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/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* 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.google.turbine.bytecode;
import static com.google.common.base.Verify.verify;
import com.google.common.io.ByteArrayDataInput;
import com.google.common.io.ByteStreams;
import java.io.ByteArrayInputStream;
/** A {@link ByteArrayDataInput} wrapper that tracks the current byte array index. */
public class ByteReader {
private final byte[] bytes;
private final IndexedByteArrayInputStream indexed;
private final ByteArrayDataInput input;
public ByteReader(byte[] bytes, int pos) {
this.bytes = bytes;
this.indexed = new IndexedByteArrayInputStream(bytes, pos, bytes.length);
this.input = ByteStreams.newDataInput(indexed);
}
public ByteArrayDataInput seek(int i) {
return ByteStreams.newDataInput(bytes, i);
}
/** The position in the input buffer. */
public int pos() {
return indexed.pos();
}
/** Reads an unsigned 8-bit integer. */
public int u1() {
return input.readUnsignedByte();
}
/** Reads an unsigned 16-bit integer in big-endian byte order. */
public int u2() {
return input.readUnsignedShort();
}
/** Reads an unsigned 32-bit integer in big-endian byte order. */
public int u4() {
return input.readInt();
}
/** Skips n bytes of input. */
public void skip(int n) {
int skipped = input.skipBytes(n);
// this is only used with {@link ByteArrayInputStream}.
verify(skipped == n, "wanted %s, read %s", n, skipped);
}
/** {@link #pos} is protected in {@link java.io.ByteArrayInputStream}. */
static class IndexedByteArrayInputStream extends ByteArrayInputStream {
IndexedByteArrayInputStream(byte[] buf, int offset, int length) {
super(buf, offset, length);
}
int pos() {
return pos;
}
}
}
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