (e.g. "b*" will match anywhere).
+                         * Advance by one char. */
+//BUG (bug 1333):
+//gsub(/\<b*/,"") on "abc" will reach this point, advance to "bc"
+//... and will erroneously match "b" even though it is NOT at the word start.
+//we need REG_NOTBOW but it does not exist...
+                        /* Subtle: this is safe only because
+                         * qrealloc allocated at least one extra byte */
+                        resbuf[residx] = *sp;
+                        if (*sp == '\0')
+                                goto ret;
+                        sp++;
+                        residx++;
                 }
         }
 
-        ds = qrealloc(ds, di + strlen(sp), &dssize);
-        strcpy(ds + di, sp);
-        setvar_p(dest, ds);
-        if (re == &sreg)
-                regfree(re);
-        return i;
+        resbuf = qrealloc(resbuf, residx + strlen(sp), &resbufsize);
+        strcpy(resbuf + residx, sp);
+ ret:
+        //bb_error_msg("end sp:'%s'%p", sp,sp);
+        setvar_p(dest ? dest : intvar[F0], resbuf);
+        if (regex == &sreg)
+                regfree(regex);
+        return match_no;
 }
 
 static NOINLINE int do_mktime(const char *ds)