Andrew's git - gitweb.git/blob

   1/*
   2 * name-hash.c
   3 *
   4 * Hashing names in the index state
   5 *
   6 * Copyright (C) 2008 Linus Torvalds
   7 */
   8#define NO_THE_INDEX_COMPATIBILITY_MACROS
   9#include "cache.h"
  10
  11/*
  12 * This removes bit 5 if bit 6 is set.
  13 *
  14 * That will make US-ASCII characters hash to their upper-case
  15 * equivalent. We could easily do this one whole word at a time,
  16 * but that's for future worries.
  17 */
  18static inline unsigned char icase_hash(unsigned char c)
  19{
  20        return c & ~((c & 0x40) >> 1);
  21}
  22
  23static unsigned int hash_name(const char *name, int namelen)
  24{
  25        unsigned int hash = 0x123;
  26
  27        do {
  28                unsigned char c = *name++;
  29                c = icase_hash(c);
  30                hash = hash*101 + c;
  31        } while (--namelen);
  32        return hash;
  33}
  34
  35static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
  36{
  37        void **pos;
  38        unsigned int hash;
  39
  40        if (ce->ce_flags & CE_HASHED)
  41                return;
  42        ce->ce_flags |= CE_HASHED;
  43        ce->next = NULL;
  44        hash = hash_name(ce->name, ce_namelen(ce));
  45        pos = insert_hash(hash, ce, &istate->name_hash);
  46        if (pos) {
  47                ce->next = *pos;
  48                *pos = ce;
  49        }
  50}
  51
  52static void lazy_init_name_hash(struct index_state *istate)
  53{
  54        int nr;
  55
  56        if (istate->name_hash_initialized)
  57                return;
  58        for (nr = 0; nr < istate->cache_nr; nr++)
  59                hash_index_entry(istate, istate->cache[nr]);
  60        istate->name_hash_initialized = 1;
  61}
  62
  63void add_name_hash(struct index_state *istate, struct cache_entry *ce)
  64{
  65        ce->ce_flags &= ~CE_UNHASHED;
  66        if (istate->name_hash_initialized)
  67                hash_index_entry(istate, ce);
  68}
  69
  70static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
  71{
  72        if (len1 != len2)
  73                return 0;
  74
  75        while (len1) {
  76                unsigned char c1 = *name1++;
  77                unsigned char c2 = *name2++;
  78                len1--;
  79                if (c1 != c2) {
  80                        c1 = toupper(c1);
  81                        c2 = toupper(c2);
  82                        if (c1 != c2)
  83                                return 0;
  84                }
  85        }
  86        return 1;
  87}
  88
  89static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
  90{
  91        int len = ce_namelen(ce);
  92
  93        /*
  94         * Always do exact compare, even if we want a case-ignoring comparison;
  95         * we do the quick exact one first, because it will be the common case.
  96         */
  97        if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
  98                return 1;
  99
 100        return icase && slow_same_name(name, namelen, ce->name, len);
 101}
 102
 103struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
 104{
 105        unsigned int hash = hash_name(name, namelen);
 106        struct cache_entry *ce;
 107
 108        lazy_init_name_hash(istate);
 109        ce = lookup_hash(hash, &istate->name_hash);
 110
 111        while (ce) {
 112                if (!(ce->ce_flags & CE_UNHASHED)) {
 113                        if (same_name(ce, name, namelen, icase))
 114                                return ce;
 115                }
 116                ce = ce->next;
 117        }
 118        return NULL;
 119}