The Bereznikers

VFP implementation of GetZipComment and GetZipFilesList for ZIP acrchives

Submitted by Sergey on March 17, 2008 - 13:45 UTC

topic:

VFP class below allows retrieval of a ZIP file comment or a list/count of files in the ZIP archive. It uses VFP low level file functions (LLFF) to directly read the ZIP file.

$SAMPLECODE$



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* Examples of using GetZipComment, GetZipFilesList and GetZipFileCount

lcZipName = "..."
DIMENSION laList[1]
loZU = NEWOBJECT("ZipUtils", "ZipUtils.fxp")
* Retrieve ZIP comment
llOK = loZU.GetZipComment(lcZipName)
IF NOT llOK
	? "Error: " + loZU.cErrorMsg
ELSE
	? "ZIP comment: " + loZU.cZipComment
ENDIF	

* Get a list of files in ZIP
lnZipFileCount = loZU.GetZipFilesList(lcZipName, @laList)
IF lnZipFileCount < 0
	? "Error: " + loZU.cErrorMsg
ELSE
	? "File count in ZIP: " + TRANSFORM(lnZipFileCount )	
ENDIF	


* Get a file count in ZIP
lnZipFileCount = loZU.GetZipFileCount(lcZipName)
IF lnZipFileCount < 0
	? "Error: " + loZU.cErrorMsg
ELSE
	? "File count in ZIP: " + TRANSFORM(lnZipFileCount )	
ENDIF


* ZipUtils.prg
DEFINE CLASS ZipUtils AS custom
	cZipComment = ""
	nErrorNum = 0
	cErrorMsg = ""
	cZipFileName = ""
	nBufferSize = 2^16-1
	hZipFile = 0

	PROCEDURE GetZipComment
	* End of central directory record:
	*  1 4 end of central directory signature (0x06054b50)
	*  5 2 number of this disk
	*  7 2 number of the disk with the start of the central directory
	*  9 2 total number of entries in the central directory on this disk
	* 11 2 total number of entries in the central directory
	* 13 4 size of the central directory
	* 17 4 offset of start of central directory with respect to the starting disk number
	* 21 2 .ZIP file comment size
	* 23 nnn ZIP file comment (variable size)

	LPARAMETERS tcZipFileName
	LOCAL lcZipSignature, lcZipEoCdrSignature, lcReadBuffer, lnPos, lcZipEoCdr, lcZipComment, lnZipCommentSize

	This.cZipComment = ""
	This.cZipFileName = tcZipFileName
	lcZipSignature = "PK" + CHR(03) + CHR(04)
	lcZipEoCdrSignature = "PK" + CHR(05) + CHR(06)

	This.hZipFile = FOPEN(tcZipFileName)
	IF This.hZipFile < 1
		This.cErrorMsg = "Cannot open ZIP file " + This.cZipFileName
		This.nErrorNum = 1
		RETURN .F.
	ENDIF
	lcReadBuffer = FREAD(This.hZipFile, This.nBufferSize)

	IF NOT( lcZipSignature $ lcReadBuffer )
		FCLOSE(This.hZipFile)
		This.cErrorMsg = "Cannot find ZIP signature for file " + This.cZipFileName
		This.nErrorNum = 2
		RETURN .F.
	ENDIF

	lnPos = 0
	FSEEK(This.hZipFile,0)
	lcReadBuffer = ""
	DO WHILE NOT FEOF(This.hZipFile)
		lcReadBuffer = RIGHT(lcReadBuffer,4) + FREAD(This.hZipFile, This.nBufferSize)
		lnPos = AT(lcZipEoCdrSignature, lcReadBuffer)
		IF lnPos > 0
			lcReadBuffer = lcReadBuffer + FREAD(This.hZipFile, This.nBufferSize)
			EXIT
		ENDIF
	ENDDO

	IF lnPos = 0
		FCLOSE(This.hZipFile)
		This.cErrorMsg = "Cannot find the end of central index signature for file " + This.cZipFileName
		This.nErrorNum = 3
		RETURN .F.
	ENDIF

	lcZipEoCdr = SUBSTR(lcReadBuffer, lnPos)
	lnZipCommentSize = ASC(SUBSTR(lcZipEoCdr,21)) + ASC(SUBSTR(lcZipEoCdr,22))*256
	This.cZipComment = SUBSTR(lcZipEoCdr,23, lnZipCommentSize)
	FCLOSE(This.hZipFile)
	RETURN .T.
	ENDPROC
	
	*-----------------------------------------------------------------------------------------
	PROCEDURE GetZipFileCount(tcZipFileName)
	RETURN This.GetZipFilesList(tcZipFileName)

	PROCEDURE GetZipFilesList
	*  1 4 central file header signature  	4 bytes (0x02014b50)
	*  5 2 version made by 	2 bytes
	*  7 2 version needed to extract 	2 bytes
	*  9 2 general purpose bit flag 	2 bytes
	* 11 2 compression method 	2 bytes
	* 13 2 last mod file time 	2 bytes
	* 15 2 last mod file date 	2 bytes
	* 17 4 crc-32 	4 bytes
	* 21 4 compressed size 	4 bytes
	* 25 4 uncompressed size 	4 bytes
	* 29 2 file name length 	2 bytes
	* 31 2 extra field length 	2 bytes
	* 33 2 file comment length 	2 bytes
	* 35 2 disk number start 	2 bytes
	* 37 2 internal file attributes 	2 bytes
	* 39 4 external file attributes 	4 bytes
	* 43 4 relative offset of local header 	4 bytes
	* 47 file name 	(variable size)
	* extra field 	(variable size)
	* file comment 	(variable size)

	LPARAMETERS tcZipFileName, taFileList
	LOCAL lcZipSignature, lcZipEoCdrSignature, lcReadBuffer, lnPos, lcZipEoCdr, lcZipComment, lnZipCommentSize
	LOCAL lcZipCfh, lnFileCount, lnFileNameLen, lnExtraFieldLen, lnFileCommentLen, lnCfhFixLen, llZipEoCdrSignature
	LOCAL llCountOnly

	This.cZipFileName = tcZipFileName
	lcZipSignature = "PK" + CHR(03) + CHR(04)
	lcZipEoCdrSignature = "PK" + CHR(05) + CHR(06)
	lcZipCfhSignature = "PK" + CHR(01) + CHR(02)

	llCountOnly = (PCOUNT() = 1)

	lnFileCount = 0

	This.hZipFile = FOPEN(tcZipFileName)

	IF This.hZipFile < 1
		This.cErrorMsg = "Cannot open ZIP file " + This.cZipFileName
		This.nErrorNum = 1
		RETURN -1
	ENDIF
	lcReadBuffer = FREAD(This.hZipFile, This.nBufferSize)

	IF NOT( lcZipSignature $ lcReadBuffer )
		FCLOSE(This.hZipFile)
		This.cErrorMsg = "Cannot find ZIP signature for file " + This.cZipFileName
		This.nErrorNum = 2
		RETURN -1
	ENDIF

	lnPos = 0
	FSEEK(This.hZipFile,0)
	lcReadBuffer = ""
	DO WHILE NOT FEOF(This.hZipFile)
		lcReadBuffer = lcReadBuffer + FREAD(This.hZipFile, This.nBufferSize)
		lnPos = AT(lcZipCfhSignature, lcReadBuffer)
		IF lnPos > 0
			lcReadBuffer = SUBSTR(lcReadBuffer, lnPos)
			EXIT
		ENDIF
	ENDDO

	IF lnPos = 0
		FCLOSE(This.hZipFile)
		This.cErrorMsg = "Cannot find central file header signature for ZIP file " + This.cZipFileName
		This.nErrorNum = 3
		RETURN -1
	ENDIF

	llZipEoCdrSignature = (lcZipEoCdrSignature $ lcReadBuffer)

	DO WHILE NOT FEOF(This.hZipFile) AND NOT llZipEoCdrSignature
		* Read one extra block in case if central file directory spins 2 blocks
		* 	Will fail if it occupies more than 2 blocks (>128 KB)
		lcReadBuffer = lcReadBuffer + FREAD(This.hZipFile, This.nBufferSize)
		llZipEoCdrSignature = (lcZipEoCdrSignature $ lcReadBuffer)
	ENDDO
	FCLOSE(This.hZipFile)

	IF NOT llZipEoCdrSignature
		This.cErrorMsg = "Cannot find the end of central index signature for ZIP file " + This.cZipFileName
		This.nErrorNum = 3
		RETURN -1
	ENDIF

	lcZipCfh = lcReadBuffer
	lcReadBuffer = ""

	ccCfhFixLen = 47

	DO WHILE lcZipCfh = lcZipCfhSignature
		lnFileCount = lnFileCount + 1
		lnFileNameLen = This.Short2Num(SUBSTR(lcZipCfh,29,2))
		lnExtraFieldLen = This.Short2Num(SUBSTR(lcZipCfh,31,2))
		lnFileCommentLen = This.Short2Num(SUBSTR(lcZipCfh,33,2))
		lnCfhLen = ccCfhFixLen + lnFileNameLen + lnExtraFieldLen + lnFileCommentLen

		IF NOT llCountOnly 
			DIMENSION taFileList[lnFileCount, 9]
			* Name
			taFileList[lnFileCount, 1] = SUBSTR(lcZipCfh, 47, lnFileNameLen)
			* Size
			taFileList[lnFileCount, 2] = This.Long2Num(SUBSTR(lcZipCfh,25,4))
			* Date & Time
			taFileList[lnFileCount, 3] = This.ConvertDosDate(This.Short2Num(SUBSTR(lcZipCfh,15,2)))
			taFileList[lnFileCount, 4] = This.ConvertDosTime(This.Short2Num(SUBSTR(lcZipCfh,13,2)))
			taFileList[lnFileCount, 5] = ""
			* Compressed size
			taFileList[lnFileCount, 6] = This.Long2Num(SUBSTR(lcZipCfh,21,4))
			* File Comment
			IF lnFileCommentLen > 0
				taFileList[lnFileCount, 7] = SUBSTR(lcZipCfh, 47 + lnFileNameLen, lnFileCommentLen )
			ELSE
				taFileList[lnFileCount, 7] = ""
			ENDIF
			taFileList[lnFileCount, 8] = ""
			taFileList[lnFileCount, 9] = ""
		ENDIF
		lcZipCfh =  SUBSTR(lcZipCfh, lnCfhLen)
	ENDDO

	RETURN lnFileCount
	ENDPROC
	*-----------------------------------------------------------------------------

	PROCEDURE Long2Num(tcLong)
	LOCAL lnNum
	lnNum = 0
	=RtlCopy2Num(@lnNum, tcLong, 4)
	RETURN lnNum

	PROCEDURE Short2Num(tcShort)
	LOCAL lnNum
	lnNum = 0
	=RtlCopy2Num(@lnNum, tcShort, 2)
	RETURN lnNum

	*-----------------------------------------------------------------------------

	PROCEDURE ConvertDosDate(tnDosDate)
	lnDosDate = BITAND(tnDosDate, 0xFFFF)
	* Year 7 bit, Month 4 bit, Day 5 bit
	RETURN DATE( 1980 + BITRSHIFT(lnDosDate, 9), ;
		BITRSHIFT(BITAND(lnDosDate, 0x1E0), 5), ;
		BITAND(lnDosDate, 0x1F))
	ENDPROC

	PROCEDURE ConvertDosTime(tnDosTime)
	lnDosTime = BITAND(tnDosTime, 0xFFFF)
	* Hours 5 bit, Minutes 6 bit, Bi-Seconds 5 bit
	RETURN PADL(BITRSHIFT(lnDosTime, 11), 2,"0") + ":" + ;
		PADL(BITRSHIFT(BITAND(lnDosTime, 0x7E0), 5), 2,"0") + ":" + ;
		PADL(BITAND(lnDosTime, 0x1F) * 2, 2,"0")
	ENDPROC


ENDDEFINE

*-----------------------------------------------------------------------------

PROCEDURE RtlCopy2Num(tnDest, tcFrom, tnLen)
DECLARE RtlMoveMemory IN WIN32API AS RtlCopy2Num ;
	INTEGER @ DestNum, STRING pVoidSource, INTEGER nLength
RETURN RtlCopy2Num(@tnDest, tcFrom, tnLen)


    
        
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