blame.c: prepare_lines should not call xrealloc for every line

Making a single preparation run for counting the lines will avoid memory
fragmentation.  Also, fix the allocated memory size which was wrong
when sizeof(int *) != sizeof(int), and would have been too small
for sizeof(int *) < sizeof(int), admittedly unlikely.

Signed-off-by: David Kastrup <dak@gnu.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/blame.c

@@ -1756,25 +1756,41 @@ static int prepare_lines(struct scoreboard *sb)
 {
 	const char *buf = sb->final_buf;
 	unsigned long len = sb->final_buf_size;
-	int num = 0, incomplete = 0, bol = 1;
+	const char *end = buf + len;
+	const char *p;
+	int *lineno;
+	int num = 0, incomplete = 0;
 
-	if (len && buf[len-1] != '\n')
-		incomplete++; /* incomplete line at the end */
-	while (len--) {
-		if (bol) {
-			sb->lineno = xrealloc(sb->lineno,
-					      sizeof(int) * (num + 1));
-			sb->lineno[num] = buf - sb->final_buf;
-			bol = 0;
-		}
-		if (*buf++ == '\n') {
+	for (p = buf;;) {
+		p = memchr(p, '\n', end - p);
+		if (p) {
+			p++;
 			num++;
-			bol = 1;
+			continue;
 		}
+		break;
 	}
-	sb->lineno = xrealloc(sb->lineno,
-			      sizeof(int) * (num + incomplete + 1));
-	sb->lineno[num + incomplete] = buf - sb->final_buf;
+
+	if (len && end[-1] != '\n')
+		incomplete++; /* incomplete line at the end */
+
+	sb->lineno = xmalloc(sizeof(*sb->lineno) * (num + incomplete + 1));
+	lineno = sb->lineno;
+
+	*lineno++ = 0;
+	for (p = buf;;) {
+		p = memchr(p, '\n', end - p);
+		if (p) {
+			p++;
+			*lineno++ = p - buf;
+			continue;
+		}
+		break;
+	}
+
+	if (incomplete)
+		*lineno++ = len;
+
 	sb->num_lines = num + incomplete;
 	return sb->num_lines;
 }