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Annotation of coherent/b/lib/libc/string/i386/memmove.s, revision 1.1

1.1     ! root        1: //////////
        !             2: / libc/string/i386/memmove.s
        !             3: / i386 C string library.
        !             4: / ANSI 4.11.2.2.
        !             5: //////////
        !             6: 
        !             7: ////////
        !             8: / void *
        !             9: / memmove(void *To, void *From, size_t Count)
        !            10: /
        !            11: / Copy a block of memory from one
        !            12: / place in physical address space to
        !            13: / another place in physical address space.
        !            14: / Copy backwards if the source precedes the destination in memory.
        !            15: / Forward copy uses memcpy(), q.v.
        !            16: / Backward copy does byte-by-byte copy rather than trying to use dwords.
        !            17: ////////
        !            18: 
        !            19: To     .equ    12                      / destination
        !            20: From   .equ    To+4                    / source
        !            21: Count  .equ    From+4                  / byte count
        !            22: 
        !            23:        .globl  memmove
        !            24:        .globl  _memcpy
        !            25: 
        !            26: memmove:
        !            27:        push    %esi
        !            28:        push    %edi
        !            29: 
        !            30:        movl    %edi, To(%esp)          / Load EDI with destination.
        !            31:        movl    %eax, %edi              / Return value to EAX.
        !            32:        movl    %ecx, Count(%esp)       / Pick up byte count.
        !            33:        jecxz   ?done                   / No work.
        !            34:        movl    %esi, From(%esp)        / Load ESI with source.
        !            35:        cmpl    %esi, %edi              / Compare pointers.
        !            36:        jz      ?done                   / From == To.
        !            37:        ja      _memcpy                 / From > To, copy forward.
        !            38:        addl    %esi, %ecx              / From < To,
        !            39:        addl    %edi, %ecx              / copy backward.
        !            40:        decl    %esi                    / Find end of From
        !            41:        decl    %edi                    / and end of To.
        !            42:        std                             / Set flag for backward copy.
        !            43:        rep                             / Copy
        !            44:        movsb                           / bytes.
        !            45:        cld                             / Clear direction flag.
        !            46: 
        !            47: ?done:
        !            48:        pop     %edi
        !            49:        pop     %esi
        !            50:        ret
        !            51: 
        !            52: / end of libc/string/i386/memmove.s

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