zlib.ZStream

zlib.ZStream

Class Declaration

 Protected Class ZStream
 Implements Readable,Writeable

Remarks

This represents a deflate stream. Depending on the initialization options this class can read/write streams compressed using deflate (with or without header/footer) or GZip.

A ZStream has a reference to a Writeable object to which all compressed output is ultimately written; this is the "output stream". Another reference is held to a Readable object which is the ultimate source for all compressed input; this is the "input stream".

Typically, when compressing you only specify the output stream and when decompressing only the input stream. However both may be used simultaneously and independently, for example if reading/writing compressed data to/from a socket.

This class implements the Readable and Writeable class interfaces.

Methods

• Close
• Constructor
• EOF
• Flush
• Lookahead
• Read
• ReadAll
• ReadError
• ReadLine
• Sync
• Write
• WriteError
• WriteLine

Properties

• BufferedReading As Boolean
• Dictionary As MemoryBlock
• Encoding As Integer
• IsReadable As Boolean
• IsWriteable As Boolean
• LastError As Int32
• Level As Integer
• Ratio As Single
• Strategy As Integer
• TotalIn As UInt32
• TotalOut As UInt32

Shared Methods

• Create
• Open

Example

This example creates an in-memory compression stream by calling Constructor(MemoryBlock), and writes some data that will be compressed using GZip at maximum compression:

  Dim output As New MemoryBlock(0)
  Dim compressor As New zlib.ZStream(output, zlib.Z_BEST_COMPRESSION, zlib.GZIP_ENCODING)
  compressor.Write("Hello, world!")
  compressor.Close

This example reads raw compressed bytes from a BinaryStream that also has sections of uncompressed bytes. BufferedReading is set to False because we need the ZStream to read exactly the number of bytes we tell it to.

  Dim binstream As BinaryStream = BinaryStream.Open(GetOpenFolderItem(""))
  Dim decompressor As zlib.ZStream = zlib.ZStream.Open(binstream, zlib.RAW_ENCODING)
  decompressor.BufferedReading = False
  
  Dim uncompressedpart1, uncompressedpart2, compressedpart1, compressedpart2 As String
  ' read raw bytes
  uncompressedpart1 = binstream.Read(LengthOfUncompressedPart1)
  ' read compressed bytes
  compressedpart1 = decompressor.Read(LengthOfCompressedPart1)
  ' read some more raw bytes
  uncompressedpart2 = binstream.Read(LengthOfUncompressedPart2)
  ' read some more compressed bytes
  compressedpart2 = decompressor.Read(LengthOfCompressedPart2)
  'etc.