1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "base/environment.h" 6 7 #include <stddef.h> 8 9 #include <vector> 10 11 #include "base/memory/ptr_util.h" 12 #include "base/strings/string_piece.h" 13 #include "base/strings/string_util.h" 14 #include "base/strings/utf_string_conversions.h" 15 #include "build/build_config.h" 16 17 #if defined(OS_POSIX) 18 #include <stdlib.h> 19 #elif defined(OS_WIN) 20 #include <windows.h> 21 #endif 22 23 namespace base { 24 25 namespace { 26 27 class EnvironmentImpl : public Environment { 28 public: 29 bool GetVar(StringPiece variable_name, std::string* result) override { 30 if (GetVarImpl(variable_name, result)) 31 return true; 32 33 // Some commonly used variable names are uppercase while others 34 // are lowercase, which is inconsistent. Let's try to be helpful 35 // and look for a variable name with the reverse case. 36 // I.e. HTTP_PROXY may be http_proxy for some users/systems. 37 char first_char = variable_name[0]; 38 std::string alternate_case_var; 39 if (IsAsciiLower(first_char)) 40 alternate_case_var = ToUpperASCII(variable_name); 41 else if (IsAsciiUpper(first_char)) 42 alternate_case_var = ToLowerASCII(variable_name); 43 else 44 return false; 45 return GetVarImpl(alternate_case_var, result); 46 } 47 48 bool SetVar(StringPiece variable_name, 49 const std::string& new_value) override { 50 return SetVarImpl(variable_name, new_value); 51 } 52 53 bool UnSetVar(StringPiece variable_name) override { 54 return UnSetVarImpl(variable_name); 55 } 56 57 private: 58 bool GetVarImpl(StringPiece variable_name, std::string* result) { 59 #if defined(OS_POSIX) 60 const char* env_value = getenv(variable_name.data()); 61 if (!env_value) 62 return false; 63 // Note that the variable may be defined but empty. 64 if (result) 65 *result = env_value; 66 return true; 67 #elif defined(OS_WIN) 68 DWORD value_length = 69 ::GetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), nullptr, 0); 70 if (value_length == 0) 71 return false; 72 if (result) { 73 std::unique_ptr<wchar_t[]> value(new wchar_t[value_length]); 74 ::GetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), value.get(), 75 value_length); 76 *result = WideToUTF8(value.get()); 77 } 78 return true; 79 #else 80 #error need to port 81 #endif 82 } 83 84 bool SetVarImpl(StringPiece variable_name, const std::string& new_value) { 85 #if defined(OS_POSIX) 86 // On success, zero is returned. 87 return !setenv(variable_name.data(), new_value.c_str(), 1); 88 #elif defined(OS_WIN) 89 // On success, a nonzero value is returned. 90 return !!SetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), 91 UTF8ToWide(new_value).c_str()); 92 #endif 93 } 94 95 bool UnSetVarImpl(StringPiece variable_name) { 96 #if defined(OS_POSIX) 97 // On success, zero is returned. 98 return !unsetenv(variable_name.data()); 99 #elif defined(OS_WIN) 100 // On success, a nonzero value is returned. 101 return !!SetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), nullptr); 102 #endif 103 } 104 }; 105 106 // Parses a null-terminated input string of an environment block. The key is 107 // placed into the given string, and the total length of the line, including 108 // the terminating null, is returned. 109 size_t ParseEnvLine(const NativeEnvironmentString::value_type* input, 110 NativeEnvironmentString* key) { 111 // Skip to the equals or end of the string, this is the key. 112 size_t cur = 0; 113 while (input[cur] && input[cur] != '=') 114 cur++; 115 *key = NativeEnvironmentString(&input[0], cur); 116 117 // Now just skip to the end of the string. 118 while (input[cur]) 119 cur++; 120 return cur + 1; 121 } 122 123 } // namespace 124 125 namespace env_vars { 126 127 #if defined(OS_POSIX) 128 // On Posix systems, this variable contains the location of the user's home 129 // directory. (e.g, /home/username/). 130 const char kHome[] = "HOME"; 131 #endif 132 133 } // namespace env_vars 134 135 Environment::~Environment() {} 136 137 // static 138 std::unique_ptr<Environment> Environment::Create() { 139 return MakeUnique<EnvironmentImpl>(); 140 } 141 142 bool Environment::HasVar(StringPiece variable_name) { 143 return GetVar(variable_name, nullptr); 144 } 145 146 #if defined(OS_WIN) 147 148 string16 AlterEnvironment(const wchar_t* env, 149 const EnvironmentMap& changes) { 150 string16 result; 151 152 // First copy all unmodified values to the output. 153 size_t cur_env = 0; 154 string16 key; 155 while (env[cur_env]) { 156 const wchar_t* line = &env[cur_env]; 157 size_t line_length = ParseEnvLine(line, &key); 158 159 // Keep only values not specified in the change vector. 160 EnvironmentMap::const_iterator found_change = changes.find(key); 161 if (found_change == changes.end()) 162 result.append(line, line_length); 163 164 cur_env += line_length; 165 } 166 167 // Now append all modified and new values. 168 for (EnvironmentMap::const_iterator i = changes.begin(); 169 i != changes.end(); ++i) { 170 if (!i->second.empty()) { 171 result.append(i->first); 172 result.push_back('='); 173 result.append(i->second); 174 result.push_back(0); 175 } 176 } 177 178 // An additional null marks the end of the list. We always need a double-null 179 // in case nothing was added above. 180 if (result.empty()) 181 result.push_back(0); 182 result.push_back(0); 183 return result; 184 } 185 186 #elif defined(OS_POSIX) 187 188 std::unique_ptr<char* []> AlterEnvironment(const char* const* const env, 189 const EnvironmentMap& changes) { 190 std::string value_storage; // Holds concatenated null-terminated strings. 191 std::vector<size_t> result_indices; // Line indices into value_storage. 192 193 // First build up all of the unchanged environment strings. These are 194 // null-terminated of the form "key=value". 195 std::string key; 196 for (size_t i = 0; env[i]; i++) { 197 size_t line_length = ParseEnvLine(env[i], &key); 198 199 // Keep only values not specified in the change vector. 200 EnvironmentMap::const_iterator found_change = changes.find(key); 201 if (found_change == changes.end()) { 202 result_indices.push_back(value_storage.size()); 203 value_storage.append(env[i], line_length); 204 } 205 } 206 207 // Now append all modified and new values. 208 for (EnvironmentMap::const_iterator i = changes.begin(); 209 i != changes.end(); ++i) { 210 if (!i->second.empty()) { 211 result_indices.push_back(value_storage.size()); 212 value_storage.append(i->first); 213 value_storage.push_back('='); 214 value_storage.append(i->second); 215 value_storage.push_back(0); 216 } 217 } 218 219 size_t pointer_count_required = 220 result_indices.size() + 1 + // Null-terminated array of pointers. 221 (value_storage.size() + sizeof(char*) - 1) / sizeof(char*); // Buffer. 222 std::unique_ptr<char* []> result(new char*[pointer_count_required]); 223 224 // The string storage goes after the array of pointers. 225 char* storage_data = reinterpret_cast<char*>( 226 &result.get()[result_indices.size() + 1]); 227 if (!value_storage.empty()) 228 memcpy(storage_data, value_storage.data(), value_storage.size()); 229 230 // Fill array of pointers at the beginning of the result. 231 for (size_t i = 0; i < result_indices.size(); i++) 232 result[i] = &storage_data[result_indices[i]]; 233 result[result_indices.size()] = 0; // Null terminator. 234 235 return result; 236 } 237 238 #endif // OS_POSIX 239 240 } // namespace base 241
