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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 javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

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

In this example we use {@code HashingSource} with a {@link BufferedSource} to make reading * from the source easier.

   {@code
 *
 *   HashingSource hashingSource = HashingSource.sha256(rawSource);
 *   BufferedSource bufferedSource = Okio.buffer(hashingSource);
 *
 *   ... // Read all of bufferedSource.
 *
 *   ByteString hash = hashingSource.hash();
 * }
*/ public final class HashingSource extends ForwardingSource { private final MessageDigest messageDigest; private final Mac mac; /** Returns a sink that uses the obsolete MD5 hash algorithm to produce 128-bit hashes. */ public static HashingSource md5(Source source) { return new HashingSource(source, "MD5"); } /** Returns a sink that uses the obsolete SHA-1 hash algorithm to produce 160-bit hashes. */ public static HashingSource sha1(Source source) { return new HashingSource(source, "SHA-1"); } /** Returns a sink that uses the SHA-256 hash algorithm to produce 256-bit hashes. */ public static HashingSource sha256(Source source) { return new HashingSource(source, "SHA-256"); } /** Returns a sink that uses the obsolete SHA-1 HMAC algorithm to produce 160-bit hashes. */ public static HashingSource hmacSha1(Source source, ByteString key) { return new HashingSource(source, key, "HmacSHA1"); } /** Returns a sink that uses the SHA-256 HMAC algorithm to produce 256-bit hashes. */ public static HashingSource hmacSha256(Source source, ByteString key) { return new HashingSource(source, key, "HmacSHA256"); } private HashingSource(Source source, String algorithm) { super(source); try { this.messageDigest = MessageDigest.getInstance(algorithm); this.mac = null; } catch (NoSuchAlgorithmException e) { throw new AssertionError(); } } private HashingSource(Source source, ByteString key, String algorithm) { super(source); 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 long read(Buffer sink, long byteCount) throws IOException { long result = super.read(sink, byteCount); if (result != -1L) { long start = sink.size - result; // Find the first segment that has new bytes. long offset = sink.size; Segment s = sink.head; while (offset > start) { s = s.prev; offset -= (s.limit - s.pos); } // Hash that segment and all the rest until the end. while (offset < sink.size) { int pos = (int) (s.pos + start - offset); if (messageDigest != null) { messageDigest.update(s.data, pos, s.limit - pos); } else { mac.update(s.data, pos, s.limit - pos); } offset += (s.limit - s.pos); start = offset; s = s.next; } } return result; } /** * Returns the hash of the bytes supplied thus far and resets the internal state of this source. * *

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 supplied. */ public ByteString hash() { byte[] result = messageDigest != null ? messageDigest.digest() : mac.doFinal(); return ByteString.of(result); } }





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