[PATCH] Rename and extend read_tree_with_tree_or_commit_sha1
[git] / sha1_file.c
1 /*
2  * GIT - The information manager from hell
3  *
4  * Copyright (C) Linus Torvalds, 2005
5  *
6  * This handles basic git sha1 object files - packing, unpacking,
7  * creation etc.
8  */
9 #include <stdarg.h>
10 #include "cache.h"
11
12 const char *sha1_file_directory = NULL;
13
14 #ifndef O_NOATIME
15 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
16 #define O_NOATIME 01000000
17 #else
18 #define O_NOATIME 0
19 #endif
20 #endif
21
22 static unsigned int sha1_file_open_flag = O_NOATIME;
23
24 static unsigned hexval(char c)
25 {
26         if (c >= '0' && c <= '9')
27                 return c - '0';
28         if (c >= 'a' && c <= 'f')
29                 return c - 'a' + 10;
30         if (c >= 'A' && c <= 'F')
31                 return c - 'A' + 10;
32         return ~0;
33 }
34
35 int get_sha1_hex(const char *hex, unsigned char *sha1)
36 {
37         int i;
38         for (i = 0; i < 20; i++) {
39                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
40                 if (val & ~0xff)
41                         return -1;
42                 *sha1++ = val;
43                 hex += 2;
44         }
45         return 0;
46 }
47
48 char * sha1_to_hex(const unsigned char *sha1)
49 {
50         static char buffer[50];
51         static const char hex[] = "0123456789abcdef";
52         char *buf = buffer;
53         int i;
54
55         for (i = 0; i < 20; i++) {
56                 unsigned int val = *sha1++;
57                 *buf++ = hex[val >> 4];
58                 *buf++ = hex[val & 0xf];
59         }
60         return buffer;
61 }
62
63 /*
64  * NOTE! This returns a statically allocated buffer, so you have to be
65  * careful about using it. Do a "strdup()" if you need to save the
66  * filename.
67  */
68 char *sha1_file_name(const unsigned char *sha1)
69 {
70         int i;
71         static char *name, *base;
72
73         if (!base) {
74                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
75                 int len = strlen(sha1_file_directory);
76                 base = xmalloc(len + 60);
77                 memcpy(base, sha1_file_directory, len);
78                 memset(base+len, 0, 60);
79                 base[len] = '/';
80                 base[len+3] = '/';
81                 name = base + len + 1;
82         }
83         for (i = 0; i < 20; i++) {
84                 static char hex[] = "0123456789abcdef";
85                 unsigned int val = sha1[i];
86                 char *pos = name + i*2 + (i > 0);
87                 *pos++ = hex[val >> 4];
88                 *pos = hex[val & 0xf];
89         }
90         return base;
91 }
92
93 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
94 {
95         char header[100];
96         unsigned char real_sha1[20];
97         SHA_CTX c;
98
99         SHA1_Init(&c);
100         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
101         SHA1_Update(&c, map, size);
102         SHA1_Final(real_sha1, &c);
103         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
104 }
105
106 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
107 {
108         char *filename = sha1_file_name(sha1);
109         struct stat st;
110         void *map;
111         int fd;
112
113         fd = open(filename, O_RDONLY | sha1_file_open_flag);
114         if (fd < 0) {
115                 /* See if it works without O_NOATIME */
116                 switch (sha1_file_open_flag) {
117                 default:
118                         fd = open(filename, O_RDONLY);
119                         if (fd >= 0)
120                                 break;
121                 /* Fallthrough */
122                 case 0:
123                         perror(filename);
124                         return NULL;
125                 }
126
127                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
128                 sha1_file_open_flag = 0;
129         }
130         if (fstat(fd, &st) < 0) {
131                 close(fd);
132                 return NULL;
133         }
134         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
135         close(fd);
136         if (-1 == (int)(long)map)
137                 return NULL;
138         *size = st.st_size;
139         return map;
140 }
141
142 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
143 {
144         int ret, bytes;
145         z_stream stream;
146         char buffer[8192];
147         char *buf;
148
149         /* Get the data stream */
150         memset(&stream, 0, sizeof(stream));
151         stream.next_in = map;
152         stream.avail_in = mapsize;
153         stream.next_out = buffer;
154         stream.avail_out = sizeof(buffer);
155
156         inflateInit(&stream);
157         ret = inflate(&stream, 0);
158         if (ret < Z_OK)
159                 return NULL;
160         if (sscanf(buffer, "%10s %lu", type, size) != 2)
161                 return NULL;
162
163         bytes = strlen(buffer) + 1;
164         buf = xmalloc(*size);
165
166         memcpy(buf, buffer + bytes, stream.total_out - bytes);
167         bytes = stream.total_out - bytes;
168         if (bytes < *size && ret == Z_OK) {
169                 stream.next_out = buf + bytes;
170                 stream.avail_out = *size - bytes;
171                 while (inflate(&stream, Z_FINISH) == Z_OK)
172                         /* nothing */;
173         }
174         inflateEnd(&stream);
175         return buf;
176 }
177
178 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
179 {
180         unsigned long mapsize;
181         void *map, *buf;
182
183         map = map_sha1_file(sha1, &mapsize);
184         if (map) {
185                 buf = unpack_sha1_file(map, mapsize, type, size);
186                 munmap(map, mapsize);
187                 return buf;
188         }
189         return NULL;
190 }
191
192 void *read_object_with_reference(const unsigned char *sha1,
193                                  const unsigned char *required_type,
194                                  unsigned long *size,
195                                  unsigned char *actual_sha1_return)
196 {
197         char type[20];
198         void *buffer;
199         unsigned long isize;
200         unsigned char actual_sha1[20];
201
202         memcpy(actual_sha1, sha1, 20);
203         while (1) {
204                 int ref_length = -1;
205                 const char *ref_type = NULL;
206
207                 buffer = read_sha1_file(actual_sha1, type, &isize);
208                 if (!buffer)
209                         return NULL;
210                 if (!strcmp(type, required_type)) {
211                         *size = isize;
212                         if (actual_sha1_return)
213                                 memcpy(actual_sha1_return, actual_sha1, 20);
214                         return buffer;
215                 }
216                 /* Handle references */
217                 else if (!strcmp(type, "commit"))
218                         ref_type = "tree ";
219                 else if (!strcmp(type, "tag"))
220                         ref_type = "object ";
221                 else {
222                         free(buffer);
223                         return NULL;
224                 }
225                 ref_length = strlen(ref_type);
226
227                 if (memcmp(buffer, ref_type, ref_length) ||
228                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
229                         free(buffer);
230                         return NULL;
231                 }
232                 /* Now we have the ID of the referred-to object in
233                  * actual_sha1.  Check again. */
234         }
235 }
236
237 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
238 {
239         int size;
240         char *compressed;
241         z_stream stream;
242         unsigned char sha1[20];
243         SHA_CTX c;
244         char *filename;
245         char hdr[50];
246         int fd, hdrlen;
247
248         /* Generate the header */
249         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
250
251         /* Sha1.. */
252         SHA1_Init(&c);
253         SHA1_Update(&c, hdr, hdrlen);
254         SHA1_Update(&c, buf, len);
255         SHA1_Final(sha1, &c);
256
257         if (returnsha1)
258                 memcpy(returnsha1, sha1, 20);
259
260         filename = sha1_file_name(sha1);
261         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
262         if (fd < 0) {
263                 if (errno != EEXIST)
264                         return -1;
265
266                 /*
267                  * We might do collision checking here, but we'd need to
268                  * uncompress the old file and check it. Later.
269                  */
270                 return 0;
271         }
272
273         /* Set it up */
274         memset(&stream, 0, sizeof(stream));
275         deflateInit(&stream, Z_BEST_COMPRESSION);
276         size = deflateBound(&stream, len+hdrlen);
277         compressed = xmalloc(size);
278
279         /* Compress it */
280         stream.next_out = compressed;
281         stream.avail_out = size;
282
283         /* First header.. */
284         stream.next_in = hdr;
285         stream.avail_in = hdrlen;
286         while (deflate(&stream, 0) == Z_OK)
287                 /* nothing */
288
289         /* Then the data itself.. */
290         stream.next_in = buf;
291         stream.avail_in = len;
292         while (deflate(&stream, Z_FINISH) == Z_OK)
293                 /* nothing */;
294         deflateEnd(&stream);
295         size = stream.total_out;
296
297         if (write(fd, compressed, size) != size)
298                 die("unable to write file");
299         close(fd);
300                 
301         return 0;
302 }
303
304 static inline int collision_check(char *filename, void *buf, unsigned int size)
305 {
306 #ifdef COLLISION_CHECK
307         void *map;
308         int fd = open(filename, O_RDONLY);
309         struct stat st;
310         int cmp;
311
312         /* Unreadable object, or object went away? Strange. */
313         if (fd < 0)
314                 return -1;
315
316         if (fstat(fd, &st) < 0 || size != st.st_size)
317                 return -1;
318
319         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
320         close(fd);
321         if (map == MAP_FAILED)
322                 return -1;
323         cmp = memcmp(buf, map, size);
324         munmap(map, size);
325         if (cmp)
326                 return -1;
327 #endif
328         return 0;
329 }
330
331 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
332 {
333         char *filename = sha1_file_name(sha1);
334         int fd;
335
336         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
337         if (fd < 0) {
338                 if (errno != EEXIST)
339                         return -1;
340                 if (collision_check(filename, buf, size))
341                         return error("SHA1 collision detected!"
342                                         " This is bad, bad, BAD!\a\n");
343                 return 0;
344         }
345         write(fd, buf, size);
346         close(fd);
347         return 0;
348 }
349
350 int write_sha1_from_fd(const unsigned char *sha1, int fd)
351 {
352         char *filename = sha1_file_name(sha1);
353
354         int local;
355         z_stream stream;
356         unsigned char real_sha1[20];
357         char buf[4096];
358         char discard[4096];
359         int ret;
360         SHA_CTX c;
361
362         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
363
364         if (local < 0)
365                 return error("Couldn't open %s\n", filename);
366
367         memset(&stream, 0, sizeof(stream));
368
369         inflateInit(&stream);
370
371         SHA1_Init(&c);
372
373         do {
374                 ssize_t size;
375                 size = read(fd, buf, 4096);
376                 if (size <= 0) {
377                         close(local);
378                         unlink(filename);
379                         if (!size)
380                                 return error("Connection closed?");
381                         perror("Reading from connection");
382                         return -1;
383                 }
384                 write(local, buf, size);
385                 stream.avail_in = size;
386                 stream.next_in = buf;
387                 do {
388                         stream.next_out = discard;
389                         stream.avail_out = sizeof(discard);
390                         ret = inflate(&stream, Z_SYNC_FLUSH);
391                         SHA1_Update(&c, discard, sizeof(discard) -
392                                     stream.avail_out);
393                 } while (stream.avail_in && ret == Z_OK);
394                 
395         } while (ret == Z_OK);
396         inflateEnd(&stream);
397
398         close(local);
399         SHA1_Final(real_sha1, &c);
400         if (ret != Z_STREAM_END) {
401                 unlink(filename);
402                 return error("File %s corrupted", sha1_to_hex(sha1));
403         }
404         if (memcmp(sha1, real_sha1, 20)) {
405                 unlink(filename);
406                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
407         }
408         
409         return 0;
410 }
411
412 int has_sha1_file(const unsigned char *sha1)
413 {
414         char *filename = sha1_file_name(sha1);
415         struct stat st;
416
417         if (!stat(filename, &st))
418                 return 1;
419         return 0;
420 }