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Buffers: new utils class for common operations on P2P message ByteBuffer

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This commit is contained in:
Andreas Schildbach 2023-03-23 14:46:01 +01:00
parent 1869fa197e
commit ce39967d83
2 changed files with 94 additions and 20 deletions
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89
core/src/main/java/org/bitcoinj/base/internal/Buffers.java Normal file
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@ -0,0 +1,89 @@
/*
* Copyright by the original author or authors.
*
* 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 org.bitcoinj.base.internal;
import org.bitcoinj.base.VarInt;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import static org.bitcoinj.base.internal.Preconditions.check;
import static org.bitcoinj.base.internal.Preconditions.checkArgument;
import static org.bitcoinj.base.internal.Preconditions.checkState;
/**
* Utility methods for common operations on Bitcoin P2P message buffers.
*/
public class Buffers {
/**
* Read given number of bytes from the buffer.
*
* @param buf buffer to read from
* @param length number of bytes to read
* @return bytes read
* @throws BufferUnderflowException if the read value extends beyond the remaining bytes of the buffer
*/
public static byte[] readBytes(ByteBuffer buf, int length) throws BufferUnderflowException {
// defensive check against cheap memory exhaustion attack
check(length <= buf.remaining(), BufferUnderflowException::new);
byte[] b = new byte[length];
buf.get(b);
return b;
}
/**
* First read a {@link VarInt} from the buffer and use it to determine the number of bytes to be read. Then read
* that many bytes into the byte array to be returned. This construct is frequently used by Bitcoin protocols.
*
* @param buf buffer to read from
* @return read bytes
* @throws BufferUnderflowException if the read value extends beyond the remaining bytes of the buffer
*/
public static byte[] readLengthPrefixedBytes(ByteBuffer buf) throws BufferUnderflowException {
int length = VarInt.read(buf).intValue();
return readBytes(buf, length);
}
/**
* First read a {@link VarInt} from the buffer and use it to determine the number of bytes to read. Then read
* that many bytes and interpret it as an UTF-8 encoded string to be returned. This construct is frequently used
* by Bitcoin protocols.
*
* @param buf buffer to read from
* @return read string
* @throws BufferUnderflowException if the read value extends beyond the remaining bytes of the buffer
*/
public static String readLengthPrefixedString(ByteBuffer buf) throws BufferUnderflowException {
return new String(readLengthPrefixedBytes(buf), StandardCharsets.UTF_8);
}
/**
* Advance buffer position by a given number of bytes.
*
* @param buf buffer to skip bytes on
* @param numBytes number of bytes to skip
* @return the buffer
* @throws BufferUnderflowException if the read value extends beyond the remaining bytes of the buffer
*/
public static ByteBuffer skipBytes(ByteBuffer buf, int numBytes) throws BufferUnderflowException {
checkArgument(numBytes >= 0);
check(numBytes <= buf.remaining(), BufferUnderflowException::new);
buf.position(buf.position() + numBytes);
return buf;
}
}

25
core/src/main/java/org/bitcoinj/core/Message.java
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@ -19,6 +19,7 @@ package org.bitcoinj.core;
import org.bitcoinj.base.Sha256Hash;
import org.bitcoinj.base.VarInt;
import org.bitcoinj.base.internal.Buffers;
import org.bitcoinj.base.internal.ByteUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@ -30,11 +31,6 @@ import java.io.OutputStream;
import java.math.BigInteger;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import static org.bitcoinj.base.internal.Preconditions.check;
import static org.bitcoinj.base.internal.Preconditions.checkArgument;
import static org.bitcoinj.base.internal.Preconditions.checkState;
/**
* <p>A Message is a data structure that can be serialized/deserialized using the Bitcoin serialization format.
@ -174,15 +170,8 @@ public abstract class Message {
return VarInt.read(payload);
}
private void checkReadLength(int length) throws BufferUnderflowException {
check(length <= payload.remaining(), BufferUnderflowException::new);
}
protected byte[] readBytes(int length) throws BufferUnderflowException {
checkReadLength(length);
byte[] b = new byte[length];
payload.get(b);
return b;
return Buffers.readBytes(payload, length);
}
protected byte readByte() throws BufferUnderflowException {
@ -190,13 +179,11 @@ public abstract class Message {
}
protected byte[] readByteArray() throws BufferUnderflowException {
final int length = readVarInt().intValue();
return readBytes(length);
return Buffers.readLengthPrefixedBytes(payload);
}
protected String readStr() throws BufferUnderflowException {
int length = readVarInt().intValue();
return length == 0 ? "" : new String(readBytes(length), StandardCharsets.UTF_8); // optimization for empty strings
return Buffers.readLengthPrefixedString(payload);
}
protected Sha256Hash readHash() throws BufferUnderflowException {
@ -204,9 +191,7 @@ public abstract class Message {
}
protected void skipBytes(int numBytes) throws BufferUnderflowException {
checkArgument(numBytes >= 0);
checkReadLength(numBytes);
payload.position(payload.position() + numBytes);
Buffers.skipBytes(payload, numBytes);
}
/** Network parameters this message was created with. */