Implement scaffolding within the new pseudo-merge compilation unit
necessary to use the pseudo-merge API from within the pack-bitmap.c
machinery.
The core of this scaffolding is two-fold:
- The `pseudo_merge` structure itself, which represents an individual
pseudo-merge bitmap. It has fields for both bitmaps, as well as
metadata about its position within the memory-mapped region, and
a few extra bits indicating whether or not it is satisfied, and
which bitmaps(s, if any) have been read, since they are initialized
lazily.
- The `pseudo_merge_map` structure, which holds an array of
pseudo_merges, as well as a pointer to the memory-mapped region
containing the pseudo-merge serialization from within a .bitmap
file.
Note that the `bitmap_index` structure is defined statically within the
pack-bitmap.o compilation unit, so we can't take in a `struct
bitmap_index *`. Instead, wrap the primary components necessary to read
the pseudo-merges in this new structure to avoid exposing the
implementation details of the `bitmap_index` structure.
Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
---
pseudo-merge.c | 10 ++++++++
pseudo-merge.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+)
diff --git a/pseudo-merge.c b/pseudo-merge.c
index 4be730563eb..1aca70ecdfb 100644
--- a/pseudo-merge.c
+++ b/pseudo-merge.c
@@ -454,3 +454,13 @@ void select_pseudo_merges(struct bitmap_writer *writer,
stop_progress(&progress);
}
+
+void free_pseudo_merge_map(struct pseudo_merge_map *pm)
+{
+ uint32_t i;
+ for (i = 0; i < pm->nr; i++) {
+ ewah_pool_free(pm->v[i].commits);
+ ewah_pool_free(pm->v[i].bitmap);
+ }
+ free(pm->v);
+}
diff --git a/pseudo-merge.h b/pseudo-merge.h
index cab54daf14b..a3f0243062c 100644
--- a/pseudo-merge.h
+++ b/pseudo-merge.h
@@ -97,4 +97,69 @@ struct pseudo_merge_commit_idx {
void select_pseudo_merges(struct bitmap_writer *writer,
struct commit **commits, size_t commits_nr);
+/*
+ * Represents a serialized view of a file containing pseudo-merge(s)
+ * (see Documentation/technical/bitmap-format.txt for a specification
+ * of the format).
+ */
+struct pseudo_merge_map {
+ /*
+ * An array of pseudo-merge(s), lazily loaded from the .bitmap
+ * file.
+ */
+ struct pseudo_merge *v;
+ size_t nr;
+ size_t commits_nr;
+
+ /*
+ * Pointers into a memory-mapped view of the .bitmap file:
+ *
+ * - map: the beginning of the .bitmap file
+ * - commits: the beginning of the pseudo-merge commit index
+ * - map_size: the size of the .bitmap file
+ */
+ const unsigned char *map;
+ const unsigned char *commits;
+
+ size_t map_size;
+};
+
+/*
+ * An individual pseudo-merge, storing a pair of lazily-loaded
+ * bitmaps:
+ *
+ * - commits: the set of commit(s) that are part of the pseudo-merge
+ * - bitmap: the set of object(s) reachable from the above set of
+ * commits.
+ *
+ * The `at` and `bitmap_at` fields are used to store the locations of
+ * each of the above bitmaps in the .bitmap file.
+ */
+struct pseudo_merge {
+ struct ewah_bitmap *commits;
+ struct ewah_bitmap *bitmap;
+
+ off_t at;
+ off_t bitmap_at;
+
+ /*
+ * `satisfied` indicates whether the given pseudo-merge has been
+ * used.
+ *
+ * `loaded_commits` and `loaded_bitmap` indicate whether the
+ * respective bitmaps have been loaded and read from the
+ * .bitmap file.
+ */
+ unsigned satisfied : 1,
+ loaded_commits : 1,
+ loaded_bitmap : 1;
+};
+
+/*
+ * Frees the given pseudo-merge map, releasing any memory held by (a)
+ * parsed EWAH bitmaps, or (b) the array of pseudo-merges itself. Does
+ * not free the memory-mapped view of the .bitmap file.
+ */
+void free_pseudo_merge_map(struct pseudo_merge_map *pm);
+
#endif
--
2.45.1.175.gbea44add9db
