Add a "max_size" parameter to diff_delta()
[git] / pack-objects.c
1 #include "cache.h"
2 #include "object.h"
3 #include "delta.h"
4
5 static const char pack_usage[] = "git-pack-objects [--window=N] base-name < object-list";
6
7 enum 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
15 struct 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
26 static struct object_entry **sorted_by_sha, **sorted_by_type;
27 static struct object_entry *objects = NULL;
28 static int nr_objects = 0, nr_alloc = 0;
29 static int delta_window = 10;
30 static const char *base_name;
31
32 struct myfile {
33         int fd;
34         unsigned long chars;
35         unsigned char buffer[8192];
36 };
37
38 static 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
49 static 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
77 static 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, ~0UL);
87         if (!delta_buf || delta_size != entry->delta_size)
88                 die("delta size changed");
89         free(buf);
90         free(otherbuf);
91         return delta_buf;
92 }
93
94 static 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                 header[0] = 'D';
118                 memcpy(header+1, entry->delta, 20);
119                 buf = delta_against(buf, size, entry);
120                 size = entry->delta_size;
121                 hdrlen = 21;
122         }
123         fwrite(header, hdrlen, 1, f);
124         datalen = fwrite_compressed(buf, size, f);
125         free(buf);
126         return hdrlen + datalen;
127 }
128
129 static void write_pack_file(void)
130 {
131         int i;
132         FILE *f = create_file("pack");
133         unsigned long offset = 0;
134         unsigned long mb;
135
136         for (i = 0; i < nr_objects; i++) {
137                 struct object_entry *entry = objects + i;
138                 entry->offset = offset;
139                 offset += write_object(f, entry);
140         }
141         fclose(f);
142         mb = offset >> 20;
143         offset &= 0xfffff;
144 }
145
146 static void write_index_file(void)
147 {
148         int i;
149         FILE *f = create_file("idx");
150         struct object_entry **list = sorted_by_sha;
151         struct object_entry **last = list + nr_objects;
152         unsigned int array[256];
153
154         /*
155          * Write the first-level table (the list is sorted,
156          * but we use a 256-entry lookup to be able to avoid
157          * having to do eight extra binary search iterations)
158          */
159         for (i = 0; i < 256; i++) {
160                 struct object_entry **next = list;
161                 while (next < last) {
162                         struct object_entry *entry = *next;
163                         if (entry->sha1[0] != i)
164                                 break;
165                         next++;
166                 }
167                 array[i] = htonl(next - sorted_by_sha);
168                 list = next;
169         }
170         fwrite(array, 256, sizeof(int), f);
171
172         /*
173          * Write the actual SHA1 entries..
174          */
175         list = sorted_by_sha;
176         for (i = 0; i < nr_objects; i++) {
177                 struct object_entry *entry = *list++;
178                 unsigned int offset = htonl(entry->offset);
179                 fwrite(&offset, 4, 1, f);
180                 fwrite(entry->sha1, 20, 1, f);
181         }
182         fclose(f);
183 }
184
185 static void add_object_entry(unsigned char *sha1)
186 {
187         unsigned int idx = nr_objects;
188         struct object_entry *entry;
189
190         if (idx >= nr_alloc) {
191                 unsigned int needed = (idx + 1024) * 3 / 2;
192                 objects = xrealloc(objects, needed * sizeof(*entry));
193                 nr_alloc = needed;
194         }
195         entry = objects + idx;
196         memset(entry, 0, sizeof(*entry));
197         memcpy(entry->sha1, sha1, 20);
198         nr_objects = idx+1;
199 }
200
201 static void check_object(struct object_entry *entry)
202 {
203         char buffer[128];
204         char type[10];
205         unsigned long mapsize;
206         z_stream stream;
207         void *map;
208
209         map = map_sha1_file(entry->sha1, &mapsize);
210         if (!map)
211                 die("unable to map %s", sha1_to_hex(entry->sha1));
212         if (unpack_sha1_header(&stream, map, mapsize, buffer, sizeof(buffer)) < 0)
213                 die("unable to unpack %s header", sha1_to_hex(entry->sha1));
214         munmap(map, mapsize);
215         if (parse_sha1_header(buffer, type, &entry->size) < 0)
216                 die("unable to parse %s header", sha1_to_hex(entry->sha1));
217         if (!strcmp(type, "commit")) {
218                 entry->type = OBJ_COMMIT;
219         } else if (!strcmp(type, "tree")) {
220                 entry->type = OBJ_TREE;
221         } else if (!strcmp(type, "blob")) {
222                 entry->type = OBJ_BLOB;
223         } else
224                 die("unable to pack object %s of type %s", sha1_to_hex(entry->sha1), type);
225 }
226
227 static void get_object_details(void)
228 {
229         int i;
230         struct object_entry *entry = objects;
231
232         for (i = 0; i < nr_objects; i++)
233                 check_object(entry++);
234 }
235
236 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
237
238 static entry_sort_t current_sort;
239
240 static int sort_comparator(const void *_a, const void *_b)
241 {
242         struct object_entry *a = *(struct object_entry **)_a;
243         struct object_entry *b = *(struct object_entry **)_b;
244         return current_sort(a,b);
245 }
246
247 static struct object_entry **create_sorted_list(entry_sort_t sort)
248 {
249         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
250         int i;
251
252         for (i = 0; i < nr_objects; i++)
253                 list[i] = objects + i;
254         current_sort = sort;
255         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
256         return list;
257 }
258
259 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
260 {
261         return memcmp(a->sha1, b->sha1, 20);
262 }
263
264 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
265 {
266         if (a->type < b->type)
267                 return -1;
268         if (a->type > b->type)
269                 return 1;
270         if (a->size < b->size)
271                 return -1;
272         if (a->size > b->size)
273                 return 1;
274         return a < b ? -1 : (a > b);
275 }
276
277 struct unpacked {
278         struct object_entry *entry;
279         void *data;
280 };
281
282 /*
283  * We search for deltas in a list sorted by type and by size, and
284  * walk the "old" chain backwards in the list, so if the type
285  * has changed or the size difference is too big, there's no point
286  * in even continuing the walk, since the other old objects are
287  * going to be even smaller or of a different type. So return -1
288  * once we determine that there's no point even trying.
289  */
290 static int try_delta(struct unpacked *cur, struct unpacked *old)
291 {
292         struct object_entry *cur_entry = cur->entry;
293         struct object_entry *old_entry = old->entry;
294         unsigned long size, oldsize, delta_size;
295         long max_size;
296         void *delta_buf;
297
298         /* Don't bother doing diffs between different types */
299         if (cur_entry->type != old_entry->type)
300                 return -1;
301
302         /* Size is guaranteed to be larger than or equal to oldsize */
303         size = cur_entry->size;
304         if (size < 50)
305                 return -1;
306         oldsize = old_entry->size;
307         if (size - oldsize > oldsize / 4)
308                 return -1;
309
310         /*
311          * NOTE!
312          *
313          * We always delta from the bigger to the smaller, since that's
314          * more space-efficient (deletes don't have to say _what_ they
315          * delete).
316          */
317         max_size = size / 2 - 20;
318         if (cur_entry->delta)
319                 max_size = cur_entry->delta_size-1;
320         delta_buf = diff_delta(cur->data, size, old->data, oldsize, &delta_size, max_size);
321         if (!delta_buf)
322                 return 0;
323         cur_entry->delta = old_entry;
324         cur_entry->delta_size = delta_size;
325         free(delta_buf);
326         return 0;
327 }
328
329 static void find_deltas(struct object_entry **list, int window)
330 {
331         unsigned int i;
332         unsigned int array_size = window * sizeof(struct unpacked);
333         struct unpacked *array = xmalloc(array_size);
334
335         memset(array, 0, array_size);
336         for (i = 0; i < nr_objects; i++) {
337                 unsigned int idx = i % window;
338                 struct object_entry *entry = list[i];
339                 struct unpacked *n = array + idx;
340                 unsigned long size;
341                 char type[10];
342                 int j;
343
344                 free(n->data);
345                 n->entry = entry;
346                 n->data = read_sha1_file(entry->sha1, type, &size);
347                 if (size != entry->size)
348                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
349                 j = window;
350                 while (--j > 0) {
351                         unsigned int other_idx = idx + j;
352                         struct unpacked *m;
353                         if (other_idx >= window)
354                                 other_idx -= window;
355                         m = array + other_idx;
356                         if (!m->entry)
357                                 break;
358                         if (try_delta(n, m) < 0)
359                                 break;
360                 }
361         }
362 }
363
364 int main(int argc, char **argv)
365 {
366         char line[128];
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;
375                                 delta_window = strtoul(arg+9, &end, 0);
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);
402         if (delta_window)
403                 find_deltas(sorted_by_type, delta_window);
404
405         write_pack_file();
406         write_index_file();
407         return 0;
408 }