src/cp-hash.c

   1 /* cp-hash.c  -- file copying (hash search routines)
   2    Copyright (C) 1989-1991, 1995-2011 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17    Written by Torbjorn Granlund, Sweden (tege@sics.se).
  18    Rewritten to use lib/hash.c by Jim Meyering.  */
  19
  20 #include <config.h>
  21
  22 #include <sys/types.h>
  23 #include "system.h"
  24
  25 #include "same.h"
  26 #include "hash.h"
  27 #include "cp-hash.h"
  28
  29 /* Use ST_DEV and ST_INO as the key, FILENAME as the value.
  30    These are used e.g., in copy.c to associate the destination name with
  31    the source device/inode pair so that if we encounter a matching dev/ino
  32    pair in the source tree we can arrange to create a hard link between
  33    the corresponding names in the destination tree.  */
  34 struct Src_to_dest
  35 {
  36   ino_t st_ino;
  37   dev_t st_dev;
  38   /* Destination file name (of non-directory or pre-existing directory)
  39      corresponding to the dev/ino of a copied file, or the destination file
  40      name corresponding to a dev/ino pair for a newly-created directory. */
  41   char *name;
  42 };
  43
  44 /* This table maps source dev/ino to destination file name.
  45    We use it to preserve hard links when copying.  */
  46 static Hash_table *src_to_dest;
  47
  48 /* Initial size of the above hash table.  */
  49 #define INITIAL_TABLE_SIZE 103
  50
  51 static size_t
  52 src_to_dest_hash (void const *x, size_t table_size)
  53 {
  54   struct Src_to_dest const *p = x;
  55
  56   /* Ignoring the device number here should be fine.  */
  57   /* The cast to uintmax_t prevents negative remainders
  58      if st_ino is negative.  */
  59   return (uintmax_t) p->st_ino % table_size;
  60 }
  61
  62 /* Compare two Src_to_dest entries.
  63    Return true if their keys are judged `equal'.  */
  64 static bool
  65 src_to_dest_compare (void const *x, void const *y)
  66 {
  67   struct Src_to_dest const *a = x;
  68   struct Src_to_dest const *b = y;
  69   return SAME_INODE (*a, *b) ? true : false;
  70 }
  71
  72 static void
  73 src_to_dest_free (void *x)
  74 {
  75   struct Src_to_dest *a = x;
  76   free (a->name);
  77   free (x);
  78 }
  79
  80 /* Remove the entry matching INO/DEV from the table
  81    that maps source ino/dev to destination file name.  */
  82 extern void
  83 forget_created (ino_t ino, dev_t dev)
  84 {
  85   struct Src_to_dest probe;
  86   struct Src_to_dest *ent;
  87
  88   probe.st_ino = ino;
  89   probe.st_dev = dev;
  90   probe.name = NULL;
  91
  92   ent = hash_delete (src_to_dest, &probe);
  93   if (ent)
  94     src_to_dest_free (ent);
  95 }
  96
  97 /* If INO/DEV correspond to an already-copied source file, return the
  98    name of the corresponding destination file.  Otherwise, return NULL.  */
  99
 100 extern char *
 101 src_to_dest_lookup (ino_t ino, dev_t dev)
 102 {
 103   struct Src_to_dest ent;
 104   struct Src_to_dest const *e;
 105   ent.st_ino = ino;
 106   ent.st_dev = dev;
 107   e = hash_lookup (src_to_dest, &ent);
 108   return e ? e->name : NULL;
 109 }
 110
 111 /* Add file NAME, copied from inode number INO and device number DEV,
 112    to the list of files we have copied.
 113    Return NULL if inserted, otherwise non-NULL. */
 114
 115 extern char *
 116 remember_copied (const char *name, ino_t ino, dev_t dev)
 117 {
 118   struct Src_to_dest *ent;
 119   struct Src_to_dest *ent_from_table;
 120
 121   ent = xmalloc (sizeof *ent);
 122   ent->name = xstrdup (name);
 123   ent->st_ino = ino;
 124   ent->st_dev = dev;
 125
 126   ent_from_table = hash_insert (src_to_dest, ent);
 127   if (ent_from_table == NULL)
 128     {
 129       /* Insertion failed due to lack of memory.  */
 130       xalloc_die ();
 131     }
 132
 133   /* Determine whether there was already an entry in the table
 134      with a matching key.  If so, free ENT (it wasn't inserted) and
 135      return the `name' from the table entry.  */
 136   if (ent_from_table != ent)
 137     {
 138       src_to_dest_free (ent);
 139       return (char *) ent_from_table->name;
 140     }
 141
 142   /* New key;  insertion succeeded.  */
 143   return NULL;
 144 }
 145
 146 /* Initialize the hash table.  */
 147 extern void
 148 hash_init (void)
 149 {
 150   src_to_dest = hash_initialize (INITIAL_TABLE_SIZE, NULL,
 151                                  src_to_dest_hash,
 152                                  src_to_dest_compare,
 153                                  src_to_dest_free);
 154   if (src_to_dest == NULL)
 155     xalloc_die ();
 156 }
 157
 158 /* Reset the hash structure in the global variable `htab' to
 159    contain no entries.  */
 160
 161 extern void
 162 forget_all (void)
 163 {
 164   hash_free (src_to_dest);
 165 }