base/config_globals.cc

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "berberis/base/config_globals.h"

#include <cstdlib>
#include <cstring>

#if defined(__BIONIC__)
#include <sys/system_properties.h>
#endif

#include <bitset>
#include <string_view>

#include "berberis/base/checks.h"
#include "berberis/base/forever_alloc.h"

namespace berberis {

namespace {

const char* g_main_executable_real_path = nullptr;

const char* g_app_package_name = nullptr;
const char* g_app_private_dir = nullptr;

const char* MakeForeverCStr(std::string_view view) {
  auto str = reinterpret_cast<char*>(AllocateForever(view.size() + 1, alignof(char)));
  memcpy(str, view.data(), view.size());
  str[view.size()] = '\0';
  return str;
}

#if defined(__BIONIC__)

bool TryReadBionicSystemPropertyImpl(const std::string_view prop_name, const char** value_ptr) {
  auto pi = __system_property_find(prop_name.data());
  if (!pi) {
    return false;
  }
  __system_property_read_callback(
      pi,
      [](void* cookie, const char*, const char* value, unsigned) {
        *reinterpret_cast<const char**>(cookie) = MakeForeverCStr(value);
      },
      value_ptr);
  return true;
}

bool TryReadBionicSystemProperty(const std::string_view prop_name, const char** value_ptr) {
  // Allow properties without ro. prefix (they override ro. properties).
  if (prop_name.size() > 3 && prop_name.substr(0, 3) == "ro." &&
      TryReadBionicSystemPropertyImpl(prop_name.substr(3), value_ptr)) {
    return true;
  }

  return TryReadBionicSystemPropertyImpl(prop_name, value_ptr);
}

#endif

bool TryReadConfig(const char* env_name,
                   [[maybe_unused]] const std::string_view prop_name,
                   const char** value_ptr) {
  if (auto env = getenv(env_name)) {
    *value_ptr = MakeForeverCStr(env);
    return true;
  }
#if defined(__BIONIC__)
  return TryReadBionicSystemProperty(prop_name, value_ptr);
#else
  return false;
#endif
}

}  // namespace

ConfigStr::ConfigStr(const char* env_name, const char* prop_name) {
  TryReadConfig(env_name, prop_name, &value_);
}

void SetMainExecutableRealPath(std::string_view path) {
  CHECK(!path.empty());
  CHECK_EQ('/', path[0]);
  g_main_executable_real_path = MakeForeverCStr(path);
}

const char* GetMainExecutableRealPath() {
  return g_main_executable_real_path;
}

void SetAppPackageName(std::string_view name) {
  CHECK(!name.empty());
  g_app_package_name = MakeForeverCStr(name);
}

const char* GetAppPackageName() {
  return g_app_package_name;
}

void SetAppPrivateDir(std::string_view name) {
  CHECK(!name.empty());
  g_app_private_dir = MakeForeverCStr(name);
}

const char* GetAppPrivateDir() {
  return g_app_private_dir;
}

}  // namespace berberis