| 1,46 → 1,41 |
|---|
| # strchr() Author: Kees J. Bot 1 Jan 1994 |
| /* strchr() Author: Kees J. Bot */ |
| /* 1 Jan 1994 */ |
| |
| # char *strchr(const char *s, int c) |
| # Look for a character in a string. |
| /* char *strchr(const char *s, int c) */ |
| /* Look for a character in a string. */ |
| /* */ |
| #include "asm.h" |
| |
| .intel_syntax |
| |
| .globl _strchr |
| |
| .text |
| .align 16 |
| _strchr: |
| push ebp |
| mov ebp, esp |
| push edi |
| ENTRY(strchr) |
| push %ebp |
| movl %esp, %ebp |
| push %edi |
| cld |
| mov edi, [ebp+8] # edi = string |
| mov edx, 16 # Look at small chunks of the string |
| movl 8(%ebp), %edi /* edi = string */ |
| movl $16, %edx /* Look at small chunks of the string */ |
| next: |
| shl edx, 1 # Chunks become bigger each time |
| mov ecx, edx |
| xorb al, al # Look for the zero at the end |
| shll $1, %edx /* Chunks become bigger each time */ |
| movl %edx, %ecx |
| xorb %al, %al /* Look for the zero at the end */ |
| |
| repne scasb |
| pushf /* Remember the flags */ |
| subl %edx, %ecx |
| negl %ecx /* Some or all of the chunk */ |
| subl %ecx, %edi /* Step back */ |
| movb 12(%ebp), %al /* The character to look for */ |
| |
| pushf # Remember the flags |
| sub ecx, edx |
| neg ecx # Some or all of the chunk |
| sub edi, ecx # Step back |
| movb al, [ebp+12] # The character to look for |
| repne scasb |
| je found |
| |
| popf # Did we find the end of string earlier? |
| |
| jne next # No, try again |
| |
| xor eax, eax # Return NULL |
| pop edi |
| pop ebp |
| popf /* Did we find the end of string earlier? */ |
| jne next /* No, try again */ |
| xorl %eax, %eax /* Return NULL */ |
| pop %edi |
| pop %ebp |
| ret |
| found: |
| pop eax # Get rid of those flags |
| lea eax, [edi-1] # Address of byte found |
| pop edi |
| pop ebp |
| pop %eax /* Get rid of those flags */ |
| leal -1(%edi), %eax /* Address of byte found */ |
| pop %edi |
| pop %ebp |
| ret |