-h- readme.txt Wed Jul 24 11:49:28 1985 USER$A:[MINOW.LZ]README.TXT;1 This is a rewrite of the Unix compress utility. It is *not* switch-compatible with Unix compress, however it is (almost) file-compatible (when compiled on Unix, or when "export" mode is selected on VMS Version 4). The advantages of this version are as follows: 1. Compress and decompress are separate programs, simplifying the problems of the small system implementor. Both run on an unmapped PDP-11 (with a maximum of 12 bits). The command interface is just lzcomp input compressed_output lzdcmp compressed_input output Input files are not deleted. 2. The compression algorithm and I/O design is intended to simplify embedding the programs (as subroutines) in some other task. (for example, in a database package.) 3. On non-Unix systems, the I/O design should be significantly faster. It should be slightly faster on Unix. The only disadvantage is that, as noted, it is not command (option) compatible with Unix compress. Also, some periferal functionality (such as the deletion of input files and the output file naming conventions) have not been implemented. On Unix (i.e., in "export" mode), the compressed data file is identical to the Unix file, *except* that lzcomp writes two CLEAR codes in a row to signal end-of-file (and lzdcmp treats two CLEAR codes in a row as signalling end-of-file). lzcomp and lzdcmp have been added to the Decus C distribution. Martin Minow decvax!minow, minow%rex.dec@decwrl.arpa -h- lzcmp1.c Wed Jul 24 11:49:28 1985 USER$A:[MINOW.LZ]LZCMP1.C;21 /* * lzcomp [-options] infile outfile */ #ifdef DOCUMENTATION title lzcomp File Compression index File compression synopsis .s.nf lzcomp [-options] [infile [outfile]] .s.f description lzcomp implements the Lempel-Ziv file compression algorithm. (Files compressed by lzcomp are uncompressed by lzdcmp.) It operates by finding common substrings and replaces them with a variable-size code. This is deterministic, and can be done with a single pass over the file. Thus, the decompression procedure needs no input table, but can track the way the table was built. Options may be given in either case. .lm +8 .p -8 -B Input file is "binary", not "human readable text". This is necessary on Dec operating systems, such as VMS and RSX-11M, that treat these files differently. (Note that binary support is rudamentary and probably insufficient as yet.) (On VMS version 4, this is ignored unless the -x option is specified or the input file is record-oriented.) .p -8 -M bits Write using the specified number of bits in the code -- necessary for big machines making files for little machines. For example, if compressing a file on VMS which is to be read on a PDP-11, you should select -M 12. .p -8 -V [n] Verbose if specified. If a value is specified, it will enable debugging code (if compiled in). .p -8 -X [n] "Export" -- write a file format that can be read by other operating systems. Only the bytes in the file are copied; file attributes are not preserved. If specified, the value determines the level of compatiblity. If not specified, or specified with an explicit value of zero, and lzcomp is running on Vax/VMS version 4 under VaxC and the input file is a disk or magtape file (block-oriented), a VMS-private output format is used which is incompatible with the Unix compress utility, but which preserves VMS file attributes. -X may take on the following values: .lm +4.s .i -4;#0##Choose VMS private format. See restrictions below. .i -4;#1##Compatible with Unix compress version 3.0: this is the default if -x is given without a value. .i -4;#2##As above, but supress "block compression" .i -4;#3##Supress block compression and do not output a compress header block. This is for compatiblity with a quite early version of Unix compress (and requires conditional-compilation to use). .lm -4.s Note that the -B (binary) option is ignored unless the input file is "record-oriented", such as a terminal or mailbox. .lm -8.s The other two arguments are the input and output filenames respectively. Redirection is supported, however, the output must be a disk/tape file. The file format is almost identical to the current Unix implementation of compress (V4.0). Files written by Unix compress should be readable by lzdcmp. Files written by lzcomp in export (-x) format will be readable by Unix compress (except that lzcomp outputs two "clear" codes to mark EOF. A patch to Unix compress is available.) VMS Restrictions VMS Private mode stores the true name and attributes of the input file into the compressed file and lzdcmp restores the attributes (and filename if requested). The following restrictions apply -- they may be lifted in the future as they are primarily due to the author's lack of understanding of the intricacies of of VMS I/O: All files must be stored on disk. The lzcomp output file must be specified directly. Also, for all usage on VMS, the compressed file must be written to, and read from disk. LZW compression algorithm This section is abstracted from Terry Welch's article referenced below. The algorithm builds a string translation table that maps substrings in the input into fixed-length codes. The compress algorithm may be described as follows: 1. Initialize table to contain single-character strings. 2. Read the first character. Set (the prefix string) to that character. 3. (step): Read next input character, K. 4. If at end of file, output code(); exit. 5. If K is in the string table: Set to K; goto step 3. 6. Else K is not in the string table. Output code(); Put K into the string table; Set to K; Goto step 3. "At each execution of the basic step an acceptable input string has been parsed off. The next character K is read and the extended string K is tested to see if it exists in the string table. If it is there, then the extended string becomes the parsed string and the step is repeated. If K is not in the string table, then it is entered, the code for the successfully parsed string is put out as comprssed data, the character K becomes the beginning of the next string, and the step is repeated." The decompression algorithm translates each received code into a prefix string and extension [suffix] character. The extension character is stored (in a push-down stack), and the prefix translated again, until the prefix is a single character, which completes decompression of this code. The entire code is then output by popping the stack. "An update to the string table is made for each code received (except the first one). When a code has been translated, its final character is used as the extension character, combined with the prior string, to add a new string to the string table. This new string is assigned a unique code value, which is the same code that the compressor assigned to that string. In this way, the decompressor incrementally reconstructs the same string table that the decompressor used.... Unfortunately ... [the algorithm] does not work for an abnormal case. The abnormal case occurs whenever an input character string contains the sequence KKK, where K already appears in the compressor string table." The decompression algorithm, augmented to handle the abnormal case, is as follows: 1. Read first input code; Store in CODE and OLDcode; With CODE = code(K), output(K); FINchar = K; 2. Read next code to CODE; INcode = CODE; If at end of file, exit; 3. If CODE not in string table (special case) then Output(FINchar); CODE = OLDcode; INcode = code(OLDcode, FINchar); 4. If CODE == code(K) then Push K onto the stack; CODE == code(); Goto 4. 5. If CODE == code(K) then Output K; FINchar = K; 6. While stack not empty Output top of stack; Pop stack; 7. Put OLDcode,K into the string table. OLDcode = INcode; Goto 2. The algorithm as implemented here introduces two additional complications. The actual codes are transmitted using a variable-length encoding. The lowest-level routines increase the number of bits in the code when the largest possible code is transmitted. Periodically, the algorithm checks that compression is still increasing. If the ratio of input bytes to output bytes decreases, the entire process is reset. This can happen if the characteristics of the input file change. VMS Private File Structure In VMS Private mode, the compressed data file contains a variable-length (but compressed) file header with the file "attributes" needed by the operating system to construct the file. This allows the decompression program to recreate the file in its original format, which is essential if ISAM databases are compressed. The overall file format is as follows: .lm +8 .p -8 LZ_SOH "start of header" signal (this value cannot appear in user data). A variable-length data record (maximum 256 bytes) containing the header name, followed by whitespace, followed by header-specific information. In this case, the name record will contain the string "vms$attributes" followed by the number of bytes in the attribute data block. (I assume that the name record will consist of a facility name, such as "vms", followed by a dollar sign, followed by a facility-unique word.) .p -8 LZ_EOR Signals "end of record". This is followed by a VMS file attributes record (generated by a VMS system library routine). .p -8 LZ_ETX Signals "end of segment". .p -8 ST_STX Signals "start of text" (i.e., start of data file). This is followed by the user data file. .p -8 LZ_ETX Signals "end of segment" .p -8 LZ_ETX Two in a row signals "end of file". .s.lm -8 Note that this format can easily be extended to include trailer records (with file counts and checksums) and/or multiple data files in one compressed file. Note also that the LZ_CLEAR code may appear in headers or data files to cause the decompression program to "readapt" to the characteristics of the input data. LZ_STX and LZ_SOH reset the compression algorithm. LZ_EOR does not. Authors The algorithm is from "A Technique for High Performance Data Compression." Terry A. Welch. IEEE Computer Vol 17, No. 6 (June 1984), pp 8-19. This revision is by Martin Minow. Unix Compress authors are as follows: .s.nf Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas) Jim McKie (decvax!mcvax!jim) Steve Davies (decvax!vax135!petsd!peora!srd) Ken Turkowski (decvax!decwrl!turtlevax!ken) James A. Woods (decvax!ihnp4!ames!jaw) Joe Orost (decvax!vax135!petsd!joe) .s.f #endif /* * Compatible with compress.c, v3.0 84/11/27 */ /*)BUILD * $(PROGRAM) = lzcomp * $(INCLUDE) = lz.h * $(FILES) = { lzcmp1.c lzcmp2.c lzcmp3.c lzio.c lzvio.c } */ #include "lz.h" #ifdef unix #include #include #endif /* * These global parameters are written to the compressed file. * The decompressor needs them. The initialized values are defaults * and are modified by command line arguments. */ short maxbits = BITS; /* settable max # bits/code */ code_int maxmaxcode = 1 << BITS; /* Totally largest code */ code_int hsize = HSIZE; /* Actual hash table size */ /* * Flags (command line arguments) to control compression. */ #if VMS_V4 flag export = 0; /* Assume vms "private" mode */ #else flag export = 1; /* Assume Unix compatible mode */ #endif flag block_compress = TRUE; /* Assume block compression */ flag binary = FALSE; /* Reading text file if FALSE */ flag noheader = FALSE; /* No magic header if TRUE */ flag verbose = VERBOSE_DEFAULT; /* Non-zero for status/debug */ flag background = FALSE; /* TRUE (Unix) if detached */ readonly flag is_compress = TRUE; /* for lzio.c (needed?) */ long fsize; /* Input file size in bytes */ char *infilename = NULL; /* For error printouts */ char *outfilename = NULL; /* For openoutput and errors */ int firstcode; /* First code after internals */ count_int tot_incount = 0; /* Total number of input bytes */ count_int tot_outcount = 0; /* Total number of output codes */ extern count_int in_count; extern count_int out_count; static long start_time; /* Time we started (in msec) */ extern long cputime(); /* Returns process time in msec */ STREAM instream; STREAM outstream; char_type inbuffer[MAXIO]; char_type outbuffer[MAXIO]; static STREAM mem_stream; jmp_buf failure; #if VMS_V4 #include types #include stat #include descrip #ifndef FDLSTUFF #define FDLSTUFF char #endif FDLSTUFF *fdl_input; FDLSTUFF *fdl_output; static struct dsc$descriptor fdl_descriptor; #endif main(argc, argv) int argc; char *argv[]; /* * Compress mainline */ { #ifndef decus /* * background is TRUE if running detached from the command terminal. */ background = (signal(SIGINT, SIG_IGN) == SIG_IGN) ? TRUE : FALSE; if (!background) background = !isatty(fileno(stderr)); if (!background) { if (verbose > 0) signal(SIGINT, abort); else { signal(SIGINT, interrupt); signal(SIGSEGV, address_error); } } #endif if (setjmp(failure) == 0) { setup(argc, argv); /* Command line parameters */ openinput(); /* Open input, set instream */ getfilesize(); /* Get input file size */ gethashsize(); /* Get actual hash table size */ initialize(); /* Set maxbits and the like */ openoutput(); /* Open output file */ if (verbose > 0) start_time = cputime(); put_magic_header(); init_compress(TRUE); compress(&instream); #if VMS_V4 if (export == 0) { outputcode((code_int) LZ_ETX); outputcode((code_int) LZ_ETX); fdl_close(fdl_input); } else #endif if (block_compress) { outputcode((code_int) LZ_CLEAR); outputcode((code_int) LZ_CLEAR); } outputcode((code_int) -1); /* Flush output buffers */ #if VMS_V4 if (export == 0) fdl_close(fdl_output); else { fclose(stdout); } #else fclose(stdout); #endif if (verbose > 0) { start_time = cputime() - start_time; tot_incount += in_count; tot_outcount += out_count; fprintf(stderr, "%ld chars in, %ld bytes out, ", tot_incount, tot_outcount); if (tot_outcount > 0) { divout("compression ratio: ", (long) tot_incount, (long) tot_outcount, ""); divout(" (", ((long) tot_incount - (long) tot_outcount) * 100, (long) tot_incount, "%)\n"); } fprintf(stderr, "%ld.%02ld seconds (process time) for compression.\n", start_time / 1000L, (start_time % 1000L) / 10L); if (start_time > 0) { divout(" ", (long) tot_incount * 10L, (start_time + 50L) / 100L, " input bytes per second.\n"); } } exit(IO_SUCCESS); } else { fprintf(stderr, "Error when compressing \"%s\" to \"%s\"\n", (infilename == NULL) ? "" : infilename, (outfilename == NULL) ? "" : outfilename); if (errno != 0) perror("lzcomp fatal error"); exit(IO_ERROR); } } divout(leader, numer, denom, trailer) char *leader; long numer; long denom; char *trailer; /* * Print numer/denom without floating point on small machines. */ { fprintf(stderr, "%s%ld.%02ld%s", leader, numer / denom, ((numer % denom) * 100L) / denom, trailer); } static initialize() /* * Mung some global values. */ { if (maxbits < INIT_BITS) /* maxbits is set by the -M */ maxbits = INIT_BITS; /* option. Make sure it's */ if (maxbits > BITS) /* within a reasonable range */ maxbits = BITS; maxmaxcode = 1 << maxbits; /* Truly biggest code */ if (export == 0) firstcode = LZ_FIRST; /* VMS private */ else if (block_compress) firstcode = LZ_CLEAR + 1; /* Default */ else firstcode = 256; /* Backwards compatible */ } put_magic_header() /* * Write the magic header bits. */ { #ifndef COMPATIBLE if (export && !noheader) { PUT(HEAD1_MAGIC, &outstream); PUT(HEAD2_MAGIC, &outstream); PUT(maxbits | ((block_compress) ? BLOCK_MASK : 0), &outstream); } #if VMS_V4 else if (export == 0) { char text[256]; /* * VMS private mode (with attribute block) */ PUT(HEAD1_MAGIC, &outstream); PUT(VMS_HEAD2_MAGIC, &outstream); PUT((char) (maxbits | BLOCK_MASK), &outstream); PUT(firstcode - 0x100, &outstream); init_compress(); outputcode(LZ_SOH); #if DEBUG if (strlen(ATT_NAME) != ATT_SIZE) { fprintf("\"%s\", expected %d, got %d\n", ATT_NAME, ATT_SIZE, strlen(ATT_NAME)); } #endif sprintf(text, "%s%d;", ATT_NAME, fdl_descriptor.dsc$w_length); mem_compress(text, strlen(text)); outputcode(LZ_EOR); mem_compress(fdl_descriptor.dsc$a_pointer, fdl_descriptor.dsc$w_length); fdl_free(&fdl_descriptor); outputcode(LZ_ETX); outputcode(LZ_STX); } #endif #endif } mem_compress(datum, length) char_type *datum; int length; /* * Compress from memory */ { mem_stream.bp = mem_stream.bstart = datum; mem_stream.bsize = length; mem_stream.bend = datum + length; mem_stream.func = lz_eof; compress(&mem_stream); } /* * This routine is used to tune the hash table size according to * the file size. If the filesize is unknown, fsize should be * set to zero. */ typedef struct TUNETAB { long fsize; code_int hsize; } TUNETAB; static readonly TUNETAB tunetab[] = { #if HSIZE > 5003 { 1 << 12, 5003 }, #endif #if HSIZE > 9001 { 1 << 13, 9001 }, #endif #if HSIZE > 18013 { 1 << 14, 18013 }, #endif #if HSIZE > 35023 { 1 << 15, 35023 }, { 47000, 50021 }, #endif { 0, 0 }, }; static gethashsize() /* * Tune the hash table parameters for small files. * We don't have a good way to find the file size on vms V3. * fsize is set to zero if we can't find it. */ { register TUNETAB *tunep; hsize = HSIZE; if (fsize > 0) { for (tunep = tunetab; tunep->fsize != 0; tunep++) { if (fsize < tunep->fsize) { hsize = tunep->hsize; break; } } } } static getfilesize() /* * Set fsize to the input filesize (in bytes) if possible. * Magic for all operating systems. */ { #ifdef rsx extern char f_efbk; /* F.EFBK -- highest block in file */ #define fdb(p,offset) (stdin->io_fdb[((int) &p + offset)] & 0xFF) #define efbk(offset) fdb(f_efbk, offset) extern char f_rtyp; /* F.RTYP -- Record type */ extern char f_ratt; /* F.RATT -- Record attributes */ /* * Note: Block number is stored high-order word first. */ fsize = efbk(2) + (efbk(3) << 8) + (efbk(0) << 16) + (efbk(1) << 24); fsize *= 512; #endif #ifdef rt11 fsize = stdin->io_size; /* Set by Decus C */ fsize *= 512; #endif #ifdef vms #if VMS_V4 struct stat statbuf; fsize = 0; if (export != 0) { if (fstat(fileno(stdin), &statbuf) == 0) fsize = (long) statbuf.st_size; } else { fsize = (long) fdl_fsize(fdl_input); } #else fsize = 0; /* Can't find filesize */ #endif #endif #ifdef unix struct stat statbuf; fsize = 0; if (fstat(fileno(stdin), &statbuf) == 0) fsize = (long) statbuf.st_size; #endif } static readonly char *helptext[] = { "The following options are valid:", "-B\tBinary file (important on VMS/RSX, ignored on Unix)", "-M val\tExplicitly set the maximum number of code bits", "-V val\tPrint status information (or debugging) to stderr", "-X val\tSet export (compatiblity) mode:", #if VMS_V4 " -X 0\tExplicitly choose VMS Private mode", #endif " -X 1\t(default if -X specified, output format is compatible", "\twith Unix compress V3.0", " -X 2\tCompatible with Unix compress 3.0, block compression", "\tsupressed.", #ifdef COMPATIBLE " -X 3No header (file is readable by old compress)", #endif NULL, }; static setup(argc, argv) int argc; char *argv[]; /* * Get parameters and open files. Exit fatally on errors. */ { register char *ap; register int c; char **hp; auto int i; int j; #ifdef vms argc = getredirection(argc, argv); #endif for (i = j = 1; i < argc; i++) { ap = argv[i]; if (*ap++ != '-' || *ap == EOS) /* Filename? */ argv[j++] = argv[i]; /* Just copy it */ else { while ((c = *ap++) != EOS) { if (islower(c)) c = toupper(c); switch (c) { case 'B': binary = TRUE; break; case 'M': maxbits = getvalue(ap, &i, argv); if (maxbits < MIN_BITS) { fprintf(stderr, "Illegal -M value\n"); goto usage; } break; case 'V': verbose = getvalue(ap, &i, argv); break; case 'X': export = getvalue(ap, &i, argv); if (export < 0 || export > 3) { fprintf(stderr, "Illegal -X value: %d\n", export); goto usage; } block_compress = "\1\1\0\0"[export]; noheader = "\0\0\0\1"[export]; export = "\0\1\1\1"[export]; break; default: fprintf(stderr, "Unknown option '%c' in \"%s\"\n", *ap, argv[i]); usage: for (hp = helptext; *hp != NULL; hp++) fprintf(stderr, "%s\n", *hp); FAIL("usage"); } /* Switch on options */ } /* Everything for -xxx */ } /* If -option */ } /* For all argc's */ /* infilename = NULL; */ /* Set "stdin" signal */ /* outfilename = NULL; */ /* Set "stdout" signal */ switch (j) { /* Any file arguments? */ case 3: /* both files given */ if (!streq(argv[2], "-")) /* But - means stdout */ outfilename = argv[2]; case 2: /* Input file given */ if (!streq(argv[1], "-")) { infilename = argv[1]; } break; case 0: /* None! */ case 1: /* No file arguments */ break; default: fprintf(stderr, "Too many file arguments\n"); FAIL("too many files"); } } static int getvalue(ap, ip, argv) register char *ap; int *ip; char *argv[]; /* * Compile a "value". We are currently scanning *ap, part of argv[*ip]. * The following are possible: * -x123 return (123) and set *ap to EOS so the caller * ap^ cycles to the next argument. * * -x 123 *ap == EOS and argv[*ip + 1][0] is a digit. * return (123) and increment *i to skip over the * next argument. * * -xy or -x y return(1), don't touch *ap or *ip. * * Note that the default for "flag option without value" is 1. This * can only cause a problem for the -M option where the value is * mandatory. However, the result of 1 is illegal as it is less * than INIT_BITS. */ { register int result; register int i; i = *ip + 1; if (isdigit(*ap)) { result = atoi(ap); *ap = EOS; } else if (*ap == EOS && argv[i] != NULL && isdigit(argv[i][0])) { result = atoi(argv[i]); *ip = i; } else { result = 1; } return (result); } openinput() { #ifdef decus if (infilename == NULL) { infilename = malloc(256 + 1); fgetname(stdin, infilename); infilename = realloc(infilename, strlen(infilename) + 1); } else { if (freopen(infilename, (binary) ? "rn" : "r", stdin) == NULL) { perror(infilename); FAIL("can't reopen input"); } } #else #ifdef vms #if VMS_V4 if (export == 0) { char *fname; char filename[256]; if ((fname = infilename) == NULL) { fgetname(stdin, filename); fname = filename; } if ((fdl_input = fdl_open(fname, &fdl_descriptor)) == NULL) { if ((fdl_status & 01) == 0) { fdl_message(NULL, fname); FAIL("can't fdl_open"); } fprintf(stderr, "Cannot open \"%s\" in vms private format,", fname); fprintf(stderr, " trying export format.\n"); export = TRUE; goto try_export; } fclose(stdin); stdin = NULL; infilename = malloc(256 + 1); infilename = realloc(fname, strlen(fname) + 1); if (verbose > 1) { fprintf(stderr, "FDL information for \"%s\"\n", filename); fdl_dump(&fdl_descriptor, stderr); } goto opened; } try_export: #endif if (infilename == NULL) { infilename = malloc(256 + 1); fgetname(stdin, infilename); infilename = realloc(infilename, strlen(infilename) + 1); } else { #if VMS_V4 if ((stdin = freopen(infilename, "r", stdin)) == NULL) { #else if (freopen(infilename, "r", stdin) == NULL) { #endif perror(infilename); exit(IO_ERROR); } } #else if (infilename == NULL) infilename = "stdin"; else { if (freopen(infilename, "r", stdin) == NULL) { perror(infilename); exit(IO_ERROR); } } #endif #endif opened: instream.bp = instream.bend = NULL; instream.bstart = inbuffer; instream.bsize = sizeof inbuffer; instream.func = lz_fill; } openoutput() /* * Open the output file (after the input file has been opened). * if outfilename == NULL, it's already open on stdout. */ { if (outfilename == NULL) { #if VMS_V4 #if 0 /* The following doesn't work */ outfilename = malloc(256 + 1); fgetname(stdout, outfilename); outfilename = realloc(outfilename, strlen(outfilename) + 1); if (export == 0) { fclose(stdout); stdout = NULL; /* Can't do terminal test below */ if ((fdl_output = fdl_create(NULL, outfilename)) == NULL) { if ((fdl_status & 01) == 0) fdl_message(NULL, outfilename); fprintf(stderr, "Can't create \"%s\"\n", outfilename); FAIL("can't fdl_create"); } } #else fprintf(stderr, "Restriction: The output file must be specified.\n"); FAIL("can't redirect on VMS V4"); #endif #else #ifdef vms outfilename = malloc(256 + 1); fgetname(stdout, outfilename); outfilename = realloc(outfilename, strlen(outfilename) + 1); #else #ifdef decus outfilename = malloc(256 + 1); fgetname(stdout, outfilename); outfilename = realloc(outfilename, strlen(outfilename) + 1); #else outfilename = ""; #endif #endif #endif } else { #if VMS_V4 if (export == 0) { fclose(stdout); stdout = NULL; /* Can't do terminal test below */ if ((fdl_output = fdl_create(NULL, outfilename)) == NULL) { if ((fdl_status & 01) == 0) fdl_message(NULL, outfilename); fprintf(stderr, "Can't create \"%s\" (VMS private)\n", outfilename); FAIL("can't fdl_create"); } } else { if (freopen(outfilename, "w", stdout) == NULL) { perror(outfilename); FAIL("can't create"); } } #else #ifdef decus if (freopen(outfilename, "wn", stdout) == NULL) { perror(outfilename); FAIL("can't create"); } #else if (freopen(outfilename, "w", stdout) == NULL) { perror(outfilename); FAIL("can't create"); } #endif #endif } if (stdout != NULL && isatty(fileno(stdout))) { fprintf(stderr, "%s: is a terminal. We object.\n", outfilename); FAIL("can't create"); } outstream.bp = outstream.bstart = outbuffer; outstream.bend = outbuffer + sizeof outbuffer; outstream.bsize = sizeof outbuffer; outstream.func = lz_flush; } -h- lzcmp2.c Wed Jul 24 11:49:28 1985 USER$A:[MINOW.LZ]LZCMP2.C;8 /* * l z c m p 2 . c * * Actually do compression. Terminology (and algorithm): * * Assume the input string is "abcd", we have just processed "ab" and * read 'c'. At this point, a "prefix code" will be assigned to "ab". * Search in the prefix:character memory (either the "fast memory" or * the hash-code table) for the code followed by this character. If * found, assign the code found to the "prefix code" and read the * next character. If not found, output the current prefix code, * generate a new prefix code and store "old_prefix:char" in the * table with "new_prefix" as its definition. * * Naming conventions: * code a variable containing a prefix code * c or char a variable containing a character * * There are three tables that are searched (dependent on compile-time * and execution time considerations): * fast Direct table-lookup -- requires a huge amount of physical * (non-paged) memory, but is very fast. * hash Hash-coded table-lookup. * cache A "look-ahead" cache for the hash table that optimizes * searching for the most frequent character. This considerably * speeds up processing for raster-images (for example) at * a modest amount of memory. * Structures are used to hold the actual tables to simplify organization * of the program. * * Subroutines: * compress() performs data compression on an input datastream. * init_compress() called by the output routine to clear tables. */ #include "lz.h" /* * General variables * Cleared by init_compress on a "hard initialization" * outputcode() in lzcmp3.c refers to next_code. */ long int in_count; /* Length of input */ long int out_count; /* Bytes written to output file */ static flag first_clear = TRUE; /* Don't zero first time */ code_int next_code; /* Next output code */ static count_int checkpoint = CHECK_GAP; /* When to test ratio again */ static long ratio = 0; /* Ratio for last segment */ /* * These global parameters are set by mainline code. Unchanged here. */ extern short maxbits; /* Settable max # bits/code */ extern short block_compress; /* For old-style compatibility */ extern code_int maxmaxcode; /* Actual maximum output code */ extern long tot_incount; /* Total input count */ extern long tot_outcount; /* Total output count */ extern code_int hsize; /* Actual hash table size */ #ifdef XENIX_16 static count_int htab0[8192]; static count_int htab1[8192]; static count_int htab2[8192]; static count_int htab3[8192]; static count_int htab4[8192]; static count_int htab5[8192]; static count_int htab6[8192]; static count_int htab7[8192]; static count_int htab8[HSIZE - 65536]; static count_int *hashtab[9] = { htab0, htab1, htab2, htab3, htab4, htab5, htab6, htab7, htab8 }; static U_short code0[16384]; static U_short code1[16384]; static U_short code2[16384]; static U_short code3[16384]; static U_short code4[HSIZE - 65536]; static U_short *codetab[5] = { code0, code1, code3, code3, code4 } #define HASH(i) (hashtab[((unsigned) (i)) >> 13][(i) & 0x1FFF]) #define CODE(i) (codetab[((unsigned) (i)) >> 14][(i) & 0x3FFF]) #else count_int hashtab[HSIZE]; U_short codetab[HSIZE]; #define HASH(i) hashtab[i] #define CODE(i) codetab[i] #endif /* * compress a datastream * * Algorithm: on large machines, for maxbits <= FBITS, use fast direct table * lookup on the prefix code / next character combination. For smaller code * size, use open addressing modular division double hashing (no chaining), ala * Knuth vol. 3, sec. 6.4 Algorithm D, along with G. Knott's relatively-prime * secondary probe. Do block compression with an adaptive reset, whereby the * code table is cleared when the compression ratio decreases, but after the * table fills. The variable-length output codes are re-sized at this point, * and a special LZ_CLEAR code is generated for the decompressor. For the * megamemory version, the sparse array is cleared indirectly through a * "shadow" output code history. Late additions: for the hashing code, * construct the table according to file size for noticeable speed improvement * on small files. Also detect and cache codes associated with the most * common character to bypass hash calculation on these codes (a characteristic * of highly-compressable raster images). Please direct questions about this * implementation to ames!jaw. */ compress(in) STREAM *in; /* Input stream structure */ /* * Compress driver. Global fsize is the size of the entire datastream * (from LZ_STX or LZ_SOH to the terminating LZ_ETX). You must * force a reinitialization -- by calling outputcode() with a new header -- * if size is changed. If the "newer" output format is chosen (with * data streams delimited by LZ_SOH/LZ_STX, init_compress will be * called automatically. Otherwise, you must call init_compress(TRUE) * before calling compress() for the first time. */ { register long hash_code; /* What we look for */ register code_int i; /* Index into vectors */ register int c; /* Current input char */ register code_int code; /* Substring code */ register int displacement; /* For secondary hash */ register code_int hsize_reg; /* Size of hash table */ register int hshift; /* For xor hasher */ if ((code = GET(in)) == EOF) return; in_count++; hsize_reg = hsize; /* * Set hash code range bound */ hshift = 0; for (hash_code = (long) hsize; hash_code < 65536L; hash_code <<= 1) hshift++; hshift = 8 - hshift; while ((c = GET(in)) != (unsigned) EOF) { in_count++; hash_code = (long) (((long) c << maxbits) + code); i = (c << hshift) ^ code; /* XOR hashing */ if (HASH(i) == hash_code) { /* Found at first slot? */ code = CODE(i); continue; } else if ((long) HASH(i) < 0) /* empty slot */ goto nomatch; displacement = hsize_reg - i; /* secondary hash */ if (i == 0) displacement = 1; probe: if ((i -= displacement) < 0) /* Wrap around? */ i += hsize_reg; if (HASH(i) == hash_code) { /* Found in hash table? */ code = CODE(i); /* Set new prefix code */ continue; /* Read next input char */ } else if ((long) HASH(i) > 0) /* If slot is occupied */ goto probe; /* Look somewhere else */ nomatch: /* * Output the current prefix and designate a new prefix. * If the input character was the "hog", save it in the * look-ahead cache table. Then, save in the hash table. */ outputcode((code_int) code); /* No match, put prefix */ #if SIGNED_COMPARE_SLOW if ((unsigned) next_code < (unsigned) maxmaxcode) { #else if (next_code < maxmaxcode) { #endif CODE(i) = next_code++; /* code -> hashtable */ HASH(i) = hash_code; } else if (block_compress && (count_int) in_count >= checkpoint) { clear(); } code = c; /* Start new substring */ } /* * At EOF, put out the final code. */ outputcode((code_int) code); } clear() /* * Check the compression ratio to see whether it is going up * or staying the same. If it is going down, the internal * statistics of the file have changed, so clear out our * tables and start over. Inform the decompressor of the * change by sending out a LZ_CLEAR code. */ { register long int rat; checkpoint = in_count + CHECK_GAP; #if DEBUG if (verbose > 2) { divout("at clear() test", in_count, out_count, ""); fprintf(stderr, ", ratio at entry: %ld.%02ld, gap %d\n", rat / 256L, ((rat & 255L) * 100L) / 256L, CHECK_GAP); } #endif if (in_count > 0x007FFFFL) { /* Shift will overflow */ rat = out_count >> 8; if (rat == 0) rat = 0x7FFFFFFFL; else { rat = in_count / rat; } } else { rat = (in_count << 8) / out_count; } if (rat > ratio) ratio = rat; else { #if DEBUG if (verbose > 0) { fprintf(stderr, "Resetting compression, in %ld, out %ld\n", in_count, out_count); fprintf(stderr, "Old ratio: %ld == (%ld.%02ld)", ratio, ratio / 256L, ((ratio & 255L) * 100L) / 256L); fprintf(stderr, ", test ratio: %ld = (%ld.%02ld), gap %d\n", rat, rat / 256L, ((rat & 255L) * 100L) / 256L, CHECK_GAP); } #endif outputcode((code_int) LZ_CLEAR); /* Calls init_compress */ } } init_compress(full_init) flag full_init; /* TRUE for full initialization */ /* * Clear the tables. Called by outputcode() on LZ_SOH, LZ_STX * (full_init TRUE) or on LZ_CLEAR (full_init FALSE). * init_compress() is not called on LZ_EOR. */ { #ifdef XENIX_16 register count_int *hp; register int n; register int j; register code_int k; k = hsize; for (j = 0; k > 0; k -= 8192) { i = (k < 8192) ? k : 8192; hp = hashtab[j++]; n = i >> 4; switch (i & 15) { case 15: *hp++ = -1; case 14: *hp++ = -1; case 13: *hp++ = -1; case 12: *hp++ = -1; case 11: *hp++ = -1; case 10: *hp++ = -1; case 9: *hp++ = -1; case 8: *hp++ = -1; case 7: *hp++ = -1; case 6: *hp++ = -1; case 5: *hp++ = -1; case 4: *hp++ = -1; case 3: *hp++ = -1; case 2: *hp++ = -1; case 1: *hp++ = -1; } while (--n >= 0) { *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; } } #else register count_int *hp; register code_int n; hp = &hashtab[0]; n = hsize >> 4; /* divide by 16 */ switch (hsize & 15) { case 15: *hp++ = -1; case 14: *hp++ = -1; case 13: *hp++ = -1; case 12: *hp++ = -1; case 11: *hp++ = -1; case 10: *hp++ = -1; case 9: *hp++ = -1; case 8: *hp++ = -1; case 7: *hp++ = -1; case 6: *hp++ = -1; case 5: *hp++ = -1; case 4: *hp++ = -1; case 3: *hp++ = -1; case 2: *hp++ = -1; case 1: *hp++ = -1; } while (--n >= 0) { *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; *hp++ = -1; } #endif if (full_init) { tot_incount += in_count; tot_outcount += out_count; in_count = 0; out_count = 0; ratio = 0; } first_clear = FALSE; next_code = firstcode; } -h- lzcmp3.c Wed Jul 24 11:49:28 1985 USER$A:[MINOW.LZ]LZCMP3.C;10 /* * l z c m p 3 . c * Output a given code. */ #include "lz.h" extern STREAM outstream; extern code_int next_code; extern code_int maxmaxcode; /* Actual maximum output code */ extern short maxbits; extern count_int out_count; static char_type buf[BITS]; static int offset; static short n_bits = INIT_BITS; /* # of bits in compressed file */ static short n_bits8 = INIT_BITS << 3; static code_int maxcode = MAXCODE(INIT_BITS); #if !vax_asm static readonly char_type lmask[9] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0, 0xE0, 0xC0, 0x80, 0x00 }; static readonly char_type rmask[9] = { 0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF }; #endif #if DEBUG extern int col; static int todump; #endif outputcode(code) code_int code; /* * Output the given code. * Inputs: * code: A n_bits-bit integer. If == -1, then EOF. This assumes * that n_bits <= (long)wordsize - 1. * Note: if not in "export" mode, the following values are special: * LZ_CLEAR (also in export mode if block_compress TRUE) * (soft) clear out compress tables and reset the * number of bits per code to the minimum. * LZ_SOH, LZ_STX (hard) clear out compress tables and reset as above. * LZ_ETX, LZ_EOR force out the current output segment, analogous * to fflush. * * Outputs: * Outputs code to the file. If the codespace has filled * (next_code >= (1 << n_bits), increase n_bits. * If LZ_CLEAR, LZ_SOH, or LZ_STX is seen, reset n_bits * to the initial value and call init_compress to reset * the lookup and cache tables. * * Assumptions: * Output chars are 8 bits long. This is deeply hardwired * into the algorithm. It is independent, however, of the * size of the input data. * * Algorithm: * Maintain a BITS character long buffer (so that 8 codes will * fit in it exactly). Use the VAX insv instruction to insert each * code in turn. When the buffer fills up empty it and start over. */ { /* * On the VAX (Unix), it is important to have the register declarations * in exactly the order given, or the asm will break. */ register int r_off, bits; register char_type *bp; #if !vax_asm register code_int r_code; #endif r_off = offset; bits = n_bits; bp = buf; if (code >= 0) { /* * Not at EOF, add the code */ #if DEBUG if (verbose > 3) { fprintf(stderr, "%c%5d %5d", ((col += 12) >= 72) ? (col = 0, '\n') : ' ', code, next_code); if (code >= LZ_CLEAR && code < firstcode) { fprintf(stderr, " = %s", lz_names[code - LZ_CLEAR]); col = 74; } } #endif #if vax_asm /* * VAX DEPENDENT!! Implementation on other machines may be * difficult. * * Translation: Insert BITS bits from the argument starting at * offset bits from the beginning of buf. */ 0; /* C compiler bug ?? */ asm("insv 4(ap),r11,r10,(r9)"); #else /* * WARNING: byte/bit numbering on the vax is simulated * by the following code */ bp += (r_off >> 3); /* -> first output slot */ r_off &= 7; /* * Since code is always >= 8 bits, only need to mask the first * hunk on the left. */ r_code = code; *bp = (*bp & rmask[r_off]) | (r_code << r_off) & lmask[r_off]; bp++; bits -= (8 - r_off); r_code >>= 8 - r_off; /* * Get any 8 bit parts in the middle ( <= 1 for up to 16 bits). */ if (bits >= 8) { *bp++ = r_code; r_code >>= 8; bits -= 8; } if (bits != 0) /* Last bits. */ *bp = r_code; #endif offset += n_bits; if (offset == n_bits8) { out_count += n_bits; lz_putbuf(buf, n_bits, &outstream); #if DEBUG if (todump > 0) { dumphex(buf, n_bits, stderr); todump -= n_bits; } #endif offset = 0; } /* * If the next entry is going to be too big for the code size, * then increase it, if possible. Note: * !export firstcode == LZ_FIRST * export && block_compress firstcode == LZ_CLEAR + 1 * export && !block_compress firstcode == LZ_CLEAR */ if (next_code > maxcode) { if (offset > 0) { lz_putbuf(buf, n_bits, &outstream); out_count += n_bits; offset = 0; #if DEBUG if (todump > 0) { dumphex(buf, n_bits, stderr); todump -= n_bits; } #endif } n_bits++; /* Need more bits */ n_bits8 += (1 << 3); if (n_bits == maxbits) maxcode = maxmaxcode; else maxcode = MAXCODE(n_bits); #if DEBUG if (verbose > 2) { fprintf(stderr, "%snext_code %d, change to %d bits max %d", (col > 0) ? "\n" : "", next_code, n_bits, maxcode); col = 74; } #endif } if (code >= LZ_CLEAR && code < firstcode) { switch (code) { case LZ_SOH: case LZ_STX: case LZ_CLEAR: if (offset > 0) { lz_putbuf(buf, n_bits, &outstream); out_count += n_bits; offset = 0; #if DEBUG if (todump > 0) { dumphex(buf, n_bits, stderr); todump -= n_bits; } #endif } n_bits = INIT_BITS; /* Reset codes */ n_bits8 = INIT_BITS << 3; maxcode = MAXCODE(INIT_BITS); init_compress(code != LZ_CLEAR); #if DEBUG if (verbose > 2) { fprintf(stderr, "\n(%s) Change to %d bits, maxcode %d, next_code = %d", lz_names[code - LZ_CLEAR], n_bits, maxcode, next_code); col = 74; todump = 32; } #endif break; case LZ_EOR: case LZ_ETX: /* Just written out */ break; default: abort(); /* Can't happen */ } } } else { /* * At EOF, write the rest of the buffer. */ if ((r_off = offset) > 0) { r_off += 7; r_off >>= 3; lz_putbuf(buf, r_off, &outstream); out_count += r_off; #if DEBUG if (todump > 0) { dumphex(buf, r_off, stderr); todump -= r_off; } #endif } offset = 0; lz_flush(&outstream); /* Flush output buffer */ #if DEBUG if (verbose > 3 || todump > 0) { fprintf(stderr, "\n*EOF*\n"); col = 0; } #endif } }