epoll的EPOLLOUT事件

/*
 * Packs up the buf and write to socket in non-blocking way
 * If all data is writen, return 1
 * If only part of data is writen, return 0, to be continue next time
 * If error occurs, return -1
 * 
 * Note, if j_socket_write() returns 0, then you can call it with NULL in buf next time, until all data is writen
 */
int j_socket_write(JSocket * jsock, const void *buf, guint32 count)
{
    guint32 size = j_socket_wdata_length(jsock);
    if (size == 0) {
        /* new data to write */
        if (buf == NULL) {
            return 1;           /* no data? must be a mistake */
        }
        gchar *len = pack_length4(count);
        j_socket_wdata_append(jsock, len, 4);
        j_socket_wdata_append(jsock, buf, count);
        g_free(len);
        size = j_socket_wdata_length(jsock);
    }

    gint n;
    count = size>4096?4096:size;

    while(size>0){  /* writes segmentation */
        n = j_socket_write_raw(jsock, j_socket_wdata(jsock), count);
        if(n<0){
            if(errno==EAGAIN){
                return 0;
            }
            return -1;  /* It's a real error */
        }
        j_socket_wdata_pop(jsock,n);
        size = j_socket_wdata_length(jsock);
        count = size>4096?4096:size;
    }
    return 1;
}