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90 lines
2.0 KiB
90 lines
2.0 KiB
/***
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*rotr.c - rotate an unsigned integer right
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*
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* Copyright (c) 1989-1991, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines _rotr() - performs a rotate right on an unsigned integer.
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*
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*Revision History:
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* 06-02-89 PHG Module created
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* 11-03-89 JCR Added _lrotl
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* 03-15-90 GJF Made calling type _CALLTYPE1, added #include
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* <cruntime.h> and fixed the copyright. Also, cleaned
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* up the formatting a bit.
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* 10-04-90 GJF New-style function declarators.
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* 04-01-91 SRW Enable #pragma function for i386 _WIN32_ builds too.
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* 09-02-92 GJF Don't build for POSIX.
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* 03-09-94 RDL Enable #pragma function for i386 _WIN32_ builds too.
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*
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*******************************************************************************/
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#ifndef _POSIX_
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#include <cruntime.h>
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#include <stdlib.h>
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#include <limits.h>
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#ifdef _MSC_VER
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#pragma function(_lrotr,_rotr)
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#endif
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#if UINT_MAX != 0xffffffff
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#error This module assumes 32-bit integers
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#endif
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#if (UINT_MAX != ULONG_MAX)
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#error This module assumes sizeof(int) == sizeof(long)
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#endif
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/***
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*unsigned _rotr(val, shift) - int rotate right
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*
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*Purpose:
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* Performs a rotate right on an unsigned integer.
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*
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* [Note: The _lrotl entry is based on the assumption
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* that sizeof(int) == sizeof(long).]
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*Entry:
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* unsigned val: value to rotate
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* int shift: number of bits to shift by
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*
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*Exit:
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* returns rotated values
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*
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*Exceptions:
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* None.
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*
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*******************************************************************************/
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unsigned long _CALLTYPE1 _lrotr (
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unsigned long val,
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int shift
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)
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{
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return( (unsigned long) _rotr((unsigned) val, shift) );
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}
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unsigned _CALLTYPE1 _rotr (
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unsigned val,
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int shift
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)
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{
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register unsigned lobit; /* non-zero means lo bit set */
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register unsigned num = val; /* number to rotate */
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shift &= 0x1f; /* modulo 32 -- this will also make
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negative shifts work */
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while (shift--) {
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lobit = num & 1; /* get high bit */
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num >>= 1; /* shift right one bit */
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if (lobit)
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num |= 0x80000000; /* set hi bit if lo bit was set */
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}
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return num;
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}
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#endif
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