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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 routines
       are  a pointer to the array to be unpacked into,	nitem which is the to-
       tal 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	termi-
       nated 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 spec-
       ify what	and how	to unpack data from the	receive	buffer.	 All variables
       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	 SPARCstation.
       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 of-
       ten 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 incompati-
	      ble  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)

NAME | SYNOPSIS | PARAMETERS | DESCRIPTION | EXAMPLES | ERRORS | SEE ALSO

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