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/*
* Copyright 2012-2020 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
*
* https://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.springframework.boot.loader.jar;
import java.io.IOException;
import org.springframework.boot.loader.data.RandomAccessData;
/**
* A ZIP File "End of central directory record" (EOCD).
*
* @author Phillip Webb
* @author Andy Wilkinson
* @author Camille Vienot
* @see Zip File Format
*/
class CentralDirectoryEndRecord {
private static final int MINIMUM_SIZE = 22;
private static final int MAXIMUM_COMMENT_LENGTH = 0xFFFF;
private static final int ZIP64_MAGICCOUNT = 0xFFFF;
private static final int MAXIMUM_SIZE = MINIMUM_SIZE + MAXIMUM_COMMENT_LENGTH;
private static final int SIGNATURE = 0x06054b50;
private static final int COMMENT_LENGTH_OFFSET = 20;
private static final int READ_BLOCK_SIZE = 256;
private final Zip64End zip64End;
private byte[] block;
private int offset;
private int size;
/**
* Create a new {@link CentralDirectoryEndRecord} instance from the specified
* {@link RandomAccessData}, searching backwards from the end until a valid block is
* located.
* @param data the source data
* @throws IOException in case of I/O errors
*/
CentralDirectoryEndRecord(RandomAccessData data) throws IOException {
this.block = createBlockFromEndOfData(data, READ_BLOCK_SIZE);
this.size = MINIMUM_SIZE;
this.offset = this.block.length - this.size;
while (!isValid()) {
this.size++;
if (this.size > this.block.length) {
if (this.size >= MAXIMUM_SIZE || this.size > data.getSize()) {
throw new IOException(
"Unable to find ZIP central directory records after reading " + this.size + " bytes");
}
this.block = createBlockFromEndOfData(data, this.size + READ_BLOCK_SIZE);
}
this.offset = this.block.length - this.size;
}
int startOfCentralDirectoryEndRecord = (int) (data.getSize() - this.size);
this.zip64End = isZip64() ? new Zip64End(data, startOfCentralDirectoryEndRecord) : null;
}
private byte[] createBlockFromEndOfData(RandomAccessData data, int size) throws IOException {
int length = (int) Math.min(data.getSize(), size);
return data.read(data.getSize() - length, length);
}
private boolean isValid() {
if (this.block.length < MINIMUM_SIZE || Bytes.littleEndianValue(this.block, this.offset + 0, 4) != SIGNATURE) {
return false;
}
// Total size must be the structure size + comment
long commentLength = Bytes.littleEndianValue(this.block, this.offset + COMMENT_LENGTH_OFFSET, 2);
return this.size == MINIMUM_SIZE + commentLength;
}
private boolean isZip64() {
return (int) Bytes.littleEndianValue(this.block, this.offset + 10, 2) == ZIP64_MAGICCOUNT;
}
/**
* Returns the location in the data that the archive actually starts. For most files
* the archive data will start at 0, however, it is possible to have prefixed bytes
* (often used for startup scripts) at the beginning of the data.
* @param data the source data
* @return the offset within the data where the archive begins
*/
long getStartOfArchive(RandomAccessData data) {
long length = Bytes.littleEndianValue(this.block, this.offset + 12, 4);
long specifiedOffset = Bytes.littleEndianValue(this.block, this.offset + 16, 4);
long zip64EndSize = (this.zip64End != null) ? this.zip64End.getSize() : 0L;
int zip64LocSize = (this.zip64End != null) ? Zip64Locator.ZIP64_LOCSIZE : 0;
long actualOffset = data.getSize() - this.size - length - zip64EndSize - zip64LocSize;
return actualOffset - specifiedOffset;
}
/**
* Return the bytes of the "Central directory" based on the offset indicated in this
* record.
* @param data the source data
* @return the central directory data
*/
RandomAccessData getCentralDirectory(RandomAccessData data) {
if (this.zip64End != null) {
return this.zip64End.getCentralDirectory(data);
}
long offset = Bytes.littleEndianValue(this.block, this.offset + 16, 4);
long length = Bytes.littleEndianValue(this.block, this.offset + 12, 4);
return data.getSubsection(offset, length);
}
/**
* Return the number of ZIP entries in the file.
* @return the number of records in the zip
*/
int getNumberOfRecords() {
if (this.zip64End != null) {
return this.zip64End.getNumberOfRecords();
}
long numberOfRecords = Bytes.littleEndianValue(this.block, this.offset + 10, 2);
return (int) numberOfRecords;
}
String getComment() {
int commentLength = (int) Bytes.littleEndianValue(this.block, this.offset + COMMENT_LENGTH_OFFSET, 2);
AsciiBytes comment = new AsciiBytes(this.block, this.offset + COMMENT_LENGTH_OFFSET + 2, commentLength);
return comment.toString();
}
/**
* A Zip64 end of central directory record.
*
* @see Chapter
* 4.3.14 of Zip64 specification
*/
private static final class Zip64End {
private static final int ZIP64_ENDTOT = 32; // total number of entries
private static final int ZIP64_ENDSIZ = 40; // central directory size in bytes
private static final int ZIP64_ENDOFF = 48; // offset of first CEN header
private final Zip64Locator locator;
private final long centralDirectoryOffset;
private final long centralDirectoryLength;
private int numberOfRecords;
private Zip64End(RandomAccessData data, int centralDirectoryEndOffset) throws IOException {
this(data, new Zip64Locator(data, centralDirectoryEndOffset));
}
private Zip64End(RandomAccessData data, Zip64Locator locator) throws IOException {
this.locator = locator;
byte[] block = data.read(locator.getZip64EndOffset(), 56);
this.centralDirectoryOffset = Bytes.littleEndianValue(block, ZIP64_ENDOFF, 8);
this.centralDirectoryLength = Bytes.littleEndianValue(block, ZIP64_ENDSIZ, 8);
this.numberOfRecords = (int) Bytes.littleEndianValue(block, ZIP64_ENDTOT, 8);
}
/**
* Return the size of this zip 64 end of central directory record.
* @return size of this zip 64 end of central directory record
*/
private long getSize() {
return this.locator.getZip64EndSize();
}
/**
* Return the bytes of the "Central directory" based on the offset indicated in
* this record.
* @param data the source data
* @return the central directory data
*/
private RandomAccessData getCentralDirectory(RandomAccessData data) {
return data.getSubsection(this.centralDirectoryOffset, this.centralDirectoryLength);
}
/**
* Return the number of entries in the zip64 archive.
* @return the number of records in the zip
*/
private int getNumberOfRecords() {
return this.numberOfRecords;
}
}
/**
* A Zip64 end of central directory locator.
*
* @see Chapter
* 4.3.15 of Zip64 specification
*/
private static final class Zip64Locator {
static final int ZIP64_LOCSIZE = 20; // locator size
static final int ZIP64_LOCOFF = 8; // offset of zip64 end
private final long zip64EndOffset;
private final int offset;
private Zip64Locator(RandomAccessData data, int centralDirectoryEndOffset) throws IOException {
this.offset = centralDirectoryEndOffset - ZIP64_LOCSIZE;
byte[] block = data.read(this.offset, ZIP64_LOCSIZE);
this.zip64EndOffset = Bytes.littleEndianValue(block, ZIP64_LOCOFF, 8);
}
/**
* Return the size of the zip 64 end record located by this zip64 end locator.
* @return size of the zip 64 end record located by this zip64 end locator
*/
private long getZip64EndSize() {
return this.offset - this.zip64EndOffset;
}
/**
* Return the offset to locate {@link Zip64End}.
* @return offset of the Zip64 end of central directory record
*/
private long getZip64EndOffset() {
return this.zip64EndOffset;
}
}
}
