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commit-graph: implement git commit-graph read

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Teach git-commit-graph to read commit graph files and summarize their contents.

Use the read subcommand to verify the contents of a commit graph file in the
tests.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee
2018-04-10 08:56:02 -04:00
committed by Junio C Hamano
parent f237c8b6fe
commit 2a2e32bdc5
5 changed files with 254 additions and 6 deletions
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137
commit-graph.c
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@ -39,11 +39,146 @@
GRAPH_OID_LEN + 8)
static char *get_commit_graph_filename(const char *obj_dir)
char *get_commit_graph_filename(const char *obj_dir)
{
return xstrfmt("%s/info/commit-graph", obj_dir);
}
static struct commit_graph *alloc_commit_graph(void)
{
struct commit_graph *g = xcalloc(1, sizeof(*g));
g->graph_fd = -1;
return g;
}
struct commit_graph *load_commit_graph_one(const char *graph_file)
{
void *graph_map;
const unsigned char *data, *chunk_lookup;
size_t graph_size;
struct stat st;
uint32_t i;
struct commit_graph *graph;
int fd = git_open(graph_file);
uint64_t last_chunk_offset;
uint32_t last_chunk_id;
uint32_t graph_signature;
unsigned char graph_version, hash_version;
if (fd < 0)
return NULL;
if (fstat(fd, &st)) {
close(fd);
return NULL;
}
graph_size = xsize_t(st.st_size);
if (graph_size < GRAPH_MIN_SIZE) {
close(fd);
die("graph file %s is too small", graph_file);
}
graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
data = (const unsigned char *)graph_map;
graph_signature = get_be32(data);
if (graph_signature != GRAPH_SIGNATURE) {
error("graph signature %X does not match signature %X",
graph_signature, GRAPH_SIGNATURE);
goto cleanup_fail;
}
graph_version = *(unsigned char*)(data + 4);
if (graph_version != GRAPH_VERSION) {
error("graph version %X does not match version %X",
graph_version, GRAPH_VERSION);
goto cleanup_fail;
}
hash_version = *(unsigned char*)(data + 5);
if (hash_version != GRAPH_OID_VERSION) {
error("hash version %X does not match version %X",
hash_version, GRAPH_OID_VERSION);
goto cleanup_fail;
}
graph = alloc_commit_graph();
graph->hash_len = GRAPH_OID_LEN;
graph->num_chunks = *(unsigned char*)(data + 6);
graph->graph_fd = fd;
graph->data = graph_map;
graph->data_len = graph_size;
last_chunk_id = 0;
last_chunk_offset = 8;
chunk_lookup = data + 8;
for (i = 0; i < graph->num_chunks; i++) {
uint32_t chunk_id = get_be32(chunk_lookup + 0);
uint64_t chunk_offset = get_be64(chunk_lookup + 4);
int chunk_repeated = 0;
chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
(uint32_t)chunk_offset);
goto cleanup_fail;
}
switch (chunk_id) {
case GRAPH_CHUNKID_OIDFANOUT:
if (graph->chunk_oid_fanout)
chunk_repeated = 1;
else
graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
break;
case GRAPH_CHUNKID_OIDLOOKUP:
if (graph->chunk_oid_lookup)
chunk_repeated = 1;
else
graph->chunk_oid_lookup = data + chunk_offset;
break;
case GRAPH_CHUNKID_DATA:
if (graph->chunk_commit_data)
chunk_repeated = 1;
else
graph->chunk_commit_data = data + chunk_offset;
break;
case GRAPH_CHUNKID_LARGEEDGES:
if (graph->chunk_large_edges)
chunk_repeated = 1;
else
graph->chunk_large_edges = data + chunk_offset;
break;
}
if (chunk_repeated) {
error("chunk id %08x appears multiple times", chunk_id);
goto cleanup_fail;
}
if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
{
graph->num_commits = (chunk_offset - last_chunk_offset)
/ graph->hash_len;
}
last_chunk_id = chunk_id;
last_chunk_offset = chunk_offset;
}
return graph;
cleanup_fail:
munmap(graph_map, graph_size);
close(fd);
exit(1);
}
static void write_graph_chunk_fanout(struct hashfile *f,
struct commit **commits,
int nr_commits)