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The Files.com Java client library provides convenient access to the Files.com API from JVM based applications.
package com.files.util;
import java.util.Collection;
import java.util.Optional;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Semaphore;
import com.files.FilesConfig;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.threadly.util.StackSuppressedRuntimeException;
public class BufferPool {
private static final Logger log = LogManager.getLogger(BufferPool.class);
private static final boolean TRACK_BUFFER_CREATION_STACK = true;
public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
public static final int T_BUFFER_SIZE = FilesConfig.getInstance().getCachedBufferTinySize();
public static final int S_BUFFER_SIZE = FilesConfig.getInstance().getCachedBufferSmallSize();
public static final int M_BUFFER_SIZE = FilesConfig.getInstance().getCachedBufferMediumSize();
public static final int L_BUFFER_SIZE = FilesConfig.getInstance().getCachedBufferLargeSize();
protected static final int T_BUFFER_TARGET_COUNT;
protected static final int S_BUFFER_TARGET_COUNT;
protected static final int M_BUFFER_TARGET_COUNT;
protected static final int MAX_ALLOCATION;
protected static final Semaphore TOTAL_ALLOCATED;
protected static final Queue T_BUFFERS = new ConcurrentLinkedQueue<>();
protected static final Queue S_BUFFERS = new ConcurrentLinkedQueue<>();
protected static final Queue M_BUFFERS = new ConcurrentLinkedQueue<>();
protected static final Queue L_BUFFERS = new ConcurrentLinkedQueue<>();
static {
MAX_ALLOCATION = FilesConfig.getInstance().getCachedBufferMaxBytes();
TOTAL_ALLOCATED = new Semaphore(MAX_ALLOCATION);
T_BUFFER_TARGET_COUNT = (int) ((MAX_ALLOCATION * .25) / T_BUFFER_SIZE);
S_BUFFER_TARGET_COUNT = (int) ((MAX_ALLOCATION * .25) / S_BUFFER_SIZE);
M_BUFFER_TARGET_COUNT = (int) ((MAX_ALLOCATION * .25) / M_BUFFER_SIZE);
// remaining % is provided as minimum cached allocations to large buffers
}
public static int getAvailableAllocation() {
return TOTAL_ALLOCATED.availablePermits();
}
public static int getTotalAllocated() {
return MAX_ALLOCATION - TOTAL_ALLOCATED.availablePermits();
}
public static int getWaitingToAllocateThreadCount() {
return TOTAL_ALLOCATED.getQueueLength();
}
public static int availableTinyBufferCount() {
return T_BUFFERS.size();
}
public static int availableSmallBufferCount() {
return S_BUFFERS.size();
}
public static int availableMediumBufferCount() {
return M_BUFFERS.size();
}
public static int availableLargeBufferCount() {
return L_BUFFERS.size();
}
public static Buffer needBuffer(int minSize) {
try {
if (minSize <= T_BUFFER_SIZE) {
return needTinyBuffer(minSize);
} else if (minSize <= S_BUFFER_SIZE) {
return needSmallBuffer(minSize);
} else if (minSize <= M_BUFFER_SIZE) {
return needMediumBuffer(minSize);
} else if (minSize <= L_BUFFER_SIZE) {
return needLargeBuffer(minSize);
} else {
throw new IllegalArgumentException("Buffer size too large: " + minSize);
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException("Interrupted waiting for buffer", e);
}
}
private static Buffer atomicPoll(Queue buffers) {
byte[] bytes = buffers.poll();
if (bytes == null) {
return null;
} else {
return new Buffer(bytes);
}
}
private static Buffer needTinyBuffer(int minSize) throws InterruptedException {
while (true) {
Buffer result = atomicPoll(T_BUFFERS);
if (result == null) {
result = tryMakeBuffer(minSize, T_BUFFER_SIZE);
if (result == null) {
// we can't allocate, lets try to find a larger buffer we can de-allocate first
Buffer larger = atomicPoll(S_BUFFERS);
if (larger == null) {
larger = atomicPoll(M_BUFFERS);
}
if (larger == null) {
larger = atomicPoll(L_BUFFERS);
}
if (larger != null) {
// use swapBuffer to make sure we get a buffer from de-allocation
return swapBuffer(larger, T_BUFFER_SIZE);
}
} else {
return result;
}
} else {
return result;
}
noBufferBlock(T_BUFFERS);
}
}
private static Buffer needSmallBuffer(int minSize) throws InterruptedException {
int attempt = 0;
while (true) {
attempt++;
Buffer result = atomicPoll(S_BUFFERS);
if (result == null) {
result = tryMakeBuffer(minSize, S_BUFFER_SIZE);
if (result == null) {
// we can't allocate, lets try to find a larger buffer we can de-allocate first
Buffer larger = atomicPoll(M_BUFFERS);
if (larger == null) {
larger = atomicPoll(L_BUFFERS);
}
if (larger != null) {
// use swapBuffer to make sure we get a buffer from de-allocation
return swapBuffer(larger, S_BUFFER_SIZE);
} else if (attempt % 2 == 1) {
// on every other attempt we make sure our failure to allocate
// is not due to large amounts of small buffers
trimCache(T_BUFFER_TARGET_COUNT, T_BUFFERS);
}
} else {
return result;
}
} else {
return result;
}
noBufferBlock(S_BUFFERS);
}
}
private static Buffer needMediumBuffer(int minSize) throws InterruptedException {
int attempt = 0;
while (true) {
attempt++;
Buffer result = atomicPoll(M_BUFFERS);
if (result == null) {
result = tryMakeBuffer(minSize, M_BUFFER_SIZE);
if (result == null) {
// we can't allocate, lets try to find a larger buffer we can de-allocate first
Buffer larger = atomicPoll(L_BUFFERS);
if (larger != null) {
// use swapBuffer to make sure we get a buffer from de-allocation
return swapBuffer(larger, M_BUFFER_SIZE);
} else if (attempt % 2 == 1) {
// make sure failure to allocate is not due to large amounts of small buffers
// trim which ever queue would save the most memory
if (((T_BUFFERS.size() - T_BUFFER_TARGET_COUNT) * T_BUFFER_SIZE)
<= ((S_BUFFERS.size() - S_BUFFER_TARGET_COUNT) * S_BUFFER_SIZE)) {
trimCache(S_BUFFER_TARGET_COUNT, S_BUFFERS);
} else {
trimCache(T_BUFFER_TARGET_COUNT, T_BUFFERS);
}
}
} else {
return result;
}
} else {
return result;
}
noBufferBlock(M_BUFFERS);
}
}
private static Buffer needLargeBuffer(int minSize) throws InterruptedException {
int attempt = 0;
while (true) {
attempt++;
Buffer result = atomicPoll(L_BUFFERS);
if (result == null) {
result = tryMakeBuffer(minSize, L_BUFFER_SIZE);
if (result == null) {
if (attempt % 2 == 1) {
// make sure failure to allocate is not due to large amounts of small buffers
// trim which ever queue would save the most memory
int tinySavings = (T_BUFFERS.size() - T_BUFFER_TARGET_COUNT) * T_BUFFER_SIZE;
int smallSavings = (S_BUFFERS.size() - S_BUFFER_TARGET_COUNT) * S_BUFFER_SIZE;
int medSavings = (M_BUFFERS.size() - M_BUFFER_TARGET_COUNT) * M_BUFFER_SIZE;
if (medSavings >= smallSavings && medSavings >= tinySavings) {
trimCache(M_BUFFER_TARGET_COUNT, M_BUFFERS);
} else if (smallSavings >= tinySavings) {
trimCache(S_BUFFER_TARGET_COUNT, S_BUFFERS);
} else {
trimCache(T_BUFFER_TARGET_COUNT, T_BUFFERS);
}
}
} else {
return result;
}
} else {
return result;
}
noBufferBlock(L_BUFFERS);
}
}
private static void noBufferBlock(Collection preferedQueue) throws InterruptedException {
synchronized (preferedQueue) {
if (preferedQueue.isEmpty()) {
preferedQueue.wait(50);
}
}
}
private static Buffer tryMakeBuffer(int minSize, int idealSize) {
if (TOTAL_ALLOCATED.tryAcquire(idealSize)) {
return new Buffer(idealSize);
} else if (TOTAL_ALLOCATED.tryAcquire(minSize)) {
return new Buffer(minSize);
} else {
return null;
}
}
private static void trimCache(int targetSize, Queue buffers) {
while (buffers.size() > targetSize) {
byte[] b = buffers.poll();
if (b != null) {
releaseBytes(b);
}
}
}
private static void cacheBytes(byte[] bytes) {
Queue bufferCache = null;
if (bytes.length == T_BUFFER_SIZE) {
bufferCache = T_BUFFERS;
} else if (bytes.length == S_BUFFER_SIZE) {
bufferCache = S_BUFFERS;
} else if (bytes.length == M_BUFFER_SIZE) {
bufferCache = M_BUFFERS;
} else if (bytes.length == L_BUFFER_SIZE) {
bufferCache = L_BUFFERS;
}
if (bufferCache == null) {
releaseBytes(bytes);
} else {
bufferCache.add(bytes);
synchronized (bufferCache) {
bufferCache.notifyAll();
}
}
}
private static void releaseBytes(byte[] b) {
TOTAL_ALLOCATED.release(b.length);
}
private static Buffer swapBuffer(Buffer larger, int newSize) {
int releaseAmount = larger.bytes.length - newSize;
synchronized (larger.bytes) {
if (releaseAmount <= 0) {
throw new IllegalStateException("Buffer smaller than new allocation");
} else if (larger.closed) {
throw new IllegalStateException("Buffer already released");
}
larger.closed = true;
}
TOTAL_ALLOCATED.release(releaseAmount);
return new Buffer(newSize);
}
public static class Buffer implements AutoCloseable {
public static final Buffer POISON_PILL = new Buffer(EMPTY_BYTE_ARRAY) {
{
closed = true;
}
};
private final StackTraceElement[] creationStack =
TRACK_BUFFER_CREATION_STACK ? Thread.currentThread().getStackTrace() : null;
private final byte[] bytes;
private int offset;
private int length;
protected volatile boolean closed = false;
public Buffer(int size) {
this.bytes = new byte[size];
this.offset = 0;
this.length = size;
}
public Buffer(byte[] bytes) {
this.bytes = bytes;
this.offset = 0;
this.length = bytes.length;
}
public byte[] getBuffer() {
if (closed) {
throw new IllegalStateException("Buffer closed");
}
return bytes;
}
public int getRemaining() {
if (closed) {
throw new IllegalStateException("Buffer closed");
}
return length - offset;
}
public void setLength(int length) {
if (length > bytes.length) {
throw new IllegalArgumentException("Length beyond byte size");
} else if (length < 0) {
throw new IllegalArgumentException("Length can't be negative");
}
this.length = length;
}
public int getOffset() {
if (closed) {
throw new IllegalStateException("Buffer closed");
}
return offset;
}
public void incrementOffset(int count) {
setOffset(offset + count);
}
public void setOffset(int offset) {
if (offset > length) {
throw new IllegalArgumentException("Offset beyond length");
} else if (offset < 0) {
throw new IllegalArgumentException("Offset can't be negative");
}
this.offset = offset;
}
public void flip() {
this.length = this.offset;
this.offset = 0;
}
public void closeAsUnhealthy() {
synchronized (bytes) {
if (closed) {
throw new IllegalStateException("Buffer already released");
}
closed = true;
releaseBytes(bytes);
}
}
@Override
public void close() {
if (closed) {
return;
}
atomicClose();
}
private void atomicClose() {
synchronized (bytes) {
if (! closed) {
closed = true;
cacheBytes(bytes);
}
}
}
private Throwable creationLogThrowable() {
if (creationStack == null) {
return null;
} else {
StackSuppressedRuntimeException ex = new StackSuppressedRuntimeException();
ex.setStackTrace(creationStack);
return ex;
}
}
@Override
protected void finalize() {
if (! closed) {
log.warn("Buffer not released!", creationLogThrowable());
atomicClose();
}
}
}
}
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