<?php
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namespace PhpZip\Model\Extra\Fields;
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use PhpZip\Exception\ZipException;
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use PhpZip\Model\Extra\ZipExtraField;
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use PhpZip\Model\ZipEntry;
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/**
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* Apk Alignment Extra Field.
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*
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* @see https://android.googlesource.com/platform/tools/apksig/+/master/src/main/java/com/android/apksig/ApkSigner.java
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* @see https://developer.android.com/studio/command-line/zipalign
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*/
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class ApkAlignmentExtraField implements ZipExtraField
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{
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/**
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* @var int Extensible data block/field header ID used for storing
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* information about alignment of uncompressed entries as
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* well as for aligning the entries's data. See ZIP
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* appnote.txt section 4.5 Extensible data fields.
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*/
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const HEADER_ID = 0xd935;
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/**
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* @var int minimum size (in bytes) of the extensible data block/field used
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* for alignment of uncompressed entries
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*/
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const MIN_SIZE = 6;
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/** @var int */
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const ALIGNMENT_BYTES = 4;
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/** @var int */
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const COMMON_PAGE_ALIGNMENT_BYTES = 4096;
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/** @var int */
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private $multiple;
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/** @var int */
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private $padding;
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/**
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* @param int $multiple
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* @param int $padding
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*/
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public function __construct($multiple, $padding)
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{
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$this->multiple = $multiple;
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$this->padding = $padding;
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}
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/**
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* Returns the Header ID (type) of this Extra Field.
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* The Header ID is an unsigned short integer (two bytes)
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* which must be constant during the life cycle of this object.
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*
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* @return int
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*/
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public function getHeaderId()
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{
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return self::HEADER_ID;
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}
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/**
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* @return int
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*/
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public function getMultiple()
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{
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return $this->multiple;
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}
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/**
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* @return int
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*/
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public function getPadding()
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{
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return $this->padding;
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}
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/**
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* @param int $multiple
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*/
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public function setMultiple($multiple)
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{
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$this->multiple = (int) $multiple;
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}
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/**
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* @param int $padding
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*/
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public function setPadding($padding)
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{
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$this->padding = (int) $padding;
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}
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/**
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* Populate data from this array as if it was in local file data.
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*
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* @param string $buffer the buffer to read data from
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* @param ZipEntry|null $entry
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*
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* @throws ZipException
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*
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* @return ApkAlignmentExtraField
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*/
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public static function unpackLocalFileData($buffer, ZipEntry $entry = null)
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{
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$length = \strlen($buffer);
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if ($length < 2) {
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// This is APK alignment field.
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// FORMAT:
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// * uint16 alignment multiple (in bytes)
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// * remaining bytes -- padding to achieve alignment of data which starts after
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// the extra field
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throw new ZipException(
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'Minimum 6 bytes of the extensible data block/field used for alignment of uncompressed entries.'
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);
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}
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$multiple = unpack('v', $buffer)[1];
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$padding = $length - 2;
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return new self($multiple, $padding);
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}
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/**
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* Populate data from this array as if it was in central directory data.
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*
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* @param string $buffer the buffer to read data from
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* @param ZipEntry|null $entry
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*
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* @throws ZipException on error
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*
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* @return ApkAlignmentExtraField
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*/
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public static function unpackCentralDirData($buffer, ZipEntry $entry = null)
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{
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return self::unpackLocalFileData($buffer, $entry);
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}
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/**
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* The actual data to put into local file data - without Header-ID
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* or length specifier.
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*
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* @return string the data
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*/
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public function packLocalFileData()
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{
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return pack('vx' . $this->padding, $this->multiple);
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}
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/**
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* The actual data to put into central directory - without Header-ID or
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* length specifier.
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*
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* @return string the data
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*/
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public function packCentralDirData()
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{
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return $this->packLocalFileData();
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}
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/**
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* @return string
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*/
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public function __toString()
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{
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return sprintf(
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'0x%04x APK Alignment: Multiple=%d Padding=%d',
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self::HEADER_ID,
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$this->multiple,
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$this->padding
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);
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}
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}
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