390 lines
8.6 KiB
C++
390 lines
8.6 KiB
C++
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/*****************************************************************************
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* *
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* CSTREAM.CPP *
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* *
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* Copyright (C) Microsoft Corporation 1990-1997 *
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* All Rights reserved. *
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* *
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*****************************************************************************/
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#include "header.h"
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#include "cstream.h"
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#ifdef _DEBUG
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#undef THIS_FILE
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static char THIS_FILE[] = __FILE__;
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#endif
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#ifdef _DEBUG
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static LONG hsemReadCount;
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static LONG hsemStartCount;
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#define PTR_SEM_READ_COUNT &hsemReadCount
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#define PTR_SEM_START_COUNT &hsemStartCount
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#else
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#define PTR_SEM_READ_COUNT NULL
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#define PTR_SEM_START_COUNT NULL
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#endif
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#ifndef SEEK_CUR
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#define SEEK_CUR 1
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#define SEEK_END 2
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#define SEEK_SET 0
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#endif
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static HANDLE hsemRead; // semaphore used for dual-cpu processing
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static HANDLE hsemStart; // semaphore used for dual-cpu processing
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static CStream *pThis;
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static BOOL fReadAheadStarted;
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static BOOL fExitThread;
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static PBYTE pbuf1; // first buffer for dual-cpu processing
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static PBYTE pbuf2; // second buffer for dual-cpu processing
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/////////////////////// CStream implementation ////////////////////////////
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// We use our own stream class instead of using the C runtime, because this
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// change alone doubled the speed of the help compiler. I.e., the C runtime
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// implementation of stream io is horribly slow. 26-Feb-1994 [ralphw]
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// Also, this CStream will take advantage of a dual-CPU and will do
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// read-aheads in a thread.
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CStream::CStream(PCSTR pszFileName)
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{
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// Only one CStream can use the read-ahead thread
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if (!pThis) {
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fDualCPU = g_fDualCPU==-1?FALSE:g_fDualCPU;
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pThis = this;
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}
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else
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fDualCPU = FALSE;
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if ((hfile = _lopen(pszFileName, OF_READ)) == HFILE_ERROR) {
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fInitialized = FALSE;
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if (fDualCPU)
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pThis = NULL;
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return;
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}
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if (fDualCPU) {
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cbBuf = DUAL_CSTREAM_BUF_SIZE;
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if (!hsemRead) {
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hsemRead = CreateSemaphore(NULL, 1, 1, NULL);
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hsemStart = CreateSemaphore(NULL, 1, 1, NULL);
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pbuf2 = (PBYTE) lcMalloc(DUAL_CSTREAM_BUF_SIZE + 2);
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pbuf1 = (PBYTE) lcMalloc(DUAL_CSTREAM_BUF_SIZE + 2);
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}
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pbuf = pbuf1;
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}
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else {
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cbBuf = CSTREAM_BUF_SIZE;
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// +2 because we add a zero just past the buffer in case anyone expects strings
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pbuf = (PBYTE) lcMalloc(CSTREAM_BUF_SIZE + 2);
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}
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ASSERT(pbuf);
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fInitialized = TRUE;
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int cread = _lread(hfile, pbuf, cbBuf);
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if (cread == HFILE_ERROR) {
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_lclose(hfile);
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fInitialized = FALSE;
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if (fDualCPU)
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pThis = NULL;
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return;
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}
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if (fDualCPU) {
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// Start reading the next buffer
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cThrdRead = HFILE_NOTREAD;
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if (!fReadAheadStarted) {
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hthrd = CreateThread(NULL, 0,
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(LPTHREAD_START_ROUTINE) &ReadAhead, NULL,
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0, &idThrd);
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ASSERT(hthrd);
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if (!hthrd)
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fDualCPU = FALSE;
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else
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fReadAheadStarted = TRUE;
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}
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else {
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ReleaseSemaphore(hsemRead, 1, PTR_SEM_READ_COUNT);
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ReleaseSemaphore(hsemStart, 1, PTR_SEM_START_COUNT); // start read-ahead thread
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}
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}
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pCurBuf = pbuf;
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pEndBuf = pbuf + cread;
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pEndBuf[1] = '\0';
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lFilePos = cread;
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lFileBuf = 0;
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pszFile = lcStrDup(pszFileName);
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fInitialized = TRUE;
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m_fEndOfFile = FALSE;
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}
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CStream::~CStream()
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{
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if (fInitialized) {
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if (fDualCPU) {
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Cleanup();
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WaitForReadAhead();
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pThis = NULL;
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}
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else
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{
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lcFree(pbuf);
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}
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lcFree(pszFile);
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_lclose(hfile);
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}
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}
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/***************************************************************************
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FUNCTION: CStream::ReadBuf
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PURPOSE: Read the next block into buffer
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PARAMETERS:
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void
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RETURNS:
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COMMENTS:
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Zero-terminates the buffer
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MODIFICATION DATES:
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13-Nov-1994 [ralphw]
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***************************************************************************/
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char CStream::ReadBuf(void)
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{
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int cread;
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if (fDualCPU) {
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ASSERT(fReadAheadStarted);
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WaitForReadAhead();
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if (pbuf == pbuf1)
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pbuf = pbuf2;
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else
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pbuf = pbuf1;
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cread = cThrdRead;
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cThrdRead = HFILE_NOTREAD;
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ReleaseSemaphore(hsemRead, 1, PTR_SEM_READ_COUNT);
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// Error-checking must occur AFTER we release the read semaphore
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if (cread == HFILE_ERROR) {
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return chEOF;
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}
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ReleaseSemaphore(hsemStart, 1, PTR_SEM_START_COUNT); // start read-ahead thread
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}
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else {
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cread = _lread(hfile, pbuf, cbBuf);
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if (cread == HFILE_ERROR) {
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return chEOF;
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}
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}
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lFileBuf = lFilePos;
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lFilePos += cread;
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pCurBuf = pbuf;
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pEndBuf = pbuf + cread;
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pEndBuf[1] = '\0';
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if (!cread) {
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m_fEndOfFile = TRUE;
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return chEOF;
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}
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return (char) *pCurBuf++;
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}
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UINT STDCALL CStream::read(void* pbDest, int cbBytes)
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{
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if (pEndBuf - pbuf < cbBuf)
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if (pEndBuf - pCurBuf < cbBytes)
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cbBytes = (int)(pEndBuf - pCurBuf);
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if (pCurBuf + cbBytes < pEndBuf) {
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memcpy(pbDest, pCurBuf, cbBytes);
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pCurBuf += cbBytes;
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return cbBytes;
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}
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PBYTE pbDst = (PBYTE) pbDest;
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// If destination buffer is larger then our internal buffer, then
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// recursively call until we have filled up the destination.
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int cbRead = (int)(pEndBuf - pCurBuf);
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memcpy(pbDest, pCurBuf, cbRead);
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pbDst += cbRead;
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ReadBuf();
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if (m_fEndOfFile)
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return cbRead;
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else
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pCurBuf--; // since ReadBuf incremented it
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return read(pbDst, cbBytes - cbRead) + cbRead;
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}
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int STDCALL CStream::seek(int pos, SEEK_TYPE seek)
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{
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ASSERT(seek != SK_END); // we don't support this one
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if (seek == SK_CUR)
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pos = lFileBuf + (int)(pCurBuf - pbuf) + pos;
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if (pos >= lFileBuf && pos < lFilePos) {
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pCurBuf = pbuf + (pos - lFileBuf);
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if (pCurBuf >= pEndBuf && pEndBuf < pbuf + cbBuf)
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m_fEndOfFile = TRUE;
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return lFileBuf + (int)(pCurBuf - pbuf);
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}
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else {
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if (fDualCPU) {
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WaitForReadAhead();
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}
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lFileBuf = _llseek(hfile, pos, SEEK_SET);
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int cread = _lread(hfile, pbuf, cbBuf);
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if (cread == HFILE_ERROR) {
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m_fEndOfFile = TRUE;
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return chEOF;
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}
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lFilePos = lFileBuf + cread;
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pCurBuf = pbuf;
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pEndBuf = pbuf + cread;
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if (fDualCPU) {
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cThrdRead = HFILE_NOTREAD;
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ReleaseSemaphore(hsemRead, 1, PTR_SEM_READ_COUNT);
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if (fReadAheadStarted)
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ReleaseSemaphore(hsemStart, 1, PTR_SEM_START_COUNT); // start read-ahead thread
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}
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if (cread == 0)
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m_fEndOfFile = TRUE;
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return lFilePos;
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}
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}
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void CStream::WaitForReadAhead(void)
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{
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for(;;) {
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WaitForSingleObject(hsemRead, INFINITE);
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if (cThrdRead == HFILE_NOTREAD) {
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ReleaseSemaphore(hsemRead, 1, PTR_SEM_READ_COUNT);
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Sleep(1); // give read-ahead thread a chance to run
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}
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else
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return;
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}
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}
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/***************************************************************************
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FUNCTION: ReadAhead
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PURPOSE: Reads the next block of data from a file
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PARAMETERS:
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pthis
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RETURNS:
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COMMENTS:
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Two semaphores control this thread:
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hsemStart: keeps the thread suspended while waiting for the
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caller to finish reading one of its blocks.
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hsemRead: used as a signal between the main thread and this
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thread as to when this thread has completed.
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Because it is theoretically possible for a thread switch to occur
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between the time the hsemStart thread starts this thread and this
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thread's call to WaitForSingleObject(hsemRead), the caller also sets
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the read return value to HFILE_NOTREAD to ensure that it does not
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attempt to use this buffer until in fact the read has completed.
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NOTE: this thread approach only makes sense on a system with more
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then one CPU.
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MODIFICATION DATES:
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05-Feb-1997 [ralphw]
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***************************************************************************/
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DWORD WINAPI ReadAhead(LPVOID pv)
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{
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/*
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* Each time through the loop, we block on hsemStart, waiting for our
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* caller to release it. The hsemRead is used to block the caller until
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* we have completed our read.
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*/
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for (;;) {
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PBYTE pbReadBuf;
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WaitForSingleObject(hsemStart, INFINITE);
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if (fExitThread)
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break;
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WaitForSingleObject(hsemRead, INFINITE);
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pbReadBuf = (pThis->pbuf == pbuf1) ? pbuf2 : pbuf1;
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pThis->cThrdRead = _lread(pThis->hfile, pbReadBuf, pThis->cbBuf);
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ReleaseSemaphore(hsemRead, 1, PTR_SEM_READ_COUNT);
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}
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ExitThread(0);
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return 0;
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}
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/***************************************************************************
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FUNCTION: CStream::Cleanup
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PURPOSE: Cleanup global variables
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PARAMETERS:
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void
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RETURNS:
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COMMENTS:
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MODIFICATION DATES:
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05-Feb-1997 [ralphw]
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***************************************************************************/
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void CStream::Cleanup(void)
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{
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if (fReadAheadStarted) {
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fExitThread = TRUE;
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ReleaseSemaphore(hsemStart, 1, PTR_SEM_START_COUNT); // start read-ahead thread
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Sleep(1); // Let the other thread run
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CloseHandle(hsemStart);
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CloseHandle(hsemRead);
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lcFree(pbuf1);
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lcFree(pbuf2);
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hsemStart = hsemRead = pbuf1 = pbuf2 = NULL;
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}
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}
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#ifdef _DEBUG
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char CStream::cget()
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{
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if (pCurBuf < pEndBuf)
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return (char) *pCurBuf++;
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else if (pEndBuf < pbuf + cbBuf) {
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m_fEndOfFile = TRUE;
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return chEOF;
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}
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else
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return ReadBuf();
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}
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#endif
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