1 2 @(#)README 8.1 (Berkeley) 06/09/93 3 4Compress version 4.0 improvements over 3.0: 5 o compress() speedup (10-50%) by changing division hash to xor 6 o decompress() speedup (5-10%) 7 o Memory requirements reduced (3-30%) 8 o Stack requirements reduced to less than 4kb 9 o Removed 'Big+Fast' compress code (FBITS) because of compress speedup 10 o Portability mods for Z8000 and PC/XT (but not zeus 3.2) 11 o Default to 'quiet' mode 12 o Unification of 'force' flags 13 o Manual page overhaul 14 o Portability enhancement for M_XENIX 15 o Removed text on #else and #endif 16 o Added "-V" switch to print version and options 17 o Added #defines for SIGNED_COMPARE_SLOW 18 o Added Makefile and "usermem" program 19 o Removed all floating point computations 20 o New programs: [deleted] 21 22The "usermem" script attempts to determine the maximum process size. Some 23editing of the script may be necessary (see the comments). [It should work 24fine on 4.3 bsd.] If you can't get it to work at all, just create file 25"USERMEM" containing the maximum process size in decimal. 26 27The following preprocessor symbols control the compilation of "compress.c": 28 29 o USERMEM Maximum process memory on the system 30 o SACREDMEM Amount to reserve for other proceses 31 o SIGNED_COMPARE_SLOW Unsigned compare instructions are faster 32 o NO_UCHAR Don't use "unsigned char" types 33 o BITS Overrules default set by USERMEM-SACREDMEM 34 o vax Generate inline assembler 35 o interdata Defines SIGNED_COMPARE_SLOW 36 o M_XENIX Makes arrays < 65536 bytes each 37 o pdp11 BITS=12, NO_UCHAR 38 o z8000 BITS=12 39 o pcxt BITS=12 40 o BSD4_2 Allow long filenames ( > 14 characters) & 41 Call setlinebuf(stderr) 42 43The difference "usermem-sacredmem" determines the maximum BITS that can be 44specified with the "-b" flag. 45 46memory: at least BITS 47------ -- ----- ---- 48 433,484 16 49 229,600 15 50 127,536 14 51 73,464 13 52 0 12 53 54The default is BITS=16. 55 56The maximum bits can be overrulled by specifying "-DBITS=bits" at 57compilation time. 58 59WARNING: files compressed on a large machine with more bits than allowed by 60a version of compress on a smaller machine cannot be decompressed! Use the 61"-b12" flag to generate a file on a large machine that can be uncompressed 62on a 16-bit machine. 63 64The output of compress 4.0 is fully compatible with that of compress 3.0. 65In other words, the output of compress 4.0 may be fed into uncompress 3.0 or 66the output of compress 3.0 may be fed into uncompress 4.0. 67 68The output of compress 4.0 not compatible with that of 69compress 2.0. However, compress 4.0 still accepts the output of 70compress 2.0. To generate output that is compatible with compress 712.0, use the undocumented "-C" flag. 72 73 -from mod.sources, submitted by vax135!petsd!joe (Joe Orost), 8/1/85 74-------------------------------- 75 76Enclosed is compress version 3.0 with the following changes: 77 781. "Block" compression is performed. After the BITS run out, the 79 compression ratio is checked every so often. If it is decreasing, 80 the table is cleared and a new set of substrings are generated. 81 82 This makes the output of compress 3.0 not compatible with that of 83 compress 2.0. However, compress 3.0 still accepts the output of 84 compress 2.0. To generate output that is compatible with compress 85 2.0, use the undocumented "-C" flag. 86 872. A quiet "-q" flag has been added for use by the news system. 88 893. The character chaining has been deleted and the program now uses 90 hashing. This improves the speed of the program, especially 91 during decompression. Other speed improvements have been made, 92 such as using putc() instead of fwrite(). 93 944. A large table is used on large machines when a relatively small 95 number of bits is specified. This saves much time when compressing 96 for a 16-bit machine on a 32-bit virtual machine. Note that the 97 speed improvement only occurs when the input file is > 30000 98 characters, and the -b BITS is less than or equal to the cutoff 99 described below. 100 101Most of these changes were made by James A. Woods (ames!jaw). Thank you 102James! 103 104To compile compress: 105 106 cc -O -DUSERMEM=usermem -o compress compress.c 107 108Where "usermem" is the amount of physical user memory available (in bytes). 109If any physical memory is to be reserved for other processes, put in 110"-DSACREDMEM sacredmem", where "sacredmem" is the amount to be reserved. 111 112The difference "usermem-sacredmem" determines the maximum BITS that can be 113specified, and the cutoff bits where the large+fast table is used. 114 115memory: at least BITS cutoff 116------ -- ----- ---- ------ 117 4,718,592 16 13 118 2,621,440 16 12 119 1,572,864 16 11 120 1,048,576 16 10 121 631,808 16 -- 122 329,728 15 -- 123 178,176 14 -- 124 99,328 13 -- 125 0 12 -- 126 127The default memory size is 750,000 which gives a maximum BITS=16 and no 128large+fast table. 129 130The maximum bits can be overruled by specifying "-DBITS=bits" at 131compilation time. 132 133If your machine doesn't support unsigned characters, define "NO_UCHAR" 134when compiling. 135 136If your machine has "int" as 16-bits, define "SHORT_INT" when compiling. 137 138After compilation, move "compress" to a standard executable location, such 139as /usr/local. Then: 140 cd /usr/local 141 ln compress uncompress 142 ln compress zcat 143 144On machines that have a fixed stack size (such as Perkin-Elmer), set the 145stack to at least 12kb. ("setstack compress 12" on Perkin-Elmer). 146 147Next, install the manual (compress.l). 148 cp compress.l /usr/man/manl 149 cd /usr/man/manl 150 ln compress.l uncompress.l 151 ln compress.l zcat.l 152 153 - or - 154 155 cp compress.l /usr/man/man1/compress.1 156 cd /usr/man/man1 157 ln compress.1 uncompress.1 158 ln compress.1 zcat.1 159 160 regards, 161 petsd!joe 162 163Here is a note from the net: 164 165>From hplabs!pesnta!amd!turtlevax!ken Sat Jan 5 03:35:20 1985 166Path: ames!hplabs!pesnta!amd!turtlevax!ken 167From: ken@turtlevax.UUCP (Ken Turkowski) 168Newsgroups: net.sources 169Subject: Re: Compress release 3.0 : sample Makefile 170Organization: CADLINC, Inc. @ Menlo Park, CA 171 172In the compress 3.0 source recently posted to mod.sources, there is a 173#define variable which can be set for optimum performance on a machine 174with a large amount of memory. A program (usermem) to calculate the 175useable amount of physical user memory is enclosed, as well as a sample 1764.2bsd Vax Makefile for compress. 177 178Here is the README file from the previous version of compress (2.0): 179 180>Enclosed is compress.c version 2.0 with the following bugs fixed: 181> 182>1. The packed files produced by compress are different on different 183> machines and dependent on the vax sysgen option. 184> The bug was in the different byte/bit ordering on the 185> various machines. This has been fixed. 186> 187> This version is NOT compatible with the original vax posting 188> unless the '-DCOMPATIBLE' option is specified to the C 189> compiler. The original posting has a bug which I fixed, 190> causing incompatible files. I recommend you NOT to use this 191> option unless you already have a lot of packed files from 192> the original posting by thomas. 193>2. The exit status is not well defined (on some machines) causing the 194> scripts to fail. 195> The exit status is now 0,1 or 2 and is documented in 196> compress.l. 197>3. The function getopt() is not available in all C libraries. 198> The function getopt() is no longer referenced by the 199> program. 200>4. Error status is not being checked on the fwrite() and fflush() calls. 201> Fixed. 202> 203>The following enhancements have been made: 204> 205>1. Added facilities of "compact" into the compress program. "Pack", 206> "Unpack", and "Pcat" are no longer required (no longer supplied). 207>2. Installed work around for C compiler bug with "-O". 208>3. Added a magic number header (\037\235). Put the bits specified 209> in the file. 210>4. Added "-f" flag to force overwrite of output file. 211>5. Added "-c" flag and "zcat" program. 'ln compress zcat' after you 212> compile. 213>6. The 'uncompress' script has been deleted; simply 214> 'ln compress uncompress' after you compile and it will work. 215>7. Removed extra bit masking for machines that support unsigned 216> characters. If your machine doesn't support unsigned characters, 217> define "NO_UCHAR" when compiling. 218> 219>Compile "compress.c" with "-O -o compress" flags. Move "compress" to a 220>standard executable location, such as /usr/local. Then: 221> cd /usr/local 222> ln compress uncompress 223> ln compress zcat 224> 225>On machines that have a fixed stack size (such as Perkin-Elmer), set the 226>stack to at least 12kb. ("setstack compress 12" on Perkin-Elmer). 227> 228>Next, install the manual (compress.l). 229> cp compress.l /usr/man/manl - or - 230> cp compress.l /usr/man/man1/compress.1 231> 232>Here is the README that I sent with my first posting: 233> 234>>Enclosed is a modified version of compress.c, along with scripts to make it 235>>run identically to pack(1), unpack(1), an pcat(1). Here is what I 236>>(petsd!joe) and a colleague (petsd!peora!srd) did: 237>> 238>>1. Removed VAX dependencies. 239>>2. Changed the struct to separate arrays; saves mucho memory. 240>>3. Did comparisons in unsigned, where possible. (Faster on Perkin-Elmer.) 241>>4. Sorted the character next chain and changed the search to stop 242>>prematurely. This saves a lot on the execution time when compressing. 243>> 244>>This version is totally compatible with the original version. Even though 245>>lint(1) -p has no complaints about compress.c, it won't run on a 16-bit 246>>machine, due to the size of the arrays. 247>> 248>>Here is the README file from the original author: 249>> 250>>>Well, with all this discussion about file compression (for news batching 251>>>in particular) going around, I decided to implement the text compression 252>>>algorithm described in the June Computer magazine. The author claimed 253>>>blinding speed and good compression ratios. It's certainly faster than 254>>>compact (but, then, what wouldn't be), but it's also the same speed as 255>>>pack, and gets better compression than both of them. On 350K bytes of 256>>>unix-wizards, compact took about 8 minutes of CPU, pack took about 80 257>>>seconds, and compress (herein) also took 80 seconds. But, compact and 258>>>pack got about 30% compression, whereas compress got over 50%. So, I 259>>>decided I had something, and that others might be interested, too. 260>>> 261>>>As is probably true of compact and pack (although I haven't checked), 262>>>the byte order within a word is probably relevant here, but as long as 263>>>you stay on a single machine type, you should be ok. (Can anybody 264>>>elucidate on this?) There are a couple of asm's in the code (extv and 265>>>insv instructions), so anyone porting it to another machine will have to 266>>>deal with this anyway (and could probably make it compatible with Vax 267>>>byte order at the same time). Anyway, I've linted the code (both with 268>>>and without -p), so it should run elsewhere. Note the longs in the 269>>>code, you can take these out if you reduce BITS to <= 15. 270>>> 271>>>Have fun, and as always, if you make good enhancements, or bug fixes, 272>>>I'd like to see them. 273>>> 274>>>=Spencer (thomas@utah-20, {harpo,hplabs,arizona}!utah-cs!thomas) 275>> 276>> regards, 277>> joe 278>> 279>>-- 280>>Full-Name: Joseph M. Orost 281>>UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!joe 282>>US Mail: MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724 283>>Phone: (201) 870-5844 284