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Annotation of driverkit/libDriver/i386/memcpy.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: /* Copyright (c) 1992 by NeXT Computer, Inc.
        !            25:  *
        !            26:  *      File:  memcpy.c
        !            27:  *
        !            28:  * HISTORY
        !            29:  * 16-Aug-93  John Immordino at NeXT
        !            30:  *      Created (stolen from mk/machdep/i386/libc/memcpy.c)
        !            31:  */
        !            32: 
        !            33: #import <driverkit/driverTypes.h>
        !            34: 
        !            35: /*
        !            36:  * 486 Facts:
        !            37:  *  - if (move <= 16 bytes) use unrolled mem-mem mov instructions
        !            38:  *  - if (move > 16 bytes) use "rep movs" [this avoids prefetch stalls]
        !            39:  *  - Aligned read is better than aligned write. Both aligned is even better.
        !            40:  */
        !            41: 
        !            42: #define MIN_TO_ALIGN   16
        !            43: 
        !            44: /*
        !            45:  * Convert a void * into a unsigned int so arithmetic can be done
        !            46:  * (Technically, the gnu C compiler is tolerant of arithmetic
        !            47:  * on void *, but ansi isn't; so we do this.)
        !            48:  */
        !            49: #define UNS(voidp)      ((unsigned int)(voidp))
        !            50: 
        !            51: /*
        !            52:  * Number of bytes addr is past an integer alignment
        !            53:  */
        !            54: #define BYTES_PAST_ALIGNMENT(voidp, boundary) (UNS(voidp) & (boundary - 1))
        !            55: 
        !            56: #if defined(NX_CURRENT_COMPILER_RELEASE) && (NX_CURRENT_COMPILER_RELEASE < 320)
        !            57: #define SIREG "e"
        !            58: #else
        !            59: #define SIREG "S"
        !            60: #endif
        !            61: 
        !            62: #define CHAR(voidp, offset)    (*(char *)(UNS(voidp) + (offset)))
        !            63: 
        !            64: static __inline__ void
        !            65: simple_fwd_char_copy(void *dst, const void *src, int len)
        !            66: {
        !            67:     asm("rep; movsb"
        !            68:        : /* no outputs */
        !            69:        : "&c" (len), "D" (dst), SIREG (src)
        !            70:        : "ecx", "esi", "edi");
        !            71: }
        !            72: 
        !            73: static __inline__ void
        !            74: simple_fwd_short_copy(void *dst, const void *src, int len)
        !            75: {
        !            76:     asm("rep; movsw"
        !            77:        : /* no outputs */
        !            78:        : "&c" (len>>1), "D" (dst), SIREG (src)
        !            79:        : "ecx", "esi", "edi");
        !            80: }
        !            81: 
        !            82: static __inline__ void
        !            83: simple_fwd_int_copy(void *dst, const void *src, int len)
        !            84: {
        !            85:     asm("rep; movsl"
        !            86:        : /* no outputs */
        !            87:        : "&c" (len>>2), "D" (dst), SIREG (src)
        !            88:        : "ecx", "esi", "edi");
        !            89: }
        !            90: 
        !            91: 
        !            92: void _IOCopyMemory(char *src, char *dst, unsigned copyLen, 
        !            93:        unsigned copyUnitSize)
        !            94: {
        !            95:     int need_to_move;
        !            96: 
        !            97:     if (src == NULL || dst == NULL || src == dst || copyLen == 0)
        !            98:        return;
        !            99:     
        !           100:     /* 
        !           101:      * Sanity check copyUnitSize
        !           102:      */
        !           103:     if (copyUnitSize == 0)
        !           104:        copyUnitSize = 1;
        !           105:     if (copyUnitSize > 2)
        !           106:        copyUnitSize = 4;
        !           107:     
        !           108:     /* 
        !           109:      * Always do a forward copy.  See if we need 
        !           110:      * a byte-size copy. 
        !           111:      */
        !           112:     if (copyUnitSize == 1) {
        !           113:        simple_fwd_char_copy(dst, src, (int)copyLen);
        !           114:        return;
        !           115:     }
        !           116:     
        !           117:     /* 
        !           118:      * Copy bytes up to a copyUnitSize boundary. 
        !           119:      */
        !           120:     if (need_to_move = BYTES_PAST_ALIGNMENT(src, copyUnitSize)) {
        !           121:        need_to_move = copyUnitSize - need_to_move;
        !           122:        simple_fwd_char_copy(dst, src, need_to_move);
        !           123:        copyLen -= need_to_move;
        !           124:        UNS(dst) += need_to_move;
        !           125:        UNS(src) += need_to_move;
        !           126:     }
        !           127: 
        !           128:     /* 
        !           129:      * Copy what we can at maximum specified size. 
        !           130:      */
        !           131:     if (copyUnitSize == 2)
        !           132:        simple_fwd_short_copy(dst, src, (int)copyLen);
        !           133:     else
        !           134:        simple_fwd_int_copy(dst, src, (int)copyLen);
        !           135: 
        !           136:     /* 
        !           137:      * Get the leftovers. 
        !           138:      */
        !           139:     if (need_to_move = (copyLen & (copyUnitSize - 1))) {
        !           140:        UNS(src) += (copyLen & ~(copyUnitSize - 1));
        !           141:        UNS(dst) += (copyLen & ~(copyUnitSize - 1));
        !           142:        switch(need_to_move) {
        !           143:            case 3: CHAR(dst, 2) = CHAR(src, 2);
        !           144:            case 2: CHAR(dst, 1) = CHAR(src, 1);
        !           145:            case 1: CHAR(dst, 0) = CHAR(src, 0);
        !           146:        }
        !           147:     }
        !           148: }

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