Smalltalk/X Webserver

Class: CompressionStream

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

Version:: rev: 1.43 date: 2019/03/13 19:15:10; user: stefan; file: CompressionStream.st directory: libbasic2; module: stx stc-classLibrary: libbasic2

Abstract superclass of streams that compress or decompress data


[instance variables:]

[class variables:]

    ZipStream

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.

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

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 raises an error - it must be redefined in concrete classes **
zdeflate: low level - deflate
returns false if the deflate operation is finished otherwise true

** This method raises an error - it must be redefined in concrete classes **
zdeflateInit: low level - deflateInit
initialize the deflate mode, write header

** This method raises an error - it must be redefined in concrete classes **
zget_avail_out: low level - get the number of available out bytes

** This method raises an error - it must be redefined in concrete classes **
zinflate: low level - inflate
returns nil if at uncompress is finished, or the number of
available bytes in the output-buffer

** This method raises an error - it must be redefined in concrete classes **
zinflateInit: low level - inflateInit
initialize the inflate mode, read and check header

** This method raises an error - it must be redefined in concrete classes **
zopen: low level - opens the zip stream
create the resources

** This method raises an error - it must be redefined in concrete classes **
zset_avail_in: count: set the 'avail_in' and compute the crc

** This method raises an error - it must be redefined in concrete classes **

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
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

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