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//
// 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 "host/libs/msg_queue/msg_queue.h"
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <fstream>
#include <iostream>
#include <memory>
#include <android-base/logging.h>
namespace cuttlefish {
// class holds `msgid` returned from msg_queue_create, and match the lifetime of
// the message queue to the lifetime of the object.
SysVMessageQueue::SysVMessageQueue(int id) { msgid = id; }
SysVMessageQueue::~SysVMessageQueue(void) {
if (msgctl(msgid, IPC_RMID, NULL) < 0) {
int error_num = errno;
LOG(ERROR) << "Could not remove message queue: " << strerror(error_num);
}
}
// SysVMessageQueue::Create would return an empty/null std::unique_ptr if
// initialization failed.
std::unique_ptr<SysVMessageQueue> SysVMessageQueue::Create(
const std::string& path, char proj_id) {
// key file must exist before calling ftok
std::fstream fs;
fs.open(path, std::ios::out);
fs.close();
// only the owning user has access
key_t key = ftok(path.c_str(), proj_id);
if (key < 0) {
int error_num = errno;
LOG(ERROR) << "Could not ftok to create IPC key: " << strerror(error_num);
return NULL;
}
int queue_id = msgget(key, 0);
if (queue_id < 0) {
queue_id = msgget(key, IPC_CREAT | IPC_EXCL | 0600);
}
auto msg = std::unique_ptr<SysVMessageQueue>(new SysVMessageQueue(queue_id));
return msg;
}
int SysVMessageQueue::Send(void* data, size_t size, bool block) {
int msgflg = block ? 0 : IPC_NOWAIT;
if (msgsnd(msgid, data, size, msgflg) < 0) {
int error_num = errno;
if (error_num == EAGAIN) {
// returns EAGAIN if queue is full and non-blocking
return EAGAIN;
}
LOG(ERROR) << "Could not send message: " << strerror(error_num);
return error_num;
}
return 0;
}
// If msgtyp is 0, then the first message in the queue is read.
// If msgtyp is greater than 0, then the first message in the queue of type
// msgtyp is read.
// If msgtyp is less than 0, then the first message in the queue with the lowest
// type less than or equal to the absolute value of msgtyp will be read.
ssize_t SysVMessageQueue::Receive(void* data, size_t size, long msgtyp,
bool block) {
// System call fails with errno set to ENOMSG if queue is empty and
// non-blocking.
int msgflg = block ? 0 : IPC_NOWAIT;
return msgrcv(msgid, data, size, msgtyp, msgflg);
}
} // namespace cuttlefish
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