base/environment.cc

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