Merge branch 'jk/pack-revindex'

In-core storage of the reverse index for .pack files (which lets
you go from a pack offset to an object name) has been streamlined.

* jk/pack-revindex:
  pack-revindex: store entries directly in packed_git
  pack-revindex: drop hash table

Author: gitster

cache.h

@@ -9,6 +9,7 @@
 #include "convert.h"
 #include "trace.h"
 #include "string-list.h"
+#include "pack-revindex.h"
 
 #include SHA1_HEADER
 #ifndef platform_SHA_CTX
@@ -1299,6 +1300,7 @@ extern struct packed_git {
 		 freshened:1,
 		 do_not_close:1;
 	unsigned char sha1[20];
+	struct revindex_entry *revindex;
 	/* something like ".git/objects/pack/xxxxx.pack" */
 	char pack_name[FLEX_ARRAY]; /* more */
 } *packed_git;

pack-bitmap.c

@@ -33,9 +33,6 @@ static struct bitmap_index {
 	/* Packfile to which this bitmap index belongs to */
 	struct packed_git *pack;
 
-	/* reverse index for the packfile */
-	struct pack_revindex *reverse_index;
-
 	/*
 	 * Mark the first `reuse_objects` in the packfile as reused:
 	 * they will be sent as-is without using them for repacking
@@ -308,7 +305,7 @@ static int load_pack_bitmap(void)
 
 	bitmap_git.bitmaps = kh_init_sha1();
 	bitmap_git.ext_index.positions = kh_init_sha1_pos();
-	bitmap_git.reverse_index = revindex_for_pack(bitmap_git.pack);
+	load_pack_revindex(bitmap_git.pack);
 
 	if (!(bitmap_git.commits = read_bitmap_1(&bitmap_git)) ||
 		!(bitmap_git.trees = read_bitmap_1(&bitmap_git)) ||
@@ -380,7 +377,7 @@ static inline int bitmap_position_packfile(const unsigned char *sha1)
 	if (!offset)
 		return -1;
 
-	return find_revindex_position(bitmap_git.reverse_index, offset);
+	return find_revindex_position(bitmap_git.pack, offset);
 }
 
 static int bitmap_position(const unsigned char *sha1)
@@ -630,7 +627,7 @@ static void show_objects_for_type(
 			if (pos + offset < bitmap_git.reuse_objects)
 				continue;
 
-			entry = &bitmap_git.reverse_index->revindex[pos + offset];
+			entry = &bitmap_git.pack->revindex[pos + offset];
 			sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
 
 			if (bitmap_git.hashes)
@@ -804,7 +801,7 @@ int reuse_partial_packfile_from_bitmap(struct packed_git **packfile,
 		return -1;
 
 	bitmap_git.reuse_objects = *entries = reuse_objects;
-	*up_to = bitmap_git.reverse_index->revindex[reuse_objects].offset;
+	*up_to = bitmap_git.pack->revindex[reuse_objects].offset;
 	*packfile = bitmap_git.pack;
 
 	return 0;
@@ -1038,7 +1035,7 @@ int rebuild_existing_bitmaps(struct packing_data *mapping,
 		struct revindex_entry *entry;
 		struct object_entry *oe;
 
-		entry = &bitmap_git.reverse_index->revindex[i];
+		entry = &bitmap_git.pack->revindex[i];
 		sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
 		oe = packlist_find(mapping, sha1, NULL);
 

pack-revindex.c

@@ -8,52 +8,13 @@
  * size is easily available by examining the pack entry header).  It is
  * also rather expensive to find the sha1 for an object given its offset.
  *
- * We build a hashtable of existing packs (pack_revindex), and keep reverse
- * index here -- pack index file is sorted by object name mapping to offset;
- * this pack_revindex[].revindex array is a list of offset/index_nr pairs
+ * The pack index file is sorted by object name mapping to offset;
+ * this revindex array is a list of offset/index_nr pairs
  * ordered by offset, so if you know the offset of an object, next offset
  * is where its packed representation ends and the index_nr can be used to
  * get the object sha1 from the main index.
  */
 
-static struct pack_revindex *pack_revindex;
-static int pack_revindex_hashsz;
-
-static int pack_revindex_ix(struct packed_git *p)
-{
-	unsigned long ui = (unsigned long)(intptr_t)p;
-	int i;
-
-	ui = ui ^ (ui >> 16); /* defeat structure alignment */
-	i = (int)(ui % pack_revindex_hashsz);
-	while (pack_revindex[i].p) {
-		if (pack_revindex[i].p == p)
-			return i;
-		if (++i == pack_revindex_hashsz)
-			i = 0;
-	}
-	return -1 - i;
-}
-
-static void init_pack_revindex(void)
-{
-	int num;
-	struct packed_git *p;
-
-	for (num = 0, p = packed_git; p; p = p->next)
-		num++;
-	if (!num)
-		return;
-	pack_revindex_hashsz = num * 11;
-	pack_revindex = xcalloc(pack_revindex_hashsz, sizeof(*pack_revindex));
-	for (p = packed_git; p; p = p->next) {
-		num = pack_revindex_ix(p);
-		num = - 1 - num;
-		pack_revindex[num].p = p;
-	}
-	/* revindex elements are lazily initialized */
-}
-
 /*
  * This is a least-significant-digit radix sort.
  *
@@ -154,14 +115,13 @@ static void sort_revindex(struct revindex_entry *entries, unsigned n, off_t max)
 /*
  * Ordered list of offsets of objects in the pack.
  */
-static void create_pack_revindex(struct pack_revindex *rix)
+static void create_pack_revindex(struct packed_git *p)
 {
-	struct packed_git *p = rix->p;
 	unsigned num_ent = p->num_objects;
 	unsigned i;
 	const char *index = p->index_data;
 
-	rix->revindex = xmalloc(sizeof(*rix->revindex) * (num_ent + 1));
+	p->revindex = xmalloc(sizeof(*p->revindex) * (num_ent + 1));
 	index += 4 * 256;
 
 	if (p->index_version > 1) {
@@ -171,55 +131,42 @@ static void create_pack_revindex(struct pack_revindex *rix)
 		for (i = 0; i < num_ent; i++) {
 			uint32_t off = ntohl(*off_32++);
 			if (!(off & 0x80000000)) {
-				rix->revindex[i].offset = off;
+				p->revindex[i].offset = off;
 			} else {
-				rix->revindex[i].offset =
+				p->revindex[i].offset =
 					((uint64_t)ntohl(*off_64++)) << 32;
-				rix->revindex[i].offset |=
+				p->revindex[i].offset |=
 					ntohl(*off_64++);
 			}
-			rix->revindex[i].nr = i;
+			p->revindex[i].nr = i;
 		}
 	} else {
 		for (i = 0; i < num_ent; i++) {
 			uint32_t hl = *((uint32_t *)(index + 24 * i));
-			rix->revindex[i].offset = ntohl(hl);
-			rix->revindex[i].nr = i;
+			p->revindex[i].offset = ntohl(hl);
+			p->revindex[i].nr = i;
 		}
 	}
 
 	/* This knows the pack format -- the 20-byte trailer
 	 * follows immediately after the last object data.
 	 */
-	rix->revindex[num_ent].offset = p->pack_size - 20;
-	rix->revindex[num_ent].nr = -1;
-	sort_revindex(rix->revindex, num_ent, p->pack_size);
+	p->revindex[num_ent].offset = p->pack_size - 20;
+	p->revindex[num_ent].nr = -1;
+	sort_revindex(p->revindex, num_ent, p->pack_size);
 }
 
-struct pack_revindex *revindex_for_pack(struct packed_git *p)
+void load_pack_revindex(struct packed_git *p)
 {
-	int num;
-	struct pack_revindex *rix;
-
-	if (!pack_revindex_hashsz)
-		init_pack_revindex();
-
-	num = pack_revindex_ix(p);
-	if (num < 0)
-		die("internal error: pack revindex fubar");
-
-	rix = &pack_revindex[num];
-	if (!rix->revindex)
-		create_pack_revindex(rix);
-
-	return rix;
+	if (!p->revindex)
+		create_pack_revindex(p);
 }
 
-int find_revindex_position(struct pack_revindex *pridx, off_t ofs)
+int find_revindex_position(struct packed_git *p, off_t ofs)
 {
 	int lo = 0;
-	int hi = pridx->p->num_objects + 1;
-	struct revindex_entry *revindex = pridx->revindex;
+	int hi = p->num_objects + 1;
+	struct revindex_entry *revindex = p->revindex;
 
 	do {
 		unsigned mi = lo + (hi - lo) / 2;
@@ -237,11 +184,13 @@ int find_revindex_position(struct pack_revindex *pridx, off_t ofs)
 
 struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs)
 {
-	struct pack_revindex *pridx = revindex_for_pack(p);
-	int pos = find_revindex_position(pridx, ofs);
+	int pos;
+
+	load_pack_revindex(p);
+	pos = find_revindex_position(p, ofs);
 
 	if (pos < 0)
 		return NULL;
 
-	return pridx->revindex + pos;
+	return p->revindex + pos;
 }

pack-revindex.h

@@ -1,18 +1,15 @@
 #ifndef PACK_REVINDEX_H
 #define PACK_REVINDEX_H
 
+struct packed_git;
+
 struct revindex_entry {
 	off_t offset;
 	unsigned int nr;
 };
 
-struct pack_revindex {
-	struct packed_git *p;
-	struct revindex_entry *revindex;
-};
-
-struct pack_revindex *revindex_for_pack(struct packed_git *p);
-int find_revindex_position(struct pack_revindex *pridx, off_t ofs);
+void load_pack_revindex(struct packed_git *p);
+int find_revindex_position(struct packed_git *p, off_t ofs);
 
 struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs);