1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncThis directory contains an update to the ZLib interface unit,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncdistributed by Borland as a Delphi supplemental component.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncThe original ZLib unit is Copyright (c) 1997,99 Borland Corp.,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncand is based on zlib version 1.0.4. There are a series of bugs
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncand security problems associated with that old zlib version, and
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncwe recommend the users to update their ZLib unit.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncSummary of modifications
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync========================
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- Improved makefile, adapted to zlib version 1.2.1.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- Some field types from TZStreamRec are changed from Integer to
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync Longint, for consistency with the zlib.h header, and for 64-bit
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The zlib_version constant is updated.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The new Z_RLE strategy has its corresponding symbolic constant.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The allocation and deallocation functions and function types
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync (TAlloc, TFree, zlibAllocMem and zlibFreeMem) are now cdecl,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync and _malloc and _free are added as C RTL stubs. As a result,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync the original C sources of zlib can be compiled out of the box,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync and linked to the ZLib unit.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncSuggestions for improvements
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync============================
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncCurrently, the ZLib unit provides only a limited wrapper around
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncthe zlib library, and much of the original zlib functionality is
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncmissing. Handling compressed file formats like ZIP/GZIP or PNG
1b33c96954667ba382fa595baf7b31290bfdd517vboxsynccannot be implemented without having this functionality.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncApplications that handle these formats are either using their own,
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncduplicated code, or not using the ZLib unit at all.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncHere are a few suggestions:
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- Checksum class wrappers around adler32() and crc32(), similar
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync to the Java classes that implement the java.util.zip.Checksum
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The ability to read and write raw deflate streams, without the
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync zlib stream header and trailer. Raw deflate streams are used
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync in the ZIP file format.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The ability to read and write gzip streams, used in the GZIP
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync file format, and normally produced by the gzip program.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- The ability to select a different compression strategy, useful
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync to PNG and MNG image compression, and to multimedia compression
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync in general. Besides the compression level
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync TCompressionLevel = (clNone, clFastest, clDefault, clMax);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync which, in fact, could have used the 'z' prefix and avoided
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync TColor-like symbols
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync TCompressionLevel = (zcNone, zcFastest, zcDefault, zcMax);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync there could be a compression strategy
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync TCompressionStrategy = (zsDefault, zsFiltered, zsHuffmanOnly, zsRle);
1b33c96954667ba382fa595baf7b31290bfdd517vboxsync- ZIP and GZIP stream handling via TStreams.
1b33c96954667ba382fa595baf7b31290bfdd517vboxsyncCosmin Truta <cosmint@cs.ubbcluj.ro>