80 lines
2.2 KiB
Plaintext
80 lines
2.2 KiB
Plaintext
/*
|
|
* File......: BYTENOT.PRG
|
|
* Author....: Forest Belt, Computer Diagnostic Services, Inc.
|
|
* CIS ID....: ?
|
|
*
|
|
* This is an original work by Forest Belt and is placed in the
|
|
* public domain.
|
|
*
|
|
* Modification history:
|
|
* ---------------------
|
|
*
|
|
* 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( <cByte> ) -> cNewByte
|
|
* $ARGUMENTS$
|
|
* <cByte> 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
|
|
|