Read() stuck on trying to read file

Question

I have a checkpoint file that receives a server state. This states represents serialized commands that pass trough my network.

I'm trying to read the file but the it gets stuck on the read while loop.

My read function:

struct message_t *pmanager_readop(int fd){
    if (fd < 0) return NULL;

    // Variables
    char *buffer = NULL;
    int result, msg_size;
    struct message_t *msg;

    // Check if file has data
    lseek (fd, 0, SEEK_END);
    int size_ckp = lseek(fd, 0, SEEK_CUR);

    if (size_ckp <= 0)
        return NULL;

    // Read message size
    result = read_all(fd, (char *) &msg_size, 4);
    if (result < 0) {
        return NULL;
    }
    msg_size = ntohl(msg_size);
    // ............

My read_all() function:

int read_all(int sock, char *buf, int len){
    int bufsize = len;
    while(len > 0){
        int res = read(sock,buf,len);

        if(res < 0){
            if (errno == EINTR) continue;
            return res;
        }
        buf += res;
        len -= res;
    }
    return bufsize;
}

I use this same function to read data from my server/client connection with the same serialization and format but with a socket descriptor, and it works perfectly.

Answer 1

You ought to handle the case that read() returns 0, telling you that the other side shut-down the connection if reading from a socket descriptor, or EOF encountered if reading from a file descriptor.