ref: a411870ee4640241e3c494367d922847da84f972
dir: purgatorio/appl/lib/deflate.b
# gzip-compatible compression filter.
implement Filter;
include "sys.m";
sys: Sys;
include "filter.m";
GZMAGIC1: con byte 16r1f;
GZMAGIC2: con byte 16r8b;
GZDEFLATE: con byte 8;
GZFTEXT: con byte 1 << 0; # file is text
GZFHCRC: con byte 1 << 1; # crc of header included
GZFEXTRA: con byte 1 << 2; # extra header included
GZFNAME: con byte 1 << 3; # name of file included
GZFCOMMENT: con byte 1 << 4; # header comment included
GZFMASK: con (byte 1 << 5) - byte 1; # mask of specified bits
GZXFAST: con byte 2; # used fast algorithm little compression
GZXBEST: con byte 4; # used maximum compression algorithm
GZOSFAT: con byte 0; # FAT file system
GZOSAMIGA: con byte 1; # Amiga
GZOSVMS: con byte 2; # VMS or OpenVMS
GZOSUNIX: con byte 3; # Unix
GZOSVMCMS: con byte 4; # VM/CMS
GZOSATARI: con byte 5; # Atari TOS
GZOSHPFS: con byte 6; # HPFS file system
GZOSMAC: con byte 7; # Macintosh
GZOSZSYS: con byte 8; # Z-System
GZOSCPM: con byte 9; # CP/M
GZOSTOPS20: con byte 10; # TOPS-20
GZOSNTFS: con byte 11; # NTFS file system
GZOSQDOS: con byte 12; # QDOS
GZOSACORN: con byte 13; # Acorn RISCOS
GZOSUNK: con byte 255;
GZCRCPOLY: con int 16redb88320;
GZOSINFERNO: con GZOSUNIX;
Hnone, Hgzip, Hzlib: con iota; # LZstate.headers
LZstate: adt
{
hist: array of byte; # [HistSize];
epos: int; # end of history buffer
pos: int; # current location in history buffer
eof: int;
hash: array of int; # [Nhash] hash chains
nexts: array of int; # [MaxOff]
me: int; # pos in hash chains
dot: int; # dawn of time in history
prevlen: int; # lazy matching state
prevoff: int;
maxchars: int; # compressor tuning
maxdefer: int;
level: int;
crctab: array of int; # for gzip trailer
crc: int;
tot: int;
sum: big; # for zlib trailer
headers: int; # which header to print, if any
outbuf: array of byte; # current output buffer;
out: int; # current position in the output buffer
bits: int; # bit shift register
nbits: int;
verbose: int;
debug: int;
lzb: ref LZblock;
slop: array of byte;
dlitlentab: array of Huff; # [Nlitlen]
dofftab: array of Huff; # [Noff];
hlitlentab: array of Huff; # [Nlitlen];
dyncode: ref Dyncode;
hdyncode: ref Dyncode;
c: chan of ref Rq;
rc: chan of int;
};
#
# lempel-ziv compressed block
#
LZblock: adt
{
litlen: array of byte; # [MaxUncBlock+1];
off: array of int; # [MaxUncBlock+1];
litlencount: array of int; # [Nlitlen];
offcount: array of int; # [Noff];
entries: int; # entries in litlen & off tables
bytes: int; # consumed from the input
excost: int; # cost of encoding extra len & off bits
};
#
# encoding of dynamic huffman trees
#
Dyncode: adt
{
nlit: int;
noff: int;
nclen: int;
ncode: int;
codetab: array of Huff; # [Nclen];
codes: array of byte; # [Nlitlen+Noff];
codeaux: array of byte; # [Nlitlen+Noff];
};
#
# huffman code table
#
Huff: adt
{
bits: int; # length of the code
encode: int; # the code
};
DeflateBlock: con 64*1024-258-1;
DeflateOut: con 258+10;
DeflateUnc: con 0; # uncompressed block
DeflateFix: con 1; # fixed huffman codes
DeflateDyn: con 2; # dynamic huffman codes
DeflateEob: con 256; # end of block code in lit/len book
LenStart: con 257; # start of length codes in litlen
Nlitlen: con 288; # number of litlen codes
Noff: con 30; # number of offset codes
Nclen: con 19; # number of codelen codes
MaxLeaf: con Nlitlen;
MaxHuffBits: con 15; # max bits in a huffman code
ChainMem: con 2 * MaxHuffBits * (MaxHuffBits + 1);
MaxUncBlock: con 64*1024-1; # maximum size of uncompressed block
MaxOff: con 32*1024;
MinMatch: con 3; # shortest match possible
MaxMatch: con 258; # longest match possible
MinMatchMaxOff: con 4096; # max profitable offset for small match;
# assumes 8 bits for len; 5+10 for offset
HistSlop: con 4096; # slop for fewer calls to lzcomp
HistSize: con MaxOff + 2*HistSlop;
Hshift: con 4; # nice compromise between space & time
Nhash: con 1<<(Hshift*MinMatch);
Hmask: con Nhash-1;
MaxOffCode: con 256; # biggest offset looked up in direct table
EstLitBits: con 8;
EstLenBits: con 4;
EstOffBits: con 5;
# conversion from len to code word
lencode := array[MaxMatch] of int;
#
# conversion from off to code word
# off <= MaxOffCode ? offcode[off] : bigoffcode[(off-1) >> 7]
#
offcode := array[MaxOffCode + 1] of int;
bigoffcode := array[256] of int;
# litlen code words LenStart-285 extra bits
litlenbase := array[Nlitlen-LenStart] of int;
litlenextra := array[Nlitlen-LenStart] of
{
0, 0, 0,
0, 0, 0, 0, 0, 1, 1, 1, 1, 2,
2, 2, 2, 3, 3, 3, 3, 4, 4, 4,
4, 5, 5, 5, 5, 0, 0, 0
};
# offset code word extra bits
offbase := array[Noff] of int;
offextra := array[] of
{
0, 0, 0, 0, 1, 1, 2, 2, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7, 8, 8,
9, 9, 10, 10, 11, 11, 12, 12, 13, 13,
0, 0,
};
# order code lengths
clenorder := array[Nclen] of
{
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};
# static huffman tables
litlentab : array of Huff;
offtab : array of Huff;
hofftab : array of Huff;
# bit reversal for brain dead endian swap in huffman codes
revtab: array of byte;
init()
{
sys = load Sys Sys->PATH;
bitcount := array[MaxHuffBits] of int;
i, j, ci, n: int;
# byte reverse table
revtab = array[256] of byte;
for(i=0; i<256; i++){
revtab[i] = byte 0;
for(j=0; j<8; j++)
if(i & (1<<j))
revtab[i] |= byte 16r80 >> j;
}
litlentab = array[Nlitlen] of Huff;
offtab = array[Noff] of Huff;
hofftab = array[Noff] of { * => Huff(0, 0) };
# static Litlen bit lengths
for(i=0; i<144; i++)
litlentab[i].bits = 8;
for(i=144; i<256; i++)
litlentab[i].bits = 9;
for(i=256; i<280; i++)
litlentab[i].bits = 7;
for(i=280; i<Nlitlen; i++)
litlentab[i].bits = 8;
for(i = 0; i < 10; i++)
bitcount[i] = 0;
bitcount[8] += 144 - 0;
bitcount[9] += 256 - 144;
bitcount[7] += 280 - 256;
bitcount[8] += Nlitlen - 280;
hufftabinit(litlentab, Nlitlen, bitcount, 9);
# static offset bit lengths
for(i = 0; i < Noff; i++)
offtab[i].bits = 5;
for(i = 0; i < 5; i++)
bitcount[i] = 0;
bitcount[5] = Noff;
hufftabinit(offtab, Noff, bitcount, 5);
bitcount[0] = 0;
bitcount[1] = 0;
mkprecode(hofftab, bitcount, 2, MaxHuffBits);
# conversion tables for lens & offs to codes
ci = 0;
for(i = LenStart; i < 286; i++){
n = ci + (1 << litlenextra[i - LenStart]);
litlenbase[i - LenStart] = ci;
for(; ci < n; ci++)
lencode[ci] = i;
}
# patch up special case for len MaxMatch
lencode[MaxMatch-MinMatch] = 285;
litlenbase[285-LenStart] = MaxMatch-MinMatch;
ci = 1;
for(i = 0; i < 16; i++){
n = ci + (1 << offextra[i]);
offbase[i] = ci;
for(; ci < n; ci++)
offcode[ci] = i;
}
ci = (LenStart - 1) >> 7;
for(; i < 30; i++){
n = ci + (1 << (offextra[i] - 7));
offbase[i] = (ci << 7) + 1;
for(; ci < n; ci++)
bigoffcode[ci] = i;
}
}
start(param: string): chan of ref Rq
{
# param contains flags:
# [0-9] - compression level
# h gzip header/trailer
# z zlib header/trailer
# v verbose
# d debug
lz := ref LZstate;
lz.level = 6;
lz.verbose = lz.debug = 0;
lz.headers = Hnone;
lz.crc = lz.tot = 0;
lz.sum = big 1;
# XXX could also put filename and modification time in param
for (i := 0; i < len param; i++) {
case param[i] {
'0' to '9' =>
lz.level = param[i] - '0';
'v' =>
lz.verbose = 1;
'h' =>
lz.headers = Hgzip;
'z' =>
lz.headers = Hzlib;
'd' =>
lz.debug = 1;
}
}
lz.hist = array[HistSize] of byte;
lz.hash = array[Nhash] of int;
lz.nexts = array[MaxOff] of int;
lz.slop = array[2*MaxMatch] of byte;
lz.dlitlentab = array[Nlitlen] of Huff;
lz.dofftab = array[Noff] of Huff;
lz.hlitlentab = array[Nlitlen] of Huff;
lz.lzb = ref LZblock;
lzb := lz.lzb;
lzb.litlen = array[MaxUncBlock+1] of byte;
lzb.off = array[MaxUncBlock+1] of int;
lzb.litlencount = array[Nlitlen] of int;
lzb.offcount = array[Noff] of int;
lz.dyncode = ref Dyncode;
lz.dyncode.codetab =array[Nclen] of Huff;
lz.dyncode.codes =array[Nlitlen+Noff] of byte;
lz.dyncode.codeaux = array[Nlitlen+Noff] of byte;
lz.hdyncode = ref Dyncode;
lz.hdyncode.codetab =array[Nclen] of Huff;
lz.hdyncode.codes =array[Nlitlen+Noff] of byte;
lz.hdyncode.codeaux = array[Nlitlen+Noff] of byte;
for(i = 0; i < MaxOff; i++)
lz.nexts[i] = 0;
for(i = 0; i < Nhash; i++)
lz.hash[i] = 0;
lz.pos = 0;
lz.epos = 0;
lz.prevlen = MinMatch - 1;
lz.prevoff = 0;
lz.eof = 0;
lz.me = 4 * MaxOff;
lz.dot = lz.me;
lz.bits = 0;
lz.nbits = 0;
if(lz.level < 5) {
lz.maxchars = 1;
lz.maxdefer = 0;
} else if(lz.level == 9) {
lz.maxchars = 4000;
lz.maxdefer = MaxMatch;
} else {
lz.maxchars = 200;
lz.maxdefer = MaxMatch / 4;
}
if (lz.headers == Hgzip)
lz.crctab = mkcrctab(GZCRCPOLY);
lz.c = chan of ref Rq;
lz.rc = chan of int;
spawn deflate(lz);
return lz.c;
}
# return (eof, nbytes)
fillbuf(lz: ref LZstate, buf: array of byte): (int, int)
{
n := 0;
while (n < len buf) {
lz.c <-= ref Rq.Fill(buf[n:], lz.rc);
nr := <-lz.rc;
if (nr == -1)
exit;
if (nr == 0)
return (1, n);
n += nr;
}
return (0, n);
}
deflate(lz: ref LZstate)
{
lz.c <-= ref Rq.Start(sys->pctl(0, nil));
header(lz);
buf := array[DeflateBlock] of byte;
out := array[DeflateBlock + DeflateOut] of byte;
eof := 0;
for (;;) {
nslop := lz.epos - lz.pos;
nbuf := 0;
if (!eof) {
(eof, nbuf) = fillbuf(lz, buf);
inblock(lz, buf[0:nbuf]);
}
if(eof && nbuf == 0 && nslop == 0) {
if(lz.nbits) {
out[0] = byte lz.bits;
lz.nbits = 0;
lz.c <-= ref Rq.Result(out[0:1], lz.rc);
if (<-lz.rc == -1)
exit;
continue;
}
footer(lz);
lz.c <-= ref Rq.Finished(nil);
exit;
}
lz.outbuf = out;
if(nslop > 2*MaxMatch) {
lz.c <-= ref Rq.Error(sys->sprint("slop too large: %d", nslop));
exit;
}
lz.slop[0:] = lz.hist[lz.pos:lz.epos]; # memmove(slop, lz.pos, nslop);
lzb := lz.lzb;
for(i := 0; i < Nlitlen; i++)
lzb.litlencount[i] = 0;
for(i = 0; i < Noff; i++)
lzb.offcount[i] = 0;
lzb.litlencount[DeflateEob]++;
lzb.bytes = 0;
lzb.entries = 0;
lzb.excost = 0;
lz.eof = 0;
n := 0;
while(n < nbuf || eof && !lz.eof){
if(!lz.eof) {
if(lz.pos >= MaxOff + HistSlop) {
lz.pos -= MaxOff + HistSlop;
lz.epos -= MaxOff + HistSlop;
lz.hist[:] = lz.hist[MaxOff + HistSlop: MaxOff + HistSlop + lz.epos];
}
m := HistSlop - (lz.epos - lz.pos);
if(lz.epos + m > HistSize) {
lz.c <-= ref Rq.Error("read too long");
exit;
}
if(m >= nbuf - n) {
m = nbuf - n;
lz.eof = eof;
}
lz.hist[lz.epos:] = buf[n:n+m];
n += m;
lz.epos += m;
}
lzcomp(lz, lzb, lz.epos - lz.pos);
}
lz.outbuf = out;
lz.out = 0;
nunc := lzb.bytes;
if(nunc < nslop)
nslop = nunc;
mkprecode(lz.dlitlentab, lzb.litlencount, Nlitlen, MaxHuffBits);
mkprecode(lz.dofftab, lzb.offcount, Noff, MaxHuffBits);
ndyn := huffcodes(lz.dyncode, lz.dlitlentab, lz.dofftab)
+ bitcost(lz.dlitlentab, lzb.litlencount, Nlitlen)
+ bitcost(lz.dofftab, lzb.offcount, Noff)
+ lzb.excost;
litcount := array[Nlitlen] of int;
for(i = 0; i < Nlitlen; i++)
litcount[i] = 0;
for(i = 0; i < nslop; i++)
litcount[int lz.slop[i]]++;
for(i = 0; i < nunc-nslop; i++)
litcount[int buf[i]]++;
litcount[DeflateEob]++;
mkprecode(lz.hlitlentab, litcount, Nlitlen, MaxHuffBits);
nhuff := huffcodes(lz.hdyncode, lz.hlitlentab, hofftab)
+ bitcost(lz.hlitlentab, litcount, Nlitlen);
nfix := bitcost(litlentab, lzb.litlencount, Nlitlen)
+ bitcost(offtab, lzb.offcount, Noff)
+ lzb.excost;
lzput(lz, lz.eof && lz.pos == lz.epos, 1);
if(lz.verbose) {
lz.c <-= ref Rq.Info(sys->sprint("block: %d bytes %d entries %d extra bits",
nunc, lzb.entries, lzb.excost));
lz.c <-= ref Rq.Info(sys->sprint("\tuncompressed %d fixed %d dynamic %d huffman %d",
(nunc + 4) * 8, nfix, ndyn, nhuff));
}
if((nunc + 4) * 8 < ndyn && (nunc + 4) * 8 < nfix && (nunc + 4) * 8 < nhuff) {
lzput(lz, DeflateUnc, 2);
lzflushbits(lz);
lz.outbuf[lz.out++] = byte(nunc);
lz.outbuf[lz.out++] = byte(nunc >> 8);
lz.outbuf[lz.out++] = byte(~nunc);
lz.outbuf[lz.out++] = byte(~nunc >> 8);
lz.outbuf[lz.out:] = lz.slop[:nslop];
lz.out += nslop;
lz.outbuf[lz.out:] = buf[:nunc - nslop];
lz.out += nunc - nslop;
} else if(ndyn < nfix && ndyn < nhuff) {
lzput(lz, DeflateDyn, 2);
wrdyncode(lz, lz.dyncode);
wrblock(lz, lzb.entries, lzb.litlen, lzb.off, lz.dlitlentab, lz.dofftab);
lzput(lz, lz.dlitlentab[DeflateEob].encode, lz.dlitlentab[DeflateEob].bits);
} else if(nhuff < nfix){
lzput(lz, DeflateDyn, 2);
wrdyncode(lz, lz.hdyncode);
for(i = 0; i < len lzb.off; i++)
lzb.off[i] = 0;
wrblock(lz, nslop, lz.slop, lzb.off, lz.hlitlentab, hofftab);
wrblock(lz, nunc-nslop, buf, lzb.off, lz.hlitlentab, hofftab);
lzput(lz, lz.hlitlentab[DeflateEob].encode, lz.hlitlentab[DeflateEob].bits);
} else {
lzput(lz, DeflateFix, 2);
wrblock(lz, lzb.entries, lzb.litlen, lzb.off, litlentab, offtab);
lzput(lz, litlentab[DeflateEob].encode, litlentab[DeflateEob].bits);
}
lz.c <-= ref Rq.Result(out[0:lz.out], lz.rc);
if (<-lz.rc == -1)
exit;
}
}
headergzip(lz: ref LZstate)
{
buf := array[20] of byte;
i := 0;
buf[i++] = byte GZMAGIC1;
buf[i++] = byte GZMAGIC2;
buf[i++] = byte GZDEFLATE;
flags := 0;
#if(file != nil)
# flags |= GZFNAME;
buf[i++] = byte flags;
mtime := 0;
buf[i++] = byte(mtime);
buf[i++] = byte(mtime>>8);
buf[i++] = byte(mtime>>16);
buf[i++] = byte(mtime>>24);
buf[i++] = byte 0;
buf[i++] = byte GZOSINFERNO;
#if((flags & GZFNAME) == GZFNAME){
# bout.puts(file);
# bout.putb(byte 0);
#}
lz.c <-= ref Rq.Result(buf[0:i], lz.rc);
if (<-lz.rc == -1)
exit;
}
headerzlib(lz: ref LZstate)
{
CIshift: con 12;
CMdeflate: con 8;
CMshift: con 8;
LVshift: con 6;
LVfastest, LVfast, LVnormal, LVbest: con iota;
level := LVnormal;
if(lz.level < 6)
level = LVfastest;
else if(lz.level >= 9)
level = LVbest;
h := 0;
h |= 7<<CIshift; # value is: (log2 of window size)-8
h |= CMdeflate<<CMshift;
h |= level<<LVshift;
h += 31-(h%31);
buf := array[2] of byte;
buf[0] = byte (h>>8);
buf[1] = byte (h>>0);
lz.c <-= ref Rq.Result(buf, lz.rc);
if (<-lz.rc == -1)
exit;
}
header(lz: ref LZstate)
{
case lz.headers {
Hgzip => headergzip(lz);
Hzlib => headerzlib(lz);
}
}
footergzip(lz: ref LZstate)
{
buf := array[8] of byte;
i := 0;
buf[i++] = byte(lz.crc);
buf[i++] = byte(lz.crc>>8);
buf[i++] = byte(lz.crc>>16);
buf[i++] = byte(lz.crc>>24);
buf[i++] = byte(lz.tot);
buf[i++] = byte(lz.tot>>8);
buf[i++] = byte(lz.tot>>16);
buf[i++] = byte(lz.tot>>24);
lz.c <-= ref Rq.Result(buf[0:i], lz.rc);
if (<-lz.rc == -1)
exit;
}
footerzlib(lz: ref LZstate)
{
buf := array[4] of byte;
i := 0;
buf[i++] = byte (lz.sum>>24);
buf[i++] = byte (lz.sum>>16);
buf[i++] = byte (lz.sum>>8);
buf[i++] = byte (lz.sum>>0);
lz.c <-= ref Rq.Result(buf, lz.rc);
if(<-lz.rc == -1)
exit;
}
footer(lz: ref LZstate)
{
case lz.headers {
Hgzip => footergzip(lz);
Hzlib => footerzlib(lz);
}
}
lzput(lz: ref LZstate, bits, nbits: int): int
{
bits = (bits << lz.nbits) | lz.bits;
for(nbits += lz.nbits; nbits >= 8; nbits -= 8){
lz.outbuf[lz.out++] = byte bits;
bits >>= 8;
}
lz.bits = bits;
lz.nbits = nbits;
return 0;
}
lzflushbits(lz: ref LZstate): int
{
if(lz.nbits & 7)
lzput(lz, 0, 8 - (lz.nbits & 7));
return 0;
}
#
# write out a block of n samples,
# given lz encoding and counts for huffman tables
# todo: inline lzput
#
wrblock(lz: ref LZstate, n: int, litlen: array of byte, off: array of int, litlentab, offtab: array of Huff): int
{
for(i := 0; i < n; i++) {
offset := off[i];
lit := int litlen[i];
if(lz.debug) {
if(offset == 0)
lz.c <-= ref Rq.Info(sys->sprint("\tlit %.2ux %c", lit, lit));
else
lz.c <-= ref Rq.Info(sys->sprint("\t<%d, %d>", offset, lit + MinMatch));
}
if(offset == 0)
lzput(lz, litlentab[lit].encode, litlentab[lit].bits);
else {
c := lencode[lit];
lzput(lz, litlentab[c].encode, litlentab[c].bits);
c -= LenStart;
if(litlenextra[c])
lzput(lz, lit - litlenbase[c], litlenextra[c]);
if(offset <= MaxOffCode)
c = offcode[offset];
else
c = bigoffcode[(offset - 1) >> 7];
lzput(lz, offtab[c].encode, offtab[c].bits);
if(offextra[c])
lzput(lz, offset - offbase[c], offextra[c]);
}
}
return n;
}
lzcomp(lz: ref LZstate, lzb: ref LZblock, max: int)
{
q, s, es, t: int;
you, m: int;
# hashcheck(lz, "start");
hist := lz.hist;
nexts := lz.nexts;
hash := lz.hash;
me := lz.me;
p := lz.pos;
ep := lz.epos;
if(p + max < ep)
ep = p + max;
if(lz.prevlen != MinMatch - 1)
p++;
#
# hash in the links for any hanging link positions,
# and calculate the hash for the current position.
#
n := MinMatch;
if(n > ep - p)
n = ep - p;
h := 0;
for(i := 0; i < n - 1; i++) {
m = me - ((MinMatch-1) - i);
if(m < lz.dot)
continue;
s = p - (me - m);
if(s < 0)
s += MaxOff + HistSlop;
h = hashit(s, hist);
for(you = hash[h]; me - you < me - m; you = nexts[you & (MaxOff-1)])
;
if(you == m)
continue;
nexts[m & (MaxOff-1)] = hash[h];
hash[h] = m;
}
for(i = 0; i < n; i++)
h = ((h << Hshift) ^ int hist[p+i]) & Hmask;
#
# me must point to the index in the next/prev arrays
# corresponding to p's position in the history
#
entries := lzb.entries;
litlencount := lzb.litlencount;
offcount := lzb.offcount;
litlen := lzb.litlen;
off := lzb.off;
prevlen := lz.prevlen;
prevoff := lz.prevoff;
maxdefer := lz.maxdefer;
maxchars := lz.maxchars;
excost := 0;
for(;;) {
es = p + MaxMatch;
if(es > ep) {
if(!lz.eof || ep != lz.epos || p >= ep)
break;
es = ep;
}
#
# look for the longest, closest string which
# matches what we are going to send. the clever
# part here is looking for a string 1 longer than
# are previous best match.
#
runlen := prevlen;
m = 0;
chars := maxchars;
matchloop:
for(you = hash[h]; me-you <= MaxOff && chars > 0; you = nexts[you & (MaxOff-1)]) {
s = p + runlen;
if(s >= es)
break;
t = s - me + you;
if(t - runlen < 0)
t += MaxOff + HistSlop;
for(; s >= p; s--) {
if(hist[s] != hist[t]) {
chars -= p + runlen - s + 1;
continue matchloop;
}
t--;
}
#
# we have a new best match.
# extend it to it's maximum length
#
t += runlen + 2;
s += runlen + 2;
for(; s < es; s++) {
if(hist[s] != hist[t])
break;
t++;
}
runlen = s - p;
m = you;
if(s == es)
break;
if(runlen > 7)
chars >>= 1;
chars -= runlen;
}
#
# back out of small matches too far in the past
#
if(runlen == MinMatch && me - m >= MinMatchMaxOff) {
runlen = MinMatch - 1;
m = 0;
}
#
# record the encoding and increment counts for huffman trees
# if we get a match, defer selecting it until we check for
# a longer match at the next position.
#
if(prevlen >= runlen && prevlen != MinMatch - 1) {
#
# old match at least as good; use that one
#
n = prevlen - MinMatch;
litlen[entries] = byte n;
n = lencode[n];
litlencount[n]++;
excost += litlenextra[n - LenStart];
off[entries++] = prevoff;
if(prevoff <= MaxOffCode)
n = offcode[prevoff];
else
n = bigoffcode[(prevoff - 1) >> 7];
offcount[n]++;
excost += offextra[n];
runlen = prevlen - 1;
prevlen = MinMatch - 1;
} else if(runlen == MinMatch - 1) {
#
# no match; just put out the literal
#
n = int hist[p];
litlen[entries] = byte n;
litlencount[n]++;
off[entries++] = 0;
runlen = 1;
} else {
if(prevlen != MinMatch - 1) {
#
# longer match now. output previous literal,
# update current match, and try again
#
n = int hist[p - 1];
litlen[entries] = byte n;
litlencount[n]++;
off[entries++] = 0;
}
prevoff = me - m;
if(runlen < maxdefer) {
prevlen = runlen;
runlen = 1;
} else {
n = runlen - MinMatch;
litlen[entries] = byte n;
n = lencode[n];
litlencount[n]++;
excost += litlenextra[n - LenStart];
off[entries++] = prevoff;
if(prevoff <= MaxOffCode)
n = offcode[prevoff];
else
n = bigoffcode[(prevoff - 1) >> 7];
offcount[n]++;
excost += offextra[n];
prevlen = MinMatch - 1;
}
}
#
# update the hash for the newly matched data
# this is constructed so the link for the old
# match in this position must at the end of a chain,
# and will expire when this match is added, ie it will
# never be examined for by the match loop.
# add to the hash chain only if we have the real hash data.
#
for(q = p + runlen; p != q; p++) {
if(p + MinMatch <= ep) {
nexts[me & (MaxOff-1)] = hash[h];
hash[h] = me;
if(p + MinMatch < ep)
h = ((h << Hshift) ^ int hist[p + MinMatch]) & Hmask;
}
me++;
}
}
#
# we can just store away the lazy state and
# pick it up next time. the last block will have eof
# so we won't have any pending matches
# however, we need to correct for how much we've encoded
#
if(prevlen != MinMatch - 1)
p--;
lzb.excost += excost;
lzb.bytes += p - lz.pos;
lzb.entries = entries;
lz.pos = p;
lz.me = me;
lz.prevlen = prevlen;
lz.prevoff = prevoff;
# hashcheck(lz, "stop");
}
#
# check all the hash list invariants are really satisfied
#
hashcheck(lz: ref LZstate, where: string)
{
s, age, a, you: int;
nexts := lz.nexts;
hash := lz.hash;
me := lz.me;
start := lz.pos;
if(lz.prevlen != MinMatch-1)
start++;
found := array [MaxOff] of byte;
for(i := 0; i < MaxOff; i++)
found[i] = byte 0;
for(i = 0; i < Nhash; i++) {
age = 0;
for(you = hash[i]; me-you <= MaxOff; you = nexts[you & (MaxOff-1)]) {
a = me - you;
if(a < age)
fatal(lz, sys->sprint("%s: out of order links age %d a %d me %d you %d",
where, age, a, me, you));
age = a;
s = start - a;
if(s < 0)
s += MaxOff + HistSlop;
if(hashit(s, lz.hist) != i)
fatal(lz, sys->sprint("%s: bad hash chain you %d me %d s %d start %d chain %d hash %d %d %d",
where, you, me, s, start, i, hashit(s - 1, lz.hist), hashit(s, lz.hist), hashit(s + 1, lz.hist)));
if(found[you & (MaxOff - 1)] != byte 0)
fatal(lz, where + ": found link again");
found[you & (MaxOff - 1)] = byte 1;
}
}
for(you = me - (MaxOff-1); you != me; you++)
found[you & (MaxOff - 1)] = byte 1;
for(i = 0; i < MaxOff; i++){
if(found[i] == byte 0 && nexts[i] != 0)
fatal(lz, sys->sprint("%s: link not found: max %d at %d", where, me & (MaxOff-1), i));
}
}
hashit(p: int, hist: array of byte): int
{
h := 0;
for(ep := p + MinMatch; p < ep; p++)
h = ((h << Hshift) ^ int hist[p]) & Hmask;
return h;
}
#
# make up the dynamic code tables, and return the number of bits
# needed to transmit them.
#
huffcodes(dc: ref Dyncode, littab, offtab: array of Huff): int
{
i, n, m, c, nlit, noff, ncode, nclen: int;
codetab := dc.codetab;
codes := dc.codes;
codeaux := dc.codeaux;
#
# trim the sizes of the tables
#
for(nlit = Nlitlen; nlit > 257 && littab[nlit-1].bits == 0; nlit--)
;
for(noff = Noff; noff > 1 && offtab[noff-1].bits == 0; noff--)
;
#
# make the code-length code
#
for(i = 0; i < nlit; i++)
codes[i] = byte littab[i].bits;
for(i = 0; i < noff; i++)
codes[i + nlit] = byte offtab[i].bits;
#
# run-length compress the code-length code
#
excost := 0;
c = 0;
ncode = nlit+noff;
for(i = 0; i < ncode; ) {
n = i + 1;
v := codes[i];
while(n < ncode && v == codes[n])
n++;
n -= i;
i += n;
if(v == byte 0) {
while(n >= 11) {
m = n;
if(m > 138)
m = 138;
codes[c] = byte 18;
codeaux[c++] = byte(m - 11);
n -= m;
excost += 7;
}
if(n >= 3) {
codes[c] = byte 17;
codeaux[c++] = byte(n - 3);
n = 0;
excost += 3;
}
}
while(n--) {
codes[c++] = v;
while(n >= 3) {
m = n;
if(m > 6)
m = 6;
codes[c] = byte 16;
codeaux[c++] = byte(m - 3);
n -= m;
excost += 3;
}
}
}
codecount := array[Nclen] of {* => 0};
for(i = 0; i < c; i++)
codecount[int codes[i]]++;
mkprecode(codetab, codecount, Nclen, 7);
for(nclen = Nclen; nclen > 4 && codetab[clenorder[nclen-1]].bits == 0; nclen--)
;
dc.nlit = nlit;
dc.noff = noff;
dc.nclen = nclen;
dc.ncode = c;
return 5 + 5 + 4 + nclen * 3 + bitcost(codetab, codecount, Nclen) + excost;
}
wrdyncode(out: ref LZstate, dc: ref Dyncode)
{
#
# write out header, then code length code lengths,
# and code lengths
#
lzput(out, dc.nlit-257, 5);
lzput(out, dc.noff-1, 5);
lzput(out, dc.nclen-4, 4);
codetab := dc.codetab;
for(i := 0; i < dc.nclen; i++)
lzput(out, codetab[clenorder[i]].bits, 3);
codes := dc.codes;
codeaux := dc.codeaux;
c := dc.ncode;
for(i = 0; i < c; i++){
v := int codes[i];
lzput(out, codetab[v].encode, codetab[v].bits);
if(v >= 16){
if(v == 16)
lzput(out, int codeaux[i], 2);
else if(v == 17)
lzput(out, int codeaux[i], 3);
else # v == 18
lzput(out, int codeaux[i], 7);
}
}
}
bitcost(tab: array of Huff, count: array of int, n: int): int
{
tot := 0;
for(i := 0; i < n; i++)
tot += count[i] * tab[i].bits;
return tot;
}
hufftabinit(tab: array of Huff, n: int, bitcount: array of int, nbits: int)
{
nc := array[MaxHuffBits + 1] of int;
code := 0;
for(bits := 1; bits <= nbits; bits++) {
code = (code + bitcount[bits-1]) << 1;
nc[bits] = code;
}
for(i := 0; i < n; i++) {
bits = tab[i].bits;
if(bits != 0) {
code = nc[bits]++ << (16 - bits);
tab[i].encode = int(revtab[code >> 8]) | (int(revtab[code & 16rff]) << 8);
}
}
}
Chain: adt
{
count: int; # occurances of everything in the chain
leaf: int; # leaves to the left of chain, or leaf value
col: byte; # ref count for collecting unused chains
gen: byte; # need to generate chains for next lower level
up: int; # Chain up in the lists
};
Chains: adt
{
lists: array of int; # [MaxHuffBits * 2]
chains: array of Chain; # [ChainMem]
nleaf: int; # number of leaves
free: int;
col: byte;
nlists: int;
};
Nil: con -1;
#
# fast, low space overhead algorithm for max depth huffman type codes
#
# J. Katajainen, A. Moffat and A. Turpin, "A fast and space-economical
# algorithm for length-limited coding," Proc. Intl. Symp. on Algorithms
# and Computation, Cairns, Australia, Dec. 1995, Lecture Notes in Computer
# Science, Vol 1004, J. Staples, P. Eades, N. Katoh, and A. Moffat, eds.,
# pp 12-21, Springer Verlag, New York, 1995.
#
mkprecode(tab: array of Huff, count: array of int, n, maxbits: int)
{
cs := ref Chains(array[MaxHuffBits * 2] of int, array[MaxLeaf+ChainMem] of Chain, 0, 0, byte 0, 0);
bits: int;
for(i := 0; i < n; i++){
tab[i].bits = 0;
tab[i].encode = 0;
}
#
# set up the sorted list of leaves
#
m := 0;
for(i = 0; i < n; i++) {
if(count[i] != 0){
cs.chains[m].count = count[i];
cs.chains[m].leaf = i;
m++;
}
}
if(m < 2) {
if(m != 0) {
m = cs.chains[0].leaf;
tab[m].bits = 1;
tab[m].encode = 0;
}
return;
}
cs.nleaf = m;
csorts(cs.chains, 0, m);
cs.free = cs.nleaf + 2;
cs.col = byte 1;
#
# initialize chains for each list
#
c := cs.chains;
cl := cs.nleaf;
c[cl].count = cs.chains[0].count;
c[cl].leaf = 1;
c[cl].col = cs.col;
c[cl].up = Nil;
c[cl].gen = byte 0;
c[cl + 1] = c[cl];
c[cl + 1].leaf = 2;
c[cl + 1].count = cs.chains[1].count;
for(i = 0; i < maxbits; i++){
cs.lists[i * 2] = cl;
cs.lists[i * 2 + 1] = cl + 1;
}
cs.nlists = 2 * maxbits;
m = 2 * m - 2;
for(i = 2; i < m; i++)
nextchain(cs, cs.nlists - 2);
bitcount := array[MaxHuffBits + 1] of int;
bits = 0;
bitcount[0] = cs.nleaf;
for(cl = cs.lists[2 * maxbits - 1]; cl != Nil; cl = c[cl].up) {
m = c[cl].leaf;
for(i = 0; i < m; i++)
tab[cs.chains[i].leaf].bits++;
bitcount[bits++] -= m;
bitcount[bits] = m;
}
hufftabinit(tab, n, bitcount, bits);
}
#
# calculate the next chain on the list
# we can always toss out the old chain
#
nextchain(cs: ref Chains, clist: int)
{
i, nleaf, sumc: int;
oc := cs.lists[clist + 1];
cs.lists[clist] = oc;
if(oc == Nil)
return;
#
# make sure we have all chains needed to make sumc
# note it is possible to generate only one of these,
# use twice that value for sumc, and then generate
# the second if that preliminary sumc would be chosen.
# however, this appears to be slower on current tests
#
chains := cs.chains;
if(chains[oc].gen != byte 0) {
nextchain(cs, clist - 2);
nextchain(cs, clist - 2);
chains[oc].gen = byte 0;
}
#
# pick up the chain we're going to add;
# collect unused chains no free ones are left
#
for(c := cs.free; ; c++) {
if(c >= ChainMem) {
cs.col++;
for(i = 0; i < cs.nlists; i++)
for(c = cs.lists[i]; c != Nil; c = chains[c].up)
chains[c].col = cs.col;
c = cs.nleaf;
}
if(chains[c].col != cs.col)
break;
}
#
# pick the cheapest of
# 1) the next package from the previous list
# 2) the next leaf
#
nleaf = chains[oc].leaf;
sumc = 0;
if(clist > 0 && cs.lists[clist-1] != Nil)
sumc = chains[cs.lists[clist-2]].count + chains[cs.lists[clist-1]].count;
if(sumc != 0 && (nleaf >= cs.nleaf || chains[nleaf].count > sumc)) {
chains[c].count = sumc;
chains[c].leaf = chains[oc].leaf;
chains[c].up = cs.lists[clist-1];
chains[c].gen = byte 1;
} else if(nleaf >= cs.nleaf) {
cs.lists[clist + 1] = Nil;
return;
} else {
chains[c].leaf = nleaf + 1;
chains[c].count = chains[nleaf].count;
chains[c].up = chains[oc].up;
chains[c].gen = byte 0;
}
cs.free = c + 1;
cs.lists[clist + 1] = c;
chains[c].col = cs.col;
}
chaincmp(chain: array of Chain, ai, bi: int): int
{
ac := chain[ai].count;
bc := chain[bi].count;
if(ac < bc)
return -1;
if(ac > bc)
return 1;
ac = chain[ai].leaf;
bc = chain[bi].leaf;
if(ac > bc)
return -1;
return ac < bc;
}
pivot(chain: array of Chain, a, n: int): int
{
j := n/6;
pi := a + j; # 1/6
j += j;
pj := pi + j; # 1/2
pk := pj + j; # 5/6
if(chaincmp(chain, pi, pj) < 0) {
if(chaincmp(chain, pi, pk) < 0) {
if(chaincmp(chain, pj, pk) < 0)
return pj;
return pk;
}
return pi;
}
if(chaincmp(chain, pj, pk) < 0) {
if(chaincmp(chain, pi, pk) < 0)
return pi;
return pk;
}
return pj;
}
csorts(chain: array of Chain, a, n: int)
{
j, pi, pj, pn: int;
while(n > 1) {
if(n > 10)
pi = pivot(chain, a, n);
else
pi = a + (n>>1);
t := chain[pi];
chain[pi] = chain[a];
chain[a] = t;
pi = a;
pn = a + n;
pj = pn;
for(;;) {
do
pi++;
while(pi < pn && chaincmp(chain, pi, a) < 0);
do
pj--;
while(pj > a && chaincmp(chain, pj, a) > 0);
if(pj < pi)
break;
t = chain[pi];
chain[pi] = chain[pj];
chain[pj] = t;
}
t = chain[a];
chain[a] = chain[pj];
chain[pj] = t;
j = pj - a;
n = n-j-1;
if(j >= n) {
csorts(chain, a, j);
a += j+1;
} else {
csorts(chain, a + (j+1), n);
n = j;
}
}
}
mkcrctab(poly: int): array of int
{
crctab := array[256] of int;
for(i := 0; i < 256; i++){
crc := i;
for(j := 0; j < 8; j++){
c := crc & 1;
crc = (crc >> 1) & 16r7fffffff;
if(c)
crc ^= poly;
}
crctab[i] = crc;
}
return crctab;
}
inblockcrc(lz: ref LZstate, buf: array of byte)
{
crc := lz.crc;
n := len buf;
crc ^= int 16rffffffff;
for(i := 0; i < n; i++)
crc = lz.crctab[int(byte crc ^ buf[i])] ^ ((crc >> 8) & 16r00ffffff);
lz.crc = crc ^ int 16rffffffff;
lz.tot += n;
}
inblockadler(lz: ref LZstate, buf: array of byte)
{
ZLADLERBASE: con big 65521;
s1 := lz.sum & big 16rffff;
s2 := (lz.sum>>16) & big 16rffff;
for(i := 0; i < len buf; i++) {
s1 = (s1 + big buf[i]) % ZLADLERBASE;
s2 = (s2 + s1) % ZLADLERBASE;
}
lz.sum = (s2<<16) + s1;
}
inblock(lz: ref LZstate, buf: array of byte)
{
case lz.headers {
Hgzip => inblockcrc(lz, buf);
Hzlib => inblockadler(lz, buf);
}
}
fatal(lz: ref LZstate, s: string)
{
lz.c <-= ref Rq.Error(s);
exit;
}