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https://github.com/git/git
synced 2024-08-25 10:45:59 +00:00
commit-graph: implement write_commit_graph()
Teach Git to write a commit graph file by checking all packed objects to see if they are commits, then store the file in the given object directory. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
parent
4ce58ee38d
commit
08fd81c9b6
1
Makefile
1
Makefile
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@ -771,6 +771,7 @@ LIB_OBJS += color.o
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LIB_OBJS += column.o
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LIB_OBJS += combine-diff.o
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LIB_OBJS += commit.o
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LIB_OBJS += commit-graph.o
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LIB_OBJS += compat/obstack.o
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LIB_OBJS += compat/terminal.o
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LIB_OBJS += config.o
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359
commit-graph.c
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359
commit-graph.c
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@ -0,0 +1,359 @@
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#include "cache.h"
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#include "config.h"
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#include "git-compat-util.h"
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#include "lockfile.h"
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#include "pack.h"
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#include "packfile.h"
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#include "commit.h"
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#include "object.h"
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#include "revision.h"
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#include "sha1-lookup.h"
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#include "commit-graph.h"
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#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
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#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
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#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
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#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
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#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
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#define GRAPH_DATA_WIDTH 36
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#define GRAPH_VERSION_1 0x1
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#define GRAPH_VERSION GRAPH_VERSION_1
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#define GRAPH_OID_VERSION_SHA1 1
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#define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
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#define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
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#define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
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#define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
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#define GRAPH_PARENT_MISSING 0x7fffffff
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#define GRAPH_EDGE_LAST_MASK 0x7fffffff
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#define GRAPH_PARENT_NONE 0x70000000
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#define GRAPH_LAST_EDGE 0x80000000
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#define GRAPH_FANOUT_SIZE (4 * 256)
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#define GRAPH_CHUNKLOOKUP_WIDTH 12
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#define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
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GRAPH_OID_LEN + 8)
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static char *get_commit_graph_filename(const char *obj_dir)
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{
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return xstrfmt("%s/info/commit-graph", obj_dir);
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}
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static void write_graph_chunk_fanout(struct hashfile *f,
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struct commit **commits,
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int nr_commits)
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{
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int i, count = 0;
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struct commit **list = commits;
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/*
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* Write the first-level table (the list is sorted,
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* but we use a 256-entry lookup to be able to avoid
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* having to do eight extra binary search iterations).
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*/
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for (i = 0; i < 256; i++) {
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while (count < nr_commits) {
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if ((*list)->object.oid.hash[0] != i)
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break;
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count++;
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list++;
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}
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hashwrite_be32(f, count);
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}
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}
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static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
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struct commit **commits, int nr_commits)
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{
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struct commit **list = commits;
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int count;
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for (count = 0; count < nr_commits; count++, list++)
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hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
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}
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static const unsigned char *commit_to_sha1(size_t index, void *table)
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{
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struct commit **commits = table;
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return commits[index]->object.oid.hash;
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}
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static void write_graph_chunk_data(struct hashfile *f, int hash_len,
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struct commit **commits, int nr_commits)
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{
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struct commit **list = commits;
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struct commit **last = commits + nr_commits;
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uint32_t num_extra_edges = 0;
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while (list < last) {
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struct commit_list *parent;
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int edge_value;
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uint32_t packedDate[2];
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parse_commit(*list);
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hashwrite(f, (*list)->tree->object.oid.hash, hash_len);
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parent = (*list)->parents;
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if (!parent)
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edge_value = GRAPH_PARENT_NONE;
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else {
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edge_value = sha1_pos(parent->item->object.oid.hash,
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commits,
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nr_commits,
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commit_to_sha1);
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if (edge_value < 0)
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edge_value = GRAPH_PARENT_MISSING;
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}
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hashwrite_be32(f, edge_value);
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if (parent)
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parent = parent->next;
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if (!parent)
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edge_value = GRAPH_PARENT_NONE;
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else if (parent->next)
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edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
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else {
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edge_value = sha1_pos(parent->item->object.oid.hash,
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commits,
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nr_commits,
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commit_to_sha1);
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if (edge_value < 0)
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edge_value = GRAPH_PARENT_MISSING;
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}
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hashwrite_be32(f, edge_value);
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if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
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do {
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num_extra_edges++;
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parent = parent->next;
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} while (parent);
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}
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if (sizeof((*list)->date) > 4)
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packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
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else
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packedDate[0] = 0;
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packedDate[1] = htonl((*list)->date);
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hashwrite(f, packedDate, 8);
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list++;
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}
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}
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static void write_graph_chunk_large_edges(struct hashfile *f,
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struct commit **commits,
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int nr_commits)
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{
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struct commit **list = commits;
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struct commit **last = commits + nr_commits;
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struct commit_list *parent;
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while (list < last) {
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int num_parents = 0;
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for (parent = (*list)->parents; num_parents < 3 && parent;
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parent = parent->next)
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num_parents++;
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if (num_parents <= 2) {
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list++;
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continue;
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}
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/* Since num_parents > 2, this initializer is safe. */
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for (parent = (*list)->parents->next; parent; parent = parent->next) {
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int edge_value = sha1_pos(parent->item->object.oid.hash,
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commits,
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nr_commits,
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commit_to_sha1);
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if (edge_value < 0)
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edge_value = GRAPH_PARENT_MISSING;
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else if (!parent->next)
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edge_value |= GRAPH_LAST_EDGE;
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hashwrite_be32(f, edge_value);
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}
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list++;
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}
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}
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static int commit_compare(const void *_a, const void *_b)
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{
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const struct object_id *a = (const struct object_id *)_a;
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const struct object_id *b = (const struct object_id *)_b;
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return oidcmp(a, b);
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}
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struct packed_commit_list {
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struct commit **list;
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int nr;
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int alloc;
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};
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struct packed_oid_list {
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struct object_id *list;
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int nr;
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int alloc;
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};
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static int add_packed_commits(const struct object_id *oid,
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struct packed_git *pack,
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uint32_t pos,
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void *data)
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{
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struct packed_oid_list *list = (struct packed_oid_list*)data;
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enum object_type type;
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off_t offset = nth_packed_object_offset(pack, pos);
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struct object_info oi = OBJECT_INFO_INIT;
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oi.typep = &type;
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if (packed_object_info(pack, offset, &oi) < 0)
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die("unable to get type of object %s", oid_to_hex(oid));
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if (type != OBJ_COMMIT)
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return 0;
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ALLOC_GROW(list->list, list->nr + 1, list->alloc);
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oidcpy(&(list->list[list->nr]), oid);
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list->nr++;
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return 0;
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}
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void write_commit_graph(const char *obj_dir)
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{
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struct packed_oid_list oids;
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struct packed_commit_list commits;
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struct hashfile *f;
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uint32_t i, count_distinct = 0;
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char *graph_name;
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int fd;
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struct lock_file lk = LOCK_INIT;
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uint32_t chunk_ids[5];
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uint64_t chunk_offsets[5];
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int num_chunks;
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int num_extra_edges;
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struct commit_list *parent;
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oids.nr = 0;
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oids.alloc = approximate_object_count() / 4;
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if (oids.alloc < 1024)
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oids.alloc = 1024;
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ALLOC_ARRAY(oids.list, oids.alloc);
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for_each_packed_object(add_packed_commits, &oids, 0);
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QSORT(oids.list, oids.nr, commit_compare);
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count_distinct = 1;
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for (i = 1; i < oids.nr; i++) {
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if (oidcmp(&oids.list[i-1], &oids.list[i]))
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count_distinct++;
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}
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if (count_distinct >= GRAPH_PARENT_MISSING)
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die(_("the commit graph format cannot write %d commits"), count_distinct);
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commits.nr = 0;
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commits.alloc = count_distinct;
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ALLOC_ARRAY(commits.list, commits.alloc);
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num_extra_edges = 0;
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for (i = 0; i < oids.nr; i++) {
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int num_parents = 0;
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if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
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continue;
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commits.list[commits.nr] = lookup_commit(&oids.list[i]);
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parse_commit(commits.list[commits.nr]);
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for (parent = commits.list[commits.nr]->parents;
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parent; parent = parent->next)
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num_parents++;
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if (num_parents > 2)
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num_extra_edges += num_parents - 1;
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commits.nr++;
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}
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num_chunks = num_extra_edges ? 4 : 3;
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if (commits.nr >= GRAPH_PARENT_MISSING)
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die(_("too many commits to write graph"));
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graph_name = get_commit_graph_filename(obj_dir);
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fd = hold_lock_file_for_update(&lk, graph_name, 0);
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if (fd < 0) {
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struct strbuf folder = STRBUF_INIT;
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strbuf_addstr(&folder, graph_name);
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strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
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if (mkdir(folder.buf, 0777) < 0)
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die_errno(_("cannot mkdir %s"), folder.buf);
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strbuf_release(&folder);
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fd = hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
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if (fd < 0)
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die_errno("unable to create '%s'", graph_name);
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}
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f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
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hashwrite_be32(f, GRAPH_SIGNATURE);
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hashwrite_u8(f, GRAPH_VERSION);
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hashwrite_u8(f, GRAPH_OID_VERSION);
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hashwrite_u8(f, num_chunks);
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hashwrite_u8(f, 0); /* unused padding byte */
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chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
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chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
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chunk_ids[2] = GRAPH_CHUNKID_DATA;
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if (num_extra_edges)
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chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
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else
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chunk_ids[3] = 0;
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chunk_ids[4] = 0;
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chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
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chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
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chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
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chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
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chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
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for (i = 0; i <= num_chunks; i++) {
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uint32_t chunk_write[3];
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chunk_write[0] = htonl(chunk_ids[i]);
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chunk_write[1] = htonl(chunk_offsets[i] >> 32);
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chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
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hashwrite(f, chunk_write, 12);
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}
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write_graph_chunk_fanout(f, commits.list, commits.nr);
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write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
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write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
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write_graph_chunk_large_edges(f, commits.list, commits.nr);
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finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
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commit_lock_file(&lk);
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free(oids.list);
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oids.alloc = 0;
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oids.nr = 0;
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}
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6
commit-graph.h
Normal file
6
commit-graph.h
Normal file
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#ifndef COMMIT_GRAPH_H
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#define COMMIT_GRAPH_H
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void write_commit_graph(const char *obj_dir);
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#endif
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