39 lines
851 B
ArmAsm
39 lines
851 B
ArmAsm
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! strchr() 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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! char *strchr(const char *s, int c)
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! Look for a character in a string.
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!
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.sect .text
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.define _strchr
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_strchr:
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push bp
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mov bp, sp
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push di
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cld
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mov di, 4(bp) ! di = string
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mov dx, #16 ! Look at small chunks of the string
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next: shl dx, #1 ! Chunks become bigger each time
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mov cx, dx
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xorb al, al ! Look for the zero at the end
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repne scasb
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pushf ! Remember the flags
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sub cx, dx
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neg cx ! Some or all of the chunk
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sub di, cx ! Step back
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movb al, 6(bp) ! The character to look for
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repne scasb
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je found
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popf ! Did we find the end of string earlier?
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jne next ! No, try again
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xor ax, ax ! Return NULL
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pop di
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pop bp
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ret
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found: pop ax ! Get rid of those flags
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lea ax, -1(di) ! Address of byte found
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pop di
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pop bp
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ret
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