rev-cache.c

   1 #include "refs.h"
   2 #include "cache.h"
   3 #include "rev-cache.h"
   4
   5 struct rev_cache **rev_cache;
   6 int nr_revs, alloc_revs;
   7
   8 struct rev_list_elem *rle_free;
   9
  10 #define BATCH_SIZE 512
  11
  12 int find_rev_cache(const unsigned char *sha1)
  13 {
  14         int lo = 0, hi = nr_revs;
  15         while (lo < hi) {
  16                 int mi = (lo + hi) / 2;
  17                 struct rev_cache *ri = rev_cache[mi];
  18                 int cmp = memcmp(sha1, ri->sha1, 20);
  19                 if (!cmp)
  20                         return mi;
  21                 if (cmp < 0)
  22                         hi = mi;
  23                 else
  24                         lo = mi + 1;
  25         }
  26         return -lo - 1;
  27 }
  28
  29 static struct rev_list_elem *alloc_list_elem(void)
  30 {
  31         struct rev_list_elem *rle;
  32         if (!rle_free) {
  33                 int i;
  34
  35                 rle = xmalloc(sizeof(*rle) * BATCH_SIZE);
  36                 for (i = 0; i < BATCH_SIZE - 1; i++) {
  37                         rle[i].ri = NULL;
  38                         rle[i].next = &rle[i + 1];
  39                 }
  40                 rle[BATCH_SIZE - 1].ri = NULL;
  41                 rle[BATCH_SIZE - 1].next = NULL;
  42                 rle_free = rle;
  43         }
  44         rle = rle_free;
  45         rle_free = rle->next;
  46         return rle;
  47 }
  48
  49 static struct rev_cache *create_rev_cache(const unsigned char *sha1)
  50 {
  51         struct rev_cache *ri;
  52         int pos = find_rev_cache(sha1);
  53
  54         if (0 <= pos)
  55                 return rev_cache[pos];
  56         pos = -pos - 1;
  57         if (alloc_revs <= ++nr_revs) {
  58                 alloc_revs = alloc_nr(alloc_revs);
  59                 rev_cache = xrealloc(rev_cache, sizeof(ri) * alloc_revs);
  60         }
  61         if (pos < nr_revs)
  62                 memmove(rev_cache + pos + 1, rev_cache + pos,
  63                         (nr_revs - pos - 1) * sizeof(ri));
  64         ri = xcalloc(1, sizeof(*ri));
  65         memcpy(ri->sha1, sha1, 20);
  66         rev_cache[pos] = ri;
  67         return ri;
  68 }
  69
  70 static unsigned char last_sha1[20];
  71
  72 static void write_one_rev_cache(FILE *rev_cache_file, struct rev_cache *ri)
  73 {
  74         unsigned char flag;
  75         struct rev_list_elem *rle;
  76
  77         if (ri->written)
  78                 return;
  79
  80         if (ri->parsed) {
  81                 /* We use last_sha1 compression only for the first parent;
  82                  * otherwise the resulting rev-cache would lose the parent
  83                  * order information.
  84                  */
  85                 if (ri->parents &&
  86                     !memcmp(ri->parents->ri->sha1, last_sha1, 20))
  87                         flag = (ri->num_parents - 1) | 0x80;
  88                 else
  89                         flag = ri->num_parents;
  90
  91                 fwrite(ri->sha1, 20, 1, rev_cache_file);
  92                 fwrite(&flag, 1, 1, rev_cache_file);
  93                 for (rle = ri->parents; rle; rle = rle->next) {
  94                         if (flag & 0x80 && rle == ri->parents)
  95                                 continue;
  96                         fwrite(rle->ri->sha1, 20, 1, rev_cache_file);
  97                 }
  98                 memcpy(last_sha1, ri->sha1, 20);
  99                 ri->written = 1;
 100         }
 101         /* recursively write children depth first */
 102         for (rle = ri->children; rle; rle = rle->next)
 103                 write_one_rev_cache(rev_cache_file, rle->ri);
 104 }
 105
 106 void write_rev_cache(const char *newpath, const char *oldpath)
 107 {
 108         /* write the following commit ancestry information in
 109          * $GIT_DIR/info/rev-cache.
 110          *
 111          * The format is:
 112          * 20-byte SHA1 (commit ID)
 113          * 1-byte flag:
 114          * - bit 0-6 records "number of parent commit SHA1s to
 115          *   follow" (i.e. up to 127 children can be listed).
 116          * - when the bit 7 is on, then "the entry immediately
 117          *   before this entry is one of the parents of this
 118          *   commit".
 119          * N x 20-byte SHA1 (parent commit IDs)
 120          */
 121         FILE *rev_cache_file;
 122         int i;
 123         struct rev_cache *ri;
 124
 125         if (!strcmp(newpath, oldpath)) {
 126                 /* If we are doing it in place */
 127                 rev_cache_file = fopen(newpath, "a");
 128         }
 129         else {
 130                 char buf[8096];
 131                 size_t sz;
 132                 FILE *oldfp = fopen(oldpath, "r");
 133                 rev_cache_file = fopen(newpath, "w");
 134                 if (oldfp) {
 135                         while (1) {
 136                                 sz = fread(buf, 1, sizeof(buf), oldfp);
 137                                 if (sz == 0)
 138                                         break;
 139                                 fwrite(buf, 1, sz, rev_cache_file);
 140                         }
 141                         fclose(oldfp);
 142                 }
 143         }
 144
 145         memset(last_sha1, 0, 20);
 146
 147         /* Go through available rev_cache structures, starting from
 148          * parentless ones first, so that we would get most out of
 149          * last_sha1 optimization by the depth first behaviour of
 150          * write_one_rev_cache().
 151          */
 152         for (i = 0; i < nr_revs; i++) {
 153                 ri = rev_cache[i];
 154                 if (ri->num_parents)
 155                         continue;
 156                 write_one_rev_cache(rev_cache_file, ri);
 157         }
 158         /* Then the rest */
 159         for (i = 0; i < nr_revs; i++) {
 160                 ri = rev_cache[i];
 161                 write_one_rev_cache(rev_cache_file, ri);
 162         }
 163         fclose(rev_cache_file);
 164 }
 165
 166 static void add_parent(struct rev_cache *child,
 167                        const unsigned char *parent_sha1)
 168 {
 169         struct rev_cache *parent = create_rev_cache(parent_sha1);
 170         struct rev_list_elem *e = alloc_list_elem();
 171
 172         /* Keep the parent list ordered in the same way the commit
 173          * object records them.
 174          */
 175         e->ri = parent;
 176         e->next = NULL;
 177         if (!child->parents_tail)
 178                 child->parents = e;
 179         else
 180                 child->parents_tail->next = e;
 181         child->parents_tail = e;
 182         child->num_parents++;
 183
 184         /* There is no inherent order of the children so we just
 185          * LIFO them together.
 186          */
 187         e = alloc_list_elem();
 188         e->next = parent->children;
 189         parent->children = e;
 190         e->ri = child;
 191         parent->num_children++;
 192 }
 193
 194 int read_rev_cache(const char *path, FILE *dumpfile, int dry_run)
 195 {
 196         unsigned char *map;
 197         int fd;
 198         struct stat st;
 199         unsigned long ofs, len;
 200         struct rev_cache *ri = NULL;
 201
 202         fd = open(path, O_RDONLY);
 203         if (fd < 0) {
 204                 if (dry_run)
 205                         return error("cannot open %s", path);
 206                 if (errno == ENOENT)
 207                         return 0;
 208                 return -1;
 209         }
 210         if (fstat(fd, &st)) {
 211                 close(fd);
 212                 return -1;
 213         }
 214         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 215         close(fd);
 216         if (map == MAP_FAILED)
 217                 return -1;
 218
 219         memset(last_sha1, 0, 20);
 220         ofs = 0;
 221         len = st.st_size;
 222         while (ofs < len) {
 223                 unsigned char sha1[20];
 224                 int flag, cnt, i;
 225                 if (len < ofs + 21)
 226                         die("rev-cache too short");
 227                 memcpy(sha1, map + ofs, 20);
 228                 flag = map[ofs + 20];
 229                 ofs += 21;
 230                 cnt = (flag & 0x7f) + ((flag & 0x80) != 0);
 231                 if (len < ofs + (flag & 0x7f) * 20)
 232                         die("rev-cache too short to have %d more parents",
 233                             (flag & 0x7f));
 234                 if (dumpfile)
 235                         fprintf(dumpfile, "%s", sha1_to_hex(sha1));
 236                 if (!dry_run) {
 237                         ri = create_rev_cache(sha1);
 238                         if (!ri)
 239                                 die("cannot create rev-cache for %s",
 240                                     sha1_to_hex(sha1));
 241                         ri->written = ri->parsed = 1;
 242                 }
 243                 i = 0;
 244                 if (flag & 0x80) {
 245                         if (!dry_run)
 246                                 add_parent(ri, last_sha1);
 247                         if (dumpfile)
 248                                 fprintf(dumpfile, " %s",
 249                                         sha1_to_hex(last_sha1));
 250                         i++;
 251                 }
 252                 while (i++ < cnt) {
 253                         if (!dry_run)
 254                                 add_parent(ri, map + ofs);
 255                         if (dumpfile)
 256                                 fprintf(dumpfile, " %s",
 257                                         sha1_to_hex(last_sha1));
 258                         ofs += 20;
 259                 }
 260                 if (dumpfile)
 261                         fprintf(dumpfile, "\n");
 262                 memcpy(last_sha1, sha1, 20);
 263         }
 264         if (ofs != len)
 265                 die("rev-cache truncated?");
 266         munmap(map, len);
 267         return 0;
 268 }
 269
 270 int record_rev_cache(const unsigned char *sha1, FILE *dumpfile)
 271 {
 272         unsigned char parent[20];
 273         char type[20];
 274         unsigned long size, ofs;
 275         unsigned int cnt, i;
 276         void *buf;
 277         struct rev_cache *ri;
 278
 279         buf = read_sha1_file(sha1, type, &size);
 280         if (!buf)
 281                 return error("%s: not found", sha1_to_hex(sha1));
 282         if (strcmp(type, "commit")) {
 283                 free(buf);
 284                 return error("%s: not a commit but a %s",
 285                              sha1_to_hex(sha1), type);
 286         }
 287         ri = create_rev_cache(sha1);
 288         if (ri->parsed)
 289                 return 0;
 290         if (dumpfile)
 291                 fprintf(dumpfile, "commit %s\n", sha1_to_hex(sha1));
 292
 293         cnt = 0;
 294         ofs = 46; /* "tree " + hex-sha1 + "\n" */
 295         while (!memcmp(buf + ofs, "parent ", 7) &&
 296                !get_sha1_hex(buf + ofs + 7, parent)) {
 297                 ofs += 48;
 298                 cnt++;
 299         }
 300         if (cnt * 48 + 46 != ofs) {
 301                 free(buf);
 302                 die("internal error in record_rev_cache");
 303         }
 304
 305         ri = create_rev_cache(sha1);
 306         ri->parsed = 1;
 307
 308         for (i = 0; i < cnt; i++) {
 309                 unsigned char parent_sha1[20];
 310
 311                 ofs = 46 + i * 48 + 7;
 312                 get_sha1_hex(buf + ofs, parent_sha1);
 313                 add_parent(ri, parent_sha1);
 314                 record_rev_cache(parent_sha1, dumpfile);
 315         }
 316         free(buf);
 317         return 0;
 318 }