fmemmove.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 167 行

/****************************************************************************
*
*                            Open Watcom Project
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*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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*  ========================================================================
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*    This file contains Original Code and/or Modifications of Original
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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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#include "variety.h"
#include <stddef.h>
#include <string.h>

#if defined(__386__)

#if defined(__FLAT__)
extern  void    movefwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movefwd =  \
        0x06            /* push es */\
        0x8e 0xc2       /* mov es,dx */\
        0x1e            /* push ds */\
        0x96            /* xchg esi,eax */\
        0x8e 0xd8       /* mov ds,ax */\
        0xd1 0xe9       /* shr cx,1 */\
        0x66 0xf3 0xa5  /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0xf3 0xa4       /* rep movsb */\
        0x1f            /* pop ds */\
        0x07            /* pop es */\
        parm [dx edi] [si eax] [ecx] \
        modify exact [edi esi ecx eax];
#else
extern  void    movefwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movefwd =  \
        0x1e            /* push ds */\
        0x96            /* xchg esi,eax */\
        0x8e 0xd8       /* mov ds,ax */\
        0xd1 0xe9       /* shr cx,1 */\
        0x66 0xf3 0xa5  /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0xf3 0xa4       /* rep movsb */\
        0x1f            /* pop ds */\
        parm [es edi] [si eax] [ecx] \
        modify exact [edi esi ecx eax];
#endif

#elif defined(M_I86)
#if defined(__SMALL_DATA__)
extern  void    movebwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movebwd =  \
        0xfd            /* std */\
        0x1e            /* push ds */\
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax */\
        0x4e            /* dec si */\
        0x4f            /* dec di */\
        0xd1 0xe9       /* shr cx,1 */\
        0xf3 0xa5       /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0x46            /* inc si */\
        0x47            /* inc di */\
        0xf3 0xa4       /* rep movsb */\
        0xfc            /* cld */\
        0x1f            /* pop ds */\
        parm [es di] [si ax] [cx] \
        modify exact [di si cx ax];

extern  void    movefwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movefwd =  \
        0x1e            /* push ds */\
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax */\
        0xd1 0xe9       /* shr cx,1 */\
        0xf3 0xa5       /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0xf3 0xa4       /* rep movsb */\
        0x1f            /* pop ds */\
        parm [es di] [si ax] [cx] \
        modify exact [di si cx ax];
#else
extern  void    movebwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movebwd =  \
        0xfd            /* std */\
        0x1e            /* push ds */\
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax */\
        0x4e            /* dec si */\
        0x4f            /* dec di */\
        0xd1 0xe9       /* shr cx,1 */\
        0xf3 0xa5       /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0x46            /* inc si */\
        0x47            /* inc di */\
        0xf3 0xa4       /* rep movsb */\
        0xfc            /* cld */\
        0x1f            /* pop ds */\
        parm [es di] [si ax] [cx] \
        modify exact [di si cx ax];

extern  void    movefwd( char _WCFAR *dst, const char _WCFAR *src, unsigned len);
#pragma aux     movefwd =  \
        0x1e            /* push ds */\
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax */\
        0xd1 0xe9       /* shr cx,1 */\
        0xf3 0xa5       /* rep movsw */\
        0x11 0xc9       /* adc cx,cx */\
        0xf3 0xa4       /* rep movsb */\
        0x1f            /* pop ds */\
        parm [es di] [si ax] [cx] \
        modify exact [di si cx ax];
#endif
#else
#error platform not supported
#endif


_WCRTLINK void _WCFAR *_fmemmove( void _WCFAR *t, const void _WCFAR *f, size_t len )
    {
        char _WCFAR *to = t;
        const char _WCFAR *from = f;
        if( from == to ) {
            return( to );
        }
        if( from < to  &&  from + len > to ) {  /* if buffers are overlapped*/
#if defined(__HUGE__) || defined(__386__)
            to += len;
            from += len;
            while( len != 0 ) {
                to--;
                from--;
                *to = *from;
                len--;
            }
#else
            movebwd(( to + len ) - 1, ( from + len ) - 1, len );
#endif
        } else {
            movefwd( to, from, len );
        }
        return( to );
    }