git-pack-objects: make "--window=x" semantics more logical.
[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;
c323ac7d
LT
29static const char *base_name;
30
31struct myfile {
32 int fd;
33 unsigned long chars;
34 unsigned char buffer[8192];
35};
36
37static FILE *create_file(const char *suffix)
38{
39 static char filename[PATH_MAX];
40 unsigned len;
41
42 len = snprintf(filename, PATH_MAX, "%s.%s", base_name, suffix);
43 if (len >= PATH_MAX)
44 die("you wascally wabbit, you");
45 return fopen(filename, "w");
46}
47
48static unsigned long fwrite_compressed(void *in, unsigned long size, FILE *f)
49{
50 z_stream stream;
51 unsigned long maxsize;
52 void *out;
53
54 memset(&stream, 0, sizeof(stream));
55 deflateInit(&stream, Z_DEFAULT_COMPRESSION);
56 maxsize = deflateBound(&stream, size);
57 out = xmalloc(maxsize);
58
59 /* Compress it */
60 stream.next_in = in;
61 stream.avail_in = size;
62
63 stream.next_out = out;
64 stream.avail_out = maxsize;
65
66 while (deflate(&stream, Z_FINISH) == Z_OK)
67 /* nothing */;
68 deflateEnd(&stream);
69
70 size = stream.total_out;
71 fwrite(out, size, 1, f);
72 free(out);
73 return size;
74}
75
76static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
77{
78 unsigned long othersize, delta_size;
79 char type[10];
80 void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
81 void *delta_buf;
82
83 if (!otherbuf)
84 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
75c42d8c
LT
85 delta_buf = diff_delta(buf, size, otherbuf, othersize, &delta_size, ~0UL);
86 if (!delta_buf || delta_size != entry->delta_size)
c323ac7d
LT
87 die("delta size changed");
88 free(buf);
89 free(otherbuf);
90 return delta_buf;
91}
92
93static unsigned long write_object(FILE *f, struct object_entry *entry)
94{
95 unsigned long size;
96 char type[10];
97 void *buf = read_sha1_file(entry->sha1, type, &size);
98 char header[21];
99 unsigned hdrlen, datalen;
100
101 if (!buf)
102 die("unable to read %s", sha1_to_hex(entry->sha1));
103 if (size != entry->size)
104 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
105
106 /*
107 * The object header is a byte of 'type' followed by four bytes of
108 * length, except for deltas that has the 20 bytes of delta sha
109 * instead.
110 */
111 header[0] = ".CTB"[entry->type];
112 datalen = htonl(size);
113 memcpy(header+1, &datalen, 4);
114 hdrlen = 5;
115 if (entry->delta) {
d38c3721 116 header[0] = 'D';
c323ac7d
LT
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;
49397104 175 for (i = 0; i < nr_objects; i++) {
c323ac7d
LT
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;
75c42d8c 294 long max_size;
c323ac7d
LT
295 void *delta_buf;
296
297 /* Don't bother doing diffs between different types */
298 if (cur_entry->type != old_entry->type)
299 return -1;
300
301 /* Size is guaranteed to be larger than or equal to oldsize */
302 size = cur_entry->size;
75c42d8c
LT
303 if (size < 50)
304 return -1;
c323ac7d
LT
305 oldsize = old_entry->size;
306 if (size - oldsize > oldsize / 4)
307 return -1;
308
309 /*
310 * NOTE!
311 *
312 * We always delta from the bigger to the smaller, since that's
313 * more space-efficient (deletes don't have to say _what_ they
314 * delete).
315 */
75c42d8c
LT
316 max_size = size / 2 - 20;
317 if (cur_entry->delta)
318 max_size = cur_entry->delta_size-1;
319 delta_buf = diff_delta(cur->data, size, old->data, oldsize, &delta_size, max_size);
c323ac7d 320 if (!delta_buf)
75c42d8c
LT
321 return 0;
322 cur_entry->delta = old_entry;
323 cur_entry->delta_size = delta_size;
c323ac7d 324 free(delta_buf);
eb41ab11 325 return 0;
c323ac7d
LT
326}
327
328static void find_deltas(struct object_entry **list, int window)
329{
330 unsigned int i;
331 unsigned int array_size = window * sizeof(struct unpacked);
332 struct unpacked *array = xmalloc(array_size);
333
334 memset(array, 0, array_size);
335 for (i = 0; i < nr_objects; i++) {
336 unsigned int idx = i % window;
337 struct object_entry *entry = list[i];
338 struct unpacked *n = array + idx;
339 unsigned long size;
340 char type[10];
341 int j;
342
343 free(n->data);
344 n->entry = entry;
345 n->data = read_sha1_file(entry->sha1, type, &size);
346 if (size != entry->size)
347 die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
78817c15
LT
348 j = window;
349 while (--j > 0) {
350 unsigned int other_idx = idx + j;
c323ac7d 351 struct unpacked *m;
78817c15
LT
352 if (other_idx >= window)
353 other_idx -= window;
c323ac7d
LT
354 m = array + other_idx;
355 if (!m->entry)
356 break;
357 if (try_delta(n, m) < 0)
358 break;
359 }
360 }
361}
362
363int main(int argc, char **argv)
364{
365 char line[128];
f846bbff 366 int window = 10;
c323ac7d
LT
367 int i;
368
369 for (i = 1; i < argc; i++) {
370 const char *arg = argv[i];
371
372 if (*arg == '-') {
373 if (!strncmp("--window=", arg, 9)) {
374 char *end;
f846bbff 375 window = strtoul(arg+9, &end, 0);
c323ac7d
LT
376 if (!arg[9] || *end)
377 usage(pack_usage);
378 continue;
379 }
380 usage(pack_usage);
381 }
382 if (base_name)
383 usage(pack_usage);
384 base_name = arg;
385 }
386
387 if (!base_name)
388 usage(pack_usage);
389
390 while (fgets(line, sizeof(line), stdin) != NULL) {
391 unsigned char sha1[20];
392 if (get_sha1_hex(line, sha1))
393 die("expected sha1, got garbage");
394 add_object_entry(sha1);
395 }
396 get_object_details();
397
398 printf("Packing %d objects\n", nr_objects);
399
400 sorted_by_sha = create_sorted_list(sha1_sort);
401 sorted_by_type = create_sorted_list(type_size_sort);
f846bbff
LT
402 if (window)
403 find_deltas(sorted_by_type, window+1);
c323ac7d
LT
404
405 write_pack_file();
406 write_index_file();
407 return 0;
408}