Andrew's git - gitweb.git/blob

   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
  12const 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
  22static unsigned int sha1_file_open_flag = O_NOATIME;
  23
  24static 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
  35int 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
  48char * 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 */
  68char *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 = malloc(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
  93int 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
 106void *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
 142void * 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 (sscanf(buffer, "%10s %lu", type, size) != 2)
 159                return NULL;
 160
 161        bytes = strlen(buffer) + 1;
 162        buf = malloc(*size);
 163        if (!buf)
 164                return NULL;
 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
 178void * 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
 192void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
 193                                         unsigned long *size,
 194                                         unsigned char *tree_sha1_return)
 195{
 196        char type[20];
 197        void *buffer;
 198        unsigned long isize;
 199        int was_commit = 0;
 200        unsigned char tree_sha1[20];
 201
 202        buffer = read_sha1_file(sha1, type, &isize);
 203
 204        /* 
 205         * We might have read a commit instead of a tree, in which case
 206         * we parse out the tree_sha1 and attempt to read from there.
 207         * (buffer + 5) is because the tree sha1 is always at offset 5
 208         * in a commit record ("tree ").
 209         */
 210        if (buffer &&
 211            !strcmp(type, "commit") &&
 212            !get_sha1_hex(buffer + 5, tree_sha1)) {
 213                free(buffer);
 214                buffer = read_sha1_file(tree_sha1, type, &isize);
 215                was_commit = 1;
 216        }
 217
 218        /*
 219         * Now do we have something and if so is it a tree?
 220         */
 221        if (!buffer || strcmp(type, "tree")) {
 222                free(buffer);
 223                return NULL;
 224        }
 225
 226        *size = isize;
 227        if (tree_sha1_return)
 228                memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
 229        return buffer;
 230}
 231
 232int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 233{
 234        int size;
 235        char *compressed;
 236        z_stream stream;
 237        unsigned char sha1[20];
 238        SHA_CTX c;
 239        char *filename;
 240        int fd;
 241
 242        /* Sha1.. */
 243        SHA1_Init(&c);
 244        SHA1_Update(&c, buf, len);
 245        SHA1_Final(sha1, &c);
 246
 247        if (returnsha1)
 248                memcpy(returnsha1, sha1, 20);
 249
 250        filename = sha1_file_name(sha1);
 251        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 252        if (fd < 0) {
 253                if (errno != EEXIST)
 254                        return -1;
 255
 256                /*
 257                 * We might do collision checking here, but we'd need to
 258                 * uncompress the old file and check it. Later.
 259                 */
 260                return 0;
 261        }
 262
 263        /* Set it up */
 264        memset(&stream, 0, sizeof(stream));
 265        deflateInit(&stream, Z_BEST_COMPRESSION);
 266        size = deflateBound(&stream, len);
 267        compressed = malloc(size);
 268
 269        /* Compress it */
 270        stream.next_in = buf;
 271        stream.avail_in = len;
 272        stream.next_out = compressed;
 273        stream.avail_out = size;
 274        while (deflate(&stream, Z_FINISH) == Z_OK)
 275                /* nothing */;
 276        deflateEnd(&stream);
 277        size = stream.total_out;
 278
 279        if (write(fd, compressed, size) != size)
 280                die("unable to write file");
 281        close(fd);
 282                
 283        return 0;
 284}
 285
 286static inline int collision_check(char *filename, void *buf, unsigned int size)
 287{
 288#ifdef COLLISION_CHECK
 289        void *map;
 290        int fd = open(filename, O_RDONLY);
 291        struct stat st;
 292        int cmp;
 293
 294        /* Unreadable object, or object went away? Strange. */
 295        if (fd < 0)
 296                return -1;
 297
 298        if (fstat(fd, &st) < 0 || size != st.st_size)
 299                return -1;
 300
 301        map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 302        close(fd);
 303        if (map == MAP_FAILED)
 304                return -1;
 305        cmp = memcmp(buf, map, size);
 306        munmap(map, size);
 307        if (cmp)
 308                return -1;
 309#endif
 310        return 0;
 311}
 312
 313int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 314{
 315        char *filename = sha1_file_name(sha1);
 316        int fd;
 317
 318        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 319        if (fd < 0) {
 320                if (errno != EEXIST)
 321                        return -1;
 322                if (collision_check(filename, buf, size))
 323                        return error("SHA1 collision detected!"
 324                                        " This is bad, bad, BAD!\a\n");
 325                return 0;
 326        }
 327        write(fd, buf, size);
 328        close(fd);
 329        return 0;
 330}