replace_object.c

   1 #include "cache.h"
   2 #include "sha1-lookup.h"
   3 #include "refs.h"
   4
   5 static struct replace_object {
   6         unsigned char sha1[2][20];
   7 } **replace_object;
   8
   9 static int replace_object_alloc, replace_object_nr;
  10
  11 static const unsigned char *replace_sha1_access(size_t index, void *table)
  12 {
  13         struct replace_object **replace = table;
  14         return replace[index]->sha1[0];
  15 }
  16
  17 static int replace_object_pos(const unsigned char *sha1)
  18 {
  19         return sha1_pos(sha1, replace_object, replace_object_nr,
  20                         replace_sha1_access);
  21 }
  22
  23 static int register_replace_object(struct replace_object *replace,
  24                                    int ignore_dups)
  25 {
  26         int pos = replace_object_pos(replace->sha1[0]);
  27
  28         if (0 <= pos) {
  29                 if (ignore_dups)
  30                         free(replace);
  31                 else {
  32                         free(replace_object[pos]);
  33                         replace_object[pos] = replace;
  34                 }
  35                 return 1;
  36         }
  37         pos = -pos - 1;
  38         if (replace_object_alloc <= ++replace_object_nr) {
  39                 replace_object_alloc = alloc_nr(replace_object_alloc);
  40                 replace_object = xrealloc(replace_object,
  41                                           sizeof(*replace_object) *
  42                                           replace_object_alloc);
  43         }
  44         if (pos < replace_object_nr)
  45                 memmove(replace_object + pos + 1,
  46                         replace_object + pos,
  47                         (replace_object_nr - pos - 1) *
  48                         sizeof(*replace_object));
  49         replace_object[pos] = replace;
  50         return 0;
  51 }
  52
  53 static int register_replace_ref(const char *refname,
  54                                 const unsigned char *sha1,
  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 (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->sha1[0])) {
  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         hashcpy(repl_obj->sha1[1], sha1);
  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 }
  88
  89 /* We allow "recursive" replacement. Only within reason, though */
  90 #define MAXREPLACEDEPTH 5
  91
  92 const unsigned char *lookup_replace_object(const unsigned char *sha1)
  93 {
  94         int pos, depth = MAXREPLACEDEPTH;
  95         const unsigned char *cur = sha1;
  96
  97         if (!read_replace_refs)
  98                 return sha1;
  99
 100         prepare_replace_object();
 101
 102         /* Try to recursively replace the object */
 103         do {
 104                 if (--depth < 0)
 105                         die("replace depth too high for object %s",
 106                             sha1_to_hex(sha1));
 107
 108                 pos = replace_object_pos(cur);
 109                 if (0 <= pos)
 110                         cur = replace_object[pos]->sha1[1];
 111         } while (0 <= pos);
 112
 113         return cur;
 114 }