//************************************************************************
//
//?RingBuffer.cpp
//
//************************************************************************

#include?“StdDCls.h“

//?This?is?a?nice?ringbuffer?implementation?that?Tom?gave?me?yesterday...
//?thanks!
#include?“RingBuffer.h“

//?fast?MOD?operation?doesn‘t?need?divide?（but?is?restricted?in?its?generality）
#define?MYMOD（xn）?（（x）?>=?（n）???（（x）-（n））?:?（x））

void?CRingBuffer::Initialize（void?*pbase?long?nBufferSize）
{
????m_nOverflowOccurred?=?0;
????m_pbase?=?（unsigned?char?*）?pbase;
????m_nTotalBytes?=?（NULL?==?m_pbase）???0?:?nBufferSize;
????m_nBytes?=?0;
????m_nInPtr?=?0;
????m_nOutPtr?=?0;
}

bool?CRingBuffer::WriteBytes（void?*pData?long?nBytes）
{
????long?p1len?p2len;
????if（nBytes?>?GetFreeSize（））
????{
????????return?false;
????}
????
????p1len?=?min（nBytes?m_nTotalBytes?-?m_nInPtr）;
????p2len?=?nBytes?-?p1len;
????//?copy?first?bit?（up?to?the?end?of?the?buffer?or?end?of?source?data?whichever?comes?first）
????RtlCopyMemory（m_pbase?+?m_nInPtr?pData?p1len）;
????if（p2len）
????{
????????//?if?there?was?an?overlap?copy?the?rest?as?well
????????RtlCopyMemory（m_pbase?（unsigned?char?*）pData?+?p1len?p2len）;
????}
????m_nInPtr?+=?nBytes;
????m_nInPtr?=?MYMOD（m_nInPtr?m_nTotalBytes）;
????
????InterlockedExchangeAdd（&m_nBytes?nBytes）;
????
????return?true;
}

bool?CRingBuffer::ReadBytes（void?*pData?long?nBytes）
{
????long?p1len?p2len;
????if（nBytes?>?m_nBytes）
????{
????????//?not?enough?data?in?buffer
????????return?false;
????}
????
????p1len?=?min（nBytes?m_nTotalBytes?-?m_nOutPtr）;
????p2len?=?nBytes?-?p1len;
????RtlCopyMemory（pData?m_pbase?+?m_nOutPtr?p1len）;
????if（p2len）
????{
????????RtlCopyMemory（（unsigned?char*）pData?+?p1len?m_pbase?p2len）;
????}

????m_nOutPtr?+=?nBytes;
????m_nOutPtr?=?MYMOD（m_nOutPtr?m_nTotalBytes）;
????
????InterlockedExchangeAdd（&m_nBytes?-nBytes）;

????return?true;
}

bool?CRingBuffer::PeekBytes（void?*pData?long?nBytes）
{
????long?p1len?p2len;
????if（nBytes?>?m_nBytes）
????{
????????//?not?enough?data?in?buffer
????????return?false;
????}
????
????p1len?=?min（nBytes?m_nTotalBytes?-?m_nOutPtr）;
????p2len?=?nBytes?-?p1len;
????RtlCopyMemory（pData?m_pbase?+?m_nOutPtr?p1len）;
????if（p2len）
????{
????????RtlCopyMemory（（unsigned?char*）pData?+?p1len?m_pbase?p2len）;
????}

????return?true;
}

bool?CRingBuffer::FlushBuffer（void）
{
????//?EnterAccess（）;
????m_nBytes?=?0;
????m_nInPtr?=?0;
????m_nOutPtr?=?0;
????//?LeaveAccess（）;
????return?true;
}

//**?end?of?RingBuffer.cpp?***********************************************
/*************************************************************************

??$Log:?RingBuffer.cppv?$
??Revision?1.1??2002/08/14?23:00:58??rbosa
??shared?code?between?the?application?and?driver?and?drivers?themselves...

?*?
?*?1?????1/25/02?2:44p?Rbosa

*****************************************