git-pack-objects: create a packed object representation.
[git/git.git] / pack-objects.c
CommitLineData
c323ac7d
LT
1#include "cache.h"
2#include "object.h"
3#include "delta.h"
4
5static const char pack_usage[] = "git-pack-objects [--window=N] base-name < object-list";
6
7enum object_type {
8 OBJ_NONE,
9 OBJ_COMMIT,
10 OBJ_TREE,
11 OBJ_BLOB,
12 OBJ_DELTA // NOTE! This is _not_ the same as a "delta" object in the filesystem
13};
14
15struct object_entry {
16 unsigned char sha1[20];
17 unsigned long size;
18 unsigned long offset;
19 unsigned int depth;
20 unsigned int flags;
21 enum object_type type;
22 unsigned long delta_size;
23 struct object_entry *delta;
24};
25
26static struct object_entry **sorted_by_sha, **sorted_by_type;
27static struct object_entry *objects = NULL;
28static int nr_objects = 0, nr_alloc = 0;
29static int delta_window = 10;
30static const char *base_name;
31
32struct myfile {
33 int fd;
34 unsigned long chars;
35 unsigned char buffer[8192];
36};
37
38static FILE *create_file(const char *suffix)
39{
40 static char filename[PATH_MAX];
41 unsigned len;
42
43 len = snprintf(filename, PATH_MAX, "%s.%s", base_name, suffix);
44 if (len >= PATH_MAX)
45 die("you wascally wabbit, you");
46 return fopen(filename, "w");
47}
48
49static unsigned long fwrite_compressed(void *in, unsigned long size, FILE *f)
50{
51 z_stream stream;
52 unsigned long maxsize;
53 void *out;
54
55 memset(&stream, 0, sizeof(stream));
56 deflateInit(&stream, Z_DEFAULT_COMPRESSION);
57 maxsize = deflateBound(&stream, size);
58 out = xmalloc(maxsize);
59
60 /* Compress it */
61 stream.next_in = in;
62 stream.avail_in = size;
63
64 stream.next_out = out;
65 stream.avail_out = maxsize;
66
67 while (deflate(&stream, Z_FINISH) == Z_OK)
68 /* nothing */;
69 deflateEnd(&stream);
70
71 size = stream.total_out;
72 fwrite(out, size, 1, f);
73 free(out);
74 return size;
75}
76
77static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
78{
79 unsigned long othersize, delta_size;
80 char type[10];
81 void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
82 void *delta_buf;
83
84 if (!otherbuf)
85 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
86 delta_buf = diff_delta(buf, size, otherbuf, othersize, &delta_size);
87 if (delta_size != entry->delta_size)
88 die("delta size changed");
89 free(buf);
90 free(otherbuf);
91 return delta_buf;
92}
93
94static unsigned long write_object(FILE *f, struct object_entry *entry)
95{
96 unsigned long size;
97 char type[10];
98 void *buf = read_sha1_file(entry->sha1, type, &size);
99 char header[21];
100 unsigned hdrlen, datalen;
101
102 if (!buf)
103 die("unable to read %s", sha1_to_hex(entry->sha1));
104 if (size != entry->size)
105 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
106
107 /*
108 * The object header is a byte of 'type' followed by four bytes of
109 * length, except for deltas that has the 20 bytes of delta sha
110 * instead.
111 */
112 header[0] = ".CTB"[entry->type];
113 datalen = htonl(size);
114 memcpy(header+1, &datalen, 4);
115 hdrlen = 5;
116 if (entry->delta) {
117 memcpy(header+1, entry->delta, 20);
118 buf = delta_against(buf, size, entry);
119 size = entry->delta_size;
120 hdrlen = 21;
121 }
122 fwrite(header, hdrlen, 1, f);
123 datalen = fwrite_compressed(buf, size, f);
124 free(buf);
125 return hdrlen + datalen;
126}
127
128static void write_pack_file(void)
129{
130 int i;
131 FILE *f = create_file("pack");
132 unsigned long offset = 0;
133 unsigned long mb;
134
135 for (i = 0; i < nr_objects; i++) {
136 struct object_entry *entry = objects + i;
137 entry->offset = offset;
138 offset += write_object(f, entry);
139 }
140 fclose(f);
141 mb = offset >> 20;
142 offset &= 0xfffff;
143}
144
145static void write_index_file(void)
146{
147 int i;
148 FILE *f = create_file("idx");
149 struct object_entry **list = sorted_by_sha;
150 struct object_entry **last = list + nr_objects;
151 unsigned int array[256];
152
153 /*
154 * Write the first-level table (the list is sorted,
155 * but we use a 256-entry lookup to be able to avoid
156 * having to do eight extra binary search iterations)
157 */
158 for (i = 0; i < 256; i++) {
159 struct object_entry **next = list;
160 while (next < last) {
161 struct object_entry *entry = *next;
162 if (entry->sha1[0] != i)
163 break;
164 next++;
165 }
166 array[i] = htonl(next - sorted_by_sha);
167 list = next;
168 }
169 fwrite(array, 256, sizeof(int), f);
170
171 /*
172 * Write the actual SHA1 entries..
173 */
174 list = sorted_by_sha;
175 for (i < 0; i < nr_objects; i++) {
176 struct object_entry *entry = *list++;
177 unsigned int offset = htonl(entry->offset);
178 fwrite(&offset, 4, 1, f);
179 fwrite(entry->sha1, 20, 1, f);
180 }
181 fclose(f);
182}
183
184static void add_object_entry(unsigned char *sha1)
185{
186 unsigned int idx = nr_objects;
187 struct object_entry *entry;
188
189 if (idx >= nr_alloc) {
190 unsigned int needed = (idx + 1024) * 3 / 2;
191 objects = xrealloc(objects, needed * sizeof(*entry));
192 nr_alloc = needed;
193 }
194 entry = objects + idx;
195 memset(entry, 0, sizeof(*entry));
196 memcpy(entry->sha1, sha1, 20);
197 nr_objects = idx+1;
198}
199
200static void check_object(struct object_entry *entry)
201{
202 char buffer[128];
203 char type[10];
204 unsigned long mapsize;
205 z_stream stream;
206 void *map;
207
208 map = map_sha1_file(entry->sha1, &mapsize);
209 if (!map)
210 die("unable to map %s", sha1_to_hex(entry->sha1));
211 if (unpack_sha1_header(&stream, map, mapsize, buffer, sizeof(buffer)) < 0)
212 die("unable to unpack %s header", sha1_to_hex(entry->sha1));
213 munmap(map, mapsize);
214 if (parse_sha1_header(buffer, type, &entry->size) < 0)
215 die("unable to parse %s header", sha1_to_hex(entry->sha1));
216 if (!strcmp(type, "commit")) {
217 entry->type = OBJ_COMMIT;
218 } else if (!strcmp(type, "tree")) {
219 entry->type = OBJ_TREE;
220 } else if (!strcmp(type, "blob")) {
221 entry->type = OBJ_BLOB;
222 } else
223 die("unable to pack object %s of type %s", sha1_to_hex(entry->sha1), type);
224}
225
226static void get_object_details(void)
227{
228 int i;
229 struct object_entry *entry = objects;
230
231 for (i = 0; i < nr_objects; i++)
232 check_object(entry++);
233}
234
235typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
236
237static entry_sort_t current_sort;
238
239static int sort_comparator(const void *_a, const void *_b)
240{
241 struct object_entry *a = *(struct object_entry **)_a;
242 struct object_entry *b = *(struct object_entry **)_b;
243 return current_sort(a,b);
244}
245
246static struct object_entry **create_sorted_list(entry_sort_t sort)
247{
248 struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
249 int i;
250
251 for (i = 0; i < nr_objects; i++)
252 list[i] = objects + i;
253 current_sort = sort;
254 qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
255 return list;
256}
257
258static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
259{
260 return memcmp(a->sha1, b->sha1, 20);
261}
262
263static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
264{
265 if (a->type < b->type)
266 return -1;
267 if (a->type > b->type)
268 return 1;
269 if (a->size < b->size)
270 return -1;
271 if (a->size > b->size)
272 return 1;
273 return a < b ? -1 : (a > b);
274}
275
276struct unpacked {
277 struct object_entry *entry;
278 void *data;
279};
280
281/*
282 * We search for deltas in a list sorted by type and by size, and
283 * walk the "old" chain backwards in the list, so if the type
284 * has changed or the size difference is too big, there's no point
285 * in even continuing the walk, since the other old objects are
286 * going to be even smaller or of a different type. So return -1
287 * once we determine that there's no point even trying.
288 */
289static int try_delta(struct unpacked *cur, struct unpacked *old)
290{
291 struct object_entry *cur_entry = cur->entry;
292 struct object_entry *old_entry = old->entry;
293 unsigned long size, oldsize, delta_size;
294 void *delta_buf;
295
296 /* Don't bother doing diffs between different types */
297 if (cur_entry->type != old_entry->type)
298 return -1;
299
300 /* Size is guaranteed to be larger than or equal to oldsize */
301 size = cur_entry->size;
302 oldsize = old_entry->size;
303 if (size - oldsize > oldsize / 4)
304 return -1;
305
306 /*
307 * NOTE!
308 *
309 * We always delta from the bigger to the smaller, since that's
310 * more space-efficient (deletes don't have to say _what_ they
311 * delete).
312 */
313 delta_buf = diff_delta(cur->data, size, old->data, oldsize, &delta_size);
314 if (!delta_buf)
315 die("unable to create delta");
316 if (delta_size + 20 < size / 2) {
317 if (!cur_entry->delta || cur_entry->delta_size > delta_size) {
318 cur_entry->delta = old_entry;
319 cur_entry->delta_size = delta_size;
320 }
321 }
322 free(delta_buf);
323}
324
325static void find_deltas(struct object_entry **list, int window)
326{
327 unsigned int i;
328 unsigned int array_size = window * sizeof(struct unpacked);
329 struct unpacked *array = xmalloc(array_size);
330
331 memset(array, 0, array_size);
332 for (i = 0; i < nr_objects; i++) {
333 unsigned int idx = i % window;
334 struct object_entry *entry = list[i];
335 struct unpacked *n = array + idx;
336 unsigned long size;
337 char type[10];
338 int j;
339
340 free(n->data);
341 n->entry = entry;
342 n->data = read_sha1_file(entry->sha1, type, &size);
343 if (size != entry->size)
344 die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
345 for (j = 0; j < window; j++) {
346 unsigned int other_idx = idx - 1 - j;
347 struct unpacked *m;
348 if (other_idx < 0)
349 other_idx += window;
350 m = array + other_idx;
351 if (!m->entry)
352 break;
353 if (try_delta(n, m) < 0)
354 break;
355 }
356 }
357}
358
359int main(int argc, char **argv)
360{
361 char line[128];
362 int i;
363
364 for (i = 1; i < argc; i++) {
365 const char *arg = argv[i];
366
367 if (*arg == '-') {
368 if (!strncmp("--window=", arg, 9)) {
369 char *end;
370 delta_window = strtoul(arg+9, &end, 0);
371 if (!arg[9] || *end)
372 usage(pack_usage);
373 continue;
374 }
375 usage(pack_usage);
376 }
377 if (base_name)
378 usage(pack_usage);
379 base_name = arg;
380 }
381
382 if (!base_name)
383 usage(pack_usage);
384
385 while (fgets(line, sizeof(line), stdin) != NULL) {
386 unsigned char sha1[20];
387 if (get_sha1_hex(line, sha1))
388 die("expected sha1, got garbage");
389 add_object_entry(sha1);
390 }
391 get_object_details();
392
393 printf("Packing %d objects\n", nr_objects);
394
395 sorted_by_sha = create_sorted_list(sha1_sort);
396 sorted_by_type = create_sorted_list(type_size_sort);
397 if (delta_window)
398 find_deltas(sorted_by_type, delta_window);
399
400 write_pack_file();
401 write_index_file();
402 return 0;
403}