/* * Copyright (c) 1999 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * "Portions Copyright (c) 1999 Apple Computer, Inc. All Rights * Reserved. This file contains Original Code and/or Modifications of * Original Code as defined in and that are subject to the Apple Public * Source License Version 1.0 (the 'License'). You may not use this file * except in compliance with the License. Please obtain a copy of the * License at http://www.apple.com/publicsource and read it before using * this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the * License for the specific language governing rights and limitations * under the License." * * @APPLE_LICENSE_HEADER_END@ */ // // bitfield.c - extract and set bit fields // // Written by Eryk Vershen (eryk@apple.com) // // See comments in bitfield.h // /* * Copyright 1996, 1997 by Apple Computer, Inc. * All Rights Reserved * * Permission to use, copy, modify, and distribute this software and * its documentation for any purpose and without fee is hereby granted, * provided that the above copyright notice appears in all copies and * that both the copyright notice and this permission notice appear in * supporting documentation. * * APPLE COMPUTER DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE. * * IN NO EVENT SHALL APPLE COMPUTER BE LIABLE FOR ANY SPECIAL, INDIRECT, OR * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT, * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include "bitfield.h" // // Defines // // // Types // // // Global Constants // const unsigned long masks[] = { 0x00000000, 0x00000001, 0x00000003, 0x00000007, 0x0000000F, 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF, 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF, 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, 0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF, 0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF, 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF, 0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF }; // // Global Variables // // // Forward declarations // // // Routines // unsigned long bitfield_set(unsigned long *bf, int base, int length, unsigned long value) { unsigned long t; unsigned long m; int s; // compute shift & mask, coerce value to correct number of bits, // zap the old bits and stuff the new value // return the masked value in case someone wants it. s = (base + 1) - length; m = masks[length]; t = value & m; *bf = (*bf & ~(m << s)) | (t << s); return t; } unsigned long bitfield_get(unsigned long bf, int base, int length) { unsigned long m; int s; // compute shift & mask // return the correct number of bits (shifted to low end) s = (base + 1) - length; m = masks[length]; return ((bf >> s) & m); }