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         struct object_id original;
  12         struct object_id replacement;
  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.hash;
  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.hash);
  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                 MOVE_ARRAY(replace_object + pos + 1, replace_object + pos,
  48                            replace_object_nr - pos - 1);
  49         replace_object[pos] = replace;
  50         return 0;
  51 }
  52
  53 static int register_replace_ref(const char *refname,
  54                                 const struct object_id *oid,
  55                                 int flag, void *cb_data)
  56 {
  57         /* Get sha1 from refname */
  58         const char *slash = strrchr(refname, '/');
  59         const char *hash = slash ? slash + 1 : refname;
  60         struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
  61
  62         if (get_oid_hex(hash, &repl_obj->original)) {
  63                 free(repl_obj);
  64                 warning("bad replace ref name: %s", refname);
  65                 return 0;
  66         }
  67
  68         /* Copy sha1 from the read ref */
  69         oidcpy(&repl_obj->replacement, oid);
  70
  71         /* Register new object */
  72         if (register_replace_object(repl_obj, 1))
  73                 die("duplicate replace ref: %s", refname);
  74
  75         return 0;
  76 }
  77
  78 static void prepare_replace_object(void)
  79 {
  80         static int replace_object_prepared;
  81
  82         if (replace_object_prepared)
  83                 return;
  84
  85         for_each_replace_ref(register_replace_ref, NULL);
  86         replace_object_prepared = 1;
  87         if (!replace_object_nr)
  88                 check_replace_refs = 0;
  89 }
  90
  91 /* We allow "recursive" replacement. Only within reason, though */
  92 #define MAXREPLACEDEPTH 5
  93
  94 /*
  95  * If a replacement for object sha1 has been set up, return the
  96  * replacement object's name (replaced recursively, if necessary).
  97  * The return value is either sha1 or a pointer to a
  98  * permanently-allocated value.  This function always respects replace
  99  * references, regardless of the value of check_replace_refs.
 100  */
 101 const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
 102 {
 103         int pos, depth = MAXREPLACEDEPTH;
 104         const unsigned char *cur = sha1;
 105
 106         prepare_replace_object();
 107
 108         /* Try to recursively replace the object */
 109         do {
 110                 if (--depth < 0)
 111                         die("replace depth too high for object %s",
 112                             sha1_to_hex(sha1));
 113
 114                 pos = replace_object_pos(cur);
 115                 if (0 <= pos)
 116                         cur = replace_object[pos]->replacement.hash;
 117         } while (0 <= pos);
 118
 119         return cur;
 120 }