| /* |
| * Copyright 2012-present Facebook, 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.buck.rules; |
| |
| import com.google.common.hash.HashCode; |
| import com.google.common.hash.Hashing; |
| import com.google.common.io.Files; |
| |
| import java.io.File; |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * OutputKey encapsulates computation of SHA-1 content hashing for outputs. |
| */ |
| public class OutputKey implements Comparable<OutputKey> { |
| @Nullable private final HashCode hashCode; |
| private final boolean idempotent; |
| |
| /** |
| * OutputKeys associated with actual outputs are non-idempotent if the outputs cannot be read |
| * during key generation. |
| */ |
| public OutputKey(File outputFile) { |
| HashCode hc; |
| try { |
| byte[] fileBytes = Files.toByteArray(outputFile); |
| hc = Hashing.sha1().hashBytes(fileBytes); |
| } catch (IOException e) { |
| // Generate a non-idempotent key for a missing/unreadable output. |
| hc = null; |
| } |
| hashCode = hc; |
| idempotent = (hc != null); |
| } |
| |
| /** |
| * OutputKeys that have no associated outputs are treated as sentinels that are distinct from |
| * other idempotent OutputKeys. |
| */ |
| public OutputKey() { |
| hashCode = null; |
| idempotent = true; |
| } |
| |
| public boolean isIdempotent() { |
| return idempotent; |
| } |
| |
| public boolean isSentinel() { |
| return (isIdempotent() && hashCode == null); |
| } |
| |
| /** |
| * Sentinel OutputKeys are output as a string of 's' characters, and non-idempotent OutputKeys are |
| * normally output as a string of 'x' characters, but when comparing two sets of OutputKeys in |
| * textual form it is necessary to mangle one of the two sets, so that non-idempotent OutputKeys |
| * are never considered equal. |
| */ |
| public String toString(boolean mangleNonIdempotent) { |
| if (isSentinel() || !isIdempotent()) { |
| String replacementChar = isSentinel() ? "s" : (!mangleNonIdempotent ? "x" : "y"); |
| return new String (new char[Hashing.sha1().bits() / 4]).replace("\0", replacementChar); |
| } |
| return hashCode.toString(); |
| } |
| |
| @Override |
| public String toString() { |
| return toString(false); |
| } |
| |
| /** |
| * Order non-idempotent OutputKeys as less than sentinels, which in turn are less than all |
| * idempotent non-sentinels. |
| * |
| * non-idempotent < sentinel < idempotent non-sentinel |
| */ |
| @Override |
| public int compareTo(OutputKey other) { |
| // Handle non-idempotent keys. |
| if (!isIdempotent()) { |
| if (!other.isIdempotent()) { |
| return 0; |
| } |
| return -1; |
| } else if (!other.isIdempotent()) { |
| return 1; |
| } |
| |
| // Handle sentinel keys. |
| if (isSentinel()) { |
| if (other.isSentinel()) { |
| return 0; |
| } |
| return -1; |
| } else if (other.isSentinel()) { |
| return 1; |
| } |
| |
| // Handle idempotent non-sentinel keys. |
| return ByteBuffer.wrap(hashCode.asBytes()).compareTo(ByteBuffer.wrap(other.hashCode.asBytes())); |
| } |
| |
| /** |
| * Treat non-idempotent OutputKeys as unequal to everything, including other non-idempotent |
| * OutputKeys. |
| */ |
| @Override |
| public boolean equals(Object that) { |
| if (!(that instanceof OutputKey)) { |
| return false; |
| } |
| OutputKey other = (OutputKey) that; |
| if (!isIdempotent() || !other.isIdempotent()) { |
| return false; |
| } |
| return (compareTo(other) == 0); |
| } |
| |
| @Override |
| public int hashCode() { |
| if (!isIdempotent()) { |
| return 0; |
| } |
| return super.hashCode(); |
| } |
| } |