42 lines
931 B
ArmAsm
42 lines
931 B
ArmAsm
/* strchr() Author: Kees J. Bot */
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/* 1 Jan 1994 */
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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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#include <machine/asm.h>
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ENTRY(strchr)
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push %ebp
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movl %esp, %ebp
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push %edi
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cld
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movl 8(%ebp), %edi /* edi = string */
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movl $16, %edx /* Look at small chunks of the string */
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next:
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shll $1, %edx /* Chunks become bigger each time */
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movl %edx, %ecx
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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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subl %edx, %ecx
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negl %ecx /* Some or all of the chunk */
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subl %ecx, %edi /* Step back */
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movb 12(%ebp), %al /* 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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xorl %eax, %eax /* Return NULL */
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pop %edi
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pop %ebp
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ret
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found:
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pop %eax /* Get rid of those flags */
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leal -1(%edi), %eax /* Address of byte found */
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pop %edi
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pop %ebp
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ret
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