On Tue, 30 Jan 2018 16:39:33 -0500
Derrick Stolee <stolee@xxxxxxxxx> wrote:
> +#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
> +#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
> +#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
> +#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
> +#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
Could all these just be string constants? sha1write can handle them well
enough.
> +static void write_graph_chunk_fanout(struct sha1file *f,
> + struct commit **commits,
> + int nr_commits)
> +{
> + uint32_t i, count = 0;
> + struct commit **list = commits;
> + struct commit **last = commits + nr_commits;
> +
> + /*
> + * Write the first-level table (the list is sorted,
> + * but we use a 256-entry lookup to be able to avoid
> + * having to do eight extra binary search iterations).
> + */
> + for (i = 0; i < 256; i++) {
> + uint32_t swap_count;
> +
> + while (list < last) {
> + if ((*list)->object.oid.hash[0] != i)
> + break;
> + count++;
> + list++;
> + }
> +
> + swap_count = htonl(count);
> + sha1write(f, &swap_count, 4);
You can use sha1write_be32() instead of swapping.
> +static void write_graph_chunk_large_edges(struct sha1file *f,
> + struct commit **commits,
> + int nr_commits)
> +{
> + struct commit **list = commits;
> + struct commit **last = commits + nr_commits;
> + struct commit_list *parent;
> +
> + while (list < last) {
> + int num_parents = 0;
> + for (parent = (*list)->parents; num_parents < 3 && parent;
> + parent = parent->next)
> + num_parents++;
> +
> + if (num_parents <= 2) {
> + list++;
> + continue;
> + }
> +
> + for (parent = (*list)->parents; parent; parent = parent->next) {
> + uint32_t int_id, swap_int_id;
> + uint32_t last_edge = 0;
> +
> + if (parent == (*list)->parents)
> + continue;
Probably better to just initialize "parent = (*list)->parents->next".
Also probably best to add a comment describing why you are doing this
(e.g. "The first parent is already in the main commit table; the large
edges table only contains the second parent onwards").
> +struct packed_commit_list {
> + struct commit **list;
> + int num;
> + int size;
> +};
> +
> +struct packed_oid_list {
> + struct object_id **list;
> + int num;
> + int size;
> +};
What are num and size? If they're nr and alloc, maybe use those names
instead.
> +static int if_packed_commit_add_to_list(const struct object_id *oid,
> + struct packed_git *pack,
> + uint32_t pos,
> + void *data)
> +{
> + struct packed_oid_list *list = (struct packed_oid_list*)data;
> + enum object_type type;
> + unsigned long size;
> + void *inner_data;
> + off_t offset = nth_packed_object_offset(pack, pos);
> + inner_data = unpack_entry(pack, offset, &type, &size);
> +
> + if (inner_data)
> + free(inner_data);
> +
> + if (type != OBJ_COMMIT)
> + return 0;
> +
> + ALLOC_GROW(list->list, list->num + 1, list->size);
> + list->list[list->num] = (struct object_id *)malloc(sizeof(struct object_id));
No need to cast return value of malloc. Also, use xmalloc?
> +struct object_id *construct_commit_graph(const char *pack_dir)
> +{
> + struct packed_oid_list oids;
> + struct packed_commit_list commits;
> + struct commit_graph_header hdr;
> + struct sha1file *f;
> + int i, count_distinct = 0;
> + struct strbuf tmp_file = STRBUF_INIT;
> + unsigned char final_hash[GIT_MAX_RAWSZ];
> + char *graph_name;
> + int fd;
> + uint32_t chunk_ids[5];
> + uint64_t chunk_offsets[5];
> + int num_long_edges;
> + struct object_id *f_hash;
> + char *fname;
> + struct commit_list *parent;
> +
> + oids.num = 0;
> + oids.size = 1024;
> + ALLOC_ARRAY(oids.list, oids.size);
> + for_each_packed_object(if_packed_commit_add_to_list, &oids, 0);
> + QSORT(oids.list, oids.num, commit_compare);
> +
> + count_distinct = 1;
> + for (i = 1; i < oids.num; i++) {
> + if (oidcmp(oids.list[i-1], oids.list[i]))
> + count_distinct++;
> + }
> +
> + commits.num = 0;
> + commits.size = count_distinct;
> + ALLOC_ARRAY(commits.list, commits.size);
> +
> + num_long_edges = 0;
> + for (i = 0; i < oids.num; i++) {
> + int num_parents = 0;
> + if (i > 0 && !oidcmp(oids.list[i-1], oids.list[i]))
> + continue;
> +
> + commits.list[commits.num] = lookup_commit(oids.list[i]);
> + parse_commit(commits.list[commits.num]);
> +
> + for (parent = commits.list[commits.num]->parents;
> + parent; parent = parent->next)
> + num_parents++;
> +
> + if (num_parents > 2)
> + num_long_edges += num_parents - 1;
> +
> + commits.num++;
> + }
> +
> + strbuf_addstr(&tmp_file, pack_dir);
> + strbuf_addstr(&tmp_file, "/tmp_graph_XXXXXX");
> +
> + fd = git_mkstemp_mode(tmp_file.buf, 0444);
> + if (fd < 0)
> + die_errno("unable to create '%s'", tmp_file.buf);
> +
> + graph_name = strbuf_detach(&tmp_file, NULL);
> + f = sha1fd(fd, graph_name);
> +
> + hdr.graph_signature = htonl(GRAPH_SIGNATURE);
> + hdr.graph_version = GRAPH_VERSION;
> + hdr.hash_version = GRAPH_OID_VERSION;
> + hdr.hash_len = GRAPH_OID_LEN;
> + hdr.num_chunks = 4;
> +
> + assert(sizeof(hdr) == 8);
> + sha1write(f, &hdr, sizeof(hdr));
Instead of assembling these into a data structure, could you just use
individual calls to sha1write_be32 and sha1write_u8? Same comment
throughout this function.
> diff --git a/commit-graph.h b/commit-graph.h
> new file mode 100644
> index 0000000000..7b3469a7df
> --- /dev/null
> +++ b/commit-graph.h
> @@ -0,0 +1,20 @@
> +#ifndef COMMIT_GRAPH_H
> +#define COMMIT_GRAPH_H
> +
> +#include "git-compat-util.h"
> +#include "commit.h"
> +
> +extern char* get_commit_graph_filename_hash(const char *pack_dir,
> + struct object_id *hash);
> +
> +struct commit_graph_header {
> + uint32_t graph_signature;
> + unsigned char graph_version;
> + unsigned char hash_version;
> + unsigned char hash_len;
> + unsigned char num_chunks;
> +};
This seems like it should be an internal detail of commit-graph.c.
(Also, as commented above, this struct might not be necessary at all.)
