36 lines
703 B
ArmAsm
36 lines
703 B
ArmAsm
! strncmp() Author: Kees J. Bot
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! 27 Jan 1994
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.sect .text; .sect .rom; .sect .data; .sect .bss
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! int strncmp(const char *s1, const char *s2, size_t cx)
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! Compare two strings.
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!
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.sect .text
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.define __strncmp
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__strncmp:
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push bp
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mov bp, sp
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push si
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push di
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xor ax, ax ! Prepare return value
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test cx, cx ! Max length is zero?
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je equal
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mov si, 4(bp) ! si = string s1
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mov di, 6(bp) ! di = string s2
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cld
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compare:
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cmpsb ! Compare two bytes
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jne unequal
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cmpb -1(si), #0 ! End of string?
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je equal
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dec cx ! Length limit reached?
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jne compare
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jmp equal
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unequal:
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ja after
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sub ax, #2 ! if (s1 < s2) ax -= 2;
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after: inc ax ! ax++, now it's -1 or 1
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equal: pop di
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pop si
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pop bp
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ret
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