TRCV(3N-SVR4)      RISC/os Reference Manual       TRCV(3N-SVR4)



NAME
     t_rcv - receive data or expedited data sent over a connec-
          tion

SYNOPSIS
     int trcv (int fd, char *buf, unsigned nbytes, int *flags);

DESCRIPTION
     This function receives either normal or expedited data.  fd
     identifies the local transport endpoint through which data
     will arrive, buf points to a receive buffer where user data
     will be placed, and nbytes specifies the size of the receive
     buffer.  flags may be set on return from trcv and specifies
     optional flags as described below.

     By default, trcv operates in synchronous mode and will wait
     for data to arrive if none is currently available.  However,
     if O_NDELAY or O_NONBLOCK is set (via t_open or fcntl),
     trcv will execute in asynchronous mode and will fail if no
     data is available.  (See TNODATA below.)

     On return from the call, if T_MORE is set in flags, this
     indicates that there is more data and the current transport
     service data unit (TSDU) or expedited transport service data
     unit (ETSDU) must be received in multiple trcv calls.  Each
     trcv with the T_MORE flag set indicates that another trcv
     must follow to get more data for the current TSDU. The end
     of the TSDU is identified by the return of a trcv call with
     the T_MORE flag not set.  If the transport provider does not
     support the concept of a TSDU as indicated in the info argu-
     ment on return from t_open or t_getinfo, the T_MORE flag is
     not meaningful and should be ignored.

     On return, the data returned is expedited data if
     T_EXPEDITED is set in flags.  If the number of bytes of
     expedited data exceeds nbytes, trcv will set T_EXPEDITED
     and T_MORE on return from the initial call.  Subsequent
     calls to retrieve the remaining ETSDU will have T_EXPEDITED
     set on return.  The end of the ETSDU is identified by the
     return of a trcv call with the T_MORE flag not set.

     If expedited data arrives after part of a TSDU has been
     retrieved, receipt of the remainder of the TSDU will be
     suspended until the ETSDU has been processed.  Only after
     the full ETSDU has been retrieved (T_MORE not set) will the
     remainder of the TSDU be available to the user.

     On failure, t_errno may be set to one of the following:

     [TBADF]            The specified file descriptor does not
                        refer to a transport endpoint.




                        Printed 11/19/92                   Page 1

TRCV(3N-SVR4)      RISC/os Reference Manual       TRCV(3N-SVR4)



     [TNODATA]          O_NDELAY or O_NONBLOCK was set, but no
                        data is currently available from the
                        transport provider.

     [TLOOK]            An asynchronous event has occurred on
                        this transport endpoint and requires
                        immediate attention.

     [TNOTSUPPORT]      This function is not supported by the
                        underlying transport provider.

     [TSYSERR]          A system error has occurred during execu-
                        tion of this function.

SEE ALSO
     t_open(3N), t_snd(3N).

DIAGNOSTICS
     On successful completion, trcv returns the number of bytes
     received, and it returns -1 on failure and t_errno is set to
     indicate the error.


































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