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1.1 ! root 1: ! 2: @(#)README 5.3 (Berkeley) 9/17/85 ! 3: ! 4: Compress 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: ! 22: The "usermem" script attempts to determine the maximum process size. Some ! 23: editing of the script may be necessary (see the comments). [It should work ! 24: fine 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: ! 27: The 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: ! 43: The difference "usermem-sacredmem" determines the maximum BITS that can be ! 44: specified with the "-b" flag. ! 45: ! 46: memory: at least BITS ! 47: ------ -- ----- ---- ! 48: 433,484 16 ! 49: 229,600 15 ! 50: 127,536 14 ! 51: 73,464 13 ! 52: 0 12 ! 53: ! 54: The default is BITS=16. ! 55: ! 56: The maximum bits can be overrulled by specifying "-DBITS=bits" at ! 57: compilation time. ! 58: ! 59: WARNING: files compressed on a large machine with more bits than allowed by ! 60: a 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 ! 62: on a 16-bit machine. ! 63: ! 64: The output of compress 4.0 is fully compatible with that of compress 3.0. ! 65: In other words, the output of compress 4.0 may be fed into uncompress 3.0 or ! 66: the output of compress 3.0 may be fed into uncompress 4.0. ! 67: ! 68: The output of compress 4.0 not compatible with that of ! 69: compress 2.0. However, compress 4.0 still accepts the output of ! 70: compress 2.0. To generate output that is compatible with compress ! 71: 2.0, use the undocumented "-C" flag. ! 72: ! 73: -from mod.sources, submitted by vax135!petsd!joe (Joe Orost), 8/1/85 ! 74: -------------------------------- ! 75: ! 76: Enclosed is compress version 3.0 with the following changes: ! 77: ! 78: 1. "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: ! 87: 2. A quiet "-q" flag has been added for use by the news system. ! 88: ! 89: 3. 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: ! 94: 4. 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: ! 101: Most of these changes were made by James A. Woods (ames!jaw). Thank you ! 102: James! ! 103: ! 104: To compile compress: ! 105: ! 106: cc -O -DUSERMEM=usermem -o compress compress.c ! 107: ! 108: Where "usermem" is the amount of physical user memory available (in bytes). ! 109: If any physical memory is to be reserved for other processes, put in ! 110: "-DSACREDMEM sacredmem", where "sacredmem" is the amount to be reserved. ! 111: ! 112: The difference "usermem-sacredmem" determines the maximum BITS that can be ! 113: specified, and the cutoff bits where the large+fast table is used. ! 114: ! 115: memory: 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: ! 127: The default memory size is 750,000 which gives a maximum BITS=16 and no ! 128: large+fast table. ! 129: ! 130: The maximum bits can be overruled by specifying "-DBITS=bits" at ! 131: compilation time. ! 132: ! 133: If your machine doesn't support unsigned characters, define "NO_UCHAR" ! 134: when compiling. ! 135: ! 136: If your machine has "int" as 16-bits, define "SHORT_INT" when compiling. ! 137: ! 138: After compilation, move "compress" to a standard executable location, such ! 139: as /usr/local. Then: ! 140: cd /usr/local ! 141: ln compress uncompress ! 142: ln compress zcat ! 143: ! 144: On machines that have a fixed stack size (such as Perkin-Elmer), set the ! 145: stack to at least 12kb. ("setstack compress 12" on Perkin-Elmer). ! 146: ! 147: Next, 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: ! 163: Here is a note from the net: ! 164: ! 165: >From hplabs!pesnta!amd!turtlevax!ken Sat Jan 5 03:35:20 1985 ! 166: Path: ames!hplabs!pesnta!amd!turtlevax!ken ! 167: From: [email protected] (Ken Turkowski) ! 168: Newsgroups: net.sources ! 169: Subject: Re: Compress release 3.0 : sample Makefile ! 170: Organization: CADLINC, Inc. @ Menlo Park, CA ! 171: ! 172: In 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 ! 174: with a large amount of memory. A program (usermem) to calculate the ! 175: useable amount of physical user memory is enclosed, as well as a sample ! 176: 4.2bsd Vax Makefile for compress. ! 177: ! 178: Here 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
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