<?php
namespace PhpZip\Model\Extra\Fields;
/**
* Info-ZIP Unicode Comment Extra Field (0x6375):.
*
* Stores the UTF-8 version of the file comment as stored in the
* central directory header. (Last Revision 20070912)
*
* Value Size Description
* ----- ---- -----------
* (UCom) 0x6375 Short tag for this extra block type ("uc")
* TSize Short total data size for this block
* Version 1 byte version of this extra field, currently 1
* ComCRC32 4 bytes Comment Field CRC32 Checksum
* UnicodeCom Variable UTF-8 version of the entry comment
*
* Currently Version is set to the number 1. If there is a need
* to change this field, the version will be incremented. Changes
* may not be backward compatible so this extra field should not be
* used if the version is not recognized.
*
* The ComCRC32 is the standard zip CRC32 checksum of the File Comment
* field in the central directory header. This is used to verify that
* the comment field has not changed since the Unicode Comment extra field
* was created. This can happen if a utility changes the File Comment
* field but does not update the UTF-8 Comment extra field. If the CRC
* check fails, this Unicode Comment extra field should be ignored and
* the File Comment field in the header should be used instead.
*
* The UnicodeCom field is the UTF-8 version of the File Comment field
* in the header. As UnicodeCom is defined to be UTF-8, no UTF-8 byte
* order mark (BOM) is used. The length of this field is determined by
* subtracting the size of the previous fields from TSize. If both the
* File Name and Comment fields are UTF-8, the new General Purpose Bit
* Flag, bit 11 (Language encoding flag (EFS)), can be used to indicate
* both the header File Name and Comment fields are UTF-8 and, in this
* case, the Unicode Path and Unicode Comment extra fields are not
* needed and should not be created. Note that, for backward
* compatibility, bit 11 should only be used if the native character set
* of the paths and comments being zipped up are already in UTF-8. It is
* expected that the same file comment storage method, either general
* purpose bit 11 or extra fields, be used in both the Local and Central
* Directory Header for a file.
*
* @see https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT section 4.6.8
*/
class UnicodeCommentExtraField extends AbstractUnicodeExtraField
{
const HEADER_ID = 0x6375;
/**
* 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 string
*/
public function __toString()
{
return sprintf(
'0x%04x UnicodeComment: "%s"',
self::HEADER_ID,
$this->getUnicodeValue()
);
}
}