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/*
 * Copyright (C) 2016 Square, Inc.
 *
 * 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.facebook.presto.jdbc.internal.okio;

import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import com.facebook.presto.jdbc.internal.javax.annotation.Nullable;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import static com.facebook.presto.jdbc.internal.okio.Util.checkOffsetAndCount;

/**
 * A sink that computes a hash of the full stream of bytes it has accepted. To use, create an
 * instance with your preferred hash algorithm. Write all of the data to the sink and then call
 * {@link #hash()} to compute the final hash value.
 *
 * 

In this example we use {@code HashingSink} with a {@link BufferedSink} to make writing to the * sink easier.

   {@code
 *
 *   HashingSink hashingSink = HashingSink.sha256(s);
 *   BufferedSink bufferedSink = Okio.buffer(hashingSink);
 *
 *   ... // Write to bufferedSink and either flush or close it.
 *
 *   ByteString hash = hashingSink.hash();
 * }
*/ public final class HashingSink extends ForwardingSink { private final @Nullable MessageDigest messageDigest; private final @Nullable Mac mac; /** Returns a sink that uses the obsolete MD5 hash algorithm to produce 128-bit hashes. */ public static HashingSink md5(Sink sink) { return new HashingSink(sink, "MD5"); } /** Returns a sink that uses the obsolete SHA-1 hash algorithm to produce 160-bit hashes. */ public static HashingSink sha1(Sink sink) { return new HashingSink(sink, "SHA-1"); } /** Returns a sink that uses the SHA-256 hash algorithm to produce 256-bit hashes. */ public static HashingSink sha256(Sink sink) { return new HashingSink(sink, "SHA-256"); } /** Returns a sink that uses the SHA-512 hash algorithm to produce 512-bit hashes. */ public static HashingSink sha512(Sink sink) { return new HashingSink(sink, "SHA-512"); } /** Returns a sink that uses the obsolete SHA-1 HMAC algorithm to produce 160-bit hashes. */ public static HashingSink hmacSha1(Sink sink, ByteString key) { return new HashingSink(sink, key, "HmacSHA1"); } /** Returns a sink that uses the SHA-256 HMAC algorithm to produce 256-bit hashes. */ public static HashingSink hmacSha256(Sink sink, ByteString key) { return new HashingSink(sink, key, "HmacSHA256"); } /** Returns a sink that uses the SHA-512 HMAC algorithm to produce 512-bit hashes. */ public static HashingSink hmacSha512(Sink sink, ByteString key) { return new HashingSink(sink, key, "HmacSHA512"); } private HashingSink(Sink sink, String algorithm) { super(sink); try { this.messageDigest = MessageDigest.getInstance(algorithm); this.mac = null; } catch (NoSuchAlgorithmException e) { throw new AssertionError(); } } private HashingSink(Sink sink, ByteString key, String algorithm) { super(sink); try { this.mac = Mac.getInstance(algorithm); this.mac.init(new SecretKeySpec(key.toByteArray(), algorithm)); this.messageDigest = null; } catch (NoSuchAlgorithmException e) { throw new AssertionError(); } catch (InvalidKeyException e) { throw new IllegalArgumentException(e); } } @Override public void write(Buffer source, long byteCount) throws IOException { checkOffsetAndCount(source.size, 0, byteCount); // Hash byteCount bytes from the prefix of source. long hashedCount = 0; for (Segment s = source.head; hashedCount < byteCount; s = s.next) { int toHash = (int) Math.min(byteCount - hashedCount, s.limit - s.pos); if (messageDigest != null) { messageDigest.update(s.data, s.pos, toHash); } else { mac.update(s.data, s.pos, toHash); } hashedCount += toHash; } // Write those bytes to the sink. super.write(source, byteCount); } /** * Returns the hash of the bytes accepted thus far and resets the internal state of this sink. * *

Warning: This method is not idempotent. Each time this method is called its * internal state is cleared. This starts a new hash with zero bytes accepted. */ public ByteString hash() { byte[] result = messageDigest != null ? messageDigest.digest() : mac.doFinal(); return ByteString.of(result); } }





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