git-web--browse: Fix check for /bin/start
[git/git.git] / symlinks.c
CommitLineData
f859c846
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1#include "cache.h"
2
92604b46 3static struct cache_def {
bad4a54f 4 char path[PATH_MAX + 1];
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5 int len;
6 int flags;
09c93066 7 int track_flags;
bad4a54f 8 int prefix_len_stat_func;
92604b46 9} cache;
c40641b7 10
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11/*
12 * Returns the length (on a path component basis) of the longest
13 * common prefix match of 'name' and the cached path string.
14 */
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15static inline int longest_match_lstat_cache(int len, const char *name,
16 int *previous_slash)
c40641b7 17{
aeabab5c 18 int max_len, match_len = 0, match_len_prev = 0, i = 0;
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19
20 max_len = len < cache.len ? len : cache.len;
21 while (i < max_len && name[i] == cache.path[i]) {
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22 if (name[i] == '/') {
23 match_len_prev = match_len;
92604b46 24 match_len = i;
aeabab5c 25 }
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26 i++;
27 }
28 /* Is the cached path string a substring of 'name'? */
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29 if (i == cache.len && cache.len < len && name[cache.len] == '/') {
30 match_len_prev = match_len;
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31 match_len = cache.len;
32 /* Is 'name' a substring of the cached path string? */
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33 } else if ((i == len && len < cache.len && cache.path[len] == '/') ||
34 (i == len && len == cache.len)) {
35 match_len_prev = match_len;
92604b46 36 match_len = len;
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37 }
38 *previous_slash = match_len_prev;
92604b46 39 return match_len;
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40}
41
bad4a54f 42static inline void reset_lstat_cache(int track_flags, int prefix_len_stat_func)
c40641b7 43{
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44 cache.path[0] = '\0';
45 cache.len = 0;
46 cache.flags = 0;
09c93066 47 cache.track_flags = track_flags;
bad4a54f 48 cache.prefix_len_stat_func = prefix_len_stat_func;
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49}
50
92604b46 51#define FL_DIR (1 << 0)
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52#define FL_NOENT (1 << 1)
53#define FL_SYMLINK (1 << 2)
54#define FL_LSTATERR (1 << 3)
55#define FL_ERR (1 << 4)
bad4a54f 56#define FL_FULLPATH (1 << 5)
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57
58/*
59 * Check if name 'name' of length 'len' has a symlink leading
09c93066 60 * component, or if the directory exists and is real, or not.
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61 *
62 * To speed up the check, some information is allowed to be cached.
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63 * This can be indicated by the 'track_flags' argument, which also can
64 * be used to indicate that we should check the full path.
65 *
66 * The 'prefix_len_stat_func' parameter can be used to set the length
67 * of the prefix, where the cache should use the stat() function
68 * instead of the lstat() function to test each path component.
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69 */
70static int lstat_cache(int len, const char *name,
bad4a54f 71 int track_flags, int prefix_len_stat_func)
c40641b7 72{
aeabab5c 73 int match_len, last_slash, last_slash_dir, previous_slash;
bad4a54f 74 int match_flags, ret_flags, save_flags, max_len, ret;
c40641b7 75 struct stat st;
f859c846 76
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77 if (cache.track_flags != track_flags ||
78 cache.prefix_len_stat_func != prefix_len_stat_func) {
09c93066 79 /*
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80 * As a safeguard we clear the cache if the values of
81 * track_flags and/or prefix_len_stat_func does not
82 * match with the last supplied values.
09c93066 83 */
bad4a54f 84 reset_lstat_cache(track_flags, prefix_len_stat_func);
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85 match_len = last_slash = 0;
86 } else {
87 /*
88 * Check to see if we have a match from the cache for
89 * the 2 "excluding" path types.
90 */
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91 match_len = last_slash =
92 longest_match_lstat_cache(len, name, &previous_slash);
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93 match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
94 if (match_flags && match_len == cache.len)
95 return match_flags;
96 /*
97 * If we now have match_len > 0, we would know that
98 * the matched part will always be a directory.
99 *
100 * Also, if we are tracking directories and 'name' is
101 * a substring of the cache on a path component basis,
102 * we can return immediately.
103 */
104 match_flags = track_flags & FL_DIR;
105 if (match_flags && len == match_len)
106 return match_flags;
107 }
c40641b7 108
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109 /*
110 * Okay, no match from the cache so far, so now we have to
111 * check the rest of the path components.
112 */
113 ret_flags = FL_DIR;
114 last_slash_dir = last_slash;
115 max_len = len < PATH_MAX ? len : PATH_MAX;
116 while (match_len < max_len) {
117 do {
118 cache.path[match_len] = name[match_len];
119 match_len++;
120 } while (match_len < max_len && name[match_len] != '/');
bad4a54f 121 if (match_len >= max_len && !(track_flags & FL_FULLPATH))
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122 break;
123 last_slash = match_len;
124 cache.path[last_slash] = '\0';
f859c846 125
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126 if (last_slash <= prefix_len_stat_func)
127 ret = stat(cache.path, &st);
128 else
129 ret = lstat(cache.path, &st);
130
131 if (ret) {
92604b46 132 ret_flags = FL_LSTATERR;
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133 if (errno == ENOENT)
134 ret_flags |= FL_NOENT;
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135 } else if (S_ISDIR(st.st_mode)) {
136 last_slash_dir = last_slash;
c40641b7 137 continue;
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138 } else if (S_ISLNK(st.st_mode)) {
139 ret_flags = FL_SYMLINK;
140 } else {
141 ret_flags = FL_ERR;
f859c846 142 }
c40641b7 143 break;
f859c846 144 }
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145
146 /*
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147 * At the end update the cache. Note that max 3 different
148 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
149 * for the moment!
92604b46 150 */
09c93066 151 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
bad4a54f 152 if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
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153 cache.path[last_slash] = '\0';
154 cache.len = last_slash;
155 cache.flags = save_flags;
156 } else if (track_flags & FL_DIR &&
bad4a54f 157 last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
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158 /*
159 * We have a separate test for the directory case,
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160 * since it could be that we have found a symlink or a
161 * non-existing directory and the track_flags says
162 * that we cannot cache this fact, so the cache would
163 * then have been left empty in this case.
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164 *
165 * But if we are allowed to track real directories, we
166 * can still cache the path components before the last
09c93066 167 * one (the found symlink or non-existing component).
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168 */
169 cache.path[last_slash_dir] = '\0';
170 cache.len = last_slash_dir;
171 cache.flags = FL_DIR;
172 } else {
bad4a54f 173 reset_lstat_cache(track_flags, prefix_len_stat_func);
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174 }
175 return ret_flags;
176}
177
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178/*
179 * Invalidate the given 'name' from the cache, if 'name' matches
180 * completely with the cache.
181 */
182void invalidate_lstat_cache(int len, const char *name)
183{
184 int match_len, previous_slash;
185
186 match_len = longest_match_lstat_cache(len, name, &previous_slash);
187 if (len == match_len) {
188 if ((cache.track_flags & FL_DIR) && previous_slash > 0) {
189 cache.path[previous_slash] = '\0';
190 cache.len = previous_slash;
191 cache.flags = FL_DIR;
192 } else
193 reset_lstat_cache(cache.track_flags,
194 cache.prefix_len_stat_func);
195 }
196}
197
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198/*
199 * Completely clear the contents of the cache
200 */
201void clear_lstat_cache(void)
202{
203 reset_lstat_cache(0, 0);
204}
205
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206#define USE_ONLY_LSTAT 0
207
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208/*
209 * Return non-zero if path 'name' has a leading symlink component
210 */
211int has_symlink_leading_path(int len, const char *name)
212{
213 return lstat_cache(len, name,
bad4a54f 214 FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
92604b46 215 FL_SYMLINK;
f859c846 216}
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217
218/*
219 * Return non-zero if path 'name' has a leading symlink component or
220 * if some leading path component does not exists.
221 */
222int has_symlink_or_noent_leading_path(int len, const char *name)
223{
224 return lstat_cache(len, name,
bad4a54f 225 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
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226 (FL_SYMLINK|FL_NOENT);
227}
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228
229/*
230 * Return non-zero if all path components of 'name' exists as a
231 * directory. If prefix_len > 0, we will test with the stat()
232 * function instead of the lstat() function for a prefix length of
233 * 'prefix_len', thus we then allow for symlinks in the prefix part as
234 * long as those points to real existing directories.
235 */
236int has_dirs_only_path(int len, const char *name, int prefix_len)
237{
238 return lstat_cache(len, name,
239 FL_DIR|FL_FULLPATH, prefix_len) &
240 FL_DIR;
241}