OpenHarmony源码分析之分布式软总线：trans_service/tcp_session.c

一、概述

tcp_session.c文件提供的接口功能主要是创建一个TCP会话并返回其地址，在tcp_session.h文件中还提供了会话的属性结构体，本文将对这两个文件进行详细分析。

二、源码分析

1. tcp_session.h

/*
 * Copyright (c) 2020 Huawei Device Co., Ltd.
 * 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.
 */
#ifndef TCP_SESSION_H
#define TCP_SESSION_H
#include "comm_defs.h"
#include "common_info_manager.h"
#define NAME_LENGTH         64      //名称长度
#define SESSION_KEY_LENGTH  32      //会话密钥长度
/*会话数据包序列号节点*/
typedef struct {
    List head;
    int seqNum;
} SessionSeqNumNode;
/*tcp会话相关属性结构体*/
typedef struct {
    char sessionName[NAME_LENGTH];//会话名称
    char deviceId[MAX_DEV_ID_LEN];//设备id
    char groupId[NAME_LENGTH];//组id
    char sessionKey[SESSION_KEY_LENGTH];//会话密钥
    long seqNum;//节点序号
    int fd;//通信套接字fd
    int busVersion;//总线版本
    int routeType;//路由类型
    bool isAccepted;
    List *seqNumList;//数据包序号链表，用于记录数据包的序列号
} TcpSession;
TcpSession* CreateTcpSession(void);
#endif // TCP_SESSION_H

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2. tcp_session.c

/*
 * Copyright (c) 2020 Huawei Device Co., Ltd.
 * 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 "tcp_session.h"
#include <arpa/inet.h>
#include <sys/select.h>
#include <sys/socket.h>
#include "os_adapter.h"
/*
函数功能：创建一个新的tcp会话并进行相关属性初始化
函数参数：无
函数返回值：
    成功：返回tcp会话结构体地址
    失败：返回NULL
详细：
*/
TcpSession *CreateTcpSession(void)
{
    TcpSession *tcpSession = (TcpSession *)malloc(sizeof(TcpSession));//申请会话地址空间
    if (tcpSession == NULL) {
        return NULL;
    }
    if (strcpy_s(tcpSession->sessionName, NAME_LENGTH, "softbus_Lite_unknown") != 0) {//为新会话初始化名字
        SOFTBUS_PRINT("[TRANS] CreateTcpSession cpy busname fail\n");
        free(tcpSession);
        return NULL;
    }
    //初始化TCP会话结构体的相关属性：
    (void)memset_s(tcpSession->deviceId, MAX_DEV_ID_LEN, 0, MAX_DEV_ID_LEN);//清空设备id空间
    (void)memset_s(tcpSession->groupId, NAME_LENGTH, 0, NAME_LENGTH);//清空组id空间
    (void)memset_s(tcpSession->sessionKey, SESSION_KEY_LENGTH, 0, SESSION_KEY_LENGTH);//清空会话密钥空间
    tcpSession->seqNum = 0;//初始化节点序号为0
    tcpSession->fd = -1;//初始化套接字fd为-1
    tcpSession->busVersion = 0;
    tcpSession->routeType = 0;
    tcpSession->isAccepted = false;
    tcpSession->seqNumList = malloc(sizeof(List));//申请链表空间
    if (tcpSession->seqNumList == NULL) {
        free(tcpSession);
        return NULL;
    }
    ListInitHead(tcpSession->seqNumList);//初始化链表头指针
    return tcpSession;
}