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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <string>
#include "mongo/base/string_data.h"
#include "mongo/util/intrusive_counter.h"
#include "mongo/util/thread_context.h"
namespace mongo {
/**
* ThreadName is a uniquely identifyable, immutable, ref-counted string.
*
* This class is used for three purposes:
* - Setting the official thread name with the OS.
* - Populating the "ctx" field for log lines.
* - Providing a thread name to gdb.
*/
class ThreadName : public RefCountable {
public:
using Id = size_t;
/**
* Create a new instance.
*
* Note that this does not set it to be the official one for the thread.
*/
explicit ThreadName(StringData name);
ThreadName(const ThreadName&) = delete;
ThreadName(ThreadName&&) = delete;
/**
* Get the official ThreadName for the current thread via the ThreadContext.
*/
static boost::intrusive_ptr<ThreadName> get(boost::intrusive_ptr<ThreadContext> context);
/**
* Set the official ThreadName for the current thread via the ThreadContext.
*
* Note that this also will set the OS thread name if the name is different from the current
* one.
*
* If a different non-anonymous thread name was previously set, this returns that name. If the
* given name was already set, a previous name was released, or the initial name was set, this
* returns an empty pointer.
*/
static boost::intrusive_ptr<ThreadName> set(boost::intrusive_ptr<ThreadContext> context,
boost::intrusive_ptr<ThreadName> name);
/**
* Release the current thread name.
*
* This does not unset the OS thread name or change the current storage. Instead, this marks the
* current name as available for reuse or replacement.
*/
static void release(boost::intrusive_ptr<ThreadContext> context);
/**
* Get a string for the current thread without new allocations.
*
* In pre-init, this returns "-". That value will mostly be associated with the main thread.
* If a thread is somehow started in pre-init and dodges our ThreadSafetyContext checks, it will
* also return "-" for this function.
*/
static StringData getStaticString();
StringData toString() const {
return _storage;
}
friend bool operator==(const ThreadName& lhs, const ThreadName& rhs) noexcept {
return lhs._id == rhs._id;
}
friend bool operator!=(const ThreadName& lhs, const ThreadName& rhs) noexcept {
return lhs._id != rhs._id;
}
private:
static Id _nextId();
const Id _id;
const std::string _storage;
};
/**
* Sets the name of the current thread.
*/
inline void setThreadName(StringData name) {
ThreadName::set(ThreadContext::get(), make_intrusive<ThreadName>(name));
}
/**
* Retrieves the name of the current thread, as previously set, or "thread#" if no name was
* previously set. The returned StringData is always null terminated so it is safe to pass to APIs
* that expect c-strings.
*/
inline StringData getThreadName() {
return ThreadName::get(ThreadContext::get())->toString();
}
} // namespace mongo
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