Remove remnants of length prefix code in strtab handling

The removed code was introduced in commit aa9b705 ("Store strings in
the string table with varint length prefix") and commit 99719da
("Transition from variable-length string size to 2-byte string size").

It involved unnecessary copying of string data and also caused string
comparison to be broken once length prefixes were removed in commit
29e3f42 ("Remove the string length prefix")..

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Eugene Loh <eugene.loh@oracle.com>

libdtrace/dt_strtab.c

@@ -125,11 +125,7 @@ dt_strtab_compare(dt_strtab_t *sp, dt_strhash_t *hp,
 		resid = sp->str_bufs[b] + sp->str_bufsz - buf;
 		n = MIN(resid, len);
 
-		if ((rv = buf[0] - str[0]) != 0)
-			return rv;
-		if ((rv = buf[1] - str[1]) != 0)
-			return rv;
-		if ((rv = strncmp(buf + 2, str + 2, n)) != 0)
+		if ((rv = strncmp(buf, str, n)) != 0)
 			return rv;
 
 		buf += n;
@@ -194,21 +190,13 @@ dt_strtab_index(dt_strtab_t *sp, const char *str)
 	size_t	slen;
 	ssize_t	rc;
 	ulong_t	h;
-	char	*s;
 
 	if (str == NULL || str[0] == '\0')
 		return 0;	/* The empty string is always at offset 0. */
 
 	slen = strlen(str);
-	s = malloc(slen + 1);
-	if (s == NULL)
-		return -1L;
-
-	memcpy(s, str, slen + 1);
-
 	h = str2hval(str, slen) % sp->str_hashsz;
-	rc = dt_strtab_xindex(sp, s, slen, h);
-	free(s);
+	rc = dt_strtab_xindex(sp, str, slen, h);
 
 	return rc;
 }
@@ -220,33 +208,22 @@ dt_strtab_insert(dt_strtab_t *sp, const char *str)
 	size_t		slen;
 	ssize_t		off;
 	ulong_t		h;
-	char		*s;
 
 	if (str == NULL || str[0] == '\0')
 		return 0;	/* The empty string is always at offset 0. */
 
 	slen = strlen(str);
-	s = malloc(slen + 1);
-	if (s == NULL)
-		return -1L;
-
-	memcpy(s, str, slen + 1);
-
 	h = str2hval(str, slen) % sp->str_hashsz;
-	off = dt_strtab_xindex(sp, s, slen, h);
-	if (off != -1) {
-		free(s);
+	off = dt_strtab_xindex(sp, str, slen, h);
+	if (off != -1)
 		return off;
-	}
 
 	/*
 	 * Create a new hash bucket, initialize it, and insert it at the front
 	 * of the hash chain for the appropriate bucket.
 	 */
-	if ((hp = malloc(sizeof(dt_strhash_t))) == NULL) {
-		free(s);
+	if ((hp = malloc(sizeof(dt_strhash_t))) == NULL)
 		return -1L;
-	}
 
 	hp->str_data = sp->str_ptr;
 	hp->str_buf = sp->str_nbufs - 1;
@@ -258,12 +235,10 @@ dt_strtab_insert(dt_strtab_t *sp, const char *str)
 	 * Now copy the string data into our buffer list, and then update
 	 * the global counts of strings and bytes.  Return str's byte offset.
 	 */
-	if (dt_strtab_copyin(sp, s, slen + 1) == -1) {
-		free(s);
+	if (dt_strtab_copyin(sp, str, slen + 1) == -1) {
 		free(hp);
 		return -1L;
 	}
-	free(s);
 
 	sp->str_nstrs++;
 	sp->str_size += slen + 1;