range-diff: split lines manually

Currently range-diff uses the 'strbuf_getline()' function for doing
its line by line processing.  In a future patch we want to do parts of
that parsing using the 'parse_git_diff_header()' function.  That
function does its own line by line reading of the input, and doesn't
use strbufs.  This doesn't match with how we do the line-by-line
processing in range-diff currently.

Switch range-diff to do our own line by line parsing, so we can re-use
the 'parse_git_diff_header()' function later.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

range-diff.c

@@ -24,6 +24,17 @@ struct patch_util {
 	struct object_id oid;
 };
 
+static size_t find_end_of_line(char *buffer, unsigned long size)
+{
+	char *eol = memchr(buffer, '\n', size);
+
+	if (!eol)
+		return size;
+
+	*eol = '\0';
+	return eol + 1 - buffer;
+}
+
 /*
  * Reads the patches into a string list, with the `util` field being populated
  * as struct object_id (will need to be free()d).
@@ -31,10 +42,12 @@ struct patch_util {
 static int read_patches(const char *range, struct string_list *list)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
-	FILE *in;
-	struct strbuf buf = STRBUF_INIT, line = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT, contents = STRBUF_INIT;
 	struct patch_util *util = NULL;
 	int in_header = 1;
+	char *line;
+	int offset, len;
+	size_t size;
 
 	argv_array_pushl(&cp.args, "log", "--no-color", "-p", "--no-merges",
 			"--reverse", "--date-order", "--decorate=no",
@@ -54,17 +67,20 @@ static int read_patches(const char *range, struct string_list *list)
 
 	if (start_command(&cp))
 		return error_errno(_("could not start `log`"));
-	in = fdopen(cp.out, "r");
-	if (!in) {
+	if (strbuf_read(&contents, cp.out, 0) < 0) {
 		error_errno(_("could not read `log` output"));
 		finish_command(&cp);
 		return -1;
 	}
 
-	while (strbuf_getline(&line, in) != EOF) {
+	line = contents.buf;
+	size = contents.len;
+	for (offset = 0; size > 0; offset += len, size -= len, line += len) {
 		const char *p;
 
-		if (skip_prefix(line.buf, "commit ", &p)) {
+		len = find_end_of_line(line, size);
+		line[len - 1] = '\0';
+		if (skip_prefix(line, "commit ", &p)) {
 			if (util) {
 				string_list_append(list, buf.buf)->util = util;
 				strbuf_reset(&buf);
@@ -75,8 +91,7 @@ static int read_patches(const char *range, struct string_list *list)
 				free(util);
 				string_list_clear(list, 1);
 				strbuf_release(&buf);
-				strbuf_release(&line);
-				fclose(in);
+				strbuf_release(&contents);
 				finish_command(&cp);
 				return -1;
 			}
@@ -85,26 +100,28 @@ static int read_patches(const char *range, struct string_list *list)
 			continue;
 		}
 
-		if (starts_with(line.buf, "diff --git")) {
+		if (starts_with(line, "diff --git")) {
 			in_header = 0;
 			strbuf_addch(&buf, '\n');
 			if (!util->diff_offset)
 				util->diff_offset = buf.len;
 			strbuf_addch(&buf, ' ');
-			strbuf_addbuf(&buf, &line);
+			strbuf_addstr(&buf, line);
 		} else if (in_header) {
-			if (starts_with(line.buf, "Author: ")) {
-				strbuf_addbuf(&buf, &line);
+			if (starts_with(line, "Author: ")) {
+				strbuf_addstr(&buf, line);
 				strbuf_addstr(&buf, "\n\n");
-			} else if (starts_with(line.buf, "    ")) {
-				strbuf_rtrim(&line);
-				strbuf_addbuf(&buf, &line);
+			} else if (starts_with(line, "    ")) {
+				p = line + len - 2;
+				while (isspace(*p) && p >= line)
+					p--;
+				strbuf_add(&buf, line, p - line + 1);
 				strbuf_addch(&buf, '\n');
 			}
 			continue;
-		} else if (starts_with(line.buf, "@@ "))
+		} else if (starts_with(line, "@@ "))
 			strbuf_addstr(&buf, "@@");
-		else if (!line.buf[0] || starts_with(line.buf, "index "))
+		else if (!line[0] || starts_with(line, "index "))
 			/*
 			 * A completely blank (not ' \n', which is context)
 			 * line is not valid in a diff.  We skip it
@@ -117,25 +134,24 @@ static int read_patches(const char *range, struct string_list *list)
 			 * we are not interested.
 			 */
 			continue;
-		else if (line.buf[0] == '>') {
+		else if (line[0] == '>') {
 			strbuf_addch(&buf, '+');
-			strbuf_add(&buf, line.buf + 1, line.len - 1);
-		} else if (line.buf[0] == '<') {
+			strbuf_addstr(&buf, line + 1);
+		} else if (line[0] == '<') {
 			strbuf_addch(&buf, '-');
-			strbuf_add(&buf, line.buf + 1, line.len - 1);
-		} else if (line.buf[0] == '#') {
+			strbuf_addstr(&buf, line + 1);
+		} else if (line[0] == '#') {
 			strbuf_addch(&buf, ' ');
-			strbuf_add(&buf, line.buf + 1, line.len - 1);
+			strbuf_addstr(&buf, line + 1);
 		} else {
 			strbuf_addch(&buf, ' ');
-			strbuf_addbuf(&buf, &line);
+			strbuf_addstr(&buf, line);
 		}
 
 		strbuf_addch(&buf, '\n');
 		util->diffsize++;
 	}
-	fclose(in);
-	strbuf_release(&line);
+	strbuf_release(&contents);
 
 	if (util)
 		string_list_append(list, buf.buf)->util = util;