TIdServerCompressionIntercept Class

Implements a server-side intercept component for compressing a data stream using the zlib library.

Pascal

TIdServerCompressionIntercept = class(TIdServerIntercept);

Description

TIdServerCompressionIntercept is a TIdServerIntercept descendant that implements an Indy intercept component for compressing a data stream using the open-source zlib compression library. As the name implies, TIdServerCompressionIntercept is used in TIdTCPServer and descendant classes to return a TIdConnectionIntercept for client connections to the multhithreaded server.

Set the CompressionLevel property to a value between 1 and 9 to enable compressing of the data stream for client connections. A setting of 0(zero) disables compression and the component is dormant. Bothe the sender (client) and receiver (server) must have compression enabled to properly exchange decompress the data stream. They do not have to use the same CompressionLevel as long as they are both set to a value between 1 and 9.

In order for this file to compile on Windows, the follow .obj files must be provided as delivered with this file:

deflate.obj inflate.obj inftrees.obj trees.obj adler32.obj infblock.obj infcodes.obj infutil.obj inffast.obj

On Linux, the shared-object file libz.so.1 must be available on the system. Most modern Linux distributions include this file.

You may sometimes get the following compiler errors with this file:

IdCompressionIntercept.pas(331) Error: Incompatible types
IdCompressionIntercept.pas(152) Error: Unsatisfied forward or external declaration: '_tr_init'
IdCompressionIntercept.pas(153) Error: Unsatisfied forward or external declaration: '_tr_tally'
IdCompressionIntercept.pas(154) Error: Unsatisfied forward or external declaration: '_tr_flush_block'
IdCompressionIntercept.pas(155) Error: Unsatisfied forward or external declaration: '_tr_align'
IdCompressionIntercept.pas(156) Error: Unsatisfied forward or external declaration: '_tr_stored_block'
IdCompressionIntercept.pas(157) Error: Unsatisfied forward or external declaration: 'adler32'
IdCompressionIntercept.pas(158) Error: Unsatisfied forward or external declaration: 'inflate_blocks_new'
IdCompressionIntercept.pas(159) Error: Unsatisfied forward or external declaration: 'inflate_blocks'
IdCompressionIntercept.pas(160) Error: Unsatisfied forward or external declaration: 'inflate_blocks_reset'
IdCompressionIntercept.pas(161) Error: Unsatisfied forward or external declaration: 'inflate_blocks_free'
IdCompressionIntercept.pas(162) Error: Unsatisfied forward or external declaration: 'inflate_set_dictionary'
IdCompressionIntercept.pas(163) Error: Unsatisfied forward or external declaration: 'inflate_trees_bits'
IdCompressionIntercept.pas(164) Error: Unsatisfied forward or external declaration: 'inflate_trees_dynamic'
IdCompressionIntercept.pas(165) Error: Unsatisfied forward or external declaration: 'inflate_trees_fixed'
IdCompressionIntercept.pas(166) Error: Unsatisfied forward or external declaration: 'inflate_trees_free'
IdCompressionIntercept.pas(167) Error: Unsatisfied forward or external declaration: 'inflate_codes_new'
IdCompressionIntercept.pas(168) Error: Unsatisfied forward or external declaration: 'inflate_codes'
IdCompressionIntercept.pas(169) Error: Unsatisfied forward or external declaration: 'inflate_codes_free'
IdCompressionIntercept.pas(170) Error: Unsatisfied forward or external declaration: '_inflate_mask'
IdCompressionIntercept.pas(171) Error: Unsatisfied forward or external declaration: 'inflate_flush'
IdCompressionIntercept.pas(172) Error: Unsatisfied forward or external declaration: 'inflate_fast'
IdCompressionIntercept.pas(189) Error: Unsatisfied forward or external declaration: 'deflateInit_'
IdCompressionIntercept.pas(196) Error: Unsatisfied forward or external declaration: 'deflate'
IdCompressionIntercept.pas(203) Error: Unsatisfied forward or external declaration: 'deflateEnd'
IdCompressionIntercept.pas(213) Error: Unsatisfied forward or external declaration: 'inflateInit_'
IdCompressionIntercept.pas(220) Error: Unsatisfied forward or external declaration: 'inflate'
IdCompressionIntercept.pas(227) Error: Unsatisfied forward or external declaration: 'inflateEnd'
IdCompressionIntercept.pas(234) Error: Unsatisfied forward or external declaration: 'inflateReset'
Indy40.dpk(196) Fatal: Could not compile used unit 'IdCompressionIntercept.pas'

Do not be alarmed. This is due to a bug in DCC32 in Delphi 4, 5, 6, plus C++Builder, 4, 5, and 6.

There is a workaround for this issue. The workaround is to compile this unit separately from the other units and than build Indy with a command such as DCC32 using the /M parameter. DO not use the /B parameter as that does force everything to be recompiled triggering the DCC32 error.

The batch files FULLC4.BAT, FULLC5.BAT, FULLC6.BAT, FULLD4.BAT, FULLD5.BAT and FULLD6.BAT now have the workaround in them so we recommend that you use those to build Indy.

Borland is aware of the issue.