Git 1.8.0.3
[git/git.git] / name-hash.c
CommitLineData
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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
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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
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23static unsigned int hash_name(const char *name, int namelen)
24{
25 unsigned int hash = 0x123;
26
27 do {
28 unsigned char c = *name++;
cd2fef59 29 c = icase_hash(c);
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30 hash = hash*101 + c;
31 } while (--namelen);
32 return hash;
33}
34
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35static void hash_index_entry_directories(struct index_state *istate, struct cache_entry *ce)
36{
37 /*
38 * Throw each directory component in the hash for quick lookup
39 * during a git status. Directory components are stored with their
40 * closing slash. Despite submodules being a directory, they never
41 * reach this point, because they are stored without a closing slash
42 * in the cache.
43 *
44 * Note that the cache_entry stored with the directory does not
45 * represent the directory itself. It is a pointer to an existing
46 * filename, and its only purpose is to represent existence of the
47 * directory in the cache. It is very possible multiple directory
48 * hash entries may point to the same cache_entry.
49 */
50 unsigned int hash;
51 void **pos;
52
53 const char *ptr = ce->name;
54 while (*ptr) {
55 while (*ptr && *ptr != '/')
56 ++ptr;
57 if (*ptr == '/') {
58 ++ptr;
59 hash = hash_name(ce->name, ptr - ce->name);
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60 pos = insert_hash(hash, ce, &istate->name_hash);
61 if (pos) {
62 ce->dir_next = *pos;
63 *pos = ce;
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64 }
65 }
66 }
67}
68
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69static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
70{
71 void **pos;
72 unsigned int hash;
73
74 if (ce->ce_flags & CE_HASHED)
75 return;
76 ce->ce_flags |= CE_HASHED;
395c7356 77 ce->next = ce->dir_next = NULL;
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78 hash = hash_name(ce->name, ce_namelen(ce));
79 pos = insert_hash(hash, ce, &istate->name_hash);
80 if (pos) {
81 ce->next = *pos;
82 *pos = ce;
83 }
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84
85 if (ignore_case)
86 hash_index_entry_directories(istate, ce);
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87}
88
89static void lazy_init_name_hash(struct index_state *istate)
90{
91 int nr;
92
93 if (istate->name_hash_initialized)
94 return;
95 for (nr = 0; nr < istate->cache_nr; nr++)
96 hash_index_entry(istate, istate->cache[nr]);
97 istate->name_hash_initialized = 1;
98}
99
100void add_name_hash(struct index_state *istate, struct cache_entry *ce)
101{
102 ce->ce_flags &= ~CE_UNHASHED;
103 if (istate->name_hash_initialized)
104 hash_index_entry(istate, ce);
105}
106
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107static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
108{
109 if (len1 != len2)
110 return 0;
111
112 while (len1) {
113 unsigned char c1 = *name1++;
114 unsigned char c2 = *name2++;
115 len1--;
116 if (c1 != c2) {
117 c1 = toupper(c1);
118 c2 = toupper(c2);
119 if (c1 != c2)
120 return 0;
121 }
122 }
123 return 1;
124}
125
126static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
127{
128 int len = ce_namelen(ce);
129
130 /*
131 * Always do exact compare, even if we want a case-ignoring comparison;
132 * we do the quick exact one first, because it will be the common case.
133 */
134 if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
135 return 1;
136
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137 if (!icase)
138 return 0;
139
140 /*
141 * If the entry we're comparing is a filename (no trailing slash), then compare
142 * the lengths exactly.
143 */
144 if (name[namelen - 1] != '/')
145 return slow_same_name(name, namelen, ce->name, len);
146
147 /*
148 * For a directory, we point to an arbitrary cache_entry filename. Just
149 * make sure the directory portion matches.
150 */
151 return slow_same_name(name, namelen, ce->name, namelen < len ? namelen : len);
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152}
153
154struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
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155{
156 unsigned int hash = hash_name(name, namelen);
157 struct cache_entry *ce;
158
159 lazy_init_name_hash(istate);
160 ce = lookup_hash(hash, &istate->name_hash);
161
162 while (ce) {
163 if (!(ce->ce_flags & CE_UNHASHED)) {
cd2fef59 164 if (same_name(ce, name, namelen, icase))
df292c79 165 return ce;
96872bc2 166 }
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167 if (icase && name[namelen - 1] == '/')
168 ce = ce->dir_next;
169 else
170 ce = ce->next;
96872bc2 171 }
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172
173 /*
174 * Might be a submodule. Despite submodules being directories,
175 * they are stored in the name hash without a closing slash.
176 * When ignore_case is 1, directories are stored in the name hash
177 * with their closing slash.
178 *
179 * The side effect of this storage technique is we have need to
180 * remove the slash from name and perform the lookup again without
181 * the slash. If a match is made, S_ISGITLINK(ce->mode) will be
182 * true.
183 */
184 if (icase && name[namelen - 1] == '/') {
185 ce = index_name_exists(istate, name, namelen - 1, icase);
186 if (ce && S_ISGITLINK(ce->ce_mode))
187 return ce;
188 }
df292c79 189 return NULL;
96872bc2 190}