Java ByteBuffer Get getZipEocdCentralDirectorySizeBytes(ByteBuffer zipEndOfCentralDirectory)

Description

Returns the size (in bytes) of the ZIP Central Directory.

License

Apache License

Declaration

static long getZipEocdCentralDirectorySizeBytes(ByteBuffer zipEndOfCentralDirectory) 

Method Source Code

//package com.java2s;
/*//from w w w. java  2 s. c  o  m
 * Copyright (C) 2016 The Android Open Source Project
 *
 * 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.
 */

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

public class Main {
    private static final int ZIP_EOCD_CENTRAL_DIR_SIZE_FIELD_OFFSET = 12;

    /**
     * Returns the size (in bytes) of the ZIP Central Directory.
     *
     * <p>NOTE: Byte order of {@code zipEndOfCentralDirectory} must be little-endian.
     */
    static long getZipEocdCentralDirectorySizeBytes(ByteBuffer zipEndOfCentralDirectory) {
        assertByteOrderLittleEndian(zipEndOfCentralDirectory);
        return getUnsignedInt32(zipEndOfCentralDirectory,
                zipEndOfCentralDirectory.position() + ZIP_EOCD_CENTRAL_DIR_SIZE_FIELD_OFFSET);
    }

    private static void assertByteOrderLittleEndian(ByteBuffer buffer) {
        if (buffer.order() != ByteOrder.LITTLE_ENDIAN) {
            throw new IllegalArgumentException("ByteBuffer byte order must be little endian");
        }
    }

    private static long getUnsignedInt32(ByteBuffer buffer, int offset) {
        return buffer.getInt(offset) & 0xffffffffL;
    }
}

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