title  "Byte Swap Functions"


; Copyright (c) 1997  Microsoft Corporation

; Module Name:

;    movemem.asm

; Abstract:

;    This module implements functions to perform byte swapping operations.


; Author:

;    Forrest Foltz (forrestf) 12-Dec-1997

; Environment:

;    User or Kernel mode.

; Revision History:


.486p
    .xlist
include ks386.inc
include callconv.inc            ; calling convention macros
    .list


; Alignment for functions in this module


CODE_ALIGNMENT macro
    align   16
endm


_TEXT$00   SEGMENT PARA PUBLIC 'CODE'
    ASSUME  DS:FLAT, ES:FLAT, SS:NOTHING, FS:NOTHING, GS:NOTHING

    PAGE
    SUBTTL "RtlUshortByteSwap"


; USHORT
; RtlUshortByteSwap(
;    IN USHORT Source
;    )

; /*++

; Routine Description:

;    The RtlfUshortByteSwap function exchanges bytes 0 and 1 of Source
;    and returns the resulting USHORT.

; Arguments:

;    (cx) Source - 16-bit value to byteswap.

; Return Value:

;    Swapped 16-bit value.



CODE_ALIGNMENT

cPublicFastCall RtlUshortByteSwap  ,1
cPublicFpo 0, 0

    mov     ah, cl
    mov     al, ch
    fstRET  RtlUshortByteSwap

fstENDP RtlUshortByteSwap


    PAGE
    SUBTTL "RtlUlongByteSwap"


; ULONG
; RtlUlongByteSwap(
;    IN ULONG Source
;    )

; /*++

; Routine Description:

;    The RtlUlongByteSwap function exchanges byte pairs 0:3 and 1:2 of
;    Source and returns the the resulting ULONG.

; Arguments:

;    (ecx) Source - 32-bit value to byteswap.

; Return Value:

;    Swapped 32-bit value.



CODE_ALIGNMENT

cPublicFastCall RtlUlongByteSwap  ,1
cPublicFpo 0, 0

    mov     eax, ecx
    bswap   eax
    fstRET  RtlUlongByteSwap

fstENDP RtlUlongByteSwap


    PAGE
    SUBTTL "RtlUlonglongByteSwap"


; ULONG
; RtlUlonglongByteSwap(
;    IN ULONGLONG Source
;    )

; /*++

; Routine Description:

;    The RtlUlonglongByteSwap function exchanges byte pairs 0:7, 1:6, 2:5,
;    and 3:4 of Source and returns the resulting ULONGLONG.

; Arguments:

;    (edx:ecx) Source - 64-bit value to byteswap.

; Return Value:

;    Swapped 64-bit value.



CODE_ALIGNMENT

cPublicFastCall RtlUlonglongByteSwap  ,1
cPublicFpo 0, 0

    mov     edx, eax
    mov     eax, ecx
    bswap   edx
    bswap   eax
    fstRET  RtlUlonglongByteSwap

fstENDP RtlUlonglongByteSwap

_TEXT$00   ends
    end