haiku/src/kits/media/ChunkCache.cpp

/*
 * Copyright (c) 2004, Marcus Overhagen
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <string.h>

#include <Locker.h>

#include "ChunkCache.h"
#include "debug.h"


ChunkCache::ChunkCache()
{
	fLocker = new BLocker("media chunk cache locker");

	// fEmptyChunkCount must be one less than the real chunk count,
	// because the buffer returned by GetNextChunk must be preserved
	// until the next call of that function, and must not be overwritten.
	fEmptyChunkCount = CHUNK_COUNT - 1;
	fReadyChunkCount = 0;
	fNeedsRefill = 1;

	fGetWaitSem = create_sem(0, "media chunk cache sem");

	fNextPut = &fChunkInfos[0];
	fNextGet = &fChunkInfos[0];
	
	for (int i = 0; i < CHUNK_COUNT; i++) {
		fChunkInfos[i].next = (i == CHUNK_COUNT -1) ? &fChunkInfos[0] : &fChunkInfos[i + 1];
		fChunkInfos[i].buffer = NULL;
		fChunkInfos[i].sizeUsed = 0;
		fChunkInfos[i].sizeMax = 0;
		fChunkInfos[i].err = B_ERROR;
	}
}


ChunkCache::~ChunkCache()
{
	delete_sem(fGetWaitSem);
	delete fLocker;
	for (int i = 0; i < CHUNK_COUNT; i++) {
		free(fChunkInfos[i].buffer);
	}
}


void
ChunkCache::MakeEmpty()
{
	fLocker->Lock();
	fEmptyChunkCount = CHUNK_COUNT - 1;
	fReadyChunkCount = 0;
	fNextPut = &fChunkInfos[0];
	fNextGet = &fChunkInfos[0];
	atomic_or(&fNeedsRefill, 1);
	fLocker->Unlock();
}


bool
ChunkCache::NeedsRefill()
{
	return atomic_or(&fNeedsRefill, 0);
}

					
status_t
ChunkCache::GetNextChunk(const void **chunkBuffer, size_t *chunkSize, media_header *mediaHeader)
{
uint8 retry_count = 0;

//	printf("ChunkCache::GetNextChunk: %p fEmptyChunkCount %ld, fReadyChunkCount %ld\n", fNextGet, fEmptyChunkCount, fReadyChunkCount);
retry:
	acquire_sem(fGetWaitSem);

	fLocker->Lock();
	if (fReadyChunkCount == 0) {
		fLocker->Unlock();
		printf("ChunkCache::GetNextChunk: %p retrying\n", fNextGet);
		// Limit to 5 retries
		retry_count++;
		if (retry_count > 4) {
			return B_ERROR;
		}
		goto retry;
	}
	fEmptyChunkCount++;
	fReadyChunkCount--;
	atomic_or(&fNeedsRefill, 1);
	fLocker->Unlock();
	
	*chunkBuffer = fNextGet->buffer;
	*chunkSize = fNextGet->sizeUsed;
	*mediaHeader = fNextGet->mediaHeader;
	status_t err = fNextGet->err;
	fNextGet = fNextGet->next;

	return err;
}


void
ChunkCache::PutNextChunk(const void *chunkBuffer, size_t chunkSize, const media_header &mediaHeader, status_t err)
{
//	printf("ChunkCache::PutNextChunk: %p fEmptyChunkCount %ld, fReadyChunkCount %ld\n", fNextPut, fEmptyChunkCount, fReadyChunkCount);

	if (err == B_OK) {
		if (fNextPut->sizeMax < chunkSize) {
//			printf("ChunkCache::PutNextChunk: %p resizing from %ld to %ld\n", fNextPut, fNextPut->sizeMax, chunkSize);
			free(fNextPut->buffer);
			fNextPut->buffer = malloc((chunkSize + 1024) & ~1023);
			fNextPut->sizeMax = chunkSize;
		}
		memcpy(fNextPut->buffer, chunkBuffer, chunkSize);
		fNextPut->sizeUsed = chunkSize;
	}
	
	fNextPut->mediaHeader = mediaHeader;
	fNextPut->err = err;

	fNextPut = fNextPut->next;

	fLocker->Lock();
	fEmptyChunkCount--;
	fReadyChunkCount++;
	if (fEmptyChunkCount == 0)
		atomic_and(&fNeedsRefill, 0);
	fLocker->Unlock();

	release_sem(fGetWaitSem);
}