commit-slab: introduce slabname##_peek() function
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>
Junio C Hamano committed
May 14, 2015 at 15:25 UTC
862e730ec1c13f28bfb7c8c9ecb39bcc92dd0922
2 files changed
+49
-13
commit-slab.h
+29
-5
@@ -15,7 +15,13 @@
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* - int *indegree_at(struct indegree *, struct commit *);
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*
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* This function locates the data associated with the given commit in
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- * the indegree slab, and returns the pointer to it.
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+ * the indegree slab, and returns the pointer to it. The location to
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+ * store the data is allocated as necessary.
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+ *
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+ * - int *indegree_peek(struct indegree *, struct commit *);
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+ *
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+ * This function is similar to indegree_at(), but it will return NULL
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+ * until a call to indegree_at() was made for the commit.
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*
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* - void init_indegree(struct indegree *);
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* void init_indegree_with_stride(struct indegree *, int);
@@ -80,8 +86,9 @@ static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s) \
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s->slab = NULL; \
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} \
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\
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-static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
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- const struct commit *c) \
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+static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s, \
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+ const struct commit *c, \
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+ int add_if_missing) \
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{ \
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int nth_slab, nth_slot; \
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\
@@ -90,6 +97,8 @@ static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
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\
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if (s->slab_count <= nth_slab) { \
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int i; \
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+ if (!add_if_missing) \
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+ return NULL; \
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s->slab = xrealloc(s->slab, \
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(nth_slab + 1) * sizeof(*s->slab)); \
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stat_ ##slabname## realloc++; \
@@ -97,10 +106,25 @@ static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
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s->slab[i] = NULL; \
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s->slab_count = nth_slab + 1; \
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} \
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- if (!s->slab[nth_slab]) \
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+ if (!s->slab[nth_slab]) { \
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+ if (!add_if_missing) \
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+ return NULL; \
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s->slab[nth_slab] = xcalloc(s->slab_size, \
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sizeof(**s->slab) * s->stride); \
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- return &s->slab[nth_slab][nth_slot * s->stride]; \
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+ } \
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+ return &s->slab[nth_slab][nth_slot * s->stride]; \
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+} \
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+ \
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+static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s, \
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+ const struct commit *c) \
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+{ \
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+ return slabname##_at_peek(s, c, 1); \
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+} \
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+ \
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+static MAYBE_UNUSED elemtype *slabname## _peek(struct slabname *s, \
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+ const struct commit *c) \
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+{ \
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+ return slabname##_at_peek(s, c, 0); \
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} \
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\
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static int stat_ ##slabname## realloc
commit.c
+20
-8
@@ -244,7 +244,12 @@ void set_commit_buffer(struct commit *commit, void *buffer, unsigned long size)
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const void *get_cached_commit_buffer(const struct commit *commit, unsigned long *sizep)
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{
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- struct commit_buffer *v = buffer_slab_at(&buffer_slab, commit);
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+ struct commit_buffer *v = buffer_slab_peek(&buffer_slab, commit);
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+ if (!v) {
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+ if (sizep)
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+ *sizep = 0;
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+ return NULL;
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+ }
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if (sizep)
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*sizep = v->size;
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return v->buffer;
@@ -271,24 +276,31 @@ const void *get_commit_buffer(const struct commit *commit, unsigned long *sizep)
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void unuse_commit_buffer(const struct commit *commit, const void *buffer)
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{
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- struct commit_buffer *v = buffer_slab_at(&buffer_slab, commit);
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- if (v->buffer != buffer)
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+ struct commit_buffer *v = buffer_slab_peek(&buffer_slab, commit);
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+ if (!(v && v->buffer == buffer))
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free((void *)buffer);
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}
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void free_commit_buffer(struct commit *commit)
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{
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- struct commit_buffer *v = buffer_slab_at(&buffer_slab, commit);
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- free(v->buffer);
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- v->buffer = NULL;
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- v->size = 0;
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+ struct commit_buffer *v = buffer_slab_peek(&buffer_slab, commit);
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+ if (v) {
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+ free(v->buffer);
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+ v->buffer = NULL;
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+ v->size = 0;
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+ }
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}
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const void *detach_commit_buffer(struct commit *commit, unsigned long *sizep)
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{
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- struct commit_buffer *v = buffer_slab_at(&buffer_slab, commit);
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+ struct commit_buffer *v = buffer_slab_peek(&buffer_slab, commit);
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void *ret;
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+ if (!v) {
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+ if (sizep)
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+ *sizep = 0;
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+ return NULL;
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+ }
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ret = v->buffer;
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if (sizep)
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*sizep = v->size;