[PATCH] Remove "delta" object representation.
[git/git.git] / pack-objects.c
CommitLineData
27225f2e 1#include <ctype.h>
c323ac7d
LT
2#include "cache.h"
3#include "object.h"
4#include "delta.h"
c38138cd 5#include "csum-file.h"
c323ac7d 6
d116a45a 7static const char pack_usage[] = "git-pack-objects [--window=N] [--depth=N] base-name < object-list";
c323ac7d
LT
8
9enum object_type {
10 OBJ_NONE,
11 OBJ_COMMIT,
12 OBJ_TREE,
13 OBJ_BLOB,
c4584ae3 14 OBJ_DELTA
c323ac7d
LT
15};
16
17struct object_entry {
18 unsigned char sha1[20];
19 unsigned long size;
20 unsigned long offset;
21 unsigned int depth;
27225f2e 22 unsigned int hash;
c323ac7d
LT
23 enum object_type type;
24 unsigned long delta_size;
25 struct object_entry *delta;
26};
27
28static struct object_entry **sorted_by_sha, **sorted_by_type;
29static struct object_entry *objects = NULL;
30static int nr_objects = 0, nr_alloc = 0;
c323ac7d 31static const char *base_name;
e1808845 32static unsigned char pack_file_sha1[20];
c323ac7d 33
c323ac7d
LT
34static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
35{
36 unsigned long othersize, delta_size;
37 char type[10];
38 void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
39 void *delta_buf;
40
41 if (!otherbuf)
42 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
8ee378a0
JH
43 delta_buf = diff_delta(otherbuf, othersize,
44 buf, size, &delta_size, ~0UL);
75c42d8c 45 if (!delta_buf || delta_size != entry->delta_size)
c323ac7d
LT
46 die("delta size changed");
47 free(buf);
48 free(otherbuf);
49 return delta_buf;
50}
51
c38138cd 52static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
c323ac7d
LT
53{
54 unsigned long size;
55 char type[10];
56 void *buf = read_sha1_file(entry->sha1, type, &size);
c4fb06c0 57 char header[25];
c323ac7d
LT
58 unsigned hdrlen, datalen;
59
60 if (!buf)
61 die("unable to read %s", sha1_to_hex(entry->sha1));
62 if (size != entry->size)
63 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
64
65 /*
66 * The object header is a byte of 'type' followed by four bytes of
67 * length, except for deltas that has the 20 bytes of delta sha
68 * instead.
69 */
70 header[0] = ".CTB"[entry->type];
c323ac7d
LT
71 hdrlen = 5;
72 if (entry->delta) {
d38c3721 73 header[0] = 'D';
c4fb06c0 74 memcpy(header+5, entry->delta, 20);
c323ac7d
LT
75 buf = delta_against(buf, size, entry);
76 size = entry->delta_size;
c4fb06c0 77 hdrlen = 25;
c323ac7d 78 }
c4fb06c0
LT
79 datalen = htonl(size);
80 memcpy(header+1, &datalen, 4);
c38138cd
LT
81 sha1write(f, header, hdrlen);
82 datalen = sha1write_compressed(f, buf, size);
c323ac7d
LT
83 free(buf);
84 return hdrlen + datalen;
85}
86
87static void write_pack_file(void)
88{
89 int i;
c38138cd 90 struct sha1file *f = sha1create("%s.%s", base_name, "pack");
c323ac7d
LT
91 unsigned long offset = 0;
92 unsigned long mb;
93
94 for (i = 0; i < nr_objects; i++) {
95 struct object_entry *entry = objects + i;
96 entry->offset = offset;
97 offset += write_object(f, entry);
98 }
e1808845 99 sha1close(f, pack_file_sha1, 1);
c323ac7d
LT
100 mb = offset >> 20;
101 offset &= 0xfffff;
102}
103
104static void write_index_file(void)
105{
106 int i;
c38138cd 107 struct sha1file *f = sha1create("%s.%s", base_name, "idx");
c323ac7d
LT
108 struct object_entry **list = sorted_by_sha;
109 struct object_entry **last = list + nr_objects;
110 unsigned int array[256];
111
112 /*
113 * Write the first-level table (the list is sorted,
114 * but we use a 256-entry lookup to be able to avoid
e1808845 115 * having to do eight extra binary search iterations).
c323ac7d
LT
116 */
117 for (i = 0; i < 256; i++) {
118 struct object_entry **next = list;
119 while (next < last) {
120 struct object_entry *entry = *next;
121 if (entry->sha1[0] != i)
122 break;
123 next++;
124 }
125 array[i] = htonl(next - sorted_by_sha);
126 list = next;
127 }
c38138cd 128 sha1write(f, array, 256 * sizeof(int));
c323ac7d
LT
129
130 /*
131 * Write the actual SHA1 entries..
132 */
133 list = sorted_by_sha;
49397104 134 for (i = 0; i < nr_objects; i++) {
c323ac7d
LT
135 struct object_entry *entry = *list++;
136 unsigned int offset = htonl(entry->offset);
c38138cd
LT
137 sha1write(f, &offset, 4);
138 sha1write(f, entry->sha1, 20);
c323ac7d 139 }
e1808845
LT
140 sha1write(f, pack_file_sha1, 20);
141 sha1close(f, NULL, 1);
c323ac7d
LT
142}
143
27225f2e 144static void add_object_entry(unsigned char *sha1, unsigned int hash)
c323ac7d
LT
145{
146 unsigned int idx = nr_objects;
147 struct object_entry *entry;
148
149 if (idx >= nr_alloc) {
150 unsigned int needed = (idx + 1024) * 3 / 2;
151 objects = xrealloc(objects, needed * sizeof(*entry));
152 nr_alloc = needed;
153 }
154 entry = objects + idx;
155 memset(entry, 0, sizeof(*entry));
156 memcpy(entry->sha1, sha1, 20);
27225f2e 157 entry->hash = hash;
c323ac7d
LT
158 nr_objects = idx+1;
159}
160
161static void check_object(struct object_entry *entry)
162{
163 char buffer[128];
164 char type[10];
165 unsigned long mapsize;
166 z_stream stream;
167 void *map;
168
169 map = map_sha1_file(entry->sha1, &mapsize);
170 if (!map)
171 die("unable to map %s", sha1_to_hex(entry->sha1));
172 if (unpack_sha1_header(&stream, map, mapsize, buffer, sizeof(buffer)) < 0)
173 die("unable to unpack %s header", sha1_to_hex(entry->sha1));
174 munmap(map, mapsize);
175 if (parse_sha1_header(buffer, type, &entry->size) < 0)
176 die("unable to parse %s header", sha1_to_hex(entry->sha1));
177 if (!strcmp(type, "commit")) {
178 entry->type = OBJ_COMMIT;
179 } else if (!strcmp(type, "tree")) {
180 entry->type = OBJ_TREE;
181 } else if (!strcmp(type, "blob")) {
182 entry->type = OBJ_BLOB;
183 } else
184 die("unable to pack object %s of type %s", sha1_to_hex(entry->sha1), type);
185}
186
187static void get_object_details(void)
188{
189 int i;
190 struct object_entry *entry = objects;
191
192 for (i = 0; i < nr_objects; i++)
193 check_object(entry++);
194}
195
196typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
197
198static entry_sort_t current_sort;
199
200static int sort_comparator(const void *_a, const void *_b)
201{
202 struct object_entry *a = *(struct object_entry **)_a;
203 struct object_entry *b = *(struct object_entry **)_b;
204 return current_sort(a,b);
205}
206
207static struct object_entry **create_sorted_list(entry_sort_t sort)
208{
209 struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
210 int i;
211
212 for (i = 0; i < nr_objects; i++)
213 list[i] = objects + i;
214 current_sort = sort;
215 qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
216 return list;
217}
218
219static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
220{
221 return memcmp(a->sha1, b->sha1, 20);
222}
223
224static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
225{
226 if (a->type < b->type)
227 return -1;
228 if (a->type > b->type)
229 return 1;
27225f2e
LT
230 if (a->hash < b->hash)
231 return -1;
232 if (a->hash > b->hash)
233 return 1;
c323ac7d
LT
234 if (a->size < b->size)
235 return -1;
236 if (a->size > b->size)
237 return 1;
238 return a < b ? -1 : (a > b);
239}
240
241struct unpacked {
242 struct object_entry *entry;
243 void *data;
244};
245
246/*
521a4f4c
LT
247 * We search for deltas _backwards_ in a list sorted by type and
248 * by size, so that we see progressively smaller and smaller files.
249 * That's because we prefer deltas to be from the bigger file
250 * to the smaller - deletes are potentially cheaper, but perhaps
251 * more importantly, the bigger file is likely the more recent
252 * one.
c323ac7d 253 */
d116a45a 254static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
c323ac7d
LT
255{
256 struct object_entry *cur_entry = cur->entry;
257 struct object_entry *old_entry = old->entry;
521a4f4c 258 unsigned long size, oldsize, delta_size, sizediff;
75c42d8c 259 long max_size;
c323ac7d
LT
260 void *delta_buf;
261
262 /* Don't bother doing diffs between different types */
263 if (cur_entry->type != old_entry->type)
264 return -1;
265
c323ac7d 266 size = cur_entry->size;
75c42d8c
LT
267 if (size < 50)
268 return -1;
c323ac7d 269 oldsize = old_entry->size;
521a4f4c
LT
270 sizediff = oldsize > size ? oldsize - size : size - oldsize;
271 if (sizediff > size / 8)
c323ac7d 272 return -1;
d116a45a
LT
273 if (old_entry->depth >= max_depth)
274 return 0;
c323ac7d
LT
275
276 /*
277 * NOTE!
278 *
279 * We always delta from the bigger to the smaller, since that's
280 * more space-efficient (deletes don't have to say _what_ they
281 * delete).
282 */
75c42d8c
LT
283 max_size = size / 2 - 20;
284 if (cur_entry->delta)
285 max_size = cur_entry->delta_size-1;
27225f2e
LT
286 if (sizediff >= max_size)
287 return -1;
8ee378a0
JH
288 delta_buf = diff_delta(old->data, oldsize,
289 cur->data, size, &delta_size, max_size);
c323ac7d 290 if (!delta_buf)
75c42d8c
LT
291 return 0;
292 cur_entry->delta = old_entry;
293 cur_entry->delta_size = delta_size;
d116a45a 294 cur_entry->depth = old_entry->depth + 1;
c323ac7d 295 free(delta_buf);
eb41ab11 296 return 0;
c323ac7d
LT
297}
298
d116a45a 299static void find_deltas(struct object_entry **list, int window, int depth)
c323ac7d 300{
521a4f4c 301 int i, idx;
c323ac7d
LT
302 unsigned int array_size = window * sizeof(struct unpacked);
303 struct unpacked *array = xmalloc(array_size);
304
305 memset(array, 0, array_size);
521a4f4c
LT
306 i = nr_objects;
307 idx = 0;
308 while (--i >= 0) {
c323ac7d
LT
309 struct object_entry *entry = list[i];
310 struct unpacked *n = array + idx;
311 unsigned long size;
312 char type[10];
313 int j;
314
315 free(n->data);
316 n->entry = entry;
317 n->data = read_sha1_file(entry->sha1, type, &size);
318 if (size != entry->size)
319 die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
78817c15
LT
320 j = window;
321 while (--j > 0) {
322 unsigned int other_idx = idx + j;
c323ac7d 323 struct unpacked *m;
78817c15
LT
324 if (other_idx >= window)
325 other_idx -= window;
c323ac7d
LT
326 m = array + other_idx;
327 if (!m->entry)
328 break;
d116a45a 329 if (try_delta(n, m, depth) < 0)
c323ac7d
LT
330 break;
331 }
521a4f4c
LT
332 idx++;
333 if (idx >= window)
334 idx = 0;
c323ac7d
LT
335 }
336}
337
338int main(int argc, char **argv)
339{
27225f2e 340 char line[PATH_MAX + 20];
d116a45a 341 int window = 10, depth = 10;
c323ac7d
LT
342 int i;
343
344 for (i = 1; i < argc; i++) {
345 const char *arg = argv[i];
346
347 if (*arg == '-') {
348 if (!strncmp("--window=", arg, 9)) {
349 char *end;
f846bbff 350 window = strtoul(arg+9, &end, 0);
c323ac7d
LT
351 if (!arg[9] || *end)
352 usage(pack_usage);
353 continue;
354 }
d116a45a
LT
355 if (!strncmp("--depth=", arg, 8)) {
356 char *end;
357 depth = strtoul(arg+8, &end, 0);
358 if (!arg[8] || *end)
359 usage(pack_usage);
360 continue;
361 }
c323ac7d
LT
362 usage(pack_usage);
363 }
364 if (base_name)
365 usage(pack_usage);
366 base_name = arg;
367 }
368
369 if (!base_name)
370 usage(pack_usage);
371
372 while (fgets(line, sizeof(line), stdin) != NULL) {
27225f2e
LT
373 unsigned int hash;
374 char *p;
c323ac7d 375 unsigned char sha1[20];
27225f2e 376
c323ac7d
LT
377 if (get_sha1_hex(line, sha1))
378 die("expected sha1, got garbage");
27225f2e
LT
379 hash = 0;
380 p = line+40;
381 while (*p) {
382 unsigned char c = *p++;
383 if (isspace(c))
384 continue;
385 hash = hash * 11 + c;
386 }
387 add_object_entry(sha1, hash);
c323ac7d
LT
388 }
389 get_object_details();
390
391 printf("Packing %d objects\n", nr_objects);
392
393 sorted_by_sha = create_sorted_list(sha1_sort);
394 sorted_by_type = create_sorted_list(type_size_sort);
d116a45a
LT
395 if (window && depth)
396 find_deltas(sorted_by_type, window+1, depth);
c323ac7d
LT
397
398 write_pack_file();
399 write_index_file();
400 return 0;
401}