read-cache.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #include "cache.h"
   7
   8 const char *sha1_file_directory = NULL;
   9 struct cache_entry **active_cache = NULL;
  10 unsigned int active_nr = 0, active_alloc = 0;
  11
  12 void usage(const char *err)
  13 {
  14         fprintf(stderr, "read-tree: %s\n", err);
  15         exit(1);
  16 }
  17
  18 static unsigned hexval(char c)
  19 {
  20         if (c >= '0' && c <= '9')
  21                 return c - '0';
  22         if (c >= 'a' && c <= 'f')
  23                 return c - 'a' + 10;
  24         if (c >= 'A' && c <= 'F')
  25                 return c - 'A' + 10;
  26         return ~0;
  27 }
  28
  29 int get_sha1_hex(char *hex, unsigned char *sha1)
  30 {
  31         int i;
  32         for (i = 0; i < 20; i++) {
  33                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  34                 if (val & ~0xff)
  35                         return -1;
  36                 *sha1++ = val;
  37                 hex += 2;
  38         }
  39         return 0;
  40 }
  41
  42 char * sha1_to_hex(unsigned char *sha1)
  43 {
  44         static char buffer[50];
  45         static const char hex[] = "0123456789abcdef";
  46         char *buf = buffer;
  47         int i;
  48
  49         for (i = 0; i < 20; i++) {
  50                 unsigned int val = *sha1++;
  51                 *buf++ = hex[val >> 4];
  52                 *buf++ = hex[val & 0xf];
  53         }
  54         return buffer;
  55 }
  56
  57 /*
  58  * NOTE! This returns a statically allocated buffer, so you have to be
  59  * careful about using it. Do a "strdup()" if you need to save the
  60  * filename.
  61  */
  62 char *sha1_file_name(unsigned char *sha1)
  63 {
  64         int i;
  65         static char *name, *base;
  66
  67         if (!base) {
  68                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
  69                 int len = strlen(sha1_file_directory);
  70                 base = malloc(len + 60);
  71                 memcpy(base, sha1_file_directory, len);
  72                 memset(base+len, 0, 60);
  73                 base[len] = '/';
  74                 base[len+3] = '/';
  75                 name = base + len + 1;
  76         }
  77         for (i = 0; i < 20; i++) {
  78                 static char hex[] = "0123456789abcdef";
  79                 unsigned int val = sha1[i];
  80                 char *pos = name + i*2 + (i > 0);
  81                 *pos++ = hex[val >> 4];
  82                 *pos = hex[val & 0xf];
  83         }
  84         return base;
  85 }
  86
  87 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size)
  88 {
  89         unsigned char real_sha1[20];
  90         SHA_CTX c;
  91
  92         SHA1_Init(&c);
  93         SHA1_Update(&c, map, size);
  94         SHA1_Final(real_sha1, &c);
  95         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
  96 }
  97
  98 void *map_sha1_file(unsigned char *sha1, unsigned long *size)
  99 {
 100         char *filename = sha1_file_name(sha1);
 101         int fd = open(filename, O_RDONLY);
 102         struct stat st;
 103         void *map;
 104
 105         if (fd < 0) {
 106                 perror(filename);
 107                 return NULL;
 108         }
 109         if (fstat(fd, &st) < 0) {
 110                 close(fd);
 111                 return NULL;
 112         }
 113         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 114         close(fd);
 115         if (-1 == (int)(long)map)
 116                 return NULL;
 117         *size = st.st_size;
 118         return map;
 119 }
 120
 121 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 122 {
 123         int ret, bytes;
 124         z_stream stream;
 125         char buffer[8192];
 126         char *buf;
 127
 128         /* Get the data stream */
 129         memset(&stream, 0, sizeof(stream));
 130         stream.next_in = map;
 131         stream.avail_in = mapsize;
 132         stream.next_out = buffer;
 133         stream.avail_out = sizeof(buffer);
 134
 135         inflateInit(&stream);
 136         ret = inflate(&stream, 0);
 137         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 138                 return NULL;
 139
 140         bytes = strlen(buffer) + 1;
 141         buf = malloc(*size);
 142         if (!buf)
 143                 return NULL;
 144
 145         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 146         bytes = stream.total_out - bytes;
 147         if (bytes < *size && ret == Z_OK) {
 148                 stream.next_out = buf + bytes;
 149                 stream.avail_out = *size - bytes;
 150                 while (inflate(&stream, Z_FINISH) == Z_OK)
 151                         /* nothing */;
 152         }
 153         inflateEnd(&stream);
 154         return buf;
 155 }
 156
 157 void * read_sha1_file(unsigned char *sha1, char *type, unsigned long *size)
 158 {
 159         unsigned long mapsize;
 160         void *map, *buf;
 161
 162         map = map_sha1_file(sha1, &mapsize);
 163         if (map) {
 164                 buf = unpack_sha1_file(map, mapsize, type, size);
 165                 munmap(map, mapsize);
 166                 return buf;
 167         }
 168         return NULL;
 169 }
 170
 171 int write_sha1_file(char *buf, unsigned len)
 172 {
 173         int size;
 174         char *compressed;
 175         z_stream stream;
 176         unsigned char sha1[20];
 177         SHA_CTX c;
 178
 179         /* Set it up */
 180         memset(&stream, 0, sizeof(stream));
 181         deflateInit(&stream, Z_BEST_COMPRESSION);
 182         size = deflateBound(&stream, len);
 183         compressed = malloc(size);
 184
 185         /* Compress it */
 186         stream.next_in = buf;
 187         stream.avail_in = len;
 188         stream.next_out = compressed;
 189         stream.avail_out = size;
 190         while (deflate(&stream, Z_FINISH) == Z_OK)
 191                 /* nothing */;
 192         deflateEnd(&stream);
 193         size = stream.total_out;
 194
 195         /* Sha1.. */
 196         SHA1_Init(&c);
 197         SHA1_Update(&c, compressed, size);
 198         SHA1_Final(sha1, &c);
 199
 200         if (write_sha1_buffer(sha1, compressed, size) < 0)
 201                 return -1;
 202         printf("%s\n", sha1_to_hex(sha1));
 203         return 0;
 204 }
 205
 206 int write_sha1_buffer(unsigned char *sha1, void *buf, unsigned int size)
 207 {
 208         char *filename = sha1_file_name(sha1);
 209         int fd;
 210
 211         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 212         if (fd < 0)
 213                 return (errno == EEXIST) ? 0 : -1;
 214         write(fd, buf, size);
 215         close(fd);
 216         return 0;
 217 }
 218
 219 static int error(const char * string)
 220 {
 221         fprintf(stderr, "error: %s\n", string);
 222         return -1;
 223 }
 224
 225 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 226 {
 227         SHA_CTX c;
 228         unsigned char sha1[20];
 229
 230         if (hdr->signature != CACHE_SIGNATURE)
 231                 return error("bad signature");
 232         if (hdr->version != 1)
 233                 return error("bad version");
 234         SHA1_Init(&c);
 235         SHA1_Update(&c, hdr, offsetof(struct cache_header, sha1));
 236         SHA1_Update(&c, hdr+1, size - sizeof(*hdr));
 237         SHA1_Final(sha1, &c);
 238         if (memcmp(sha1, hdr->sha1, 20))
 239                 return error("bad header sha1");
 240         return 0;
 241 }
 242
 243 int read_cache(void)
 244 {
 245         int fd, i;
 246         struct stat st;
 247         unsigned long size, offset;
 248         void *map;
 249         struct cache_header *hdr;
 250
 251         errno = EBUSY;
 252         if (active_cache)
 253                 return error("more than one cachefile");
 254         errno = ENOENT;
 255         sha1_file_directory = getenv(DB_ENVIRONMENT);
 256         if (!sha1_file_directory)
 257                 sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
 258         if (access(sha1_file_directory, X_OK) < 0)
 259                 return error("no access to SHA1 file directory");
 260         fd = open(".dircache/index", O_RDONLY);
 261         if (fd < 0)
 262                 return (errno == ENOENT) ? 0 : error("open failed");
 263
 264         size = 0; // avoid gcc warning
 265         map = (void *)-1;
 266         if (!fstat(fd, &st)) {
 267                 map = NULL;
 268                 size = st.st_size;
 269                 errno = EINVAL;
 270                 if (size > sizeof(struct cache_header))
 271                         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 272         }
 273         close(fd);
 274         if (-1 == (int)(long)map)
 275                 return error("mmap failed");
 276
 277         hdr = map;
 278         if (verify_hdr(hdr, size) < 0)
 279                 goto unmap;
 280
 281         active_nr = hdr->entries;
 282         active_alloc = alloc_nr(active_nr);
 283         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 284
 285         offset = sizeof(*hdr);
 286         for (i = 0; i < hdr->entries; i++) {
 287                 struct cache_entry *ce = map + offset;
 288                 offset = offset + ce_size(ce);
 289                 active_cache[i] = ce;
 290         }
 291         return active_nr;
 292
 293 unmap:
 294         munmap(map, size);
 295         errno = EINVAL;
 296         return error("verify header failed");
 297 }
 298