Linux socket編程（五） 文件傳輸

　　這一篇給之前寫的聊天室再加上文件傳輸：

　　以下是對文件操作的封裝

      FileOperator.h

#ifndef FILEOPERATOR_H
#define FILEOPERATOR_H

#include <stdio.h>

#define WRITE_CREATE_MODE "a+b"

#include <fcntl.h>
#include <string>

class FileOperator
{
    public:
        FileOperator();
        ~FileOperator();
        bool Open(const char* fileName,const char* option);
        int WriteToFile(const std::string& buffer);
        int ReadFromFile(std::string& buffer);
        void Close();

    private:
        FILE* filePtr;
};

#endif

 

FileOperator.cpp

#include "FileOperator.h"
#include <sys/sendfile.h>
#include <memory.h>

const int MAX_BUFFERLENGTH=512;

FileOperator::FileOperator()
:filePtr(NULL)
{}

FileOperator::~FileOperator()
{
    Close();
}

bool FileOperator::Open(const char* fileName,const char* option)
{
    filePtr=fopen(fileName,option);
    return filePtr!=NULL;
}


int FileOperator::WriteToFile(const std::string& buffer)
{
    int writeBytes=::fwrite(buffer.c_str(),sizeof(char),buffer.size(),filePtr);

    if(writeBytes<0)
    {
        perror("error from fwrite");
        return -1;
    }
    else if(writeBytes==0)
            return 0;
    else
        return writeBytes;
}

int FileOperator::ReadFromFile(std::string& buffer)
{
    char bufferArray[MAX_BUFFERLENGTH+1];
    buffer.clear();
    memset(bufferArray,0,MAX_BUFFERLENGTH+1);

    int numberRead=fread(bufferArray,sizeof(char),MAX_BUFFERLENGTH+1,filePtr);
    if(numberRead==-1)
    {
        perror("error in Socket::Receive");
        return -1;
    }
    else if(numberRead==0)
        return 0;
    else
    {
        buffer=bufferArray;
        return numberRead;
    }
}

void FileOperator::Close()
{
    if(filePtr!=NULL)
        fclose(filePtr);
}

那怎么發送文件呢

void ClientSocket::SendFile(const std::string& fileName)
{
    FileOperator fileOperator;
    fileOperator.Open(fileName.c_str(),"rb");
    std::string buffer;

    int readBytes;
    Send("File");

    while((readBytes = fileOperator.ReadFromFile(buffer))>0)
    {
        if(Send(buffer)<0)
        {
            perror("failed to send file");
            break;
        }
    }

}

接收文件

void ServerSocket::RecvFile(Socket* clientSocket)
{
    std::string message;
    FileOperator fileOperator;
    //using IP address to name received file
    fileOperator.Open(clientSocket->GetAddress().c_str(),WRITE_CREATE_MODE);

    int recvBytes;
    int writeBytes;

    while((recvBytes=Socket::Receive(*clientSocket,message))>0)
    {
        std::cout<<"message length: "<<message.size()<<"\n";
        writeBytes=fileOperator.WriteToFile(message);
        std::cout<<"writeBytes: "<<writeBytes<<"\n";

        if(writeBytes<recvBytes)
        {
            perror("write to file failed");
            Socket::Send(*clientSocket,"Error when server receiving file.");
            return;
        }

        //if all bytes has been wrote
        if(recvBytes==0 || recvBytes!=MAXRECEIVE)
            break;

    }

    if(recvBytes >=0 )
        Socket::Send(*clientSocket,"server has received your file.");
}

要注意的是發送文件時，如果文件較大，客戶端很可能會阻塞，這個時候可以開一個新線程來發送文件。

不過，這個只是很簡單的文件傳輸，復雜點的有空再慢慢研究。