45 lines
1.0 KiB
ArmAsm
45 lines
1.0 KiB
ArmAsm
# strncmp() Author: Kees J. Bot 1 Jan 1994
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# int strncmp(const char *s1, const char *s2, size_t ecx)
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# Compare two strings.
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#
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.intel_syntax
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.globl __strncmp
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.text
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.align 16
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__strncmp:
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push ebp
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mov ebp, esp
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push esi
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push edi
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test ecx, ecx # Max length is zero?
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je done
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mov esi, [ebp+8] # esi = string s1
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mov edi, [ebp+12] # edi = 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 done
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cmpb [esi-1], 0 # End of string?
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je done
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dec ecx # Length limit reached?
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jne compare
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done:
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seta al # al = (s1 > s2)
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setb ah # ah = (s1 < s2)
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subb al, ah
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movsx eax, al # eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1
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pop edi
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pop esi
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pop ebp
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ret
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