Class: CompressionStream

• Inheritance
• Description
• Class protocol
  • class initialization
  • defaults
  • error handling
  • instance creation
  • queries
• Instance protocol
  • accessing
  • error handling
  • finalization
  • low level
  • private
  • queries
  • reading
  • startup & release
  • writing

Inheritance:

   Object
   |
   +--Stream
      |
      +--CompressionStream
         |
         +--BZip2Stream
         |
         +--ZipStream

Package:

stx:libbasic2

Category:

Streams-Compressed

Version:

rev: 1.54 date: 2023/07/18 14:19:16

user: stefan

file: CompressionStream.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

Abstract superclass of streams that compress or decompress data


[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:

 initialize

 defaultSuppressHeaderAndChecksum

 zerror: anError

 readOpenOn: aStream

open to read data from an compressed stream

 readOpenOn: aStream suppressHeaderAndChecksum: aBoolean

open to read data from an compressed stream

 writeOpenOn: aStream

open to write data compressed to stream

 writeOpenOn: aStream suppressHeaderAndChecksum: aBoolean

open to write data compressed to stream

 isAbstract

Return if this class is an abstract class.
True is returned here for myself only; false for subclasses.
Abstract subclasses must redefine this again.

Instance protocol:

 binary

switch to binary mode - default is text

 binary: beBinaryBool

ExternalStream protocol compatibility:
switch to binary or text mode - default is text

 propagateClose

 propagateClose: aBoolean

close the underlying stream if the zip stream is closed

 text

switch to text mode - default is text

 errorNotOpen

report an error, that the stream has not been opened

 errorReadOnly

report an error, that the stream is a readOnly stream

 errorWriteOnly

report an error, that the stream is a writeOnly stream

 invalidArgument

called if a method is invoked with invalid parameters

 zerror: anError

 executor

redefined to return a lightweight copy
- all we need is the memory handle

 finalize

the compressin-stream was garbage collected;
close the underlying zip-stream

 finalizeCopy: aZStream

used for finalization to close the underlying zip-stream

 z_nextAvailableInto: aCollection startingAt: offset maxCount: maxCount

read the next available bytes into a collection, a string or byteArray;
returns the size read

 zclose

low level close of the zip stream

** This method must be redefined in concrete classes (subclassResponsibility) **

 zdeflate

low level - deflate
returns false if the deflate operation is finished, otherwise true

** This method must be redefined in concrete classes (subclassResponsibility) **

 zdeflateInit

low level - deflateInit
initialize the deflate mode, write header

** This method must be redefined in concrete classes (subclassResponsibility) **

 zget_avail_out

low level - get the number of available out bytes

** This method must be redefined in concrete classes (subclassResponsibility) **

 zinflate

low level - inflate
returns nil if at uncompress is finished, or the number of
available bytes in the output-buffer

** This method must be redefined in concrete classes (subclassResponsibility) **

 zinflateInit

low level - inflateInit
initialize the inflate mode, read and check header

** This method must be redefined in concrete classes (subclassResponsibility) **

 zopen

low level - opens the zip stream
create the resources

** This method must be redefined in concrete classes (subclassResponsibility) **

 zset_avail_in: count

set the 'avail_in' and compute the crc

** This method must be redefined in concrete classes (subclassResponsibility) **

 closeZStream

close the zip-stream

 contentsSpecies

return the kind of object to be returned by sub-collection builders

 fillBuffer

Fill the inputBytes buffer.
returns true if data is available for reading;
false if the stream is at end.
Updates the readLimit and position.

 onStreamPutBytes: count from: data

write compressed data to the (output) stream

 atEnd

return true if the end of the compressed input stream has been reached

 bufferSizeForNormalCopy

chunk size when reading from/writing to a Stream

 isBinary

return true, if the stream is in binary (as opposed to text-) mode.
The default when created is false

 isHeaderAndChecksumSuppressed

answer true if the checksum and header are suppressed;
the default is true (backward compatibility)

 isOpen

return true, if this stream is open

 isReadable

return true, if this stream can be read from

 isWritable

return true, if this stream can be written to

 contents

return the entire contents of and close the stream

 next

return the next element,
as character (text mode) or byte (binary mode).
Possibly raises ReadPastEnd error, if there are no more elements

 next: n

return the next count elements of the stream as a collection.
Redefined to return a String or ByteArray and for optimization

 next: n into: aBuffer startingAt: startIndex

read the next n elements of the stream into aBuffer.
Return the number of bytes read.

 nextByte

return the next element, a byte
raise an error, if there are no more elements

 nextByteOrNil

return the next element, a byte
return nil, if there are no more elements

 nextBytes: numBytes into: aByteCollection startingAt: initialIndex

can do it faster here than in super class

 nextOrNil

return the next element,
as character (text mode) or byte (binary mode).
return nil, if there are no more elements

 skip: count

skip count objects, return the receiver
redefined for optimization

 close

close the zip-stream

 openWithMode: aMode on: aStream

open the zip-stream on a stream
can be reimplemented to do some additional stuff (e.g. gzip header) like
in the ZipStream

 openWithMode: aMode on: aStream suppressHeaderAndChecksum: aBoolean

open the zip-stream on a stream
can be reimplemented to do some additional stuff (e.g. gzip header) like
in the ZipStream

 setInputStream: aStream

change the input stream (i.e. continue reading from aStream).
Useful if the input arrives in chunks, and we have to continue decompressing
from the next chunk (passing a readStream on the next chunk here).

 streamOpenWithMode: aMode on: aStream

 streamOpenWithMode: aMode on: aStream suppressHeaderAndChecksum: aBoolean

open the compression stream on a stream
#readonly uncompress the data derived from the read-stream, aStream
#writeonly compress the data and write to the write-stream, aStream

 contents: contents

write the entire contents to and close the stream

 flush

flush the input and output buffer

 nextPut: aByteOrCharacter

write the argument, aByteOrCharacter.
Answer aByteOrCharacter

 nextPutAll: aCollection

Write each of the objects in aCollection to the receiver stream.
Answer the receiver.

 nextPutBytes: count from: aStringOrBytes startingAt: startIndex

Write each of the objects in aCollection to the receiver stream.
Answer the receiver.