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factorize revindex code out of builtin-pack-objects.c
No functional change. This is needed to fix verify-pack in a later patch. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,142 @@ | ||
| #include "cache.h" | ||
| #include "pack-revindex.h" | ||
|
|
||
| /* | ||
| * Pack index for existing packs give us easy access to the offsets into | ||
| * corresponding pack file where each object's data starts, but the entries | ||
| * do not store the size of the compressed representation (uncompressed | ||
| * 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 | ||
| * 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. | ||
| */ | ||
|
|
||
| struct pack_revindex { | ||
| struct packed_git *p; | ||
| struct revindex_entry *revindex; | ||
| }; | ||
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| static struct pack_revindex *pack_revindex; | ||
| static int pack_revindex_hashsz; | ||
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||
| static int pack_revindex_ix(struct packed_git *p) | ||
| { | ||
| unsigned long ui = (unsigned long)p; | ||
| int i; | ||
|
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| 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; | ||
| } | ||
|
|
||
| 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(sizeof(*pack_revindex), pack_revindex_hashsz); | ||
| 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 */ | ||
| } | ||
|
|
||
| static int cmp_offset(const void *a_, const void *b_) | ||
| { | ||
| const struct revindex_entry *a = a_; | ||
| const struct revindex_entry *b = b_; | ||
| return (a->offset < b->offset) ? -1 : (a->offset > b->offset) ? 1 : 0; | ||
| } | ||
|
|
||
| /* | ||
| * Ordered list of offsets of objects in the pack. | ||
| */ | ||
| static void create_pack_revindex(struct pack_revindex *rix) | ||
| { | ||
| struct packed_git *p = rix->p; | ||
| int num_ent = p->num_objects; | ||
| int i; | ||
| const char *index = p->index_data; | ||
|
|
||
| rix->revindex = xmalloc(sizeof(*rix->revindex) * (num_ent + 1)); | ||
| index += 4 * 256; | ||
|
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| if (p->index_version > 1) { | ||
| const uint32_t *off_32 = | ||
| (uint32_t *)(index + 8 + p->num_objects * (20 + 4)); | ||
| const uint32_t *off_64 = off_32 + p->num_objects; | ||
| for (i = 0; i < num_ent; i++) { | ||
| uint32_t off = ntohl(*off_32++); | ||
| if (!(off & 0x80000000)) { | ||
| rix->revindex[i].offset = off; | ||
| } else { | ||
| rix->revindex[i].offset = | ||
| ((uint64_t)ntohl(*off_64++)) << 32; | ||
| rix->revindex[i].offset |= | ||
| ntohl(*off_64++); | ||
| } | ||
| rix->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; | ||
| } | ||
| } | ||
|
|
||
| /* 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; | ||
| qsort(rix->revindex, num_ent, sizeof(*rix->revindex), cmp_offset); | ||
| } | ||
|
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| struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs) | ||
| { | ||
| int num; | ||
| int lo, hi; | ||
| struct pack_revindex *rix; | ||
| struct revindex_entry *revindex; | ||
|
|
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| num = pack_revindex_ix(p); | ||
| if (num < 0) | ||
| die("internal error: pack revindex uninitialized"); | ||
|
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| rix = &pack_revindex[num]; | ||
| if (!rix->revindex) | ||
| create_pack_revindex(rix); | ||
| revindex = rix->revindex; | ||
|
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||
| lo = 0; | ||
| hi = p->num_objects + 1; | ||
| do { | ||
| int mi = (lo + hi) / 2; | ||
| if (revindex[mi].offset == ofs) { | ||
| return revindex + mi; | ||
| } else if (ofs < revindex[mi].offset) | ||
| hi = mi; | ||
| else | ||
| lo = mi + 1; | ||
| } while (lo < hi); | ||
| die("internal error: pack revindex corrupt"); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,12 @@ | ||
| #ifndef PACK_REVINDEX_H | ||
| #define PACK_REVINDEX_H | ||
|
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| struct revindex_entry { | ||
| off_t offset; | ||
| unsigned int nr; | ||
| }; | ||
|
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| void init_pack_revindex(void); | ||
| struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs); | ||
|
|
||
| #endif |