UNPACK(3PVM)							  PVM Version 3.4						      UNPACK(3PVM)

NAME

       pvm_unpack - Unpack the active message buffer into arrays of prescribed data type.

SYNOPSIS

       C
	    int info = pvm_unpackf( const char *fmt, ... )
	    int info = pvm_upkbyte( char *xp, int nitem, int stride)
	    int info = pvm_upkcplx( float *cp, int nitem, int stride)
	    int info = pvm_upkdcplx( double *zp, int nitem, int stride)
	    int info = pvm_upkdouble( double *dp, int nitem, int stride)
	    int info = pvm_upkfloat( float *fp, int nitem, int stride)
	    int info = pvm_upkint( int *ip, int nitem, int stride)
	    int info = pvm_upkuint( unsigned int *ip, int nitem, int stride )
	    int info = pvm_upkushort( unsigned short *ip, int nitem, int stride )
	    int info = pvm_upkulong( unsigned long *ip, int nitem, int stride )
	    int info = pvm_upklong( long *ip, int nitem, int stride)
	    int info = pvm_upkshort( short *jp, int nitem, int stride)
	    int info = pvm_upkstr( char *sp )

       Fortran
	    call pvmfunpack( what, xp, nitem, stride, info )

PARAMETERS

       fmt     Printf-like format expression specifying what to pack. (See discussion)

       nitem   The total number of items to be unpacked (not the number of bytes).

       stride  The  stride  to be used when packing the items.	For example, if stride = 2 in pvm_upkcplx, then every other complex number will be
	       unpacked.

       xp      Pointer to the beginning of a block of bytes. Can be any data type, but must match the corresponding pack data type.

       cp      Complex array at least nitem*stride items long.

       zp      Double precision complex array at least nitem*stride items long.

       dp      Double precision real array at least nitem*stride items long.

       fp      Real array at least nitem*stride items long.

       ip      Integer array at least nitem*stride items long.

       jp      Integer*2 array at least nitem*stride items long.

       sp      Pointer to a null terminated character string.

       what    Integer specifying the type of data being unpacked.

									  what options
		    STRING	   0	REAL4	       4
		    BYTE1	   1	COMPLEX8       5
		    INTEGER2	   2	REAL8	       6
		    INTEGER4	   3	COMPLEX16      7

       info    Integer status code returned by the routine.  Values less than zero indicate an error.

DESCRIPTION

       Each of the pvm_upk* routines unpacks an array of the given data type from the active receive buffer.  The arguments for each of  the  rou-
       tines are a pointer to the array to be unpacked into, nitem which is the total number of items to unpack, and stride which is the stride to
       use when unpacking.

       An exception is pvm_upkstr() which by definition unpacks a NULL terminated character string and thus does not need nitem  or  stride  argu-
       ments.  The Fortran routine pvmfunpack( STRING, ... ) expects nitem to be the number of characters in the string and stride to be 1.

       If the unpacking is successful, info will be 0. If some error occurs then info will be < 0.

       A single variable (not an array) can be unpacked by setting nitem = 1 and stride = 1.

       The  routine  pvm_unpackf() uses a printf-like format expression to specify what and how to unpack data from the receive buffer.  All vari-
       ables are passed as addresses.  A BNF-like description of the format syntax is:
	   format : null | init | format fmt
	   init : null | '%' '+'
	   fmt : '%' count stride modifiers fchar
	   fchar : 'c' | 'd' | 'f' | 'x' | 's'
	   count : null | [0-9]+ | '*'
	   stride : null | '.' ( [0-9]+ | '*' )
	   modifiers : null | modifiers mchar
	   mchar : 'h' | 'l' | 'u'

       Formats:
	 +  means initsend - must match an int (how) in the param list.
	 c  pack/unpack bytes
	 d  integer
	 f  float
	 x  complex float
	 s  string

       Modifiers:
	 h  short (int)
	 l  long  (int, float, complex float)
	 u  unsigned (int)

       Future extensions to the what argument in pvmfunpack will include 64 bit types when XDR encoding of these types	is  available.	 Meanwhile
       users  should  be aware that precision can be lost when passing data from a 64 bit machine like a Cray to a 32 bit machine like a SPARCsta-
       tion. As a mnemonic the what argument name includes the number of bytes of  precision  to  expect.  By  setting	encoding  to  PVMRAW  (see
       pvmfinitsend) data can be transferred between two 64 bit machines with full precision even if the PVM configuration is heterogeneous.

       Messages  should  be  unpacked  exactly like they were packed to insure data integrity.	Packing integers and unpacking them as floats will
       often fail because a type encoding will have occurred transferring the data between heterogeneous hosts. Packing 10 integers and 100 floats
       then trying to unpack only 3 integers and the 100 floats will also fail.

EXAMPLES

       C:
	    info = pvm_recv( tid, msgtag );
	    info = pvm_upkstr( string );
	    info = pvm_upkint( &size, 1, 1 );
	    info = pvm_upkint( array, size, 1 );
	    info = pvm_upkdouble( matrix, size*size, 1 );

	    int count, *iarry;
	    double darry[4];
	       pvm_unpackf("%d", &count);
	       pvm_unpackf("%*d %4lf", count, iarry, darry);

       Fortran:
	    CALL PVMFRECV( TID, MSGTAG, INFO );
	    CALL PVMFUNPACK( INTEGER4, NSIZE, 1, 1, INFO )
	    CALL PVMFUNPACK( STRING, STEPNAME, 8, 1, INFO )
	    CALL PVMFUNPACK( REAL4, A(5,1), NSIZE, NSIZE , INFO )

ERRORS

       PvmNoData
	      Reading beyond the end of the receive buffer.  Most likely cause is trying to unpack more items than were originally packed into the
	      buffer.

       PvmBadMsg
	      The received message can not be decoded.	Most likely because the hosts are heterogeneous and the  user  specified  an  incompatible
	      encoding.  Try setting the encoding to PvmDataDefault (see pvm_mkbuf).

       PvmNoBuf
	      There is no active receive buffer to unpack.

SEE ALSO

       pvm_pack(3PVM) pvm_send(3PVM), pvm_recv(3PVM), pvm_pkmesg(3PVM)

								  30 August, 1993						      UNPACK(3PVM)