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- // Copyright 2019 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/process/environment_internal.h"
- #include <stddef.h>
- #include "build/build_config.h"
- #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
- #include <string.h>
- #endif
- #include <vector>
- namespace base {
- namespace internal {
- namespace {
- #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || BUILDFLAG(IS_WIN)
- // 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] != '=')
- cur++;
- *key = NativeEnvironmentString(&input[0], cur);
- // Now just skip to the end of the string.
- while (input[cur])
- cur++;
- return cur + 1;
- }
- #endif
- } // namespace
- #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_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()) {
- result_indices.push_back(value_storage.size());
- value_storage.append(env[i], line_length);
- }
- }
- // Now append all modified and new values.
- for (const auto& i : changes) {
- if (!i.second.empty()) {
- result_indices.push_back(value_storage.size());
- value_storage.append(i.first);
- value_storage.push_back('=');
- value_storage.append(i.second);
- value_storage.push_back(0);
- }
- }
- 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.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;
- }
- #elif BUILDFLAG(IS_WIN)
- NativeEnvironmentString AlterEnvironment(const wchar_t* env,
- const EnvironmentMap& changes) {
- NativeEnvironmentString result;
- // First build up all of the unchanged environment strings.
- const wchar_t* ptr = env;
- while (*ptr) {
- std::wstring key;
- size_t line_length = ParseEnvLine(ptr, &key);
- // Keep only values not specified in the change vector.
- if (changes.find(key) == changes.end()) {
- result.append(ptr, line_length);
- }
- ptr += line_length;
- }
- // Now append all modified and new values.
- for (const auto& i : changes) {
- // Windows environment blocks cannot handle keys or values with NULs.
- CHECK_EQ(std::wstring::npos, i.first.find(L'\0'));
- CHECK_EQ(std::wstring::npos, i.second.find(L'\0'));
- if (!i.second.empty()) {
- result += i.first;
- result.push_back('=');
- result += i.second;
- result.push_back('\0');
- }
- }
- // Add the terminating NUL.
- result.push_back('\0');
- return result;
- }
- #endif // BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
- } // namespace internal
- } // namespace base
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