@matheusbsbs / matheus-bagliano / commits / 08fd81c9b6

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>

Derrick Stolee committed Apr 2, 2018 at 16:34 UTC 08fd81c9b6495a395a527985d18aa51c4ae66cdc
3 files changed +366
Makefile
+1
@@ -771,6 +771,7 @@ LIB_OBJS += color.o
771 LIB_OBJS += column.o
772 LIB_OBJS += combine-diff.o
773 LIB_OBJS += commit.o
774 +LIB_OBJS += commit-graph.o
775 LIB_OBJS += compat/obstack.o
776 LIB_OBJS += compat/terminal.o
777 LIB_OBJS += config.o
commit-graph.c new
+359
@@ -0,0 +1,359 @@
1 +#include "cache.h"
2 +#include "config.h"
3 +#include "git-compat-util.h"
4 +#include "lockfile.h"
5 +#include "pack.h"
6 +#include "packfile.h"
7 +#include "commit.h"
8 +#include "object.h"
9 +#include "revision.h"
10 +#include "sha1-lookup.h"
11 +#include "commit-graph.h"
12 +
13 +#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
14 +#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
15 +#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
16 +#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
17 +#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
18 +
19 +#define GRAPH_DATA_WIDTH 36
20 +
21 +#define GRAPH_VERSION_1 0x1
22 +#define GRAPH_VERSION GRAPH_VERSION_1
23 +
24 +#define GRAPH_OID_VERSION_SHA1 1
25 +#define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
26 +#define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
27 +#define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
28 +
29 +#define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
30 +#define GRAPH_PARENT_MISSING 0x7fffffff
31 +#define GRAPH_EDGE_LAST_MASK 0x7fffffff
32 +#define GRAPH_PARENT_NONE 0x70000000
33 +
34 +#define GRAPH_LAST_EDGE 0x80000000
35 +
36 +#define GRAPH_FANOUT_SIZE (4 * 256)
37 +#define GRAPH_CHUNKLOOKUP_WIDTH 12
38 +#define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
39 + GRAPH_OID_LEN + 8)
40 +
41 +
42 +static char *get_commit_graph_filename(const char *obj_dir)
43 +{
44 + return xstrfmt("%s/info/commit-graph", obj_dir);
45 +}
46 +
47 +static void write_graph_chunk_fanout(struct hashfile *f,
48 + struct commit **commits,
49 + int nr_commits)
50 +{
51 + int i, count = 0;
52 + struct commit **list = commits;
53 +
54 + /*
55 + * Write the first-level table (the list is sorted,
56 + * but we use a 256-entry lookup to be able to avoid
57 + * having to do eight extra binary search iterations).
58 + */
59 + for (i = 0; i < 256; i++) {
60 + while (count < nr_commits) {
61 + if ((*list)->object.oid.hash[0] != i)
62 + break;
63 + count++;
64 + list++;
65 + }
66 +
67 + hashwrite_be32(f, count);
68 + }
69 +}
70 +
71 +static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
72 + struct commit **commits, int nr_commits)
73 +{
74 + struct commit **list = commits;
75 + int count;
76 + for (count = 0; count < nr_commits; count++, list++)
77 + hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
78 +}
79 +
80 +static const unsigned char *commit_to_sha1(size_t index, void *table)
81 +{
82 + struct commit **commits = table;
83 + return commits[index]->object.oid.hash;
84 +}
85 +
86 +static void write_graph_chunk_data(struct hashfile *f, int hash_len,
87 + struct commit **commits, int nr_commits)
88 +{
89 + struct commit **list = commits;
90 + struct commit **last = commits + nr_commits;
91 + uint32_t num_extra_edges = 0;
92 +
93 + while (list < last) {
94 + struct commit_list *parent;
95 + int edge_value;
96 + uint32_t packedDate[2];
97 +
98 + parse_commit(*list);
99 + hashwrite(f, (*list)->tree->object.oid.hash, hash_len);
100 +
101 + parent = (*list)->parents;
102 +
103 + if (!parent)
104 + edge_value = GRAPH_PARENT_NONE;
105 + else {
106 + edge_value = sha1_pos(parent->item->object.oid.hash,
107 + commits,
108 + nr_commits,
109 + commit_to_sha1);
110 +
111 + if (edge_value < 0)
112 + edge_value = GRAPH_PARENT_MISSING;
113 + }
114 +
115 + hashwrite_be32(f, edge_value);
116 +
117 + if (parent)
118 + parent = parent->next;
119 +
120 + if (!parent)
121 + edge_value = GRAPH_PARENT_NONE;
122 + else if (parent->next)
123 + edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
124 + else {
125 + edge_value = sha1_pos(parent->item->object.oid.hash,
126 + commits,
127 + nr_commits,
128 + commit_to_sha1);
129 + if (edge_value < 0)
130 + edge_value = GRAPH_PARENT_MISSING;
131 + }
132 +
133 + hashwrite_be32(f, edge_value);
134 +
135 + if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
136 + do {
137 + num_extra_edges++;
138 + parent = parent->next;
139 + } while (parent);
140 + }
141 +
142 + if (sizeof((*list)->date) > 4)
143 + packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
144 + else
145 + packedDate[0] = 0;
146 +
147 + packedDate[1] = htonl((*list)->date);
148 + hashwrite(f, packedDate, 8);
149 +
150 + list++;
151 + }
152 +}
153 +
154 +static void write_graph_chunk_large_edges(struct hashfile *f,
155 + struct commit **commits,
156 + int nr_commits)
157 +{
158 + struct commit **list = commits;
159 + struct commit **last = commits + nr_commits;
160 + struct commit_list *parent;
161 +
162 + while (list < last) {
163 + int num_parents = 0;
164 + for (parent = (*list)->parents; num_parents < 3 && parent;
165 + parent = parent->next)
166 + num_parents++;
167 +
168 + if (num_parents <= 2) {
169 + list++;
170 + continue;
171 + }
172 +
173 + /* Since num_parents > 2, this initializer is safe. */
174 + for (parent = (*list)->parents->next; parent; parent = parent->next) {
175 + int edge_value = sha1_pos(parent->item->object.oid.hash,
176 + commits,
177 + nr_commits,
178 + commit_to_sha1);
179 +
180 + if (edge_value < 0)
181 + edge_value = GRAPH_PARENT_MISSING;
182 + else if (!parent->next)
183 + edge_value |= GRAPH_LAST_EDGE;
184 +
185 + hashwrite_be32(f, edge_value);
186 + }
187 +
188 + list++;
189 + }
190 +}
191 +
192 +static int commit_compare(const void *_a, const void *_b)
193 +{
194 + const struct object_id *a = (const struct object_id *)_a;
195 + const struct object_id *b = (const struct object_id *)_b;
196 + return oidcmp(a, b);
197 +}
198 +
199 +struct packed_commit_list {
200 + struct commit **list;
201 + int nr;
202 + int alloc;
203 +};
204 +
205 +struct packed_oid_list {
206 + struct object_id *list;
207 + int nr;
208 + int alloc;
209 +};
210 +
211 +static int add_packed_commits(const struct object_id *oid,
212 + struct packed_git *pack,
213 + uint32_t pos,
214 + void *data)
215 +{
216 + struct packed_oid_list *list = (struct packed_oid_list*)data;
217 + enum object_type type;
218 + off_t offset = nth_packed_object_offset(pack, pos);
219 + struct object_info oi = OBJECT_INFO_INIT;
220 +
221 + oi.typep = &type;
222 + if (packed_object_info(pack, offset, &oi) < 0)
223 + die("unable to get type of object %s", oid_to_hex(oid));
224 +
225 + if (type != OBJ_COMMIT)
226 + return 0;
227 +
228 + ALLOC_GROW(list->list, list->nr + 1, list->alloc);
229 + oidcpy(&(list->list[list->nr]), oid);
230 + list->nr++;
231 +
232 + return 0;
233 +}
234 +
235 +void write_commit_graph(const char *obj_dir)
236 +{
237 + struct packed_oid_list oids;
238 + struct packed_commit_list commits;
239 + struct hashfile *f;
240 + uint32_t i, count_distinct = 0;
241 + char *graph_name;
242 + int fd;
243 + struct lock_file lk = LOCK_INIT;
244 + uint32_t chunk_ids[5];
245 + uint64_t chunk_offsets[5];
246 + int num_chunks;
247 + int num_extra_edges;
248 + struct commit_list *parent;
249 +
250 + oids.nr = 0;
251 + oids.alloc = approximate_object_count() / 4;
252 +
253 + if (oids.alloc < 1024)
254 + oids.alloc = 1024;
255 + ALLOC_ARRAY(oids.list, oids.alloc);
256 +
257 + for_each_packed_object(add_packed_commits, &oids, 0);
258 +
259 + QSORT(oids.list, oids.nr, commit_compare);
260 +
261 + count_distinct = 1;
262 + for (i = 1; i < oids.nr; i++) {
263 + if (oidcmp(&oids.list[i-1], &oids.list[i]))
264 + count_distinct++;
265 + }
266 +
267 + if (count_distinct >= GRAPH_PARENT_MISSING)
268 + die(_("the commit graph format cannot write %d commits"), count_distinct);
269 +
270 + commits.nr = 0;
271 + commits.alloc = count_distinct;
272 + ALLOC_ARRAY(commits.list, commits.alloc);
273 +
274 + num_extra_edges = 0;
275 + for (i = 0; i < oids.nr; i++) {
276 + int num_parents = 0;
277 + if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
278 + continue;
279 +
280 + commits.list[commits.nr] = lookup_commit(&oids.list[i]);
281 + parse_commit(commits.list[commits.nr]);
282 +
283 + for (parent = commits.list[commits.nr]->parents;
284 + parent; parent = parent->next)
285 + num_parents++;
286 +
287 + if (num_parents > 2)
288 + num_extra_edges += num_parents - 1;
289 +
290 + commits.nr++;
291 + }
292 + num_chunks = num_extra_edges ? 4 : 3;
293 +
294 + if (commits.nr >= GRAPH_PARENT_MISSING)
295 + die(_("too many commits to write graph"));
296 +
297 + graph_name = get_commit_graph_filename(obj_dir);
298 + fd = hold_lock_file_for_update(&lk, graph_name, 0);
299 +
300 + if (fd < 0) {
301 + struct strbuf folder = STRBUF_INIT;
302 + strbuf_addstr(&folder, graph_name);
303 + strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
304 +
305 + if (mkdir(folder.buf, 0777) < 0)
306 + die_errno(_("cannot mkdir %s"), folder.buf);
307 + strbuf_release(&folder);
308 +
309 + fd = hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
310 +
311 + if (fd < 0)
312 + die_errno("unable to create '%s'", graph_name);
313 + }
314 +
315 + f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
316 +
317 + hashwrite_be32(f, GRAPH_SIGNATURE);
318 +
319 + hashwrite_u8(f, GRAPH_VERSION);
320 + hashwrite_u8(f, GRAPH_OID_VERSION);
321 + hashwrite_u8(f, num_chunks);
322 + hashwrite_u8(f, 0); /* unused padding byte */
323 +
324 + chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
325 + chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
326 + chunk_ids[2] = GRAPH_CHUNKID_DATA;
327 + if (num_extra_edges)
328 + chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
329 + else
330 + chunk_ids[3] = 0;
331 + chunk_ids[4] = 0;
332 +
333 + chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
334 + chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
335 + chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
336 + chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
337 + chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
338 +
339 + for (i = 0; i <= num_chunks; i++) {
340 + uint32_t chunk_write[3];
341 +
342 + chunk_write[0] = htonl(chunk_ids[i]);
343 + chunk_write[1] = htonl(chunk_offsets[i] >> 32);
344 + chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
345 + hashwrite(f, chunk_write, 12);
346 + }
347 +
348 + write_graph_chunk_fanout(f, commits.list, commits.nr);
349 + write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
350 + write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
351 + write_graph_chunk_large_edges(f, commits.list, commits.nr);
352 +
353 + finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
354 + commit_lock_file(&lk);
355 +
356 + free(oids.list);
357 + oids.alloc = 0;
358 + oids.nr = 0;
359 +}
commit-graph.h new
+6
@@ -0,0 +1,6 @@
1 +#ifndef COMMIT_GRAPH_H
2 +#define COMMIT_GRAPH_H
3 +
4 +void write_commit_graph(const char *obj_dir);
5 +
6 +#endif