From 07162fa301835387e4da4278326ec1ff45d1dc3e Mon Sep 17 00:00:00 2001 From: Aki Date: Wed, 29 Sep 2021 21:52:57 +0200 Subject: Squashed 'zlib/' content from commit cacf7f1 git-subtree-dir: zlib git-subtree-split: cacf7f1d4e3d44d871b605da3b647f07d718623f --- contrib/delphi/readme.txt | 76 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 contrib/delphi/readme.txt (limited to 'contrib/delphi/readme.txt') diff --git a/contrib/delphi/readme.txt b/contrib/delphi/readme.txt new file mode 100644 index 0000000..2dc9a8b --- /dev/null +++ b/contrib/delphi/readme.txt @@ -0,0 +1,76 @@ + +Overview +======== + +This directory contains an update to the ZLib interface unit, +distributed by Borland as a Delphi supplemental component. + +The original ZLib unit is Copyright (c) 1997,99 Borland Corp., +and is based on zlib version 1.0.4. There are a series of bugs +and security problems associated with that old zlib version, and +we recommend the users to update their ZLib unit. + + +Summary of modifications +======================== + +- Improved makefile, adapted to zlib version 1.2.1. + +- Some field types from TZStreamRec are changed from Integer to + Longint, for consistency with the zlib.h header, and for 64-bit + readiness. + +- The zlib_version constant is updated. + +- The new Z_RLE strategy has its corresponding symbolic constant. + +- The allocation and deallocation functions and function types + (TAlloc, TFree, zlibAllocMem and zlibFreeMem) are now cdecl, + and _malloc and _free are added as C RTL stubs. As a result, + the original C sources of zlib can be compiled out of the box, + and linked to the ZLib unit. + + +Suggestions for improvements +============================ + +Currently, the ZLib unit provides only a limited wrapper around +the zlib library, and much of the original zlib functionality is +missing. Handling compressed file formats like ZIP/GZIP or PNG +cannot be implemented without having this functionality. +Applications that handle these formats are either using their own, +duplicated code, or not using the ZLib unit at all. + +Here are a few suggestions: + +- Checksum class wrappers around adler32() and crc32(), similar + to the Java classes that implement the java.util.zip.Checksum + interface. + +- The ability to read and write raw deflate streams, without the + zlib stream header and trailer. Raw deflate streams are used + in the ZIP file format. + +- The ability to read and write gzip streams, used in the GZIP + file format, and normally produced by the gzip program. + +- The ability to select a different compression strategy, useful + to PNG and MNG image compression, and to multimedia compression + in general. Besides the compression level + + TCompressionLevel = (clNone, clFastest, clDefault, clMax); + + which, in fact, could have used the 'z' prefix and avoided + TColor-like symbols + + TCompressionLevel = (zcNone, zcFastest, zcDefault, zcMax); + + there could be a compression strategy + + TCompressionStrategy = (zsDefault, zsFiltered, zsHuffmanOnly, zsRle); + +- ZIP and GZIP stream handling via TStreams. + + +-- +Cosmin Truta -- cgit v1.1