reactos/lib/rtl/i386/zeromemory_asm.s

   1 /*
   2  * COPYRIGHT:       See COPYING in the top level directory
   3  * PROJECT:         ReactOS kernel
   4  * FILE:            zeromemory_asm.S
   5  * PURPOSE:         Memory functions
   6  * PROGRAMMERS:     Patrick Baggett (baggett.patrick@gmail.com)
   7  *                  Alex Ionescu (alex@relsoft.net)
   8  *                  Magnus Olsen (magnusolsen@greatlord.com)
   9  */
  10
  11 .intel_syntax noprefix
  12
  13 /* GLOBALS ****************************************************************/
  14
  15 .globl  _RtlZeroMemory@8          // (no bug) (max optimze code)
  16
  17 /* FUNCTIONS ***************************************************************/
  18
  19 _RtlZeroMemory@8:
  20     mov ecx,dword [esp + 8 ]     // Length
  21     cmp ecx,0// if (Length==0) goto .zero
  22         je 3f
  23
  24     pushad   // Save all register on the stack
  25     mov edi, dword [esp + (4 + 32)]        // Destination
  26     xor eax,eax        // ZeroFillByte = 0
  27
  28 // code for take four byte each time it loop
  29     mov ebx,ecx        // temp_Length = Length
  30     shr ecx,2// Length = Length / sizeof(ULONG)
  31     jz 1f    // if (Length==0) goto .1byte
  32
  33     shl ecx,2// Length = Length * sizeof(ULONG)
  34     sub ebx,ecx        // temp_Length = temp_Length - Length//
  35     jz 2f    // if (temp_Length==0) goto .4byte
  36
  37 // move 4byte and 1byte
  38     shr ecx,2// Length = Length / sizeof(ULONG)
  39     cld      // clear d flag
  40     rep stosd// while (Length!=0) { (ULONG *) Destination[Length-1]=ZeroFillByte// Legnth = Legnth - 1 }
  41     mov ecx,ebx        // Length = temp_Length
  42     rep stosb// while (Length!=0) { (UCHAR *) Destination[Length-1]=ZeroFillByte// Legnth = Legnth - 1 }
  43     popad    // restore register
  44     ret 8    // return
  45
  46 // move 1byte
  47 1:
  48     mov ecx,dword [esp + (12 +32) ]        // Length
  49     cld      // clear d flag
  50     rep stosb// while (Length!=0) { (UCHAR *) Destination[Length-1]=ZeroFillByte// Legnth = Legnth - 1 }
  51     popad    // restore register
  52     ret 8    // return
  53
  54 // move 4bytes
  55 2:
  56     shr ecx,2// Length = Length / sizeof(ULONG)
  57     cld      // clear d flag
  58     rep stosd// while (Length!=0) { (ULONG *) Destination[Length-1]=ZeroFillByte// Legnth = Legnth - 1 }
  59     popad    // restore register
  60 3:
  61     ret 8    // return