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authorJunio C Hamano <gitster@pobox.com>2015-05-14 15:25:52 -0700
committerJunio C Hamano <gitster@pobox.com>2015-05-22 14:40:30 -0700
commit862e730ec1c13f28bfb7c8c9ecb39bcc92dd0922 (patch)
tree83f241cbdd890926053221fd0932ab6d47217108 /commit-slab.h
parent282616c72d1d08a77ca4fe1186cb708c38408d87 (diff)
downloadgit-862e730ec1c13f28bfb7c8c9ecb39bcc92dd0922.tar.gz
commit-slab: introduce slabname##_peek() functionjc/commit-slab
There is no API to ask "Does this commit have associated data in slab?". If an application wants to (1) parse just a few commits at the beginning of a process, (2) store data for only these commits, and then (3) start processing many commits, taking into account the data stored (for a few of them) in the slab, the application would use slabname##_at() to allocate a space to store data in (2), but there is no API other than slabname##_at() to use in step (3). This allocates and wastes new space for these commits the caller is only interested in checking if they have data stored in step (2). Introduce slabname##_peek(), which is similar to slabname##_at() but returns NULL when there is no data already associated to it in such a use case. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'commit-slab.h')
-rw-r--r--commit-slab.h34
1 files changed, 29 insertions, 5 deletions
diff --git a/commit-slab.h b/commit-slab.h
index 375c9c751a..9d12ce299c 100644
--- a/commit-slab.h
+++ b/commit-slab.h
@@ -15,7 +15,13 @@
* - int *indegree_at(struct indegree *, struct commit *);
*
* This function locates the data associated with the given commit in
- * the indegree slab, and returns the pointer to it.
+ * the indegree slab, and returns the pointer to it. The location to
+ * store the data is allocated as necessary.
+ *
+ * - int *indegree_peek(struct indegree *, struct commit *);
+ *
+ * This function is similar to indegree_at(), but it will return NULL
+ * until a call to indegree_at() was made for the commit.
*
* - void init_indegree(struct indegree *);
* void init_indegree_with_stride(struct indegree *, int);
@@ -80,8 +86,9 @@ static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s) \
s->slab = NULL; \
} \
\
-static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
- const struct commit *c) \
+static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s, \
+ const struct commit *c, \
+ int add_if_missing) \
{ \
int nth_slab, nth_slot; \
\
@@ -90,6 +97,8 @@ static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
\
if (s->slab_count <= nth_slab) { \
int i; \
+ if (!add_if_missing) \
+ return NULL; \
s->slab = xrealloc(s->slab, \
(nth_slab + 1) * sizeof(*s->slab)); \
stat_ ##slabname## realloc++; \
@@ -97,10 +106,25 @@ static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
s->slab[i] = NULL; \
s->slab_count = nth_slab + 1; \
} \
- if (!s->slab[nth_slab]) \
+ if (!s->slab[nth_slab]) { \
+ if (!add_if_missing) \
+ return NULL; \
s->slab[nth_slab] = xcalloc(s->slab_size, \
sizeof(**s->slab) * s->stride); \
- return &s->slab[nth_slab][nth_slot * s->stride]; \
+ } \
+ return &s->slab[nth_slab][nth_slot * s->stride]; \
+} \
+ \
+static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
+ const struct commit *c) \
+{ \
+ return slabname##_at_peek(s, c, 1); \
+} \
+ \
+static MAYBE_UNUSED elemtype *slabname## _peek(struct slabname *s, \
+ const struct commit *c) \
+{ \
+ return slabname##_at_peek(s, c, 0); \
} \
\
static int stat_ ##slabname## realloc