118 lines
5.0 KiB
Plaintext
118 lines
5.0 KiB
Plaintext
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/*
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* $Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $
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*
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* Revision 4.0 85/07/30 12:50:00 joe
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* Removed ferror() calls in output routine on every output except first.
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* Prepared for release to the world.
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*
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* Revision 3.6 85/07/04 01:22:21 joe
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* Remove much wasted storage by overlaying hash table with the tables
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* used by decompress: tab_suffix[1<<BITS], stack[8000]. Updated USERMEM
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* computations. Fixed dump_tab() DEBUG routine.
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*
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* Revision 3.5 85/06/30 20:47:21 jaw
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* Change hash function to use exclusive-or. Rip out hash cache. These
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* speedups render the megamemory version defunct, for now. Make decoder
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* stack global. Parts of the RCS trunks 2.7, 2.6, and 2.1 no longer apply.
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*
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* Revision 3.4 85/06/27 12:00:00 ken
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* Get rid of all floating-point calculations by doing all compression ratio
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* calculations in fixed point.
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*
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* Revision 3.3 85/06/24 21:53:24 joe
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* Incorporate portability suggestion for M_XENIX. Got rid of text on #else
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* and #endif lines. Cleaned up #ifdefs for vax and interdata.
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*
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* Revision 3.2 85/06/06 21:53:24 jaw
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* Incorporate portability suggestions for Z8000, IBM PC/XT from mailing list.
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* Default to "quiet" output (no compression statistics).
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*
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* Revision 3.1 85/05/12 18:56:13 jaw
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* Integrate decompress() stack speedups (from early pointer mods by McKie).
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* Repair multi-file USERMEM gaffe. Unify 'force' flags to mimic semantics
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* of SVR2 'pack'. Streamline block-compress table clear logic. Increase
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* output byte count by magic number size.
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*
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* Revision 3.0 84/11/27 11:50:00 petsd!joe
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* Set HSIZE depending on BITS. Set BITS depending on USERMEM. Unrolled
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* loops in clear routines. Added "-C" flag for 2.0 compatibility. Used
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* unsigned compares on Perkin-Elmer. Fixed foreground check.
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*
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* Revision 2.7 84/11/16 19:35:39 ames!jaw
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* Cache common hash codes based on input statistics; this improves
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* performance for low-density raster images. Pass on #ifdef bundle
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* from Turkowski.
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*
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* Revision 2.6 84/11/05 19:18:21 ames!jaw
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* Vary size of hash tables to reduce time for small files.
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* Tune PDP-11 hash function.
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*
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* Revision 2.5 84/10/30 20:15:14 ames!jaw
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* Junk chaining; replace with the simpler (and, on the VAX, faster)
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* double hashing, discussed within. Make block compression standard.
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*
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* Revision 2.4 84/10/16 11:11:11 ames!jaw
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* Introduce adaptive reset for block compression, to boost the rate
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* another several percent. (See mailing list notes.)
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*
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* Revision 2.3 84/09/22 22:00:00 petsd!joe
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* Implemented "-B" block compress. Implemented REVERSE sorting of tab_next.
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* Bug fix for last bits. Changed fwrite to putchar loop everywhere.
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*
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* Revision 2.2 84/09/18 14:12:21 ames!jaw
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* Fold in news changes, small machine typedef from thomas,
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* #ifdef interdata from joe.
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*
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* Revision 2.1 84/09/10 12:34:56 ames!jaw
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* Configured fast table lookup for 32-bit machines.
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* This cuts user time in half for b <= FBITS, and is useful for news batching
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* from VAX to PDP sites. Also sped up decompress() [fwrite->putc] and
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* added signal catcher [plus beef in writeerr()] to delete effluvia.
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*
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* Revision 2.0 84/08/28 22:00:00 petsd!joe
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* Add check for foreground before prompting user. Insert maxbits into
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* compressed file. Force file being uncompressed to end with ".Z".
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* Added "-c" flag and "zcat". Prepared for release.
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*
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* Revision 1.10 84/08/24 18:28:00 turtlevax!ken
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* Will only compress regular files (no directories), added a magic number
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* header (plus an undocumented -n flag to handle old files without headers),
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* added -f flag to force overwriting of possibly existing destination file,
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* otherwise the user is prompted for a response. Will tack on a .Z to a
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* filename if it doesn't have one when decompressing. Will only replace
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* file if it was compressed.
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*
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* Revision 1.9 84/08/16 17:28:00 turtlevax!ken
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* Removed scanargs(), getopt(), added .Z extension and unlimited number of
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* filenames to compress. Flags may be clustered (-Ddvb12) or separated
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* (-D -d -v -b 12), or combination thereof. Modes and other status is
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* copied with copystat(). -O bug for 4.2 seems to have disappeared with
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* 1.8.
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*
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* Revision 1.8 84/08/09 23:15:00 joe
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* Made it compatible with vax version, installed jim's fixes/enhancements
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*
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* Revision 1.6 84/08/01 22:08:00 joe
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* Sped up algorithm significantly by sorting the compress chain.
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*
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* Revision 1.5 84/07/13 13:11:00 srd
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* Added C version of vax asm routines. Changed structure to arrays to
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* save much memory. Do unsigned compares where possible (faster on
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* Perkin-Elmer)
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*
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* Revision 1.4 84/07/05 03:11:11 thomas
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* Clean up the code a little and lint it. (Lint complains about all
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* the regs used in the asm, but I'm not going to "fix" this.)
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*
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* Revision 1.3 84/07/05 02:06:54 thomas
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* Minor fixes.
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*
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* Revision 1.2 84/07/05 00:27:27 thomas
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* Add variable bit length output.
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*
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*/
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static char rcs_ident[] =
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"$Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $";
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