35 lines
731 B
ArmAsm
35 lines
731 B
ArmAsm
/* strncmp() Author: Kees J. Bot */
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/* 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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#include <machine/asm.h>
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ENTRY(_strncmp)
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push %ebp
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movl %esp, %ebp
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push %esi
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push %edi
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testl %ecx, %ecx /* Max length is zero? */
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je done
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movl 8(%ebp), %esi /* esi = string s1 */
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movl 12(%ebp), %edi /* 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 $0, -1(%esi) /* End of string? */
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je done
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decl %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 %ah, %al
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movsbl %al, %eax /* 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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