Update #0 - First Release

sources/main/java/com/google/common/hash/Hasher.java

@@ -0,0 +1,131 @@
+/*
+ * 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 java.nio.charset.Charset;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * A {@link PrimitiveSink} that can compute a hash code after reading the input.
+ * Each hasher should translate all multibyte values ({@link #putInt(int)},
+ * {@link #putLong(long)}, etc) to bytes in little-endian order.
+ *
+ * <p>
+ * <b>Warning:</b> The result of calling any methods after calling {@link #hash}
+ * is undefined.
+ *
+ * <p>
+ * <b>Warning:</b> Using a specific character encoding when hashing a
+ * {@link CharSequence} with {@link #putString(CharSequence, Charset)} is
+ * generally only useful for cross-language compatibility (otherwise prefer
+ * {@link #putUnencodedChars}). However, the character encodings must be
+ * identical across languages. Also beware that {@link Charset} definitions may
+ * occasionally change between Java releases.
+ *
+ * <p>
+ * <b>Warning:</b> Chunks of data that are put into the {@link Hasher} are not
+ * delimited. The resulting {@link HashCode} is dependent only on the bytes
+ * inserted, and the order in which they were inserted, not how those bytes were
+ * chunked into discrete put() operations. For example, the following three
+ * expressions all generate colliding hash codes:
+ * 
+ * <pre>
+ *    {@code
+ *
+ *   newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
+ *   newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
+ *   newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()}
+ * </pre>
+ *
+ * <p>
+ * If you wish to avoid this, you should either prepend or append the size of
+ * each chunk. Keep in mind that when dealing with char sequences, the encoded
+ * form of two concatenated char sequences is not equivalent to the
+ * concatenation of their encoded form. Therefore,
+ * {@link #putString(CharSequence, Charset)} should only be used consistently
+ * with <i>complete</i> sequences and not broken into chunks.
+ *
+ * @author Kevin Bourrillion
+ * @since 11.0
+ */
+@Beta
+public interface Hasher extends PrimitiveSink {
+	@Override
+	Hasher putByte(byte b);
+
+	@Override
+	Hasher putBytes(byte[] bytes);
+
+	@Override
+	Hasher putBytes(byte[] bytes, int off, int len);
+
+	@Override
+	Hasher putShort(short s);
+
+	@Override
+	Hasher putInt(int i);
+
+	@Override
+	Hasher putLong(long l);
+
+	/**
+	 * Equivalent to {@code putInt(Float.floatToRawIntBits(f))}.
+	 */
+	@Override
+	Hasher putFloat(float f);
+
+	/**
+	 * Equivalent to {@code putLong(Double.doubleToRawLongBits(d))}.
+	 */
+	@Override
+	Hasher putDouble(double d);
+
+	/**
+	 * Equivalent to {@code putByte(b ? (byte) 1 : (byte) 0)}.
+	 */
+	@Override
+	Hasher putBoolean(boolean b);
+
+	@Override
+	Hasher putChar(char c);
+
+	/**
+	 * Equivalent to processing each {@code char} value in the {@code CharSequence},
+	 * in order. The input must not be updated while this method is in progress.
+	 *
+	 * @since 15.0 (since 11.0 as putString(CharSequence)).
+	 */
+	@Override
+	Hasher putUnencodedChars(CharSequence charSequence);
+
+	/**
+	 * Equivalent to {@code putBytes(charSequence.toString().getBytes(charset))}.
+	 */
+	@Override
+	Hasher putString(CharSequence charSequence, Charset charset);
+
+	/**
+	 * A simple convenience for {@code funnel.funnel(object, this)}.
+	 */
+	<T> Hasher putObject(T instance, Funnel<? super T> funnel);
+
+	/**
+	 * Computes a hash code based on the data that have been provided to this
+	 * hasher. The result is unspecified if this method is called more than once on
+	 * the same instance.
+	 */
+	HashCode hash();
+}