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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 <vector>
namespace base {
namespace internal {
namespace {
#if defined(OS_POSIX) || defined(OS_FUCHSIA) || defined(OS_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 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()) {
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 defined(OS_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 // OS_POSIX || OS_FUCHSIA
} // namespace internal
} // namespace base
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