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Support an up-front block allocation in DefaultAllocator.

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Oliver Woodman 2015-05-22 21:37:21 +01:00
parent 79d557dd80
commit 91bcec82f5
1 changed files with 78 additions and 15 deletions
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93
library/src/main/java/com/google/android/exoplayer/upstream/DefaultAllocator.java
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@ -25,41 +25,72 @@ import java.util.Arrays;
*/
public final class DefaultAllocator implements Allocator {
private static final int INITIAL_RECYCLED_ALLOCATION_CAPACITY = 100;
private static final int AVAILABLE_EXTRA_CAPACITY = 100;
private final int individualAllocationSize;
private final byte[] initialAllocationBlock;
private int allocatedCount;
private int recycledCount;
private Allocation[] recycledAllocations;
private int availableCount;
private Allocation[] availableAllocations;
/**
* Constructs an empty pool.
* Constructs an initially empty pool.
*
* @param individualAllocationSize The length of each individual allocation.
*/
public DefaultAllocator(int individualAllocationSize) {
this(individualAllocationSize, 0);
}
/**
* Constructs a pool with some {@link Allocation}s created up front.
* <p>
* Note: Initial {@link Allocation}s will never be discarded by {@link #trim(int)}.
*
* @param individualAllocationSize The length of each individual allocation.
* @param initialAllocationCount The number of allocations to create up front.
*/
public DefaultAllocator(int individualAllocationSize, int initialAllocationCount) {
Assertions.checkArgument(individualAllocationSize > 0);
Assertions.checkArgument(initialAllocationCount >= 0);
this.individualAllocationSize = individualAllocationSize;
this.recycledAllocations = new Allocation[INITIAL_RECYCLED_ALLOCATION_CAPACITY];
this.availableCount = initialAllocationCount;
this.availableAllocations = new Allocation[initialAllocationCount + AVAILABLE_EXTRA_CAPACITY];
if (initialAllocationCount > 0) {
initialAllocationBlock = new byte[initialAllocationCount * individualAllocationSize];
for (int i = 0; i < initialAllocationCount; i++) {
int allocationOffset = i * individualAllocationSize;
availableAllocations[i] = new Allocation(initialAllocationBlock, allocationOffset);
}
} else {
initialAllocationBlock = null;
}
}
@Override
public synchronized Allocation allocate() {
allocatedCount++;
return recycledCount > 0 ? recycledAllocations[--recycledCount]
: new Allocation(new byte[individualAllocationSize], 0);
Allocation allocation;
if (availableCount > 0) {
allocation = availableAllocations[--availableCount];
availableAllocations[availableCount] = null;
} else {
allocation = new Allocation(new byte[individualAllocationSize], 0);
}
return allocation;
}
@Override
public synchronized void release(Allocation allocation) {
// Weak sanity check that the allocation probably originated from this pool.
Assertions.checkArgument(allocation.data.length == individualAllocationSize);
Assertions.checkArgument(allocation.data == initialAllocationBlock
|| allocation.data.length == individualAllocationSize);
allocatedCount--;
if (recycledCount == recycledAllocations.length) {
recycledAllocations = Arrays.copyOf(recycledAllocations, recycledAllocations.length * 2);
if (availableCount == availableAllocations.length) {
availableAllocations = Arrays.copyOf(availableAllocations, availableAllocations.length * 2);
}
recycledAllocations[recycledCount++] = allocation;
availableAllocations[availableCount++] = allocation;
// Wake up threads waiting for the allocated size to drop.
notifyAll();
}
@ -67,11 +98,43 @@ public final class DefaultAllocator implements Allocator {
@Override
public synchronized void trim(int targetSize) {
int targetAllocationCount = Util.ceilDivide(targetSize, individualAllocationSize);
int targetRecycledAllocationCount = Math.max(0, targetAllocationCount - allocatedCount);
if (targetRecycledAllocationCount < recycledCount) {
Arrays.fill(recycledAllocations, targetRecycledAllocationCount, recycledCount, null);
recycledCount = targetRecycledAllocationCount;
int targetAvailableCount = Math.max(0, targetAllocationCount - allocatedCount);
if (targetAvailableCount >= availableCount) {
// We're already at or below the target.
return;
}
if (initialAllocationBlock != null) {
// Some allocations are backed by an initial block. We need to make sure that we hold onto all
// such allocations. Re-order the available allocations so that the ones backed by the initial
// block come first.
int lowIndex = 0;
int highIndex = availableCount - 1;
while (lowIndex <= highIndex) {
Allocation lowAllocation = availableAllocations[lowIndex];
if (lowAllocation.data == initialAllocationBlock) {
lowIndex++;
} else {
Allocation highAllocation = availableAllocations[lowIndex];
if (highAllocation.data != initialAllocationBlock) {
highIndex--;
} else {
availableAllocations[lowIndex++] = highAllocation;
availableAllocations[highIndex--] = lowAllocation;
}
}
}
// lowIndex is the index of the first allocation not backed by an initial block.
targetAvailableCount = Math.max(targetAvailableCount, lowIndex);
if (targetAvailableCount >= availableCount) {
// We're already at or below the target.
return;
}
}
// Discard allocations beyond the target.
Arrays.fill(availableAllocations, targetAvailableCount, availableCount, null);
availableCount = targetAvailableCount;
}
@Override