git/dump-pack-idx-v1.c

   1 /*
   2  * dump-pack-idx-v1: Dump the 'SHA1 offset' list from a .idx v1 file
   3  */
   4 #include <stdio.h>
   5 #include <fcntl.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <string.h>
   9 #include <sys/types.h>
  10 #include <sys/stat.h>
  11 #include <sys/mman.h>
  12 #include <arpa/inet.h>
  13
  14 #define FAN_OUT_SIZE (4 * 256)
  15 #define PACK_IDX_SIGNATURE 0xff744f63
  16
  17 struct pack_idx_header {
  18         uint32_t idx_signature;
  19         uint32_t idx_version;
  20 };
  21
  22 static inline void hashcpy(unsigned char *sha_dst,
  23                            const unsigned char *sha_src)
  24 {
  25         memcpy(sha_dst, sha_src, 20);
  26 }
  27
  28 static char *sha1_to_hex(const unsigned char *sha1)
  29 {
  30         static int bufno;
  31         static char hexbuffer[4][50];
  32         static const char hex[] = "0123456789abcdef";
  33         char *buffer = hexbuffer[3 & ++bufno], *buf = buffer;
  34         int i;
  35
  36         for (i = 0; i < 20; i++) {
  37                 unsigned int val = *sha1++;
  38                 *buf++ = hex[val >> 4];
  39                 *buf++ = hex[val & 0xf];
  40         }
  41         *buf = '\0';
  42
  43         return buffer;
  44 }
  45
  46 static void dump_index_v1(void *base, off_t size)
  47 {
  48         unsigned char *list;
  49         unsigned long nr_sha1, i;
  50
  51         list = base + FAN_OUT_SIZE;
  52         nr_sha1 = (size - (FAN_OUT_SIZE + 40)) / 24;
  53         for (i = 0; i < nr_sha1; i++) {
  54                 unsigned char sha1[20];
  55                 unsigned int offset;
  56
  57                 memcpy(&offset, list, sizeof(offset));
  58                 hashcpy(sha1, list + 4);
  59                 printf("%s %u\n", sha1_to_hex(sha1), ntohl(offset));
  60                 list += 24;
  61         }
  62 }
  63
  64 static void usage(void)
  65 {
  66         printf("dump-pack-idx-v1 [ -f -v ] < pack-idx >\n");
  67 }
  68
  69 int main(int argc, char *argv[])
  70 {
  71         void *idx;
  72         char *idx_file;
  73         struct stat buf;
  74         struct pack_idx_header *hdr;
  75         int version, force, show_version, opt, err, fd;
  76
  77         version = 1;
  78         show_version = force = 0;
  79
  80         while ((opt = getopt(argc, argv, "vf")) != -1) {
  81                 switch (opt) {
  82                 case 'v':
  83                         show_version = 1;
  84                         break;
  85                 case 'f':
  86                         force = 1;
  87                         break;
  88                 default:
  89                         usage();
  90                         exit(1);
  91                 }
  92         }
  93
  94         if (optind >= argc) {
  95                 usage();
  96                 exit(1);
  97         }
  98         idx_file = argv[optind];
  99
 100         if (!strstr(idx_file, ".idx") && !force) {
 101                 fprintf(stderr,
 102                         "ERROR: '%s' doesn't seem to be an .idx file, try '-f'"
 103                         " if you know what you're doing\n", idx_file);
 104                 exit(1);
 105         }
 106
 107         fd = open(idx_file, O_RDONLY);
 108         if (fd < 0) {
 109                 perror("open()");
 110                 exit(1);
 111         }
 112
 113         err = fstat(fd, &buf);
 114         if (err) {
 115                 perror("fstat()");
 116                 exit(1);
 117         }
 118
 119         idx = mmap(NULL, buf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 120         close(fd);
 121         if (idx == MAP_FAILED) {
 122                 perror("mmap()");
 123                 exit(1);
 124         }
 125
 126         hdr = idx;
 127         if (hdr->idx_signature == htonl(PACK_IDX_SIGNATURE))
 128                 version = ntohl(hdr->idx_version);
 129
 130         if (show_version) {
 131                 printf("version: %d\n", version);
 132                 exit(0);
 133         }
 134
 135         if (version != 1) {
 136                 printf("Only dumps index v1, this is index v%d\n", version);
 137                 exit(1);
 138         }
 139
 140         dump_index_v1(idx, buf.st_size);
 141
 142         munmap(idx, buf.st_size);
 143         return 0;
 144 }