1 // Copyright 2016 The Bazel Authors. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 package com.google.devtools.build.android.desugar; 15 16 import com.google.devtools.build.android.desugar.io.CoreLibraryRewriter; 17 import com.google.devtools.build.android.desugar.io.IndexedInputs; 18 import com.google.devtools.build.android.desugar.io.InputFileProvider; 19 import java.io.IOException; 20 import java.io.InputStream; 21 import javax.annotation.Nullable; 22 import org.objectweb.asm.ClassReader; 23 24 class ClassReaderFactory { 25 private final IndexedInputs indexedInputs; 26 private final CoreLibraryRewriter rewriter; 27 ClassReaderFactory(IndexedInputs indexedInputs, CoreLibraryRewriter rewriter)28 public ClassReaderFactory(IndexedInputs indexedInputs, CoreLibraryRewriter rewriter) { 29 this.rewriter = rewriter; 30 this.indexedInputs = indexedInputs; 31 } 32 33 /** 34 * Returns a reader for the given/internal/Class$Name if the class is defined in the wrapped input 35 * and {@code null} otherwise. For simplicity this method turns checked into runtime exceptions 36 * under the assumption that all classes have already been read once when this method is called. 37 */ 38 @Nullable readIfKnown(String internalClassName)39 public ClassReader readIfKnown(String internalClassName) { 40 String filename = rewriter.unprefix(internalClassName) + ".class"; 41 InputFileProvider inputFileProvider = indexedInputs.getInputFileProvider(filename); 42 43 if (inputFileProvider != null) { 44 try (InputStream bytecode = inputFileProvider.getInputStream(filename)) { 45 // ClassReader doesn't take ownership and instead eagerly reads the stream's contents 46 return rewriter.reader(bytecode); 47 } catch (IOException e) { 48 // We should've already read through all files in the Jar once at this point, so we don't 49 // expect failures reading some files a second time. 50 throw new IllegalStateException("Couldn't load " + internalClassName, e); 51 } 52 } 53 54 return null; 55 } 56 57 /** 58 * Returns {@code true} if the given given/internal/Class$Name is defined in the wrapped input. 59 */ isKnown(String internalClassName)60 public boolean isKnown(String internalClassName) { 61 String filename = rewriter.unprefix(internalClassName) + ".class"; 62 return indexedInputs.getInputFileProvider(filename) != null; 63 } 64 } 65