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Guava library, with additional type annotations for verification
/*
* 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 com.google.common.base.Preconditions;
import com.google.errorprone.annotations.Immutable;
import java.io.ByteArrayOutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.Charset;
import java.util.Arrays;
import org.checkerframework.checker.index.qual.LTLengthOf;
import org.checkerframework.checker.index.qual.LengthOf;
import org.checkerframework.checker.index.qual.NonNegative;
import org.checkerframework.common.value.qual.MinLen;
/**
* Skeleton implementation of {@link HashFunction}, appropriate for non-streaming algorithms. All
* the hash computation done using {@linkplain #newHasher()} are delegated to the {@linkplain
* #hashBytes(byte[], int, int)} method.
*
* @author Dimitris Andreou
*/
@Immutable
abstract class AbstractNonStreamingHashFunction extends AbstractHashFunction {
@Override
public Hasher newHasher() {
return newHasher(32);
}
@Override
public Hasher newHasher(@NonNegative int expectedInputSize) {
Preconditions.checkArgument(expectedInputSize >= 0);
return new BufferingHasher(expectedInputSize);
}
@SuppressWarnings("value:argument.type.incompatible")/* Since ByteBuffer is a mutable length data structure, `ByteBuffer.allocate(4)`
returns the new byte buffer with 4 as capacity, therefore `ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN).putLong(input).array()`
returns an array of length 4 */
@Override
public HashCode hashInt(int input) {
return hashBytes(ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN).putInt(input).array());
}
@SuppressWarnings("value:argument.type.incompatible")/* Since ByteBuffer is a mutable length data structure, `ByteBuffer.allocate(8)`
returns the new byte buffer with 8 as capacity, therefore `ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN).putLong(input).array()`
returns an array of length 8 */
@Override
public HashCode hashLong(long input) {
return hashBytes(ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN).putLong(input).array());
}
@SuppressWarnings("value:argument.type.incompatible") /* Since ByteBuffer is a mutable length data structure and input
has min length of 1,`ByteBuffer.allocate(len * 2)` returns the new byte buffer with min length of 2 as capacity,
therefore ByteBuffer.allocate(len * 2).order(ByteOrder.LITTLE_ENDIAN) returns an array of non negative length */
@Override
public HashCode hashUnencodedChars(@MinLen(1) CharSequence input) {
int len = input.length();
ByteBuffer buffer = ByteBuffer.allocate(len * 2).order(ByteOrder.LITTLE_ENDIAN);
for (int i = 0; i < len; i++) {
buffer.putChar(input.charAt(i));
}
return hashBytes(buffer.array());
}
@SuppressWarnings("value:argument.type.incompatible")//If `input` has min of 1, since `getBytes(charset)`
// the resultant byte array, the array returned also has min length of 1
@Override
public HashCode hashString(@MinLen(1) CharSequence input, Charset charset) {
return hashBytes(input.toString().getBytes(charset));
}
@Override
public abstract HashCode hashBytes(byte[] input, @NonNegative @LTLengthOf(value = "#1", offset = "#3 - 1") int off, @LTLengthOf(value = "#1", offset = "#2 - 1") int len);
@SuppressWarnings("lowerbound:argument.type.incompatible")/* Since invariants: mark <= position <= limit <= capacity,
and position is initialized as 0, `input.remaining()` return `limit - position` with lowest possible value as 0.
*/
@Override
public HashCode hashBytes(ByteBuffer input) {
return newHasher(input.remaining()).putBytes(input).hash();
}
/** In-memory stream-based implementation of Hasher. */
private final class BufferingHasher extends AbstractHasher {
final ExposedByteArrayOutputStream stream;
BufferingHasher(@NonNegative int expectedInputSize) {
this.stream = new ExposedByteArrayOutputStream(expectedInputSize);
}
@Override
public Hasher putByte(byte b) {
stream.write(b);
return this;
}
@Override
public Hasher putBytes(byte[] bytes, @NonNegative @LTLengthOf(value = "#1", offset = "#3 - 1") int off, @NonNegative @LTLengthOf(value = "#1", offset = "#2 - 1") int len) {
stream.write(bytes, off, len);
return this;
}
@Override
public Hasher putBytes(ByteBuffer bytes) {
stream.write(bytes);
return this;
}
@SuppressWarnings(value = {"upperbound:argument.type.incompatible",// `stream.byteArray()` return an array of length 32
// Since `stream.length()` return the length of return byte array, 0 + stream.length - 1 is always < stream.length.
"lowerbound:argument.type.incompatible"/*`stream.length` returns `count` of the pre-compiled class `ByteArrayOutputStream`.
therefore, `count` should be annotated as @NonNegative in `ByteArrayOutputStream` */})
@Override
public HashCode hash() {
return hashBytes(stream.byteArray(), 0, stream.length());
}
}
// Just to access the byte[] without introducing an unnecessary copy
private static final class ExposedByteArrayOutputStream extends ByteArrayOutputStream {
ExposedByteArrayOutputStream(@NonNegative int expectedInputSize) {
super(expectedInputSize);
}
@SuppressWarnings({"lowerbound:argument.type.incompatible", "lowerbound:assignment.type.incompatible"})/* Since invariants: position <= limit <= capacity,
and position is initialized as 0, `input.remaining()` return `limit - position` with lowest possible value as 0. */
void write(ByteBuffer input) {
@NonNegative int remaining = input.remaining();
if (count + remaining > buf.length) {
buf = Arrays.copyOf(buf, count + remaining);
}
input.get(buf, count, remaining);
count += remaining;
}
@SuppressWarnings("value:return.type.incompatible")//`buf` array in the pre-compiled class `ByteArrayOutputStream`
// should be annotated as @MinLen(1)
byte @MinLen(1)[] byteArray() {
return buf;
}
int length() {
return count;
}
}
}