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