pack-objects: move in_pack out of struct object_entry

Instead of using 8 bytes (on 64 bit arch) to store a pointer to a
pack. Use an index instead since the number of packs should be
relatively small.

This limits the number of packs we can handle to 1k. Since we can't be
sure people can never run into the situation where they have more than
1k pack files. Provide a fall back route for it.

If we find out they have too many packs, the new in_pack_by_idx[]
array (which has at most 1k elements) will not be used. Instead we
allocate in_pack[] array that holds nr_objects elements. This is
similar to how the optional in_pack_pos field is handled.

The new simple test is just to make sure the too-many-packs code path
is at least executed. The true test is running

    make test GIT_TEST_FULL_IN_PACK_ARRAY=1

to take advantage of other special case tests.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 37 insertions, 1 deletions

diff --git a/pack-objects.h b/pack-objects.h
index 71ea992..7bedd5a 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -1,8 +1,11 @@
 #ifndef PACK_OBJECTS_H
 #define PACK_OBJECTS_H
 
+#include "object-store.h"
+
 #define OE_DFS_STATE_BITS	2
 #define OE_DEPTH_BITS		12
+#define OE_IN_PACK_BITS		10
 
 /*
  * State flags for depth-first search used for analyzing delta cycles.
@@ -65,7 +68,7 @@ enum dfs_state {
 struct object_entry {
 	struct pack_idx_entry idx;
 	unsigned long size;	/* uncompressed size */
-	struct packed_git *in_pack;	/* already in pack */
+	unsigned in_pack_idx:OE_IN_PACK_BITS;	/* already in pack */
 	off_t in_pack_offset;
 	struct object_entry *delta;	/* delta base object */
 	struct object_entry *delta_child; /* deltified objects who bases me */
@@ -100,8 +103,18 @@ struct packing_data {
 	uint32_t index_size;
 
 	unsigned int *in_pack_pos;
+
+	/*
+	 * Only one of these can be non-NULL and they have different
+	 * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
+	 * the pack of an object using in_pack_idx field. If not,
+	 * in_pack[] array is used the same way as in_pack_pos[]
+	 */
+	struct packed_git **in_pack_by_idx;
+	struct packed_git **in_pack;
 };
 
+void prepare_packing_data(struct packing_data *pdata);
 struct object_entry *packlist_alloc(struct packing_data *pdata,
 				    const unsigned char *sha1,
 				    uint32_t index_pos);
@@ -158,4 +171,27 @@ static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 	pack->in_pack_pos[e - pack->objects] = pos;
 }
 
+static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
+					    const struct object_entry *e)
+{
+	if (pack->in_pack_by_idx)
+		return pack->in_pack_by_idx[e->in_pack_idx];
+	else
+		return pack->in_pack[e - pack->objects];
+}
+
+void oe_map_new_pack(struct packing_data *pack,
+		     struct packed_git *p);
+static inline void oe_set_in_pack(struct packing_data *pack,
+				  struct object_entry *e,
+				  struct packed_git *p)
+{
+	if (!p->index)
+		oe_map_new_pack(pack, p);
+	if (pack->in_pack_by_idx)
+		e->in_pack_idx = p->index;
+	else
+		pack->in_pack[e - pack->objects] = p;
+}
+
 #endif