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| 2753 | jermar | 1 | /* |
| 2 | * Copyright (c) 2008 Jakub Jermar |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * |
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| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | * - Redistributions in binary form must reproduce the above copyright |
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| 12 | * notice, this list of conditions and the following disclaimer in the |
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| 13 | * documentation and/or other materials provided with the distribution. |
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| 14 | * - The name of the author may not be used to endorse or promote products |
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| 15 | * derived from this software without specific prior written permission. |
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| 16 | * |
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 27 | */ |
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| 28 | |||
| 29 | /** @addtogroup libc |
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| 30 | * @{ |
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| 31 | */ |
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| 32 | |||
| 33 | /** |
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| 34 | * @file |
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| 35 | * @brief |
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| 36 | */ |
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| 37 | |||
| 38 | #include <stdlib.h> |
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| 39 | |||
| 40 | /** Token types used for tokenization of path. */ |
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| 41 | typedef enum { |
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| 42 | TK_INVALID, |
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| 43 | TK_SLASH, |
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| 44 | TK_DOT, |
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| 45 | TK_DOTDOT, |
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| 46 | TK_COMP, |
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| 47 | TK_NUL |
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| 48 | } tokval_t; |
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| 49 | |||
| 50 | typedef struct { |
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| 51 | tokval_t kind; |
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| 52 | char *start; |
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| 53 | char *stop; |
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| 54 | } token_t; |
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| 55 | |||
| 56 | /** Fake up the TK_SLASH token. */ |
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| 57 | static token_t slash_token(char *start) |
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| 58 | { |
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| 59 | token_t ret; |
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| 60 | ret.kind = TK_SLASH; |
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| 61 | ret.start = start; |
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| 62 | ret.stop = start; |
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| 63 | return ret; |
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| 64 | } |
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| 65 | |||
| 66 | /** Given a token, return the next token. */ |
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| 67 | static token_t next_token(token_t *cur) |
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| 68 | { |
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| 69 | token_t ret; |
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| 70 | |||
| 71 | if (cur->stop[1] == '\0') { |
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| 72 | ret.kind = TK_NUL; |
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| 73 | ret.start = cur->stop + 1; |
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| 74 | ret.stop = ret.start; |
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| 75 | return ret; |
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| 76 | } |
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| 77 | if (cur->stop[1] == '/') { |
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| 78 | ret.kind = TK_SLASH; |
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| 79 | ret.start = cur->stop + 1; |
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| 80 | ret.stop = ret.start; |
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| 81 | return ret; |
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| 82 | } |
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| 83 | if (cur->stop[1] == '.' && (!cur->stop[2] || cur->stop[2] == '/')) { |
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| 84 | ret.kind = TK_DOT; |
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| 85 | ret.start = cur->stop + 1; |
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| 86 | ret.stop = ret.start; |
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| 87 | return ret; |
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| 88 | } |
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| 89 | if (cur->stop[1] == '.' && cur->stop[2] == '.' && |
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| 90 | (!cur->stop[3] || cur->stop[3] == '/')) { |
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| 91 | ret.kind = TK_DOTDOT; |
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| 92 | ret.start = cur->stop + 1; |
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| 93 | ret.stop = cur->stop + 2; |
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| 94 | return ret; |
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| 95 | } |
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| 96 | unsigned i; |
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| 97 | for (i = 1; cur->stop[i] && cur->stop[i] != '/'; i++) |
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| 98 | ; |
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| 99 | ret.kind = TK_COMP; |
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| 100 | ret.start = &cur->stop[1]; |
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| 101 | ret.stop = &cur->stop[i - 1]; |
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| 102 | return ret; |
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| 103 | } |
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| 104 | |||
| 105 | /** States used by canonify(). */ |
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| 106 | typedef enum { |
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| 107 | S_INI, |
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| 108 | S_A, |
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| 109 | S_B, |
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| 110 | S_C, |
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| 111 | S_ACCEPT, |
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| 112 | S_RESTART, |
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| 113 | S_REJECT |
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| 114 | } state_t; |
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| 115 | |||
| 116 | typedef struct { |
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| 117 | state_t s; |
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| 118 | void (* f)(token_t *, token_t *, token_t *); |
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| 119 | } change_state_t; |
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| 120 | |||
| 121 | /* |
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| 122 | * Actions that can be performed when transitioning from one |
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| 123 | * state of canonify() to another. |
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| 124 | */ |
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| 125 | static void set_first_slash(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 126 | { |
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| 127 | *tfsl = *t; |
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| 128 | } |
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| 129 | static void save_component(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 130 | { |
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| 131 | *tlcomp = *t; |
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| 132 | } |
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| 133 | static void terminate_slash(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 134 | { |
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| 135 | if (tfsl->stop[1]) /* avoid writing to a well-formatted path */ |
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| 136 | tfsl->stop[1] = '\0'; |
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| 137 | } |
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| 138 | static void remove_trailing_slash(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 139 | { |
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| 140 | t->start[-1] = '\0'; |
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| 141 | } |
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| 142 | /** Eat the extra '/'.. |
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| 143 | * |
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| 144 | * @param t The current TK_SLASH token. |
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| 145 | */ |
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| 146 | static void shift_slash(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 147 | { |
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| 148 | char *p = t->start; |
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| 149 | char *q = t->stop + 1; |
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| 150 | while ((*p++ = *q++)) |
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| 151 | ; |
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| 152 | } |
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| 153 | /** Eat the extra '.'. |
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| 154 | * |
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| 155 | * @param t The current TK_DOT token. |
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| 156 | */ |
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| 157 | static void shift_dot(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 158 | { |
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| 159 | char *p = t->start; |
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| 160 | char *q = t->stop + 1; |
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| 161 | while ((*p++ = *q++)) |
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| 162 | ; |
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| 163 | } |
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| 164 | /** Collapse the TK_COMP TK_SLASH TK_DOTDOT pattern. |
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| 165 | * |
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| 166 | * @param t The current TK_DOTDOT token. |
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| 167 | * @param tlcomp The last TK_COMP token. |
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| 168 | */ |
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| 169 | static void shift_dotdot(token_t *t, token_t *tfsl, token_t *tlcomp) |
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| 170 | { |
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| 171 | char *p = tlcomp->start; |
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| 172 | char *q = t->stop + 1; |
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| 173 | while ((*p++ = *q++)) |
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| 174 | ; |
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| 175 | } |
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| 176 | |||
| 177 | /** Transition function for canonify(). */ |
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| 178 | static change_state_t trans[4][6] = { |
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| 179 | [S_INI] = { |
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| 180 | [TK_SLASH] = { |
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| 181 | .s = S_A, |
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| 182 | .f = set_first_slash, |
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| 183 | }, |
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| 184 | [TK_DOT] = { |
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| 185 | .s = S_REJECT, |
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| 186 | .f = NULL, |
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| 187 | }, |
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| 188 | [TK_DOTDOT] = { |
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| 189 | .s = S_REJECT, |
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| 190 | .f = NULL, |
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| 191 | }, |
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| 192 | [TK_COMP] = { |
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| 193 | .s = S_REJECT, |
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| 194 | .f = NULL, |
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| 195 | }, |
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| 196 | [TK_NUL] = { |
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| 197 | .s = S_REJECT, |
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| 198 | .f = NULL, |
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| 199 | }, |
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| 200 | [TK_INVALID] = { |
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| 201 | .s = S_REJECT, |
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| 202 | .f = NULL, |
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| 203 | }, |
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| 204 | }, |
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| 205 | [S_A] = { |
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| 206 | [TK_SLASH] = { |
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| 207 | .s = S_A, |
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| 208 | .f = set_first_slash, |
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| 209 | }, |
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| 210 | [TK_DOT] = { |
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| 211 | .s = S_A, |
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| 212 | .f = NULL, |
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| 213 | }, |
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| 214 | [TK_DOTDOT] = { |
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| 215 | .s = S_A, |
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| 216 | .f = NULL, |
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| 217 | }, |
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| 218 | [TK_COMP] = { |
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| 219 | .s = S_B, |
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| 220 | .f = save_component, |
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| 221 | }, |
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| 222 | [TK_NUL] = { |
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| 223 | .s = S_ACCEPT, |
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| 224 | .f = terminate_slash, |
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| 225 | }, |
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| 226 | [TK_INVALID] = { |
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| 227 | .s = S_REJECT, |
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| 228 | .f = NULL, |
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| 229 | }, |
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| 230 | }, |
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| 231 | [S_B] = { |
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| 232 | [TK_SLASH] = { |
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| 233 | .s = S_C, |
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| 234 | .f = NULL, |
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| 235 | }, |
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| 236 | [TK_DOT] = { |
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| 237 | .s = S_REJECT, |
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| 238 | .f = NULL, |
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| 239 | }, |
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| 240 | [TK_DOTDOT] = { |
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| 241 | .s = S_REJECT, |
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| 242 | .f = NULL, |
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| 243 | }, |
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| 244 | [TK_COMP] = { |
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| 245 | .s = S_REJECT, |
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| 246 | .f = NULL, |
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| 247 | }, |
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| 248 | [TK_NUL] = { |
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| 249 | .s = S_ACCEPT, |
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| 250 | .f = NULL, |
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| 251 | }, |
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| 252 | [TK_INVALID] = { |
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| 253 | .s = S_REJECT, |
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| 254 | .f = NULL, |
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| 255 | }, |
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| 256 | }, |
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| 257 | [S_C] = { |
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| 258 | [TK_SLASH] = { |
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| 259 | .s = S_RESTART, |
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| 260 | .f = shift_slash, |
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| 261 | }, |
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| 262 | [TK_DOT] = { |
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| 263 | .s = S_RESTART, |
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| 264 | .f = shift_dot, |
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| 265 | }, |
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| 266 | [TK_DOTDOT] = { |
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| 267 | .s = S_RESTART, |
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| 268 | .f = shift_dotdot, |
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| 269 | }, |
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| 270 | [TK_COMP] = { |
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| 271 | .s = S_B, |
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| 272 | .f = save_component, |
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| 273 | }, |
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| 274 | [TK_NUL] = { |
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| 275 | .s = S_ACCEPT, |
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| 276 | .f = remove_trailing_slash, |
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| 277 | }, |
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| 278 | [TK_INVALID] = { |
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| 279 | .s = S_REJECT, |
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| 280 | .f = NULL, |
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| 281 | }, |
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| 282 | } |
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| 283 | }; |
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| 284 | |||
| 285 | /** Canonify a file system path. |
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| 286 | * |
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| 287 | * A file system path is canonical, if the following holds: |
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| 288 | * 1) the path is absolute (i.e. a/b/c is not canonical) |
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| 289 | * 2) there is no trailing slash in the path (i.e. /a/b/c is not canonical) |
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| 290 | * 3) there is no extra slash in the path (i.e. /a//b/c is not canonical) |
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| 291 | * 4) there is no '.' component in the path (i.e. /a/./b/c is not canonical) |
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| 292 | * 5) there is no '..' component in the path (i.e. /a/b/../c is not canonical) |
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| 293 | * |
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| 294 | * This function makes a potentially non-canonical file system path canonical. |
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| 295 | * It works in-place and requires a NULL-terminated input string. |
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| 296 | * |
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| 297 | * @param path Path to be canonified. |
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| 298 | * @param lenp Pointer where the length of the final path will be |
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| 299 | * stored. Can be NULL. |
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| 300 | * |
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| 301 | * @return Canonified path or NULL on failure. |
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| 302 | */ |
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| 303 | char *canonify(char *path, size_t *lenp) |
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| 304 | { |
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| 305 | state_t state; |
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| 306 | token_t t; |
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| 307 | token_t tfsl; /* first slash */ |
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| 308 | token_t tlcomp; /* last component */ |
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| 309 | if (*path != '/') |
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| 310 | return NULL; |
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| 311 | tfsl = slash_token(path); |
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| 312 | restart: |
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| 313 | state = S_INI; |
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| 314 | t = tfsl; |
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| 315 | tlcomp = tfsl; |
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| 316 | while (state != S_ACCEPT && state != S_RESTART && state != S_REJECT) { |
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| 317 | if (trans[state][t.kind].f) |
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| 318 | trans[state][t.kind].f(&t, &tfsl, &tlcomp); |
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| 319 | state = trans[state][t.kind].s; |
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| 320 | t = next_token(&t); |
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| 321 | } |
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| 322 | |||
| 323 | switch (state) { |
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| 324 | case S_RESTART: |
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| 325 | goto restart; |
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| 326 | case S_REJECT: |
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| 327 | return NULL; |
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| 328 | case S_ACCEPT: |
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| 329 | if (lenp) |
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| 330 | *lenp = (size_t)((tlcomp.stop - tfsl.start) + 1); |
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| 331 | return tfsl.start; |
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| 332 | default: |
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| 333 | abort(); |
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| 334 | } |
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| 335 | } |
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| 336 | |||
| 337 | /** |
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| 338 | * @} |
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| 339 | */ |