DirextX编程

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Visual C++

smartcache.c：源码内容
							//
// smartcache.c
// 2002-12-05
// Added by Lu Qiming(luqiming@263.net), to do smart input buffer
#include "global.h"
#include "smartcache.h"
#include <malloc.h>
#include <stdio.h>
///////////////////////////////////////////////////////////////////
// There is a serious problem, Because the different instances of 
// this decoder filter will shart all global variables.
// It's very dangerous!
// So this decoder filter is forbidden to be used more than twice 
// in one application, even if intelligent connecting.
// The same potential problems with the C-CODE MPEG DECODING. 
// 2002-12-26
////////////////////////////////////////////////////////////////////
unsigned char * gInputCache = NULL;
static long gCacheSize   = 1024 * 1024;
static long gMinWorkSize = 10 * 1024;
static long gReadingOffset = 0;
static long gWritingOffset = 0;
static BOOL gIsFlushing = FALSE;
static CRITICAL_SECTION singleAccess;
static BOOL inputWaiting  = FALSE;
static BOOL outputWaiting = FALSE;
static BOOL cacheChecking = TRUE;
static int  waitingCounter;
static void MakeSpace(void);
static long HasEnoughSpace(long inNeedSize);
static long HasEnoughData(long inNeedSize);
//FILE * fp = NULL;
long InitSmartCache(void)
{
	gInputCache = malloc(gCacheSize);
	gReadingOffset = 0;
	gWritingOffset = 0;
	inputWaiting  = FALSE;
	outputWaiting = FALSE;
	cacheChecking = TRUE;  // When checking, maybe return to the cache header
	// Critical section to access smart cache
	InitializeCriticalSection(&singleAccess); 
	return (gInputCache != NULL);
}
void ReleaseSmartCache(void)
{
	DeleteCriticalSection(&singleAccess);
	if (gInputCache)
	{
		free(gInputCache);
		gInputCache = NULL;
	}
}
// Blocking receive...
long ReceiveToSmartCache(unsigned char * inData, long inLength)
{	
	while (!gIsFlushing && !HasEnoughSpace(inLength))
	{
		inputWaiting = TRUE;
		MakeSpace();
		Sleep(2);
	//	fp = fopen("C:\hqmpgdectime.txt", "a");
	//	fprintf(fp, "Receiving sleep, current data length: %10d!n", gWritingOffset - gReadingOffset);
	//	fclose(fp);
	}
	inputWaiting = FALSE;
	if (!gIsFlushing && HasEnoughSpace(inLength))
	{
		EnterCriticalSection(&singleAccess); // Enter
		memcpy(gInputCache + gWritingOffset, inData, inLength);
		gWritingOffset += inLength;
		LeaveCriticalSection(&singleAccess); // Leave
		return 1;
	}
	return 0;
}
// Blocking read...
long FetchDataFromSmartCache(BYTE * outBuffer, ULONG inLength)
{
	if (inLength <= 0)
		return 0;
	while (!gIsFlushing && !HasEnoughData(inLength))
	{
		outputWaiting = TRUE;
		Sleep(1);
	}
	outputWaiting = FALSE;
	
	if (!gIsFlushing && HasEnoughData(inLength))
	{
		EnterCriticalSection(&singleAccess); // Enter
		memcpy(outBuffer, gInputCache + gReadingOffset, inLength);
		gReadingOffset += inLength;
		LeaveCriticalSection(&singleAccess); // Leave
		return inLength;
	}
	return 0;
}
long GetAvailableInSmartCache(void)
{
	return (gWritingOffset - gReadingOffset);
}
// Determine whether enough space to hold coming mpeg data
static long HasEnoughSpace(long inNeedSize)
{
	return (inNeedSize <= gCacheSize - gWritingOffset);
}
// Determine data in smart cache at this moment is enough to decode
static long HasEnoughData(long inNeedSize)
{
	return (inNeedSize <= gWritingOffset - gReadingOffset);
}
static void MakeSpace(void)
{
	long workingSize = gWritingOffset - gReadingOffset;
	// When cache checking, don't drop any data
	if (!cacheChecking && workingSize < gMinWorkSize)
	{
		EnterCriticalSection(&singleAccess); // Enter
		memmove(gInputCache, gInputCache + gReadingOffset, workingSize);
		gReadingOffset = 0;
		gWritingOffset = workingSize;
		LeaveCriticalSection(&singleAccess); // Leave
	}
}
void BeginFlushSmartCache(void)
{
	gIsFlushing = TRUE;
	waitingCounter = 0;
	while (inputWaiting && waitingCounter < 15)  // Make sure NOT block in receiving or reading
	{
		waitingCounter++;
		Sleep(1);
	}
	waitingCounter = 0;
	while (outputWaiting && waitingCounter < 15)
	{
		waitingCounter++;
		Sleep(1);
	}
//	Sleep(10);
	EnterCriticalSection(&singleAccess); // Enter
	gReadingOffset = 0;
	gWritingOffset = 0;
	LeaveCriticalSection(&singleAccess); // Leave
}
void EndFlushSmartCache(void)
{
	gIsFlushing = FALSE;
}
BOOL CheckInputWaiting(void)
{
	return inputWaiting;
}
BOOL CheckOutputWaiting(void)
{
	return outputWaiting;
}
// We can reuse the data having been read out
void SetCacheChecking(void)
{
	cacheChecking = TRUE;
}
void ResetCacheChecking(void)
{
	cacheChecking = FALSE;
	EnterCriticalSection(&singleAccess); // Enter
	gReadingOffset = 0;
	LeaveCriticalSection(&singleAccess); // Leave
}

						