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instance.cpp
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instance.cpp
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// Copyright 2014 MongoDB Inc.
//
// 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 <mongocxx/config/private/prelude.hh>
#include <atomic>
#include <type_traits>
#include <utility>
#include <bsoncxx/stdx/make_unique.hpp>
#include <mongocxx/exception/error_code.hpp>
#include <mongocxx/exception/logic_error.hpp>
#include <mongocxx/instance.hpp>
#include <mongocxx/logger.hpp>
#include <mongocxx/private/libmongoc.hh>
#if !defined(__has_feature)
#define __has_feature(x) 0
#endif
namespace mongocxx {
MONGOCXX_INLINE_NAMESPACE_BEGIN
namespace {
log_level convert_log_level(::mongoc_log_level_t mongoc_log_level) {
switch (mongoc_log_level) {
case MONGOC_LOG_LEVEL_ERROR:
return log_level::k_error;
case MONGOC_LOG_LEVEL_CRITICAL:
return log_level::k_critical;
case MONGOC_LOG_LEVEL_WARNING:
return log_level::k_warning;
case MONGOC_LOG_LEVEL_MESSAGE:
return log_level::k_message;
case MONGOC_LOG_LEVEL_INFO:
return log_level::k_info;
case MONGOC_LOG_LEVEL_DEBUG:
return log_level::k_debug;
case MONGOC_LOG_LEVEL_TRACE:
return log_level::k_trace;
default:
MONGOCXX_UNREACHABLE;
}
}
void null_log_handler(::mongoc_log_level_t, const char*, const char*, void*) {}
void user_log_handler(::mongoc_log_level_t mongoc_log_level,
const char* log_domain,
const char* message,
void* user_data) {
(*static_cast<logger*>(user_data))(convert_log_level(mongoc_log_level),
stdx::string_view{log_domain},
stdx::string_view{message});
}
// A region of memory that acts as a sentintel value indicating that an instance object is being
// destroyed. We only care about the address of this object, never its contents.
typename std::aligned_storage<sizeof(instance), alignof(instance)>::type sentinel;
std::atomic<instance*> current_instance{nullptr};
static_assert(std::is_standard_layout<decltype(current_instance)>::value,
"Must be standard layout");
static_assert(std::is_trivially_destructible<decltype(current_instance)>::value,
"Must be trivially destructible");
} // namespace
class instance::impl {
public:
impl(std::unique_ptr<logger> logger) : _user_logger(std::move(logger)) {
libmongoc::init();
if (_user_logger) {
libmongoc::log_set_handler(user_log_handler, _user_logger.get());
// The libmongoc namespace mocking system doesn't play well with varargs
// functions, so we use a bare mongoc_log call here.
mongoc_log(MONGOC_LOG_LEVEL_INFO, "mongocxx", "libmongoc logging callback enabled");
} else {
libmongoc::log_set_handler(null_log_handler, nullptr);
}
libmongoc::handshake_data_append("mongocxx", MONGOCXX_VERSION_STRING, NULL);
}
~impl() {
// If we had a user logger, remove it so that it can't be used by the driver after it goes
// out of scope
if (_user_logger) {
libmongoc::log_set_handler(null_log_handler, nullptr);
}
// Under ASAN, we don't want to clean up libmongoc, because it causes libraries to become
// unloaded, and then ASAN sees non-rooted allocations that it consideres leaks. These are
// also inscrutable, because the stack refers into an unloaded library, which ASAN can't
// report. Note that this only works if we have built mongoc so that it doesn't do its
// unfortunate automatic invocation of 'cleanup'.
#if !__has_feature(address_sanitizer)
libmongoc::cleanup();
#endif
}
const std::unique_ptr<logger> _user_logger;
};
instance::instance() : instance(nullptr) {}
instance::instance(std::unique_ptr<logger> logger) {
instance* expected = nullptr;
if (!current_instance.compare_exchange_strong(expected, this)) {
throw logic_error{error_code::k_cannot_recreate_instance};
}
_impl = stdx::make_unique<impl>(std::move(logger));
}
instance::instance(instance&&) noexcept = default;
instance& instance::operator=(instance&&) noexcept = default;
instance::~instance() {
current_instance.store(reinterpret_cast<instance*>(&sentinel));
_impl.reset();
}
instance& instance::current() {
if (!current_instance.load()) {
static instance the_instance;
}
instance* curr = current_instance.load();
if (curr == reinterpret_cast<instance*>(&sentinel)) {
throw logic_error{error_code::k_instance_destroyed};
}
return *curr;
}
MONGOCXX_INLINE_NAMESPACE_END
} // namespace mongocxx