/*
 * recvbuf - recv a length-prefixed packet
 *
 * This routine receives a message packet in the form
 *
 *     ---------------------------------------
 *     | length  |  message                  |
 *     ---------------------------------------
 *
 * where "length" is always exactly 4 bytes.
 *
 *
 * It uses the "MSG_PEEK" flag of _recv to obtain the length field,
 * placing it in the specified variable.  "MSG_PEEK" allows you to
 * retrieve information from the message without removing it from
 * the stream.  The routine then invokes _recv again, using the
 * length variable to specify how much data to read from the
 * socket stream
 *
 *
 *
 * Modification history:
 *
 * 07 May 93  nfnm  Initial implementation
 * 12 Aug 93  pjt   Documentation and minor modifications
 *
 */
recvbuf: procedure
parse arg socket

/*
 * Peek at the message to get its length - put that value in the
 * variable bufferlength
 */
recvrc = _recv(socket, "bufferlength", 4, MSG_PEEK)
if recvrc < 0 then call error "recv"

/*
 * Actually receive the full message packet, including its length
 * prefix
 */
recvrc = _recv(socket, "buffer", bufferlength, "")
if recvrc < 0 then call error "recv"

/*
 * Remove the length prefix from the message and return only the
 * message
 */
message = substr(buffer,5)
return message