name-hash.c

   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  */
  18 static inline unsigned char icase_hash(unsigned char c)
  19 {
  20         return c & ~((c & 0x40) >> 1);
  21 }
  22
  23 static 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
  35 static 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
  52 static 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
  63 void 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
  70 static 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
  89 static 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
 103 struct 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 }