Linux(程序设计):50---readv、writev函数解析处理HTTP报文-CFANZ编程社区

readv、writev函数的用法见文章

程序设计

HTTP响应报文通常包含1个状态行、多个头部字段、1个空行和文档。其中，前3部分的内容可能被Web服务器放置在一个内存中，而文档的内容则通常被读入到另一块单独的内存中（通过read或者mmap函数），我们并不需要将这部分的内容拼接到一起在发送，而可以使用writev函数将它们同时写出，代码如下

//ser_writrv.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <libgen.h>

#define BUFFER_SIZE 1024
static const char* status_line[2] = { "200 OK", "500 Internal server error" };

int main( int argc, char* argv[] )
{
    if( argc <= 3 )
    {
        printf( "usage: %s ip_address port_number filename\n", basename( argv[0] ) );
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi( argv[2] );
    const char* file_name = argv[3];

    struct sockaddr_in address;
    bzero( &address, sizeof( address ) );
    address.sin_family = AF_INET;
    inet_pton( AF_INET, ip, &address.sin_addr );
    address.sin_port = htons( port );

    int sock = socket( PF_INET, SOCK_STREAM, 0 );
    assert( sock >= 0 );

    int ret = bind( sock, ( struct sockaddr* )&address, sizeof( address ) );
    assert( ret != -1 );

    ret = listen( sock, 5 );
    assert( ret != -1 );

    struct sockaddr_in client;
    socklen_t client_addrlength = sizeof( client );
    int connfd = accept( sock, ( struct sockaddr* )&client, &client_addrlength );
    if ( connfd < 0 )
    {
        printf( "errno is: %d\n", errno );
    }
    else
    {
        char header_buf[ BUFFER_SIZE ];
        memset( header_buf, '\0', BUFFER_SIZE );
        char* file_buf;
        struct stat file_stat;
        int valid = 1;
        int len = 0;
        if( stat( file_name, &file_stat ) < 0 )
        {
            valid = 0;
        }
        else
        {
            if( S_ISDIR( file_stat.st_mode ) )
            {
                valid = 0;
            }
            else if( file_stat.st_mode & S_IROTH )
            {
                int fd = open( file_name, O_RDONLY );
                file_buf = (char*)malloc(file_stat.st_size + 1);
                memset( file_buf, '\0', file_stat.st_size + 1 );
                if ( read( fd, file_buf, file_stat.st_size ) < 0 )
                {
                    valid = 0;
                }
            }
            else
            {
                valid = 0;
            }
        }

        if( valid )
        {
            ret = snprintf( header_buf, BUFFER_SIZE-1, "%s %s\r\n", "HTTP/1.1", status_line[0] );
            len += ret;
            ret = snprintf( header_buf + len, BUFFER_SIZE-1-len, 
                             "Content-Length: %d\r\n", file_stat.st_size );
            len += ret;
            ret = snprintf( header_buf + len, BUFFER_SIZE-1-len, "%s", "\r\n" );
            struct iovec iv[2];
            iv[ 0 ].iov_base = header_buf;
            iv[ 0 ].iov_len = strlen( header_buf );
            iv[ 1 ].iov_base = file_buf;
            iv[ 1 ].iov_len = file_stat.st_size;
            ret = writev( connfd, iv, 2 );
        }
        else
        {
            ret = snprintf( header_buf, BUFFER_SIZE-1, "%s %s\r\n", "HTTP/1.1",status_line[1] );
            len += ret;
            ret = snprintf( header_buf + len, BUFFER_SIZE-1-len, "%s", "\r\n" );
            send( connfd, header_buf, strlen( header_buf ), 0 );
        }
        close( connfd );
        free(file_buf);
    }

    close( sock );
    return 0;
}