lstat_cache(): introduce has_symlink_or_noent_leading_path() function
[git/git.git] / symlinks.c
CommitLineData
f859c846
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1#include "cache.h"
2
92604b46 3static struct cache_def {
f859c846 4 char path[PATH_MAX];
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5 int len;
6 int flags;
09c93066 7 int track_flags;
92604b46 8} cache;
c40641b7 9
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10/*
11 * Returns the length (on a path component basis) of the longest
12 * common prefix match of 'name' and the cached path string.
13 */
14static inline int longest_match_lstat_cache(int len, const char *name)
c40641b7 15{
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16 int max_len, match_len = 0, i = 0;
17
18 max_len = len < cache.len ? len : cache.len;
19 while (i < max_len && name[i] == cache.path[i]) {
20 if (name[i] == '/')
21 match_len = i;
22 i++;
23 }
24 /* Is the cached path string a substring of 'name'? */
25 if (i == cache.len && cache.len < len && name[cache.len] == '/')
26 match_len = cache.len;
27 /* Is 'name' a substring of the cached path string? */
28 else if ((i == len && len < cache.len && cache.path[len] == '/') ||
29 (i == len && len == cache.len))
30 match_len = len;
31 return match_len;
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32}
33
09c93066 34static inline void reset_lstat_cache(int track_flags)
c40641b7 35{
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36 cache.path[0] = '\0';
37 cache.len = 0;
38 cache.flags = 0;
09c93066 39 cache.track_flags = track_flags;
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40}
41
92604b46 42#define FL_DIR (1 << 0)
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43#define FL_NOENT (1 << 1)
44#define FL_SYMLINK (1 << 2)
45#define FL_LSTATERR (1 << 3)
46#define FL_ERR (1 << 4)
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47
48/*
49 * Check if name 'name' of length 'len' has a symlink leading
09c93066 50 * component, or if the directory exists and is real, or not.
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51 *
52 * To speed up the check, some information is allowed to be cached.
53 * This can be indicated by the 'track_flags' argument.
54 */
55static int lstat_cache(int len, const char *name,
56 int track_flags)
c40641b7 57{
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58 int match_len, last_slash, last_slash_dir;
59 int match_flags, ret_flags, save_flags, max_len;
c40641b7 60 struct stat st;
f859c846 61
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62 if (cache.track_flags != track_flags) {
63 /*
64 * As a safeguard we clear the cache if the value of
65 * track_flags does not match with the last supplied
66 * value.
67 */
68 reset_lstat_cache(track_flags);
69 match_len = last_slash = 0;
70 } else {
71 /*
72 * Check to see if we have a match from the cache for
73 * the 2 "excluding" path types.
74 */
75 match_len = last_slash = longest_match_lstat_cache(len, name);
76 match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
77 if (match_flags && match_len == cache.len)
78 return match_flags;
79 /*
80 * If we now have match_len > 0, we would know that
81 * the matched part will always be a directory.
82 *
83 * Also, if we are tracking directories and 'name' is
84 * a substring of the cache on a path component basis,
85 * we can return immediately.
86 */
87 match_flags = track_flags & FL_DIR;
88 if (match_flags && len == match_len)
89 return match_flags;
90 }
c40641b7 91
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92 /*
93 * Okay, no match from the cache so far, so now we have to
94 * check the rest of the path components.
95 */
96 ret_flags = FL_DIR;
97 last_slash_dir = last_slash;
98 max_len = len < PATH_MAX ? len : PATH_MAX;
99 while (match_len < max_len) {
100 do {
101 cache.path[match_len] = name[match_len];
102 match_len++;
103 } while (match_len < max_len && name[match_len] != '/');
104 if (match_len >= max_len)
105 break;
106 last_slash = match_len;
107 cache.path[last_slash] = '\0';
f859c846 108
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109 if (lstat(cache.path, &st)) {
110 ret_flags = FL_LSTATERR;
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111 if (errno == ENOENT)
112 ret_flags |= FL_NOENT;
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113 } else if (S_ISDIR(st.st_mode)) {
114 last_slash_dir = last_slash;
c40641b7 115 continue;
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116 } else if (S_ISLNK(st.st_mode)) {
117 ret_flags = FL_SYMLINK;
118 } else {
119 ret_flags = FL_ERR;
f859c846 120 }
c40641b7 121 break;
f859c846 122 }
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123
124 /*
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125 * At the end update the cache. Note that max 3 different
126 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
127 * for the moment!
92604b46 128 */
09c93066 129 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
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130 if (save_flags && last_slash > 0 && last_slash < PATH_MAX) {
131 cache.path[last_slash] = '\0';
132 cache.len = last_slash;
133 cache.flags = save_flags;
134 } else if (track_flags & FL_DIR &&
135 last_slash_dir > 0 && last_slash_dir < PATH_MAX) {
136 /*
137 * We have a separate test for the directory case,
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138 * since it could be that we have found a symlink or a
139 * non-existing directory and the track_flags says
140 * that we cannot cache this fact, so the cache would
141 * then have been left empty in this case.
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142 *
143 * But if we are allowed to track real directories, we
144 * can still cache the path components before the last
09c93066 145 * one (the found symlink or non-existing component).
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146 */
147 cache.path[last_slash_dir] = '\0';
148 cache.len = last_slash_dir;
149 cache.flags = FL_DIR;
150 } else {
09c93066 151 reset_lstat_cache(track_flags);
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152 }
153 return ret_flags;
154}
155
156/*
157 * Return non-zero if path 'name' has a leading symlink component
158 */
159int has_symlink_leading_path(int len, const char *name)
160{
161 return lstat_cache(len, name,
162 FL_SYMLINK|FL_DIR) &
163 FL_SYMLINK;
f859c846 164}
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165
166/*
167 * Return non-zero if path 'name' has a leading symlink component or
168 * if some leading path component does not exists.
169 */
170int has_symlink_or_noent_leading_path(int len, const char *name)
171{
172 return lstat_cache(len, name,
173 FL_SYMLINK|FL_NOENT|FL_DIR) &
174 (FL_SYMLINK|FL_NOENT);
175}