Class: ZipStream

• Inheritance
• Description
• Class protocol
  • ZipInterface compatibility - compress/uncompress
  • ZipInterface compatibility - crc
  • class initialization
  • instance creation
  • queries
• Instance protocol
  • low level
  • startup & release
• Examples

Inheritance:

   Object
   |
   +--Stream
      |
      +--CompressionStream
         |
         +--ZipStream

Package:

stx:libbasic2

Category:

Streams-Compressed

Version:

rev: 1.55 date: 2022/05/11 13:57:13

user: stefan

file: ZipStream.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

Zip compression and decompression (as used in gzip and zip)


[instance variables:]

[class variables:]

copyright
COPYRIGHT (c) 2002 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 compress: anUncompressedByteArrayOrString

compress anUncompressedByteArrayOrString and return it

Usage example(s):

self compress:'hello world hello world hello world hello world hello world'.

 compress: anUncompressedByteArrayOrString into: aCompressedByteArrayOrString

compress anUncompressedByteArrayOrString into aCompressedByteArrayOrString;
return the number of bytes in the destination buffer

Usage example(s):

|buffer len1 len2 compressed uncompressed| buffer := String new:100. len1 := self compress:'hello world hello world hello world hello world hello world' into:buffer. compressed := buffer copyTo:len1. len2 := self uncompress:compressed into:buffer. uncompressed := buffer copyTo:len2.

 flatBytesIn: bytesIn from: start to: stop into: bytesOut doCompress: doCompress

compress or uncompress the bytesIn buffer into the bytesOut buffer;
returns the un/compressed size; on error an exception is raised

 uncompress: aCompressedByteArrayOrString into: anUncompressedByteArrayOrString

uncompress aCompressedByteArrayOrString into anUncompressedByteArrayOrString;
return the number of bytes in the destination buffer

 uncompressRaw: bytesIn from: start to: stop into: bytesOut

uncompress the bytesIn buffer into the bytesOut buffer;
returns the uncompressed size; on error an exception is raised.
Raw means: do not expect a zlib or gzip header and checksum in bytesIn.

 crc32Add: aCharacterOrByte crc: crc

Update a running crc with aCharacterOrByte
and return the updated crc

 crc32BytesIn: bytesIn from: start to: stop crc: crc

Update a running crc with the bytes buf[start.. stop]
and return the updated crc

 initialize

setup class attributes derived from the library

 readOpenAsZipStreamOn: aStream

open to read data compressed from stream,
the default readOpenOn: will open ZipStream as gzip stream

 readOpenAsZipStreamOn: aStream suppressFileHeader: suppressFileHeader suppressZipHeaderAndChecksum: suppressZipHeaderAndChecksum

open to read data compressed from stream,
the default readOpenOn: will open ZipStream as gzip stream

 readOpenAsZipStreamOn: aStream suppressHeaderAndChecksum: aBoolean

open to read data compressed from stream,
the default readOpenOn: will open ZipStream as gzip stream

 writeOpenAsZipStreamOn: aStream

open to write data compressed to stream,
the default writeOpenOn: will open ZipStream as gzip stream

 writeOpenAsZipStreamOn: aStream suppressFileHeader: suppressFileHeader suppressZipHeaderAndChecksum: suppressZipHeaderAndChecksum

open to write data compressed to stream,
the default writeOpenOn: will open ZipStream as gzip stream

 writeOpenAsZipStreamOn: aStream suppressHeaderAndChecksum: aBoolean

open to write data compressed to stream,
the default writeOpenOn: will open ZipStream as gzip stream

 maxDistanceCodes

 maxLiteralCodes

Instance protocol:

 zclose

low level close of the zip stream

 zdeflate

low level - deflate

 zdeflateInit

low level - deflateInit

 zget_avail_out

low level - get the number of available out bytes

 zget_windowBits

answer the bits used for inflateInit2 or deflateInit2...
a negative WindowBits value suppresses the zlib header and the checksum...

 zinflate

low level - inflate

 zinflateInit

low level - inflateInit

 zopen

low level - opens the zip stream

 zset_avail_in: count

set the 'avail_in' and compute the crc

 openWithMode: aMode on: aStream suppressFileHeader: suppressFileHeader suppressZipHeaderAndChecksum: suppressZipHeaderAndChecksum

open stream and write or check gzip header
suppressFileHeader:
if true, the gzip header (magic number and a few extra fields) is not written/read
suppressZipHeaderAndChecksum
controls if the gzip checksum and 2 header bytes should be written/checked

 openWithMode: aMode on: aStream suppressHeaderAndChecksum: aBoolean

open stream and write or check gzip header.
Caveat:
Backward compatibility: aBoolean controls if the gzip checksum and 2 header bytes should be written/checked
(i.e. NOT the file header with the zip magic)

 readHeader

Check for the gzip magic id

 writeHeader

write the gzip magic id

Examples:

    |compressedDataStream zipStream compressedData uncompressedData|

    compressedDataStream := #[] writeStream.
    zipStream := ZipStream writeOpenOn:compressedDataStream.
    zipStream nextPutAll:'hallo Welt'.
    zipStream close.

    compressedData := compressedDataStream contents.

    zipStream := ZipStream readOpenOn:(compressedData readStream).

    zipStream notNil ifTrue:[
        |stream c|

        stream := '' writeStream.

        [ (c := zipStream nextOrNil) notNil ] whileTrue:[
            stream nextPut:c
        ].
        stream close.
        uncompressedData := stream contents.
    ].
    ^ uncompressedData

    |fstream zipStream c|

    fstream := FileStream newTemporary.
    zipStream := ZipStream writeOpenOn:fstream.
    zipStream nextPutAll:'hallo Welt(1) - test....'.
    zipStream cr.
    zipStream nextPutAll:'hallo Welt(2) - test....'.
    zipStream cr.

    zipStream close.
    fstream close.

    fstream := fstream fileName readStream.
    zipStream := ZipStream readOpenOn:fstream.

    Transcript showCR:zipStream contents.

    zipStream close.
    fstream close.
    fstream fileName delete.