_memicmp.asm

来自「C语言库函数的原型,有用的拿去」· 汇编 代码 · 共 131 行

        page        ,132
        title        memicmp - compare blocks of memory, ignore case
;***
;memicmp.asm - compare memory, ignore case
;
;       Copyright (c) Microsoft Corporation. All rights reserved.
;
;Purpose:
;       defines __ascii_memicmp() - compare two blocks of memory for lexical
;       order. Case is ignored in the comparison.
;
;*******************************************************************************

        .xlist
        include cruntime.inc
        .list

page
;***
;int __ascii_memicmp(first, last, count) - compare two blocks of memory, ignore case
;
;Purpose:
;       Compares count bytes of the two blocks of memory stored at first
;       and last.  The characters are converted to lowercase before
;       comparing (not permanently), so case is ignored in the search.
;
;       Algorithm:
;       int
;       _memicmp (first, last, count)
;               char *first, *last;
;               unsigned count;
;               {
;               if (!count)
;                       return(0);
;               while (--count && tolower(*first) == tolower(*last))
;                       {
;                       first++;
;                       last++;
;                       }
;               return(tolower(*first) - tolower(*last));
;               }
;
;Entry:
;       char *first, *last - memory buffers to compare
;       unsigned count - maximum length to compare
;
;Exit:
;       returns <0 if first < last
;       returns 0 if first == last
;       returns >0 if first > last
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************

        CODESEG

        public  __ascii_memicmp
__ascii_memicmp proc \
        uses edi esi ebx, \
        first:ptr byte, \
        last:ptr byte, \
        count:IWORD

        mov     ecx,[count]     ; cx = count
        or      ecx,ecx
        jz      short toend     ; if count=0, nothing to do

        mov     esi,[first]     ; si = first
        mov     edi,[last]      ; di = last

        ; C locale

        mov     bh,'A'
        mov     bl,'Z'
        mov     dh,'a'-'A'      ; add to cap to make lower

        align   4

lupe:
        mov     ah,[esi]        ; ah = *first
        add     esi,1           ; first++
        mov     al,[edi]        ; al = *last
        add     edi,1           ; last++

        cmp     ah,al           ; test for equality BEFORE converting case
        je      short dolupe

        cmp     ah,bh           ; ah < 'A' ??
        jb      short skip1

        cmp     ah,bl           ; ah > 'Z' ??
        ja      short skip1

        add     ah,dh           ; make lower case

skip1:
        cmp     al,bh           ; al < 'A' ??
        jb      short skip2

        cmp     al,bl           ; al > 'Z' ??
        ja      short skip2

        add     al,dh           ; make lower case

skip2:
        cmp     ah,al           ; *first == *last ??
        jne     short differ    ; nope, found mismatched chars

dolupe:
        sub     ecx,1
        jnz     short lupe

        jmp     short toend     ; cx = 0, return 0

differ:
        mov     ecx,-1          ; assume last is bigger
                                ; *** can't use "or ecx,-1" due to flags ***
        jb      short toend     ; last is, in fact, bigger (return -1)
        neg     ecx             ; first is bigger (return 1)

toend:
        mov     eax,ecx         ; move return value to ax

        ret                     ; _cdecl return

__ascii_memicmp endp
        end