HW12/socket_wrapper.c

#include <signal.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <poll.h>

#include "socket_wrapper.h"

int getBufferSizeFrom(int sock){
    int buffer_sz;
    socklen_t len = sizeof(buffer_sz);
    //getsockopt is thread-safe
    if(getsockopt(sock,SOL_SOCKET,SO_SNDBUF,&buffer_sz,&len) < 0){
        perror("failed to get sock buffer size: getsockopt");
        buffer_sz = DEFAULT_BUF_SIZE;/*set to default*/
    }
    if(buffer_sz < MINIMUM_BUF_SIZE)
        buffer_sz = MINIMUM_BUF_SIZE;
    return buffer_sz;
}

ssize_t timeout_recv(int fd,void * buf,size_t n,int timeout)
{
    ssize_t ret;
    int poll_ret;
    struct pollfd fd_single;
    fd_single.fd = fd;
    fd_single.events = POLL_IN;
    poll_ret = (poll(&fd_single,1,timeout * 1000));
    if (poll_ret < 0) return -1;
    else if(poll_ret == 0) return -2;
    switch (fd_single.revents){
    case POLLHUP: //We'll treat hangups state like timeouts state.
        return -2;
    case POLLERR:
    case POLLNVAL:
        return -1;
    case POLL_IN:
        ret = recv(fd,buf,n,0);
        assert(ret != 0);
        return ret;
    default:
        assert(0 && "unreachable");
    }
    assert(0 && "unreachable");
}

ssize_t recv_until_byte(int fd,void * buf, size_t n,int timeout){
    ssize_t cur = 0;
    uint8_t * b = buf;
    while (cur < n)
    {
        ssize_t r = timeout_recv(fd,&b[cur],n-cur,timeout);
        if (r < 0){
            return r;
        }
        cur += r;
    }
    assert(cur == n);
    return cur;
}