strcpy.S

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/*-
 * Copyright (c) 2002-2018 The UbixOS Project.
 * All rights reserved.
 *
 * This was developed by Christopher W. Olsen for the UbixOS Project.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met:
 *
 * 1) Redistributions of source code must retain the above copyright notice, this list of
 *    conditions, the following disclaimer and the list of authors.
 * 2) Redistributions in binary form must reproduce the above copyright notice, this list of
 *    conditions, the following disclaimer and the list of authors in the documentation and/or
 *    other materials provided with the distribution.
 * 3) Neither the name of the UbixOS Project nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

 #include <i386/asmacros.h>

 ENTRY(strcpy)
        movl    4(%esp),%ecx            /* dst address */
        movl    8(%esp),%edx            /* src address */
        pushl   %ecx                    /* push dst address */

        .align 2,0x90
L1:     movb    (%edx),%al              /* unroll loop, but not too much */
        movb    %al,(%ecx)
        testb   %al,%al
        je      L2
        movb    1(%edx),%al
        movb    %al,1(%ecx)
        testb   %al,%al
        je      L2
        movb    2(%edx),%al
        movb    %al,2(%ecx)
        testb   %al,%al
        je      L2
        movb    3(%edx),%al
        movb    %al,3(%ecx)
        testb   %al,%al
        je      L2
        movb    4(%edx),%al
        movb    %al,4(%ecx)
        testb   %al,%al
        je      L2
        movb    5(%edx),%al
        movb    %al,5(%ecx)
        testb   %al,%al
        je      L2
        movb    6(%edx),%al
        movb    %al,6(%ecx)
        testb   %al,%al
        je      L2
        movb    7(%edx),%al
        movb    %al,7(%ecx)
        addl    $8,%edx
        addl    $8,%ecx
        testb   %al,%al
        jne     L1
L2:     popl    %eax                    /* pop dst address */
        ret
END(strcpy)