/* * Copyright (C) 2011 The Guava Authors * * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except * in compliance with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software distributed under the License * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express * or implied. See the License for the specific language governing permissions and limitations under * the License. */ package com.google.common.hash; import static com.google.common.base.Preconditions.checkArgument; import com.google.common.base.Preconditions; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.charset.Charset; /** * Skeleton implementation of {@link HashFunction}. Provides default implementations which * invokes the appropriate method on {@link #newHasher()}, then return the result of * {@link Hasher#hash}. * *
Invocations of {@link #newHasher(int)} also delegate to {@linkplain #newHasher()}, ignoring * the expected input size parameter. * * @author Kevin Bourrillion */ abstract class AbstractStreamingHashFunction implements HashFunction { @Override public HashCode hashString(CharSequence input) { return newHasher().putString(input).hash(); } @Override public HashCode hashString(CharSequence input, Charset charset) { return newHasher().putString(input, charset).hash(); } @Override public HashCode hashLong(long input) { return newHasher().putLong(input).hash(); } @Override public HashCode hashBytes(byte[] input) { return newHasher().putBytes(input).hash(); } @Override public HashCode hashBytes(byte[] input, int off, int len) { return newHasher().putBytes(input, off, len).hash(); } @Override public Hasher newHasher(int expectedInputSize) { Preconditions.checkArgument(expectedInputSize >= 0); return newHasher(); } /** * A convenience base class for implementors of {@code Hasher}; handles accumulating data * until an entire "chunk" (of implementation-dependent length) is ready to be hashed. * * @author kevinb@google.com (Kevin Bourrillion) * @author andreou@google.com (Dimitris Andreou) */ // TODO(kevinb): this class still needs some design-and-document-for-inheritance love protected static abstract class AbstractStreamingHasher extends AbstractHasher { /** Buffer via which we pass data to the hash algorithm (the implementor) */ private final ByteBuffer buffer; /** Number of bytes to be filled before process() invocation(s). */ private final int bufferSize; /** Number of bytes processed per process() invocation. */ private final int chunkSize; /** * Constructor for use by subclasses. This hasher instance will process chunks of the specified * size. * * @param chunkSize the number of bytes available per {@link #process(ByteBuffer)} invocation; * must be at least 4 */ protected AbstractStreamingHasher(int chunkSize) { this(chunkSize, chunkSize); } /** * Constructor for use by subclasses. This hasher instance will process chunks of the specified * size, using an internal buffer of {@code bufferSize} size, which must be a multiple of * {@code chunkSize}. * * @param chunkSize the number of bytes available per {@link #process(ByteBuffer)} invocation; * must be at least 4 * @param bufferSize the size of the internal buffer. Must be a multiple of chunkSize */ protected AbstractStreamingHasher(int chunkSize, int bufferSize) { // TODO(kevinb): check more preconditions (as bufferSize >= chunkSize) if this is ever public checkArgument(bufferSize % chunkSize == 0); // TODO(user): benchmark performance difference with longer buffer this.buffer = ByteBuffer .allocate(bufferSize + 7) // always space for a single primitive .order(ByteOrder.LITTLE_ENDIAN); this.bufferSize = bufferSize; this.chunkSize = chunkSize; } /** * Processes the available bytes of the buffer (at most {@code chunk} bytes). */ protected abstract void process(ByteBuffer bb); /** * This is invoked for the last bytes of the input, which are not enough to * fill a whole chunk. The passed {@code ByteBuffer} is guaranteed to be * non-empty. * *
This implementation simply pads with zeros and delegates to
* {@link #process(ByteBuffer)}.
*/
protected void processRemaining(ByteBuffer bb) {
bb.position(bb.limit()); // move at the end
bb.limit(chunkSize + 7); // get ready to pad with longs
while (bb.position() < chunkSize) {
bb.putLong(0);
}
bb.limit(chunkSize);
bb.flip();
process(bb);
}
@Override
public final Hasher putBytes(byte[] bytes) {
return putBytes(bytes, 0, bytes.length);
}
@Override
public final Hasher putBytes(byte[] bytes, int off, int len) {
return putBytes(ByteBuffer.wrap(bytes, off, len).order(ByteOrder.LITTLE_ENDIAN));
}
private final Hasher putBytes(ByteBuffer readBuffer) {
// If we have room for all of it, this is easy
if (readBuffer.remaining() <= buffer.remaining()) {
buffer.put(readBuffer);
munchIfFull();
return this;
}
// First add just enough to fill buffer size, and munch that
int bytesToCopy = bufferSize - buffer.position();
for (int i = 0; i < bytesToCopy; i++) {
buffer.put(readBuffer.get());
}
munch(); // buffer becomes empty here, since chunkSize divides bufferSize
// Now process directly from the rest of the input buffer
while (readBuffer.remaining() >= chunkSize) {
process(readBuffer);
}
// Finally stick the remainder back in our usual buffer
buffer.put(readBuffer);
return this;
}
@Override
public final Hasher putString(CharSequence charSequence) {
for (int i = 0; i < charSequence.length(); i++) {
putChar(charSequence.charAt(i));
}
return this;
}
@Override
public final Hasher putByte(byte b) {
buffer.put(b);
munchIfFull();
return this;
}
@Override
public final Hasher putShort(short s) {
buffer.putShort(s);
munchIfFull();
return this;
}
@Override
public final Hasher putChar(char c) {
buffer.putChar(c);
munchIfFull();
return this;
}
@Override
public final Hasher putInt(int i) {
buffer.putInt(i);
munchIfFull();
return this;
}
@Override
public final Hasher putLong(long l) {
buffer.putLong(l);
munchIfFull();
return this;
}
@Override
public final