88 lines
2.5 KiB
Plaintext
88 lines
2.5 KiB
Plaintext
/*
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* File......: BITSET.PRG
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* Author....: Forest Belt, Computer Diagnostic Services, Inc.
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* CIS ID....: ?
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*
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* This is an original work by Forest Belt and is placed in the
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* public domain.
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*
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* Modification history:
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* ---------------------
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*
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* Rev 1.2 15 Aug 1991 23:02:52 GLENN
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* Forest Belt proofread/edited/cleaned up doc
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*
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* Rev 1.1 14 Jun 1991 19:51:00 GLENN
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* Minor edit to file header
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*
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* Rev 1.0 01 Apr 1991 01:00:42 GLENN
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* Nanforum Toolkit
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*
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*/
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/* $DOC$
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* $FUNCNAME$
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* FT_BITSET()
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* $CATEGORY$
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* String
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* $ONELINER$
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* Set selected bit in a byte
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* $SYNTAX$
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* FT_BITSET( <cByte>, <nBitPos> ) -> cByte
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* $ARGUMENTS$
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* <cByte> is a character from CHR(0) to CHR(255).
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*
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* <nBitPos> is a number from 0 to 7 conforming to standard right-to-left
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* bit numbering convention and representing the position of the bit
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* within the byte.
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* $RETURNS$
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* Returns new byte, with designated bit set. If parameters are faulty,
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* returns NIL.
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* $DESCRIPTION$
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* In effect, ORs argument byte with a byte that has only the target bit
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* set. If bit is already set, it remains set.
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* Note: Calls FT_ISBIT() which is also in this Library.
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*
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* This function is presented to illustrate that bit-wise operations
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* are possible with Clipper code. For greater speed, write .C or
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* .ASM versions and use the Clipper Extend system.
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* $EXAMPLES$
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* This code would set bit 4 in a byte represented by CHR(107):
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*
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* cNewbyte := FT_BITSET( CHR(107), 4 )
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* ? ASC( cNewbyte ) // result: 123
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* ? cNewbyte // result: '{'
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*
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*
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* This code would set bit 5 in the byte represented by the letter 'A'.
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*
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* ? FT_BITSET( 'A', 5 ) // result: 'a'
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* // bit 5 set
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*
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* For a demonstration of Clipper bit manipulations, compile and
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* link the program BITTEST.PRG in the Nanforum Toolkit source code.
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* $SEEALSO$
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* FT_BITCLR() FT_ISBIT()
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* $END$
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*/
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FUNCTION FT_BITSET(cInByte, nBitpos)
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LOCAL cByte
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IF valtype(cInbyte) != "C" .or. valtype(nBitpos) != "N" // parameter check
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cByte := NIL
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ELSE
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IF (nBitPos > 7) .or. (nBitPos < 0) .or. (nBitPos != int(nBitPos))
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cByte := NIL
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ELSE
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cByte := iif( FT_ISBIT(cInByte, nBitpos), cInByte, ;
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chr(asc(cInByte) + (2 ^ nBitpos)))
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ENDIF
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ENDIF
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RETURN cByte
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