1 | /* |
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2 | * shvar.c |
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3 | * |
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4 | * Implementation of non-destructively reading/writing files containing |
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5 | * only shell variable declarations and full-line comments. |
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6 | * |
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7 | * Includes explicit inheritance mechanism intended for use with |
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8 | * Red Hat Linux ifcfg-* files. There is no protection against |
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9 | * inheritance loops; they will generally cause stack overflows. |
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10 | * Furthermore, they are only intended for one level of inheritance; |
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11 | * the value setting algorithm assumes this. |
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12 | * |
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13 | * Copyright 1999,2000 Red Hat, Inc. |
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14 | * |
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15 | * This is free software; you can redistribute it and/or modify it |
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16 | * under the terms of the GNU General Public License as published by |
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17 | * the Free Software Foundation; either version 2 of the License, or |
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18 | * (at your option) any later version. |
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19 | * |
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20 | * This program is distributed in the hope that it will be useful, but |
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21 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
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22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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23 | * General Public License for more details. |
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24 | * |
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25 | * You should have received a copy of the GNU General Public License |
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26 | * along with this program; if not, write to the Free Software |
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27 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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28 | * |
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29 | */ |
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30 | |
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31 | #include <fcntl.h> |
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32 | #include <stdio.h> |
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33 | #include <stdlib.h> |
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34 | #include <string.h> |
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35 | #include <sys/types.h> |
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36 | #include <sys/stat.h> |
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37 | #include <unistd.h> |
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38 | |
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39 | #include "shvar.h" |
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40 | |
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41 | /* Open the file <name>, returning a shvarFile on success and NULL on failure. |
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42 | Add a wrinkle to let the caller specify whether or not to create the file |
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43 | (actually, return a structure anyway) if it doesn't exist. */ |
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44 | static shvarFile * |
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45 | svOpenFile(const char *name, gboolean create) |
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46 | { |
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47 | shvarFile *s = NULL; |
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48 | int closefd = 0; |
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49 | |
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50 | s = g_malloc0(sizeof(shvarFile)); |
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51 | |
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52 | s->fd = open(name, O_RDWR); /* NOT O_CREAT */ |
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53 | if (s->fd == -1) { |
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54 | /* try read-only */ |
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55 | s->fd = open(name, O_RDONLY); /* NOT O_CREAT */ |
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56 | if (s->fd != -1) closefd = 1; |
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57 | } |
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58 | s->fileName = g_strdup(name); |
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59 | |
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60 | if (s->fd != -1) { |
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61 | struct stat buf; |
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62 | char *p, *q; |
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63 | |
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64 | if (fstat(s->fd, &buf) < 0) goto bail; |
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65 | s->arena = g_malloc0(buf.st_size + 1); |
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66 | |
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67 | if (read(s->fd, s->arena, buf.st_size) < 0) goto bail; |
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68 | |
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69 | /* we'd use g_strsplit() here, but we want a list, not an array */ |
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70 | for(p = s->arena; (q = strchr(p, '\n')) != NULL; p = q + 1) { |
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71 | s->lineList = g_list_append(s->lineList, g_strndup(p, q - p)); |
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72 | } |
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73 | |
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74 | /* closefd is set if we opened the file read-only, so go ahead and |
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75 | close it, because we can't write to it anyway */ |
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76 | if (closefd) { |
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77 | close(s->fd); |
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78 | s->fd = -1; |
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79 | } |
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80 | |
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81 | return s; |
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82 | } |
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83 | |
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84 | if (create) { |
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85 | return s; |
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86 | } |
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87 | |
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88 | bail: |
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89 | if (s->fd != -1) close(s->fd); |
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90 | if (s->arena) g_free (s->arena); |
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91 | if (s->fileName) g_free (s->fileName); |
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92 | g_free (s); |
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93 | return NULL; |
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94 | } |
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95 | |
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96 | /* Open the file <name>, return shvarFile on success, NULL on failure */ |
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97 | shvarFile * |
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98 | svNewFile(const char *name) |
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99 | { |
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100 | return svOpenFile(name, FALSE); |
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101 | } |
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102 | |
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103 | /* Create a new file structure, returning actual data if the file exists, |
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104 | * and a suitable starting point if it doesn't. */ |
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105 | shvarFile * |
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106 | svCreateFile(const char *name) |
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107 | { |
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108 | return svOpenFile(name, TRUE); |
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109 | } |
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110 | |
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111 | /* remove escaped characters in place */ |
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112 | static void |
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113 | unescape(char *s) { |
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114 | int len, i; |
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115 | |
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116 | len = strlen(s); |
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117 | if ((s[0] == '"' || s[0] == '\'') && s[0] == s[len-1]) { |
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118 | i = len - 2; |
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119 | memmove(s, s+1, i); |
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120 | s[i+1] = '\0'; |
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121 | len = i; |
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122 | } |
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123 | for (i = 0; i < len; i++) { |
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124 | if (s[i] == '\\') { |
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125 | memmove(s+i, s+i+1, len-(i+1)); |
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126 | len--; |
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127 | } |
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128 | s[len] = '\0'; |
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129 | } |
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130 | } |
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131 | |
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132 | |
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133 | /* create a new string with all necessary characters escaped. |
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134 | * caller must free returned string |
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135 | */ |
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136 | static const char escapees[] = "\"'\\$~`"; /* must be escaped */ |
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137 | static const char spaces[] = " \t|&;()<>"; /* only require "" */ |
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138 | static char * |
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139 | escape(const char *s) { |
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140 | char *new; |
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141 | int i, j, mangle = 0, space = 0; |
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142 | int newlen, slen; |
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143 | static int esclen, splen; |
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144 | |
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145 | if (!esclen) esclen = strlen(escapees); |
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146 | if (!splen) splen = strlen(spaces); |
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147 | slen = strlen(s); |
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148 | |
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149 | for (i = 0; i < slen; i++) { |
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150 | if (strchr(escapees, s[i])) mangle++; |
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151 | if (strchr(spaces, s[i])) space++; |
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152 | } |
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153 | if (!mangle && !space) return strdup(s); |
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154 | |
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155 | newlen = slen + mangle + 3; /* 3 is extra ""\0 */ |
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156 | new = g_malloc0(newlen); |
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157 | if (!new) return NULL; |
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158 | |
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159 | j = 0; |
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160 | new[j++] = '"'; |
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161 | for (i = 0; i < slen; i++) { |
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162 | if (strchr(escapees, s[i])) { |
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163 | new[j++] = '\\'; |
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164 | } |
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165 | new[j++] = s[i]; |
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166 | } |
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167 | new[j++] = '"'; |
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168 | g_assert(j == slen + mangle + 2); /* j is the index of the '\0' */ |
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169 | |
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170 | return new; |
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171 | } |
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172 | |
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173 | /* Get the value associated with the key, and leave the current pointer |
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174 | * pointing at the line containing the value. The char* returned MUST |
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175 | * be freed by the caller. |
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176 | */ |
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177 | char * |
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178 | svGetValue(shvarFile *s, const char *key) |
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179 | { |
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180 | char *value = NULL; |
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181 | char *line; |
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182 | char *keyString; |
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183 | int len; |
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184 | |
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185 | g_assert(s); |
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186 | g_assert(key); |
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187 | |
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188 | keyString = g_malloc0(strlen(key) + 2); |
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189 | strcpy(keyString, key); |
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190 | keyString[strlen(key)] = '='; |
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191 | len = strlen(keyString); |
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192 | |
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193 | for (s->current = s->lineList; s->current; s->current = s->current->next) { |
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194 | line = s->current->data; |
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195 | if (!strncmp(keyString, line, len)) { |
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196 | value = g_strdup(line + len); |
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197 | unescape(value); |
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198 | break; |
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199 | } |
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200 | } |
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201 | g_free(keyString); |
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202 | |
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203 | if (value) { |
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204 | if (value[0]) { |
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205 | return value; |
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206 | } else { |
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207 | g_free(value); |
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208 | return NULL; |
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209 | } |
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210 | } |
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211 | if (s->parent) value = svGetValue(s->parent, key); |
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212 | return value; |
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213 | } |
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214 | |
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215 | /* return 1 if <key> resolves to any truth value (e.g. "yes", "y", "true") |
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216 | * return 0 if <key> resolves to any non-truth value (e.g. "no", "n", "false") |
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217 | * return <default> otherwise |
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218 | */ |
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219 | int |
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220 | svTrueValue(shvarFile *s, const char *key, int def) |
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221 | { |
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222 | char *tmp; |
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223 | int returnValue = def; |
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224 | |
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225 | tmp = svGetValue(s, key); |
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226 | if (!tmp) return returnValue; |
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227 | |
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228 | if ( (!strcasecmp("yes", tmp)) || |
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229 | (!strcasecmp("true", tmp)) || |
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230 | (!strcasecmp("t", tmp)) || |
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231 | (!strcasecmp("y", tmp)) ) returnValue = 1; |
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232 | else |
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233 | if ( (!strcasecmp("no", tmp)) || |
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234 | (!strcasecmp("false", tmp)) || |
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235 | (!strcasecmp("f", tmp)) || |
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236 | (!strcasecmp("n", tmp)) ) returnValue = 0; |
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237 | |
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238 | g_free (tmp); |
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239 | return returnValue; |
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240 | } |
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241 | |
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242 | |
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243 | /* Set the variable <key> equal to the value <value>. |
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244 | * If <key> does not exist, and the <current> pointer is set, append |
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245 | * the key=value pair after that line. Otherwise, prepend the pair |
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246 | * to the top of the file. Here's the algorithm, as the C code |
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247 | * seems to be rather dense: |
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248 | * |
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249 | * if (value == NULL), then: |
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250 | * if val2 (parent): change line to key= or append line key= |
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251 | * if val1 (this) : delete line |
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252 | * else noop |
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253 | * else use this table: |
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254 | * val2 |
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255 | * NULL value other |
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256 | * v NULL append line noop append line |
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257 | * a |
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258 | * l value noop noop noop |
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259 | * 1 |
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260 | * other change line delete line change line |
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261 | * |
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262 | * No changes are ever made to the parent config file, only to the |
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263 | * specific file passed on the command line. |
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264 | * |
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265 | */ |
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266 | void |
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267 | svSetValue(shvarFile *s, const char *key, const char *value) |
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268 | { |
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269 | char *newval = NULL, *val1 = NULL, *val2 = NULL; |
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270 | char *keyValue; |
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271 | |
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272 | g_assert(s); |
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273 | g_assert(key); |
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274 | /* value may be NULL */ |
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275 | |
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276 | if (value) newval = escape(value); |
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277 | keyValue = g_strdup_printf("%s=%s", key, newval ? newval : ""); |
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278 | |
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279 | val1 = svGetValue(s, key); |
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280 | if (val1 && newval && !strcmp(val1, newval)) goto bail; |
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281 | if (s->parent) val2 = svGetValue(s->parent, key); |
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282 | |
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283 | if (!newval || !newval[0]) { |
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284 | /* delete value somehow */ |
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285 | if (val2) { |
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286 | /* change/append line to get key= */ |
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287 | if (s->current) s->current->data = keyValue; |
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288 | else s->lineList = g_list_append(s->lineList, keyValue); |
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289 | s->freeList = g_list_append(s->freeList, keyValue); |
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290 | s->modified = 1; |
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291 | } else if (val1) { |
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292 | /* delete line */ |
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293 | s->lineList = g_list_remove_link(s->lineList, s->current); |
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294 | g_list_free_1(s->current); |
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295 | s->modified = 1; |
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296 | goto bail; /* do not need keyValue */ |
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297 | } |
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298 | goto end; |
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299 | } |
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300 | |
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301 | if (!val1) { |
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302 | if (val2 && !strcmp(val2, newval)) goto end; |
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303 | /* append line */ |
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304 | s->lineList = g_list_append(s->lineList, keyValue); |
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305 | s->freeList = g_list_append(s->freeList, keyValue); |
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306 | s->modified = 1; |
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307 | goto end; |
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308 | } |
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309 | |
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310 | /* deal with a whole line of noops */ |
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311 | if (val1 && !strcmp(val1, newval)) goto end; |
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312 | |
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313 | /* At this point, val1 && val1 != value */ |
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314 | if (val2 && !strcmp(val2, newval)) { |
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315 | /* delete line */ |
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316 | s->lineList = g_list_remove_link(s->lineList, s->current); |
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317 | g_list_free_1(s->current); |
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318 | s->modified = 1; |
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319 | goto bail; /* do not need keyValue */ |
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320 | } else { |
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321 | /* change line */ |
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322 | if (s->current) s->current->data = keyValue; |
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323 | else s->lineList = g_list_append(s->lineList, keyValue); |
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324 | s->freeList = g_list_append(s->freeList, keyValue); |
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325 | s->modified = 1; |
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326 | } |
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327 | |
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328 | end: |
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329 | if (newval) free(newval); |
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330 | if (val1) free(val1); |
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331 | if (val2) free(val2); |
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332 | return; |
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333 | |
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334 | bail: |
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335 | if (keyValue) free (keyValue); |
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336 | goto end; |
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337 | } |
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338 | |
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339 | /* Write the current contents iff modified. Returns -1 on error |
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340 | * and 0 on success. Do not write if no values have been modified. |
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341 | * The mode argument is only used if creating the file, not if |
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342 | * re-writing an existing file, and is passed unchanged to the |
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343 | * open() syscall. |
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344 | */ |
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345 | int |
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346 | svWriteFile(shvarFile *s, int mode) |
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347 | { |
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348 | FILE *f; |
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349 | int tmpfd; |
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350 | |
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351 | if (s->modified) { |
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352 | if (s->fd == -1) |
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353 | s->fd = open(s->fileName, O_WRONLY|O_CREAT, mode); |
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354 | if (s->fd == -1) |
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355 | return -1; |
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356 | if (ftruncate(s->fd, 0) < 0) |
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357 | return -1; |
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358 | |
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359 | tmpfd = dup(s->fd); |
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360 | f = fdopen(tmpfd, "w"); |
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361 | fseek(f, 0, SEEK_SET); |
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362 | for (s->current = s->lineList; s->current; s->current = s->current->next) { |
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363 | char *line = s->current->data; |
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364 | fprintf(f, "%s\n", line); |
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365 | } |
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366 | fclose(f); |
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367 | } |
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368 | |
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369 | return 0; |
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370 | } |
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371 | |
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372 | |
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373 | /* Close the file descriptor (if open) and delete the shvarFile. |
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374 | * Returns -1 on error and 0 on success. |
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375 | */ |
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376 | int |
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377 | svCloseFile(shvarFile *s) |
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378 | { |
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379 | |
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380 | g_assert(s); |
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381 | |
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382 | if (s->fd != -1) close(s->fd); |
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383 | |
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384 | g_free(s->arena); |
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385 | for (s->current = s->freeList; s->current; s->current = s->current->next) { |
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386 | g_free(s->current->data); |
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387 | } |
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388 | g_free(s->fileName); |
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389 | g_list_free(s->freeList); |
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390 | g_list_free(s->lineList); /* implicitly frees s->current */ |
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391 | g_free(s); |
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392 | return 0; |
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393 | } |
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