Category : Dbase (Clipper, FoxBase, etc) Languages Source Code
Archive   : NFSRC21.ZIP
Filename : BYTENOT.PRG

/*
* File......: BYTENOT.PRG
* Author....: Forest Belt, Computer Diagnostic Services, Inc.
* Date......: $Date: 15 Aug 1991 23:05:00 $
* Revision..: $Revision: 1.2 $
* Log file..: $Logfile: E:/nanfor/src/bytenot.prv $
*
* This is an original work by Forest Belt and is placed in the
* public domain.
*
* Modification history:
* ---------------------
*
* $Log: E:/nanfor/src/bytenot.prv $
*
* Rev 1.2 15 Aug 1991 23:05:00 GLENN
* Forest Belt proofread/edited/cleaned up doc
*
* Rev 1.1 10 May 1991 23:54:40 GLENN
* Documentation correction. The "oneliner" said two characters were NOTted,
* but this function just takes one byte.
*
* Rev 1.0 01 Apr 1991 01:00:54 GLENN
* Nanforum Toolkit
*
*/



/* $DOC$
* $FUNCNAME$
* FT_BYTENOT()
* $CATEGORY$
* String
* $ONELINER$
* Perform bit-wise NOT on an ASCII character (byte)
* $SYNTAX$
* FT_BYTENOT( ) -> cNewByte
* $ARGUMENTS$
* is a character from CHR(0) to CHR(255).
* May be passed in CHR() form, as character literal, or
* as expression evaluating to CHR() value.
* $RETURNS$
* Returns resulting byte, in CHR() form. If parameters are faulty,
* returns NIL.
* $DESCRIPTION$
* Can be used for bitwise byte manipulation. In effect, this is a
* bit-by-bit NOT (one's complement) operation. Equivalent to the
* NOT assembler instruction.
*
* This function is presented to illustrate that bit-wise operations
* are possible with Clipper code. For greater speed, write .C or
* .ASM versions and use the Clipper Extend system.
* $EXAMPLES$
* This code performs a bitwise NOT on byte represented by CHR(32):
*
* cNewByte := FT_BYTENOT( CHR(32) )
* ? ASC( cNewByte ) // result: 223
*
* For a demonstration of Clipper bit manipulations, compile and
* link the program BITTEST.PRG in the Nanforum Toolkit source code.
* $SEEALSO$

* FT_BYTEOR() FT_BYTEXOR() FT_BYTENEG() FT_BYTEAND()
* $END$
*/

FUNCTION FT_BYTENOT(cByte)

LOCAL nCounter, cNewByte

IF valtype(cByte) != "C"
cNewByte := NIL
ELSE
cNewByte := chr(0)
FOR nCounter := 0 to 7 // test each bit position
IF .not. FT_ISBIT(cByte, nCounter)
cNewByte := FT_BITSET(cNewByte, nCounter)
ENDIF
NEXT
ENDIF

RETURN cNewByte