[PATCH v2] Rewrite fsck.c:fsck_commit() replace memcmp() with starts_with()

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2 messages, 2 authors, 2016-06-15 · open the first message on its own page

[PATCH v2] Rewrite fsck.c:fsck_commit() replace memcmp() with starts_with()

From: blacksimit <hidden>
Date: 2016-06-15 23:00:25 

From: Oguzhan Unlu <redacted>

My solution to make lines containing buffer += a_number; clearer to anyone is following; I defined a new int, magic_num, then assigned lengths of used strings to magic_num and then changed assignment lines through using magic_num so that where the number which is added to buffer is known although I eliminated 3rd parameter of memcmp() when using starts_with().   

Signed-off-by: Oguzhan Unlu <redacted>
---
 I didn't use skip_prefix() in this microproject and I plan to apply for GSOC 2014. I expect your feedbacks!
 fsck.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fsck.c b/fsck.c
index d43be98..4e5ca30 100644
--- a/fsck.c
+++ b/fsck.c
@@ -289,14 +289,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 	struct commit_graft *graft;
 	int parents = 0;
 	int err;
-
+    int magic_num;
+    
+    magic_num = strlen("tree "); /* magic_num is 5 */
 	if (!starts_with(buffer, "tree "))
 		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+magic_num, tree_sha1) || buffer[45] != '\n')
 		return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
 	buffer += 46;
+    magic_num = strlen("parent "); /* magic_num is 7 */
 	while (starts_with(buffer, "parent ")) {
-		if (get_sha1_hex(buffer+7, sha1) || buffer[47] != '\n')
+		if (get_sha1_hex(buffer+magic_num, sha1) || buffer[47] != '\n')
 			return error_func(&commit->object, FSCK_ERROR, "invalid 'parent' line format - bad sha1");
 		buffer += 48;
 		parents++;
@@ -322,15 +325,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 		if (p || parents)
 			return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
 	}
+    magic_num = strlen("author "); /* magic_num is 7 */
 	if (!starts_with(buffer, "author "))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
-	buffer += 7;
+	buffer += magic_num;
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
+    magic_num = strlen("committer"); /* magic_num is 7 */
 	if (!starts_with(buffer, "committer "))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
-	buffer += strlen("committer ");
+	buffer += magic_num;
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
-- 
1.9.1.286.g5172cb3

Re: [PATCH v2] Rewrite fsck.c:fsck_commit() replace memcmp() with starts_with()

From: Eric Sunshine <hidden>
Date: 2016-06-15 23:00:25 

In addition to the valuable review comments by Junio and Matthieu, see
a few more below...

On Fri, Mar 21, 2014 at 12:37 PM, blacksimit [off-list ref] wrote:
From: Oguzhan Unlu <redacted>

My solution to make lines containing buffer += a_number; clearer to anyone is following; I defined a new int, magic_num, then assigned lengths of used strings to magic_num and then changed assignment lines through using magic_num so that where the number which is added to buffer is known although I eliminated 3rd parameter of memcmp() when using starts_with().
The process you describe here is effectively what skip_prefix() does
except that you are doing the bookkeeping manually, whereas
skip_prefix() handles the details for you. This should be a good clue
that skip_prefix() is a better solution.

When writing a commit message, try to keep it impersonal; omit
statements like "My solution" and "I defined".

Use imperative mood, which means that the commit message should tell
the code how to change itself. For instance "replace X with Y" or
"retry operation X upon failure".

Let the code speak for itself. It's obvious that skip_prefix() takes
one less argument than memcmp(), so there is no need to talk about it
in the commit message.

Finally, explain why the change is a good thing.
quoted hunk
Signed-off-by: Oguzhan Unlu <redacted>
---
 I didn't use skip_prefix() in this microproject and I plan to apply for GSOC 2014. I expect your feedbacks!
 fsck.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fsck.c b/fsck.c
index d43be98..4e5ca30 100644
--- a/fsck.c
+++ b/fsck.c
@@ -289,14 +289,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
        struct commit_graft *graft;
        int parents = 0;
        int err;
-
+    int magic_num;
+
+    magic_num = strlen("tree "); /* magic_num is 5 */
        if (!starts_with(buffer, "tree "))
                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+magic_num, tree_sha1) || buffer[45] != '\n')
                return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
        buffer += 46;
+    magic_num = strlen("parent "); /* magic_num is 7 */
        while (starts_with(buffer, "parent ")) {
-               if (get_sha1_hex(buffer+7, sha1) || buffer[47] != '\n')
+               if (get_sha1_hex(buffer+magic_num, sha1) || buffer[47] != '\n')
                        return error_func(&commit->object, FSCK_ERROR, "invalid 'parent' line format - bad sha1");
                buffer += 48;
                parents++;
@@ -322,15 +325,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
                if (p || parents)
                        return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
        }
+    magic_num = strlen("author "); /* magic_num is 7 */
        if (!starts_with(buffer, "author "))
                return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
-       buffer += 7;
+       buffer += magic_num;
        err = fsck_ident(&buffer, &commit->object, error_func);
        if (err)
                return err;
+    magic_num = strlen("committer"); /* magic_num is 7 */
        if (!starts_with(buffer, "committer "))
                return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
-       buffer += strlen("committer ");
+       buffer += magic_num;
        err = fsck_ident(&buffer, &commit->object, error_func);
        if (err)
                return err;
--
1.9.1.286.g5172cb3
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