replace_object.c

   1 #include "cache.h"
   2 #include "sha1-lookup.h"
   3 #include "refs.h"
   4 #include "commit.h"
   5
   6 /*
   7  * An array of replacements.  The array is kept sorted by the original
   8  * sha1.
   9  */
  10 static struct replace_object {
  11         unsigned char original[20];
  12         unsigned char replacement[20];
  13 } **replace_object;
  14
  15 static int replace_object_alloc, replace_object_nr;
  16
  17 static const unsigned char *replace_sha1_access(size_t index, void *table)
  18 {
  19         struct replace_object **replace = table;
  20         return replace[index]->original;
  21 }
  22
  23 static int replace_object_pos(const unsigned char *sha1)
  24 {
  25         return sha1_pos(sha1, replace_object, replace_object_nr,
  26                         replace_sha1_access);
  27 }
  28
  29 static int register_replace_object(struct replace_object *replace,
  30                                    int ignore_dups)
  31 {
  32         int pos = replace_object_pos(replace->original);
  33
  34         if (0 <= pos) {
  35                 if (ignore_dups)
  36                         free(replace);
  37                 else {
  38                         free(replace_object[pos]);
  39                         replace_object[pos] = replace;
  40                 }
  41                 return 1;
  42         }
  43         pos = -pos - 1;
  44         ALLOC_GROW(replace_object, replace_object_nr + 1, replace_object_alloc);
  45         replace_object_nr++;
  46         if (pos < replace_object_nr)
  47                 memmove(replace_object + pos + 1,
  48                         replace_object + pos,
  49                         (replace_object_nr - pos - 1) *
  50                         sizeof(*replace_object));
  51         replace_object[pos] = replace;
  52         return 0;
  53 }
  54
  55 static int register_replace_ref(const char *refname,
  56                                 const struct object_id *oid,
  57                                 int flag, void *cb_data)
  58 {
  59         /* Get sha1 from refname */
  60         const char *slash = strrchr(refname, '/');
  61         const char *hash = slash ? slash + 1 : refname;
  62         struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
  63
  64         if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->original)) {
  65                 free(repl_obj);
  66                 warning("bad replace ref name: %s", refname);
  67                 return 0;
  68         }
  69
  70         /* Copy sha1 from the read ref */
  71         hashcpy(repl_obj->replacement, oid->hash);
  72
  73         /* Register new object */
  74         if (register_replace_object(repl_obj, 1))
  75                 die("duplicate replace ref: %s", refname);
  76
  77         return 0;
  78 }
  79
  80 static void prepare_replace_object(void)
  81 {
  82         static int replace_object_prepared;
  83
  84         if (replace_object_prepared)
  85                 return;
  86
  87         for_each_replace_ref(register_replace_ref, NULL);
  88         replace_object_prepared = 1;
  89         if (!replace_object_nr)
  90                 check_replace_refs = 0;
  91 }
  92
  93 /* We allow "recursive" replacement. Only within reason, though */
  94 #define MAXREPLACEDEPTH 5
  95
  96 /*
  97  * If a replacement for object sha1 has been set up, return the
  98  * replacement object's name (replaced recursively, if necessary).
  99  * The return value is either sha1 or a pointer to a
 100  * permanently-allocated value.  This function always respects replace
 101  * references, regardless of the value of check_replace_refs.
 102  */
 103 const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
 104 {
 105         int pos, depth = MAXREPLACEDEPTH;
 106         const unsigned char *cur = sha1;
 107
 108         prepare_replace_object();
 109
 110         /* Try to recursively replace the object */
 111         do {
 112                 if (--depth < 0)
 113                         die("replace depth too high for object %s",
 114                             sha1_to_hex(sha1));
 115
 116                 pos = replace_object_pos(cur);
 117                 if (0 <= pos)
 118                         cur = replace_object[pos]->replacement;
 119         } while (0 <= pos);
 120
 121         return cur;
 122 }