[PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[Othman Darraz]

use of starts_with() instead of memcmp()

use of skip_prefix instead of memcmp() and strlen()

Signed-off-by: Othman Darraz <darrazo16@gmail.com>
---

I am planning to apply to GSOC 214
 fsck.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fsck.c b/fsck.c
index 64bf279..5eae856 100644
--- a/fsck.c
+++ b/fsck.c
@@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 	int parents = 0;
 	int err;
 
-	if (memcmp(buffer, "tree ", 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')
 		return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
@@ -322,15 +322,15 @@ 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))
+	if (starts_with(buffer, "author "))
 		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 = (char* )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;
-- 
1.9.0.258.g00eda23.dirty

Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[Eric Sunshine]

Thanks for the submission. Comments below to give you a taste of the
Git review process...

On Tue, Mar 18, 2014 at 6:41 PM, Othman Darraz <darrazo16@gmail.com> wrote:
> use of starts_with() instead of memcmp()
>
> use of skip_prefix instead of memcmp() and strlen()

Write proper sentences to explain and justify the change; not sentence
fragments.

> Signed-off-by: Othman Darraz <darrazo16@gmail.com>
> ---
>
> I am planning to apply to GSOC 214

Your logic in these changes is rather severely flawed. Running the
test suite (t1450, in particular), as the GSoC microproject page
suggests, would have clued you in that something was amiss.

>  fsck.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fsck.c b/fsck.c
> index 64bf279..5eae856 100644
> --- a/fsck.c
> +++ b/fsck.c
> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
>         int parents = 0;
>         int err;
>
> -       if (memcmp(buffer, "tree ", 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')

One of the reasons for using starts_with() rather than memcmp() is
that it allows you to eliminate magic numbers, such as 5. However, if
you look closely at this code fragment, you will see that the magic
number is still present in the expression 'buffer+5'. starts_with(),
might be a better fit.

>                 return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
> @@ -322,15 +322,15 @@ 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))
> +       if (starts_with(buffer, "author "))
>                 return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
>         buffer += 7;

Same problem here with magic number 7.

>         err = fsck_ident(&buffer, &commit->object, error_func);
>         if (err)
>                 return err;
> -       if (memcmp(buffer, "committer ", strlen("committer ")))
> +       buffer = (char* )skip_prefix(buffer,"committer ");

Style: (char *)
Style: whitespace: skip_prefix(foo, "bar")

Regarding the (char *) cast: Is 'buffer' ever modified in this
function? If not, would it make sense to make it 'const' (and fix any
other small fallout from that change)?

> +       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;
> --
> 1.9.0.258.g00eda23.dirty

Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[Eric Sunshine]

On Tue, Mar 18, 2014 at 7:09 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
>> diff --git a/fsck.c b/fsck.c
>> index 64bf279..5eae856 100644
>> --- a/fsck.c
>> +++ b/fsck.c
>> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
>>         int parents = 0;
>>         int err;
>>
>> -       if (memcmp(buffer, "tree ", 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')
>
> One of the reasons for using starts_with() rather than memcmp() is
> that it allows you to eliminate magic numbers, such as 5. However, if
> you look closely at this code fragment, you will see that the magic
> number is still present in the expression 'buffer+5'. starts_with(),
> might be a better fit.

Of course, I meant "skip_prefix() might be a better fit".

Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[Eric Sunshine]

On Wed, Mar 19, 2014 at 5:04 AM, Othman Darraz <darrazo16@gmail.com> wrote:
> 2014-03-19 0:12 GMT+01:00 Eric Sunshine <sunshine@sunshineco.com>:
>> On Tue, Mar 18, 2014 at 7:09 PM, Eric Sunshine <sunshine@sunshineco.com>
>> wrote:
>>
>> >> diff --git a/fsck.c b/fsck.c
>> >> index 64bf279..5eae856 100644
>> >> --- a/fsck.c
>> >> +++ b/fsck.c
>> >> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit,
>> >> fsck_error error_func)
>> >>         int parents = 0;
>> >>         int err;
>> >>
>> >> -       if (memcmp(buffer, "tree ", 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')
>> >
>> > One of the reasons for using starts_with() rather than memcmp() is
>> > that it allows you to eliminate magic numbers, such as 5. However, if
>> > you look closely at this code fragment, you will see that the magic
>> > number is still present in the expression 'buffer+5'. starts_with(),
>> > might be a better fit.
>>
>> Of course, I meant "skip_prefix() might be a better fit".
>
> Thank you for your review and feedbacks.
>  Actually I made a mistake because I misunderstood how to run the tests, I
> was using the wrong Makefile.

For quick initial testing, you can just run the single test script.
For instance:

    (cd t && ./t1450-fsck.sh)

Once you have that running correctly, then run the entire test suite
to ensure that your changes didn't break anything else.

> Secondly I think , as well, that skip_prefix()
> is a better fit. Nevertheless, as the variable buffer change in this
> function, using skip_prefix() implies the use of cast.

Yes, the variable named 'buffer' changes, but does the content of the
memory referenced by 'buffer' ever change? If not, then 'buffer' could
be made 'const', thus eliminating the need for the cast. (Note that
changing it to 'const' might involve a bit of extra work, but the
question is still pertinent.)

> I will make the
> changes right now.
>
> Thank you for your time.
>
> Othman DARRAZ

Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

[Michael Haggerty]

On 03/19/2014 12:09 AM, Eric Sunshine wrote:
> Thanks for the submission. Comments below to give you a taste of the
> Git review process...
> 
> On Tue, Mar 18, 2014 at 6:41 PM, Othman Darraz <darrazo16@gmail.com> wrote:
>> use of starts_with() instead of memcmp()
>>
>> use of skip_prefix instead of memcmp() and strlen()
> 
> Write proper sentences to explain and justify the change; not sentence
> fragments.
> 
>> Signed-off-by: Othman Darraz <darrazo16@gmail.com>
>> ---
>>
>> I am planning to apply to GSOC 214
> 
> Your logic in these changes is rather severely flawed. Running the
> test suite (t1450, in particular), as the GSoC microproject page
> suggests, would have clued you in that something was amiss.
> 
>>  fsck.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/fsck.c b/fsck.c
>> index 64bf279..5eae856 100644
>> --- a/fsck.c
>> +++ b/fsck.c
>> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
>>         int parents = 0;
>>         int err;
>>
>> -       if (memcmp(buffer, "tree ", 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')
> 
> One of the reasons for using starts_with() rather than memcmp() is
> that it allows you to eliminate magic numbers, such as 5. However, if
> you look closely at this code fragment, you will see that the magic
> number is still present in the expression 'buffer+5'. starts_with(),
> might be a better fit.

Eric, I think you meant to say that *skip_prefix()* might be a better fit.

> [...]

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/