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The AWS Java SDK for Amazon S3 module holds the client classes that are used for communicating with Amazon Simple Storage Service
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/*
* Copyright 2017-2024 Amazon.com, Inc. or its affiliates. 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.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.services.s3.internal.eventstreaming;
import java.nio.ByteBuffer;
import java.util.zip.CRC32;
import java.util.zip.Checksum;
import static java.lang.String.format;
final class Prelude {
static final int LENGTH = 8;
static final int LENGTH_WITH_CRC = LENGTH + 4;
private final int totalLength;
private final long headersLength;
private Prelude(int totalLength, long headersLength) {
this.totalLength = totalLength;
this.headersLength = headersLength;
}
static Prelude decode(ByteBuffer buf) {
buf = buf.duplicate();
long computedPreludeCrc = computePreludeCrc(buf);
long totalLength = intToUnsignedLong(buf.getInt());
long headersLength = intToUnsignedLong(buf.getInt());
long wirePreludeCrc = intToUnsignedLong(buf.getInt());
if (computedPreludeCrc != wirePreludeCrc) {
throw new IllegalArgumentException(format("Prelude checksum failure: expected 0x%x, computed 0x%x",
wirePreludeCrc, computedPreludeCrc));
}
if (headersLength < 0 || headersLength > 131072) {
throw new IllegalArgumentException("Illegal headers_length value: " + headersLength);
}
long payloadLength = (totalLength - headersLength) - Message.MESSAGE_OVERHEAD;
if (payloadLength < 0 || payloadLength > 16777216) {
throw new IllegalArgumentException("Illegal payload size: " + payloadLength);
}
return new Prelude(toIntExact(totalLength), headersLength);
}
private static long intToUnsignedLong(int i) {
return ((long) i) & 0xffffffffL;
}
private static int toIntExact(long value) {
if ((int) value != value) {
throw new ArithmeticException("integer overflow");
}
return (int) value;
}
private static long computePreludeCrc(ByteBuffer buf) {
byte[] prelude = new byte[Prelude.LENGTH];
buf.duplicate().get(prelude);
Checksum crc = new CRC32();
crc.update(prelude, 0, prelude.length);
return crc.getValue();
}
int getTotalLength() {
return totalLength;
}
long getHeadersLength() {
return headersLength;
}
}
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