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)