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1.1 ! root 1: Enclosed is compress version 3.0 with the following changes: ! 2: ! 3: 1. "Block" compression is performed. After the BITS run out, the ! 4: compression ratio is checked every so often. If it is decreasing, ! 5: the table is cleared and a new set of substrings are generated. ! 6: ! 7: This makes the output of compress 3.0 not compatable with that of ! 8: compress 2.0. However, compress 3.0 still accepts the output of ! 9: compress 2.0. To generate output that is compatable with compress ! 10: 2.0, use the undocumented "-C" flag. ! 11: ! 12: 2. A quiet "-q" flag has been added for use by the news system. ! 13: ! 14: 3. The character chaining has been deleted and the program now uses ! 15: hashing. This improves the speed of the program, especially ! 16: during decompression. Other speed improvements have been made, ! 17: such as using putc() instead of fwrite(). ! 18: ! 19: 4. A large table is used on large machines when a relatively small ! 20: number of bits is specified. This saves much time when compressing ! 21: for a 16-bit machine on a 32-bit virtual machine. Note that the ! 22: speed improvement only occurs when the input file is > 30000 ! 23: characters, and the -b BITS is less than or equal to the cutoff ! 24: described below. ! 25: ! 26: Most of these changes were made by James A. Woods (ames!jaw). Thank you ! 27: James! ! 28: ! 29: Version 3.0 has been beta tested on many machines. ! 30: ! 31: To compile compress: ! 32: ! 33: cc -O -DUSERMEM=usermem -o compress compress.c ! 34: ! 35: Where "usermem" is the amount of physical user memory available (in bytes). ! 36: If any physical memory is to be reserved for other processes, put in ! 37: "-DSACREDMEM sacredmem", where "sacredmem" is the amount to be reserved. ! 38: ! 39: The difference "usermem-sacredmem" determines the maximum BITS that can be ! 40: specified, and the cutoff bits where the large+fast table is used. ! 41: ! 42: memory: at least BITS cutoff ! 43: ------ -- ----- ---- ------ ! 44: 4,718,592 16 13 ! 45: 2,621,440 16 12 ! 46: 1,572,864 16 11 ! 47: 1,048,576 16 10 ! 48: 631,808 16 -- ! 49: 329,728 15 -- ! 50: 178,176 14 -- ! 51: 99,328 13 -- ! 52: 0 12 -- ! 53: ! 54: The default memory size is 750,000 which gives a maximum BITS=16 and no ! 55: large+fast table. ! 56: ! 57: The maximum bits can be overrulled by specifying "-DBITS=bits" at ! 58: compilation time. ! 59: ! 60: If your machine doesn't support unsigned characters, define "NO_UCHAR" ! 61: when compiling. ! 62: ! 63: If your machine has "int" as 16-bits, define "SHORT_INT" when compiling. ! 64: ! 65: After compilation, move "compress" to a standard executable location, such ! 66: as /usr/local. Then: ! 67: cd /usr/local ! 68: ln compress uncompress ! 69: ln compress zcat ! 70: ! 71: On machines that have a fixed stack size (such as Perkin-Elmer), set the ! 72: stack to at least 12kb. ("setstack compress 12" on Perkin-Elmer). ! 73: ! 74: Next, install the manual (compress.l). ! 75: cp compress.l /usr/man/manl ! 76: cd /usr/man/manl ! 77: ln compress.l uncompress.l ! 78: ln compress.l zcat.l ! 79: ! 80: - or - ! 81: ! 82: cp compress.l /usr/man/man1/compress.1 ! 83: cd /usr/man/man1 ! 84: ln compress.1 uncompress.1 ! 85: ln compress.1 zcat.1 ! 86: ! 87: The zmore shell script and manual page are for use on systems that have a ! 88: "more(1)" program. Install the shell script and the manual page in a "bin" ! 89: and "man" directory, respectively. If your system doesn't have the ! 90: "more(1)" program, just skip "zmore". ! 91: ! 92: regards, ! 93: petsd!joe ! 94: ! 95: Here is the README file from the previous version of compress (2.0): ! 96: ! 97: >Enclosed is compress.c version 2.0 with the following bugs fixed: ! 98: > ! 99: >1. The packed files produced by compress are different on different ! 100: > machines and dependent on the vax sysgen option. ! 101: > The bug was in the different byte/bit ordering on the ! 102: > various machines. This has been fixed. ! 103: > ! 104: > This version is NOT compatible with the original vax posting ! 105: > unless the '-DCOMPATIBLE' option is specified to the C ! 106: > compiler. The original posting has a bug which I fixed, ! 107: > causing incompatible files. I recommend you NOT to use this ! 108: > option unless you already have a lot of packed files from ! 109: > the original posting by thomas. ! 110: >2. The exit status is not well defined (on some machines) causing the ! 111: > scripts to fail. ! 112: > The exit status is now 0,1 or 2 and is documented in ! 113: > compress.l. ! 114: >3. The function getopt() is not available in all C libraries. ! 115: > The function getopt() is no longer referenced by the ! 116: > program. ! 117: >4. Error status is not being checked on the fwrite() and fflush() calls. ! 118: > Fixed. ! 119: > ! 120: >The following enhancements have been made: ! 121: > ! 122: >1. Added facilities of "compact" into the compress program. "Pack", ! 123: > "Unpack", and "Pcat" are no longer required (no longer supplied). ! 124: >2. Installed work around for C compiler bug with "-O". ! 125: >3. Added a magic number header (\037\235). Put the bits specified ! 126: > in the file. ! 127: >4. Added "-f" flag to force overwrite of output file. ! 128: >5. Added "-c" flag and "zcat" program. 'ln compress zcat' after you ! 129: > compile. ! 130: >6. The 'uncompress' script has been deleted; simply ! 131: > 'ln compress uncompress' after you compile and it will work. ! 132: >7. Removed extra bit masking for machines that support unsigned ! 133: > characters. If your machine doesn't support unsigned characters, ! 134: > define "NO_UCHAR" when compiling. ! 135: > ! 136: >Compile "compress.c" with "-O -o compress" flags. Move "compress" to a ! 137: >standard executable location, such as /usr/local. Then: ! 138: > cd /usr/local ! 139: > ln compress uncompress ! 140: > ln compress zcat ! 141: > ! 142: >On machines that have a fixed stack size (such as Perkin-Elmer), set the ! 143: >stack to at least 12kb. ("setstack compress 12" on Perkin-Elmer). ! 144: > ! 145: >Next, install the manual (compress.l). ! 146: > cp compress.l /usr/man/manl - or - ! 147: > cp compress.l /usr/man/man1/compress.1 ! 148: > ! 149: >Here is the README that I sent with my first posting: ! 150: > ! 151: >>Enclosed is a modified version of compress.c, along with scripts to make it ! 152: >>run identically to pack(1), unpack(1), an pcat(1). Here is what I ! 153: >>(petsd!joe) and a colleague (petsd!peora!srd) did: ! 154: >> ! 155: >>1. Removed VAX dependencies. ! 156: >>2. Changed the struct to separate arrays; saves mucho memory. ! 157: >>3. Did comparisons in unsigned, where possible. (Faster on Perkin-Elmer.) ! 158: >>4. Sorted the character next chain and changed the search to stop ! 159: >>prematurely. This saves a lot on the execution time when compressing. ! 160: >> ! 161: >>This version is totally compatible with the original version. Even though ! 162: >>lint(1) -p has no complaints about compress.c, it won't run on a 16-bit ! 163: >>machine, due to the size of the arrays. ! 164: >> ! 165: >>Here is the README file from the original author: ! 166: >> ! 167: >>>Well, with all this discussion about file compression (for news batching ! 168: >>>in particular) going around, I decided to implement the text compression ! 169: >>>algorithm described in the June Computer magazine. The author claimed ! 170: >>>blinding speed and good compression ratios. It's certainly faster than ! 171: >>>compact (but, then, what wouldn't be), but it's also the same speed as ! 172: >>>pack, and gets better compression than both of them. On 350K bytes of ! 173: >>>unix-wizards, compact took about 8 minutes of CPU, pack took about 80 ! 174: >>>seconds, and compress (herein) also took 80 seconds. But, compact and ! 175: >>>pack got about 30% compression, whereas compress got over 50%. So, I ! 176: >>>decided I had something, and that others might be interested, too. ! 177: >>> ! 178: >>>As is probably true of compact and pack (although I haven't checked), ! 179: >>>the byte order within a word is probably relevant here, but as long as ! 180: >>>you stay on a single machine type, you should be ok. (Can anybody ! 181: >>>elucidate on this?) There are a couple of asm's in the code (extv and ! 182: >>>insv instructions), so anyone porting it to another machine will have to ! 183: >>>deal with this anyway (and could probably make it compatible with Vax ! 184: >>>byte order at the same time). Anyway, I've linted the code (both with ! 185: >>>and without -p), so it should run elsewhere. Note the longs in the ! 186: >>>code, you can take these out if you reduce BITS to <= 15. ! 187: >>> ! 188: >>>Have fun, and as always, if you make good enhancements, or bug fixes, ! 189: >>>I'd like to see them. ! 190: >>> ! 191: >>>=Spencer (thomas@utah-20, {harpo,hplabs,arizona}!utah-cs!thomas) ! 192: >> ! 193: >> regards, ! 194: >> joe ! 195: >> ! 196: >>-- ! 197: >>Full-Name: Joseph M. Orost ! 198: >>UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!joe ! 199: >>US Mail: MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724 ! 200: >>Phone: (201) 870-5844
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