cs50 server.c request()

/**
 * Reads (without blocking) an HTTP request's headers into memory dynamically allocated on heap.
 * Stores address thereof in *message and length thereof in *length.
 */
bool request(char** message, size_t* length)
{
    // ensure socket is open
    if (cfd == -1)
    {
        return false;
    }

    // initialize message and its length
    *message = NULL;
    *length = 0;

    // read message
    while (*length < LimitRequestLine + LimitRequestFields * LimitRequestFieldSize + 4)
    {
        // read from socket
        BYTE buffer[BYTES];
        ssize_t bytes = read(cfd, buffer, BYTES);
        if (bytes < 0)
        {
            if (*message != NULL)
            {
                free(*message);
                *message = NULL;
            }
            *length = 0;
            break;
        }

        // append bytes to message
        *message = realloc(*message, *length + bytes + 1);
        if (*message == NULL)
        {
            *length = 0;
            break;
        }
        memcpy(*message + *length, buffer, bytes);
        *length += bytes;

        // null-terminate message thus far
        *(*message + *length) = '\0';

        // search for CRLF CRLF
        int offset = (*length - bytes < 3) ? *length - bytes : 3;
        char* haystack = *message + *length - bytes - offset;
        char* needle = strstr(haystack, "\r\n\r\n");
        if (needle != NULL)
        {
            // trim to one CRLF and null-terminate
            *length = needle - *message + 2;
            *message = realloc(*message, *length + 1);
            if (*message == NULL)
            {
                break;
            }
            *(*message + *length) = '\0';

            // ensure request-line is no longer than LimitRequestLine
            haystack = *message;
            needle = strstr(haystack, "\r\n");
            if (needle == NULL || (needle - haystack + 2) > LimitRequestLine)
            {
                break;
            }

            // count fields in message
            int fields = 0;
            haystack = needle + 2;
            while (*haystack != '\0')
            {
                // look for CRLF
                needle = strstr(haystack, "\r\n");
                if (needle == NULL)
                {
                    break;
                }

                // ensure field is no longer than LimitRequestFieldSize
                if (needle - haystack + 2 > LimitRequestFieldSize)
                {
                    break;
                }

                // look beyond CRLF
                haystack = needle + 2;
            }

            // if we didn't get to end of message, we must have erred
            if (*haystack != '\0')
            {
                break;
            }

            // ensure message has no more than LimitRequestFields
            if (fields > LimitRequestFields)
            {
                break;
            }

            // valid
            return true;
        }
    }

    // invalid
    if (*message != NULL)
    {
        free(*message);
    }
    *message = NULL;
    *length = 0;
    return false;
}