[PATCH v3 2/2] fsck.c:fsck_commit replace memcmp by skip_prefix

[Ashwin Jha <ajha.dev@gmail.com>]

Replace memcmp by skip_prefix as it serves the dual
purpose of checking the string for a prefix as well
as skipping that prefix.

Signed-off-by: Ashwin Jha <ajha.dev@gmail.com>
---

fsck_commit(): After the first patch in this series, it is now safe to replace
memcmp() with skip_prefix().

Previous versions can be found at [v1] and [v2]:
[v1]: http://git.661346.n2.nabble.com/PATCH-GSoC-Miniproject-15-Rewrite-fsck-c-fsck-commit-td7606180.html
[v2]: http://git.661346.n2.nabble.com/PATCH-Modify-fsck-commit-Replace-memcmp-by-skip-prefix-td7606321.html

 fsck.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/fsck.c b/fsck.c
index b5f017f..2232ce3 100644
--- a/fsck.c
+++ b/fsck.c
@@ -6,6 +6,7 @@
 #include "commit.h"
 #include "tag.h"
 #include "fsck.h"
+#include "git-compat-util.h"
 
 static int fsck_walk_tree(struct tree *tree, fsck_walk_func walk, void *data)
 {
@@ -284,21 +285,23 @@ static int fsck_ident(const char **ident, struct object *obj, fsck_error error_f
 
 static int fsck_commit(struct commit *commit, fsck_error error_func)
 {
-	const char *buffer = commit->buffer;
+	const char *parent_id, *buffer = commit->buffer;
 	unsigned char tree_sha1[20], sha1[20];
 	struct commit_graft *graft;
 	int parents = 0;
 	int err;
 
-	if (memcmp(buffer, "tree ", 5))
+	buffer = skip_prefix(buffer, "tree ");
+	if (!buffer)
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
-	if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n')
+	if (get_sha1_hex(buffer, tree_sha1) || buffer[40] != '\n')
 		return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
-	buffer += 46;
-	while (!memcmp(buffer, "parent ", 7)) {
-		if (get_sha1_hex(buffer+7, sha1) || buffer[47] != '\n')
+	buffer += 41;
+	while ((parent_id = skip_prefix(buffer, "parent "))) {
+		buffer = parent_id;
+		if (get_sha1_hex(buffer, sha1) || buffer[40] != '\n')
 			return error_func(&commit->object, FSCK_ERROR, "invalid 'parent' line format - bad sha1");
-		buffer += 48;
+		buffer += 41;
 		parents++;
 	}
 	graft = lookup_commit_graft(commit->object.sha1);
@@ -322,15 +325,15 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 		if (p || parents)
 			return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
 	}
-	if (memcmp(buffer, "author ", 7))
+	buffer = skip_prefix(buffer, "author ");
+	if (!buffer)
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
-	buffer += 7;
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
-	if (memcmp(buffer, "committer ", strlen("committer ")))
+	buffer = skip_prefix(buffer, "committer ");
+	if (!buffer)
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
-	buffer += strlen("committer ");
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
-- 
1.9.1