blob: 9a56135c7f891bfa88444f96bde9afc933fb704b [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/environment.h"
#include <stddef.h>
#include <vector>
#include "base/memory/ptr_util.h"
#include "base/strings/string_piece.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "build/build_config.h"
#if defined(OS_WIN)
#include <windows.h>
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
#include <stdlib.h>
namespace base {
namespace {
class EnvironmentImpl : public Environment {
bool GetVar(StringPiece variable_name, std::string* result) override {
if (GetVarImpl(variable_name, result))
return true;
// Some commonly used variable names are uppercase while others
// are lowercase, which is inconsistent. Let's try to be helpful
// and look for a variable name with the reverse case.
// I.e. HTTP_PROXY may be http_proxy for some users/systems.
char first_char = variable_name[0];
std::string alternate_case_var;
if (IsAsciiLower(first_char))
alternate_case_var = ToUpperASCII(variable_name);
else if (IsAsciiUpper(first_char))
alternate_case_var = ToLowerASCII(variable_name);
return false;
return GetVarImpl(alternate_case_var, result);
bool SetVar(StringPiece variable_name,
const std::string& new_value) override {
return SetVarImpl(variable_name, new_value);
bool UnSetVar(StringPiece variable_name) override {
return UnSetVarImpl(variable_name);
bool GetVarImpl(StringPiece variable_name, std::string* result) {
#if defined(OS_WIN)
DWORD value_length =
::GetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), nullptr, 0);
if (value_length == 0)
return false;
if (result) {
std::unique_ptr<wchar_t[]> value(new wchar_t[value_length]);
::GetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), value.get(),
*result = WideToUTF8(value.get());
return true;
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
const char* env_value = getenv(;
if (!env_value)
return false;
// Note that the variable may be defined but empty.
if (result)
*result = env_value;
return true;
bool SetVarImpl(StringPiece variable_name, const std::string& new_value) {
#if defined(OS_WIN)
// On success, a nonzero value is returned.
return !!SetEnvironmentVariable(UTF8ToWide(variable_name).c_str(),
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
// On success, zero is returned.
return !setenv(, new_value.c_str(), 1);
bool UnSetVarImpl(StringPiece variable_name) {
#if defined(OS_WIN)
// On success, a nonzero value is returned.
return !!SetEnvironmentVariable(UTF8ToWide(variable_name).c_str(), nullptr);
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
// On success, zero is returned.
return !unsetenv(;
// Parses a null-terminated input string of an environment block. The key is
// placed into the given string, and the total length of the line, including
// the terminating null, is returned.
size_t ParseEnvLine(const NativeEnvironmentString::value_type* input,
NativeEnvironmentString* key) {
// Skip to the equals or end of the string, this is the key.
size_t cur = 0;
while (input[cur] && input[cur] != '=')
*key = NativeEnvironmentString(&input[0], cur);
// Now just skip to the end of the string.
while (input[cur])
return cur + 1;
} // namespace
namespace env_vars {
#if defined(OS_POSIX) || defined(OS_FUCHSIA)
// On Posix systems, this variable contains the location of the user's home
// directory. (e.g, /home/username/).
const char kHome[] = "HOME";
} // namespace env_vars
Environment::~Environment() = default;
// static
std::unique_ptr<Environment> Environment::Create() {
return std::make_unique<EnvironmentImpl>();
bool Environment::HasVar(StringPiece variable_name) {
return GetVar(variable_name, nullptr);
#if defined(OS_WIN)
string16 AlterEnvironment(const wchar_t* env,
const EnvironmentMap& changes) {
string16 result;
// First copy all unmodified values to the output.
size_t cur_env = 0;
string16 key;
while (env[cur_env]) {
const wchar_t* line = &env[cur_env];
size_t line_length = ParseEnvLine(line, &key);
// Keep only values not specified in the change vector.
EnvironmentMap::const_iterator found_change = changes.find(key);
if (found_change == changes.end())
result.append(line, line_length);
cur_env += line_length;
// Now append all modified and new values.
for (EnvironmentMap::const_iterator i = changes.begin();
i != changes.end(); ++i) {
if (!i->second.empty()) {
// An additional null marks the end of the list. We always need a double-null
// in case nothing was added above.
if (result.empty())
return result;
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
std::unique_ptr<char* []> AlterEnvironment(const char* const* const env,
const EnvironmentMap& changes) {
std::string value_storage; // Holds concatenated null-terminated strings.
std::vector<size_t> result_indices; // Line indices into value_storage.
// First build up all of the unchanged environment strings. These are
// null-terminated of the form "key=value".
std::string key;
for (size_t i = 0; env[i]; i++) {
size_t line_length = ParseEnvLine(env[i], &key);
// Keep only values not specified in the change vector.
auto found_change = changes.find(key);
if (found_change == changes.end()) {
value_storage.append(env[i], line_length);
// Now append all modified and new values.
for (const auto& i : changes) {
if (!i.second.empty()) {
size_t pointer_count_required =
result_indices.size() + 1 + // Null-terminated array of pointers.
(value_storage.size() + sizeof(char*) - 1) / sizeof(char*); // Buffer.
std::unique_ptr<char* []> result(new char*[pointer_count_required]);
// The string storage goes after the array of pointers.
char* storage_data = reinterpret_cast<char*>(
&result.get()[result_indices.size() + 1]);
if (!value_storage.empty())
memcpy(storage_data,, value_storage.size());
// Fill array of pointers at the beginning of the result.
for (size_t i = 0; i < result_indices.size(); i++)
result[i] = &storage_data[result_indices[i]];
result[result_indices.size()] = 0; // Null terminator.
return result;
#endif // OS_WIN
} // namespace base