| 0,0 → 1,47 |
|---|
| # memset() Author: Kees J. Bot |
| # 2 Jan 1994 |
| # void *memset(void *s, int c, size_t n) |
| # Set a chunk of memory to the same byte value. |
| # |
| |
| .intel_syntax |
| |
| .global _memset |
| |
| .text |
| .align 16 |
| _memset: |
| push ebp |
| mov ebp, esp |
| push edi |
| mov edi, [8+ebp] # The string |
| movzx eax, byte ptr [12+ebp] # The fill byte |
| mov ecx, [16+ebp] # Length |
| cld |
| cmp ecx, 16 |
| jb sbyte # Don't bother being smart with short arrays |
| test edi, 1 |
| jnz sbyte # Bit 0 set, use byte store |
| test edi, 2 |
| jnz sword # Bit 1 set, use word store |
| slword: |
| movb ah, al |
| mov edx, eax |
| sal edx, 16 |
| or eax, edx # One byte to four bytes |
| shrd edx, ecx, 2 # Save low two bits of ecx in edx |
| shr ecx, 2 |
| rep stosd # Store longwords. |
| shld ecx, edx, 2 # Restore low two bits |
| sword: |
| movb ah, al # One byte to two bytes |
| shr ecx, 1 |
| rep stosw # Store words |
| adc ecx, ecx # One more byte? |
| sbyte: |
| rep stosb # Store bytes |
| done: |
| mov eax, [8+ebp] # Return some value you have no need for |
| pop edi |
| pop ebp |
| ret |