129 lines
3.9 KiB
C++
129 lines
3.9 KiB
C++
// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/process/environment_internal.h"
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#include <stddef.h>
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#include <vector>
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namespace base {
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namespace internal {
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namespace {
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#if defined(OS_POSIX) || defined(OS_FUCHSIA) || defined(OS_WIN)
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// Parses a null-terminated input string of an environment block. The key is
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// placed into the given string, and the total length of the line, including
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// the terminating null, is returned.
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size_t ParseEnvLine(const NativeEnvironmentString::value_type* input,
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NativeEnvironmentString* key) {
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// Skip to the equals or end of the string, this is the key.
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size_t cur = 0;
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while (input[cur] && input[cur] != '=')
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cur++;
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*key = NativeEnvironmentString(&input[0], cur);
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// Now just skip to the end of the string.
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while (input[cur])
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cur++;
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return cur + 1;
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}
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#endif
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} // namespace
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#if defined(OS_POSIX) || defined(OS_FUCHSIA)
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std::unique_ptr<char* []> AlterEnvironment(const char* const* const env,
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const EnvironmentMap& changes) {
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std::string value_storage; // Holds concatenated null-terminated strings.
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std::vector<size_t> result_indices; // Line indices into value_storage.
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// First build up all of the unchanged environment strings. These are
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// null-terminated of the form "key=value".
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std::string key;
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for (size_t i = 0; env[i]; i++) {
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size_t line_length = ParseEnvLine(env[i], &key);
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// Keep only values not specified in the change vector.
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auto found_change = changes.find(key);
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if (found_change == changes.end()) {
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result_indices.push_back(value_storage.size());
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value_storage.append(env[i], line_length);
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}
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}
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// Now append all modified and new values.
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for (const auto& i : changes) {
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if (!i.second.empty()) {
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result_indices.push_back(value_storage.size());
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value_storage.append(i.first);
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value_storage.push_back('=');
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value_storage.append(i.second);
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value_storage.push_back(0);
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}
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}
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size_t pointer_count_required =
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result_indices.size() + 1 + // Null-terminated array of pointers.
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(value_storage.size() + sizeof(char*) - 1) / sizeof(char*); // Buffer.
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std::unique_ptr<char*[]> result(new char*[pointer_count_required]);
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// The string storage goes after the array of pointers.
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char* storage_data =
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reinterpret_cast<char*>(&result.get()[result_indices.size() + 1]);
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if (!value_storage.empty())
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memcpy(storage_data, value_storage.data(), value_storage.size());
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// Fill array of pointers at the beginning of the result.
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for (size_t i = 0; i < result_indices.size(); i++)
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result[i] = &storage_data[result_indices[i]];
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result[result_indices.size()] = 0; // Null terminator.
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return result;
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}
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#elif defined(OS_WIN)
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NativeEnvironmentString AlterEnvironment(const wchar_t* env,
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const EnvironmentMap& changes) {
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NativeEnvironmentString result;
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// First build up all of the unchanged environment strings.
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const wchar_t* ptr = env;
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while (*ptr) {
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std::wstring key;
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size_t line_length = ParseEnvLine(ptr, &key);
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// Keep only values not specified in the change vector.
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if (changes.find(key) == changes.end()) {
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result.append(ptr, line_length);
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}
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ptr += line_length;
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}
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// Now append all modified and new values.
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for (const auto& i : changes) {
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// Windows environment blocks cannot handle keys or values with NULs.
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CHECK_EQ(std::wstring::npos, i.first.find(L'\0'));
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CHECK_EQ(std::wstring::npos, i.second.find(L'\0'));
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if (!i.second.empty()) {
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result += i.first;
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result.push_back('=');
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result += i.second;
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result.push_back('\0');
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}
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}
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// Add the terminating NUL.
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result.push_back('\0');
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return result;
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}
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#endif // OS_POSIX || OS_FUCHSIA
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} // namespace internal
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} // namespace base
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