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Annotation of 43BSDTahoe/new/X/libibm/libsrc/reversebits.c, revision 1.1

1.1     ! root        1: #ifndef lint
        !             2: static char *rcsid_reversebits_c = "$Header: reversebits.c,v 10.1 86/11/19 10:44:01 jg Exp $";
        !             3: #endif lint
        !             4: /* reversebits.c - bit reversal code
        !             5:  *
        !             6:  *     ReverseCharBits         reverse bits in each byte
        !             7:  *     ReverseShortBits        reverse bits in each short
        !             8:  *
        !             9:  *     Author:
        !            10:  *             Scott Bates
        !            11:  *             Brown University
        !            12:  *             IRIS, Box 1946
        !            13:  *             Providence, RI 02912
        !            14:  *
        !            15:  *
        !            16:  *             Copyright (c) 1986 Brown University
        !            17:  *
        !            18:  * Permission to use, copy, modify and distribute this software and its
        !            19:  * documentation for any purpose and without fee is hereby granted, provided
        !            20:  * that the above copyright notice appear in all copies, and that both
        !            21:  * that copyright notice and this permission notice appear in supporting
        !            22:  * documentation, and that the name of Brown University not be used in
        !            23:  * advertising or publicity pertaining to distribution of the software
        !            24:  * without specific, written prior permission. Brown University makes no
        !            25:  * representations about the suitability of this software for any purpose.
        !            26:  * It is provided "as-is" without express or implied warranty.
        !            27:  */
        !            28: 
        !            29: #include "private.h"
        !            30: 
        !            31: u_char BitsReversed[256] = {
        !            32:        0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50,
        !            33:        0xD0, 0x30, 0xB0, 0x70, 0xF0, 0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8,
        !            34:        0x68, 0xE8, 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, 0x04,
        !            35:        0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94, 0x54, 0xD4,
        !            36:        0x34, 0xB4, 0x74, 0xF4, 0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C,
        !            37:        0xEC, 0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, 0x02, 0x82,
        !            38:        0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, 0x12, 0x92, 0x52, 0xD2, 0x32,
        !            39:        0xB2, 0x72, 0xF2, 0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
        !            40:        0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA, 0x06, 0x86, 0x46,
        !            41:        0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6,
        !            42:        0x76, 0xF6, 0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 0x1E,
        !            43:        0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE, 0x01, 0x81, 0x41, 0xC1,
        !            44:        0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71,
        !            45:        0xF1, 0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99,
        !            46:        0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, 0x05, 0x85, 0x45, 0xC5, 0x25,
        !            47:        0xA5, 0x65, 0xE5, 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
        !            48:        0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, 0x1D, 0x9D, 0x5D,
        !            49:        0xDD, 0x3D, 0xBD, 0x7D, 0xFD, 0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3,
        !            50:        0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, 0x0B,
        !            51:        0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 0x1B, 0x9B, 0x5B, 0xDB,
        !            52:        0x3B, 0xBB, 0x7B, 0xFB, 0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67,
        !            53:        0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, 0x0F, 0x8F,
        !            54:        0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, 0x3F,
        !            55:        0xBF, 0x7F, 0xFF
        !            56: };
        !            57: 
        !            58: /*
        !            59:  * reverse bits in each byte
        !            60:  */
        !            61: 
        !            62: ReverseCharBits(charbits, charcount)
        !            63:        register u_char *charbits;
        !            64:        register charcount;
        !            65: {
        !            66:        register u_char *bits = (u_char *) &BitsReversed[0];
        !            67: 
        !            68: #ifdef TRACE_X
        !            69:         fprintf (stderr, "In ReverseCharBits\n");
        !            70:         fflush (stderr);
        !            71: #endif TRACE_X
        !            72: 
        !            73:        /*
        !            74:         * Do table look-up for each byte
        !            75:         */
        !            76: 
        !            77:        do {
        !            78:                *charbits = *(bits + *charbits);
        !            79:                charbits++;
        !            80:        } while(--charcount);
        !            81: }
        !            82: 
        !            83: /*
        !            84:  * reverse bits in each short
        !            85:  */
        !            86: 
        !            87: ReverseShortBits(shortbits, shortcount)
        !            88:        register u_short *shortbits;
        !            89:        register shortcount;
        !            90: {
        !            91:        register u_char *bits = (u_char *) &BitsReversed[0];
        !            92:        register u_char *charbits = (u_char *) shortbits;
        !            93:        register u_short tmpbits;
        !            94: 
        !            95: #ifdef TRACE_X
        !            96:         fprintf (stderr, "In ReverseShortBits\n");
        !            97:         fflush (stderr);
        !            98: #endif TRACE_X
        !            99: 
        !           100:        do {
        !           101:                tmpbits = (u_short) *(bits + *charbits++);
        !           102:                tmpbits |=  (u_short) (*(bits + *charbits++) << 8);
        !           103:                *shortbits++ = tmpbits;
        !           104:        } while(--shortcount);
        !           105: }

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