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