1 /* 2 * Copyright 2016 Google Inc. All Rights Reserved. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.turbine.bytecode; 18 19 import static com.google.common.base.Verify.verify; 20 21 import com.google.common.io.ByteArrayDataInput; 22 import com.google.common.io.ByteStreams; 23 import java.io.ByteArrayInputStream; 24 25 /** A {@link ByteArrayDataInput} wrapper that tracks the current byte array index. */ 26 public class ByteReader { 27 28 private final byte[] bytes; 29 private final IndexedByteArrayInputStream indexed; 30 private final ByteArrayDataInput input; 31 32 public ByteReader(byte[] bytes, int pos) { 33 this.bytes = bytes; 34 this.indexed = new IndexedByteArrayInputStream(bytes, pos, bytes.length); 35 this.input = ByteStreams.newDataInput(indexed); 36 } 37 38 public ByteArrayDataInput seek(int i) { 39 return ByteStreams.newDataInput(bytes, i); 40 } 41 42 /** The position in the input buffer. */ 43 public int pos() { 44 return indexed.pos(); 45 } 46 47 /** Reads an unsigned 8-bit integer. */ 48 public int u1() { 49 return input.readUnsignedByte(); 50 } 51 52 /** Reads an unsigned 16-bit integer in big-endian byte order. */ 53 public int u2() { 54 return input.readUnsignedShort(); 55 } 56 57 /** Reads an unsigned 32-bit integer in big-endian byte order. */ 58 public int u4() { 59 return input.readInt(); 60 } 61 62 /** Skips n bytes of input. */ 63 public void skip(int n) { 64 int skipped = input.skipBytes(n); 65 // this is only used with {@link ByteArrayInputStream}. 66 verify(skipped == n, "wanted %s, read %s", n, skipped); 67 } 68 69 /** {@link #pos} is protected in {@link java.io.ByteArrayInputStream}. */ 70 static class IndexedByteArrayInputStream extends ByteArrayInputStream { 71 72 IndexedByteArrayInputStream(byte[] buf, int offset, int length) { 73 super(buf, offset, length); 74 } 75 76 int pos() { 77 return pos; 78 } 79 } 80 } 81
