[PATCH 03/11] sha1_object_info_extended(): hint about objects in delta-base cache

[Junio C Hamano <gitster@pobox.com>]

An object found in the delta-base cache is not guaranteed to
stay there, but we know it came from a pack and it is likely
to give us a quick access if we read_sha1_file() it right now,
which is a piece of useful information.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 cache.h     |    3 ++-
 sha1_file.c |    9 +++++++++
 2 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/cache.h b/cache.h
index dfd2d61..7511b07 100644
--- a/cache.h
+++ b/cache.h
@@ -1031,7 +1031,8 @@ struct object_info {
 	enum {
 		OI_CACHED,
 		OI_LOOSE,
-		OI_PACKED
+		OI_PACKED,
+		OI_DBCACHED,
 	} whence;
 	union {
 		/*
diff --git a/sha1_file.c b/sha1_file.c
index 9b16cd8..4d1d3ef 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1695,6 +1695,13 @@ static unsigned long pack_entry_hash(struct packed_git *p, off_t base_offset)
 	return hash % MAX_DELTA_CACHE;
 }
 
+static int in_delta_base_cache(struct packed_git *p, off_t base_offset)
+{
+	unsigned long hash = pack_entry_hash(p, base_offset);
+	struct delta_base_cache_entry *ent = delta_base_cache + hash;
+	return (ent->data && ent->p == p && ent->base_offset == base_offset);
+}
+
 static void *cache_or_unpack_entry(struct packed_git *p, off_t base_offset,
 	unsigned long *base_size, enum object_type *type, int keep_cache)
 {
@@ -2141,6 +2148,8 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi)
 	if (status < 0) {
 		mark_bad_packed_object(e.p, sha1);
 		status = sha1_object_info_extended(sha1, oi);
+	} else if (in_delta_base_cache(e.p, e.offset)) {
+		oi->whence = OI_CACHED;
 	} else {
 		oi->whence = OI_PACKED;
 		oi->u.packed.offset = e.offset;
-- 
1.7.5.1.365.g32b65