Class: ZipStream

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

Inheritance:

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

Package:

stx:libbasic2

Category:

Streams-Compressed

Version:

rev: 1.49 date: 2018/12/18 11:52:15

user: cg

file: ZipStream.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Author:

Claus Atzkern

Description:

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


[instance variables:]

[class variables:]

Related information:

Class protocol:

 compress: anUncompressedByteArrayOrString into: aCompressedByteArrayOrString

|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

Modified (format): / 18-12-2018 / 12:53:09 / Claus Gittinger

 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.