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refs/packed-backend.c: refactor `find_reference_location()` 

The function `find_reference_location()` is used to perform a
binary search-like function over the contents of a repository's
`$GIT_DIR/packed-refs` file.

The search it implements is unlike a standard binary search in that the
records it searches over are not of a fixed width, so the comparison
must locate the end of a record before comparing it.

Extract the core routine of `find_reference_location()` in order to
implement a function in the following patch which will find the first
location in the `packed-refs` file that *doesn't* match the given
pattern.

The behavior of `find_reference_location()` is unchanged.

Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Taylor Blau 2023-07-10 17:12:25 -04:00 committed by Junio C Hamano
parent b269ac53c0
commit d22d941ac0
1 changed files with 22 additions and 16 deletions
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38
refs/packed-backend.c
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@ -527,22 +527,8 @@ static int load_contents(struct snapshot *snapshot)
return 1;
}

/*
* Find the place in `snapshot->buf` where the start of the record for
* `refname` starts. If `mustexist` is true and the reference doesn't
* exist, then return NULL. If `mustexist` is false and the reference
* doesn't exist, then return the point where that reference would be
* inserted, or `snapshot->eof` (which might be NULL) if it would be
* inserted at the end of the file. In the latter mode, `refname`
* doesn't have to be a proper reference name; for example, one could
* search for "refs/replace/" to find the start of any replace
* references.
*
* The record is sought using a binary search, so `snapshot->buf` must
* be sorted.
*/
static const char *find_reference_location(struct snapshot *snapshot,
const char *refname, int mustexist)
static const char *find_reference_location_1(struct snapshot *snapshot,
const char *refname, int mustexist)
{
/*
* This is not *quite* a garden-variety binary search, because
@ -588,6 +574,26 @@ static const char *find_reference_location(struct snapshot *snapshot,
return lo;
}

/*
* Find the place in `snapshot->buf` where the start of the record for
* `refname` starts. If `mustexist` is true and the reference doesn't
* exist, then return NULL. If `mustexist` is false and the reference
* doesn't exist, then return the point where that reference would be
* inserted, or `snapshot->eof` (which might be NULL) if it would be
* inserted at the end of the file. In the latter mode, `refname`
* doesn't have to be a proper reference name; for example, one could
* search for "refs/replace/" to find the start of any replace
* references.
*
* The record is sought using a binary search, so `snapshot->buf` must
* be sorted.
*/
static const char *find_reference_location(struct snapshot *snapshot,
const char *refname, int mustexist)
{
return find_reference_location_1(snapshot, refname, mustexist);
}

/*
* Create a newly-allocated `snapshot` of the `packed-refs` file in
* its current state and return it. The return value will already have