1 2/* 3 * $Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $ 4 * 5 * Revision 4.0 85/07/30 12:50:00 joe 6 * Removed ferror() calls in output routine on every output except first. 7 * Prepared for release to the world. 8 * 9 * Revision 3.6 85/07/04 01:22:21 joe 10 * Remove much wasted storage by overlaying hash table with the tables 11 * used by decompress: tab_suffix[1<<BITS], stack[8000]. Updated USERMEM 12 * computations. Fixed dump_tab() DEBUG routine. 13 * 14 * Revision 3.5 85/06/30 20:47:21 jaw 15 * Change hash function to use exclusive-or. Rip out hash cache. These 16 * speedups render the megamemory version defunct, for now. Make decoder 17 * stack global. Parts of the RCS trunks 2.7, 2.6, and 2.1 no longer apply. 18 * 19 * Revision 3.4 85/06/27 12:00:00 ken 20 * Get rid of all floating-point calculations by doing all compression ratio 21 * calculations in fixed point. 22 * 23 * Revision 3.3 85/06/24 21:53:24 joe 24 * Incorporate portability suggestion for M_XENIX. Got rid of text on #else 25 * and #endif lines. Cleaned up #ifdefs for vax and interdata. 26 * 27 * Revision 3.2 85/06/06 21:53:24 jaw 28 * Incorporate portability suggestions for Z8000, IBM PC/XT from mailing list. 29 * Default to "quiet" output (no compression statistics). 30 * 31 * Revision 3.1 85/05/12 18:56:13 jaw 32 * Integrate decompress() stack speedups (from early pointer mods by McKie). 33 * Repair multi-file USERMEM gaffe. Unify 'force' flags to mimic semantics 34 * of SVR2 'pack'. Streamline block-compress table clear logic. Increase 35 * output byte count by magic number size. 36 * 37 * Revision 3.0 84/11/27 11:50:00 petsd!joe 38 * Set HSIZE depending on BITS. Set BITS depending on USERMEM. Unrolled 39 * loops in clear routines. Added "-C" flag for 2.0 compatibility. Used 40 * unsigned compares on Perkin-Elmer. Fixed foreground check. 41 * 42 * Revision 2.7 84/11/16 19:35:39 ames!jaw 43 * Cache common hash codes based on input statistics; this improves 44 * performance for low-density raster images. Pass on #ifdef bundle 45 * from Turkowski. 46 * 47 * Revision 2.6 84/11/05 19:18:21 ames!jaw 48 * Vary size of hash tables to reduce time for small files. 49 * Tune PDP-11 hash function. 50 * 51 * Revision 2.5 84/10/30 20:15:14 ames!jaw 52 * Junk chaining; replace with the simpler (and, on the VAX, faster) 53 * double hashing, discussed within. Make block compression standard. 54 * 55 * Revision 2.4 84/10/16 11:11:11 ames!jaw 56 * Introduce adaptive reset for block compression, to boost the rate 57 * another several percent. (See mailing list notes.) 58 * 59 * Revision 2.3 84/09/22 22:00:00 petsd!joe 60 * Implemented "-B" block compress. Implemented REVERSE sorting of tab_next. 61 * Bug fix for last bits. Changed fwrite to putchar loop everywhere. 62 * 63 * Revision 2.2 84/09/18 14:12:21 ames!jaw 64 * Fold in news changes, small machine typedef from thomas, 65 * #ifdef interdata from joe. 66 * 67 * Revision 2.1 84/09/10 12:34:56 ames!jaw 68 * Configured fast table lookup for 32-bit machines. 69 * This cuts user time in half for b <= FBITS, and is useful for news batching 70 * from VAX to PDP sites. Also sped up decompress() [fwrite->putc] and 71 * added signal catcher [plus beef in writeerr()] to delete effluvia. 72 * 73 * Revision 2.0 84/08/28 22:00:00 petsd!joe 74 * Add check for foreground before prompting user. Insert maxbits into 75 * compressed file. Force file being uncompressed to end with ".Z". 76 * Added "-c" flag and "zcat". Prepared for release. 77 * 78 * Revision 1.10 84/08/24 18:28:00 turtlevax!ken 79 * Will only compress regular files (no directories), added a magic number 80 * header (plus an undocumented -n flag to handle old files without headers), 81 * added -f flag to force overwriting of possibly existing destination file, 82 * otherwise the user is prompted for a response. Will tack on a .Z to a 83 * filename if it doesn't have one when decompressing. Will only replace 84 * file if it was compressed. 85 * 86 * Revision 1.9 84/08/16 17:28:00 turtlevax!ken 87 * Removed scanargs(), getopt(), added .Z extension and unlimited number of 88 * filenames to compress. Flags may be clustered (-Ddvb12) or separated 89 * (-D -d -v -b 12), or combination thereof. Modes and other status is 90 * copied with copystat(). -O bug for 4.2 seems to have disappeared with 91 * 1.8. 92 * 93 * Revision 1.8 84/08/09 23:15:00 joe 94 * Made it compatible with vax version, installed jim's fixes/enhancements 95 * 96 * Revision 1.6 84/08/01 22:08:00 joe 97 * Sped up algorithm significantly by sorting the compress chain. 98 * 99 * Revision 1.5 84/07/13 13:11:00 srd 100 * Added C version of vax asm routines. Changed structure to arrays to 101 * save much memory. Do unsigned compares where possible (faster on 102 * Perkin-Elmer) 103 * 104 * Revision 1.4 84/07/05 03:11:11 thomas 105 * Clean up the code a little and lint it. (Lint complains about all 106 * the regs used in the asm, but I'm not going to "fix" this.) 107 * 108 * Revision 1.3 84/07/05 02:06:54 thomas 109 * Minor fixes. 110 * 111 * Revision 1.2 84/07/05 00:27:27 thomas 112 * Add variable bit length output. 113 * 114 */ 115 116static char rcs_ident[] = 117 "$Header: compress.c,v 4.0 85/07/30 12:50:00 joe Release $"; 118