ref: 9f76a7f6819ac04552b4fb6588156f3e4089d1d7
dir: /appl/lib/inflate.b/
# gzip-compatible decompression 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 1 << 0; # file is text
GZFHCRC: con 1 << 1; # crc of header included
GZFEXTRA: con 1 << 2; # extra header included
GZFNAME: con 1 << 3; # name of file included
GZFCOMMENT: con 1 << 4; # header comment included
GZFMASK: con (1 << 5) - 1; # mask of specified bits
GZXBEST: con byte 2; # used maximum compression algorithm
GZXFAST: con byte 4; # used fast algorithm little compression
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;
# huffman code table
Huff: adt
{
bits: int; # length of the code
encode: int; # the code
};
# huffman decode table
DeHuff: adt
{
l1: array of L1; # the table
nb1: int; # no. of bits in first level
nb2: int; # no. of bits in second level
};
# first level of decode table
L1: adt
{
bits: int; # length of the code
decode: int; # the symbol
l2: array of L2;
};
# second level
L2: adt
{
bits: int; # length of the code
decode: int; # the symbol
};
DeflateUnc: con 0; # uncompressed block
DeflateFix: con 1; # fixed huffman codes
DeflateDyn: con 2; # dynamic huffman codes
DeflateErr: con 3; # reserved BTYPE (error)
DeflateEob: con 256; # end of block code in lit/len book
LenStart: con 257; # start of length codes in litlen
LenEnd: con 285; # greatest valid length code
Nlitlen: con 288; # number of litlen codes
Noff: con 30; # number of offset codes
Nclen: con 19; # number of codelen codes
MaxHuffBits: con 15; # max bits in a huffman code
RunlenBits: con 7; # max bits in a run-length huffman code
MaxOff: con 32*1024; # max lempel-ziv distance
Blocksize: con 32 * 1024;
# tables from RFC 1951, section 3.2.5
litlenbase := array[Noff] of
{
3, 4, 5, 6, 7, 8, 9, 10, 11, 13,
15, 17, 19, 23, 27, 31, 35, 43, 51, 59,
67, 83, 99, 115, 131, 163, 195, 227, 258
};
litlenextra := array[Noff] 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
};
offbase := array[Noff] of
{
1, 2, 3, 4, 5, 7, 9, 13, 17, 25,
33, 49, 65, 97, 129, 193, 257, 385, 513, 769,
1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577
};
offextra := array[Noff] 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
};
# order of run-length codes
clenorder := array[Nclen] of
{
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};
# fixed huffman tables
litlentab: array of Huff;
offtab: array of Huff;
# their decoding table counterparts
litlendec: ref DeHuff;
offdec: ref DeHuff;
revtab: array of byte; # bit reversal for endian swap of huffman codes
mask: array of int; # for masking low-order n bits of an int
Hnone, Hgzip, Hzlib: con iota; # State.headers
State: adt {
ibuf, obuf: array of byte;
c: chan of ref Rq;
rc: chan of int;
in: int; # next byte to consume from input buffer
ein: int; # valid bytes in input buffer
out: int; # valid bytes in output buffer
hist: array of byte; # history buffer for lempel-ziv backward references
usehist: int; # == 1 if 'hist' is valid
crctab: array of int;
crc, tot: int; # for gzip trailer
sum: big; # for zlib trailer
reg: int; # 24-bit shift register
nbits: int; # number of valid bits in reg
svreg: int; # save reg for efficient ungets
svn: int; # number of bits gotten in last call to getn()
# reg bits are consumed from right to left
# so low-order byte of reg came first in the input stream
headers: int;
};
init()
{
sys = load Sys Sys->PATH;
# 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;
}
}
# bit-masking table
mask = array[MaxHuffBits+1] of int;
for(i = 0; i <= MaxHuffBits; i++)
mask[i] = (1 << i) - 1;
litlentab = array[Nlitlen] of Huff;
# 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;
bitcount := array[MaxHuffBits+1] of { * => 0 };
bitcount[8] += 144 - 0;
bitcount[9] += 256 - 144;
bitcount[7] += 280 - 256;
bitcount[8] += Nlitlen - 280;
hufftabinit(litlentab, Nlitlen, bitcount, 9);
litlendec = decodeinit(litlentab, Nlitlen, 9, 0);
offtab = array[Noff] of Huff;
# 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);
offdec = decodeinit(offtab, Noff, 5, 0);
}
start(params: string): chan of ref Rq
{
s := ref State;
s.c = chan of ref Rq;
s.rc = chan of int;
s.ibuf = array[Blocksize] of byte;
s.obuf = array[Blocksize] of byte;
s.in = 0;
s.ein = 0;
s.out = 0;
s.usehist = 0;
s.reg = 0;
s.nbits = 0;
s.crc = 0;
s.tot = 0;
s.sum = big 1;
s.hist = array[Blocksize] of byte;
s.headers = Hnone;
if(params != nil) {
if(params[0] == 'h')
s.headers = Hgzip;
if(params[0] == 'z')
s.headers = Hzlib;
}
if (s.headers == Hgzip)
s.crctab = mkcrctab(GZCRCPOLY);
spawn inflate(s);
return s.c;
}
inflate(s: ref State)
{
s.c <-= ref Rq.Start(sys->pctl(0, nil));
header(s);
for(;;) {
bfinal := getn(s, 1, 0);
btype := getn(s, 2, 0);
case(btype) {
DeflateUnc =>
flushbits(s);
unclen := getb(s);
unclen |= getb(s) << 8;
nlen := getb(s);
nlen |= getb(s) << 8;
if(unclen != (~nlen & 16rFFFF))
fatal(s, "corrupted data");
for(; unclen > 0; unclen--) {
# inline putb(s, getb(s));
b := byte getb(s);
if(s.out >= MaxOff)
flushout(s);
s.obuf[s.out++] = b;
}
DeflateFix =>
decodeblock(s, litlendec, offdec);
DeflateDyn =>
dynhuff(s);
DeflateErr =>
fatal(s, "bad block type");
}
if(bfinal) {
if(s.out) {
outblock(s);
s.c <- = ref Rq.Result(s.obuf[0:s.out], s.rc);
flag := <- s.rc;
if (flag == -1)
exit;
}
flushbits(s);
footer(s);
s.c <-= ref Rq.Finished(s.ibuf[s.in - s.nbits/8:s.ein]);
exit;
}
}
}
headergzip(s: ref State)
{
if(byte getb(s) != GZMAGIC1 || byte getb(s) != GZMAGIC2)
fatal(s, "not a gzip file");
if(byte getb(s) != GZDEFLATE)
fatal(s, "not compressed with deflate");
flags := getb(s);
if(flags & ~GZFMASK)
fatal(s, "reserved flag bits set");
# read modification time (ignored)
mtime := getb(s);
mtime |= (getb(s) << 8);
mtime |= (getb(s) << 16);
mtime |= (getb(s) << 24);
s.c <-= ref Rq.Info("mtime " + string mtime);
getb(s); # xfl
getb(s); # os
# skip optional "extra field"
if(flags & GZFEXTRA) {
skip := getb(s);
skip |= getb(s) << 8;
while (skip-- > 0)
getb(s);
}
# read optional filename (ignored)
file: string;
if(flags & GZFNAME){
n := 0;
while(c := getb(s))
file[n++] = c;
s.c <-= ref Rq.Info("file " + file);
}
# skip optional comment
if(flags & GZFCOMMENT) {
while(getb(s))
;
}
# skip optional CRC16 field
if(flags & GZFHCRC) {
getb(s);
getb(s);
}
}
headerzlib(s: ref State)
{
Fdict: con 1<<5;
CMshift: con 8;
CMmask: con (1<<4)-1;
CMdeflate: con 8;
h := 0;
h |= getb(s)<<8;
h |= getb(s);
if(h % 31 != 0)
fatal(s, "invalid zlib header");
if(h&Fdict)
fatal(s, "preset dictionary not supported");
if(((h>>CMshift)&CMmask) != CMdeflate)
fatal(s, "zlib compression method not deflate");
}
header(s: ref State)
{
case s.headers {
Hgzip => headergzip(s);
Hzlib => headerzlib(s);
}
}
footergzip(s: ref State)
{
fcrc := getword(s);
if(s.crc != fcrc)
fatal(s, sys->sprint("crc mismatch: computed %ux, expected %ux", s.crc, fcrc));
ftot := getword(s);
if(s.tot != ftot)
fatal(s, sys->sprint("byte count mismatch: computed %d, expected %d", s.tot, ftot));
}
footerzlib(s: ref State)
{
sum := big 0;
sum = (sum<<8)|big getb(s);
sum = (sum<<8)|big getb(s);
sum = (sum<<8)|big getb(s);
sum = (sum<<8)|big getb(s);
if(sum != s.sum)
fatal(s, sys->sprint("adler32 mismatch: computed %bux, expected %bux", s.sum, sum));
}
footer(s: ref State)
{
case s.headers {
Hgzip => footergzip(s);
Hzlib => footerzlib(s);
}
}
getword(s: ref State): int
{
n := 0;
for(i := 0; i < 4; i++)
n |= getb(s) << (8 * i);
return n;
}
#
# uncompress a block using given huffman decoding tables
#
decodeblock(s: ref State, litlendec, offdec: ref DeHuff)
{
b: byte;
for(;;) {
sym := decodesym(s, litlendec);
if(sym < DeflateEob) { # literal byte
# inline putb(s, byte sym);
b = byte sym;
if(s.out >= MaxOff)
flushout(s);
s.obuf[s.out++] = b;
} else if(sym == DeflateEob) { # End-of-block
break;
} else { # lempel-ziv <length, distance>
if(sym > LenEnd)
fatal(s, "symbol too long");
xbits := litlenextra[sym - LenStart];
xtra := 0;
if(xbits)
xtra = getn(s, xbits, 0);
length := litlenbase[sym - LenStart] + xtra;
sym = decodesym(s, offdec);
if(sym >= Noff)
fatal(s, "symbol too long");
xbits = offextra[sym];
if(xbits)
xtra = getn(s, xbits, 0);
else
xtra = 0;
dist := offbase[sym] + xtra;
if(dist > s.out && s.usehist == 0)
fatal(s, "corrupted data");
for(i := 0; i < length; i++) {
# inline putb(lzbyte(dist));
ix := s.out - dist;
if(dist <= s.out)
b = s.obuf[ix];
else
b = s.hist[MaxOff + ix];
if(s.out >= MaxOff)
flushout(s);
s.obuf[s.out++] = b;
}
}
}
}
#
# decode next symbol in input stream using given huffman decoding table
#
decodesym(s: ref State, dec: ref DeHuff): int
{
code, bits, n: int;
l1 := dec.l1;
nb1 := dec.nb1;
nb2 := dec.nb2;
code = getn(s, nb1, 1);
l2 := l1[code].l2;
if(l2 == nil) { # first level table has answer
bits = l1[code].bits;
if(bits == 0)
fatal(s, "corrupt data");
if(nb1 > bits) {
# inline ungetn(nb1 - bits);
n = nb1 - bits;
s.reg = s.svreg >> (s.svn - n);
s.nbits += n;
}
return l1[code].decode;
}
# must advance to second-level table
code = getn(s, nb2, 1);
bits = l2[code].bits;
if(bits == 0)
fatal(s, "corrupt data");
if(nb1 + nb2 > bits) {
# inline ungetn(nb1 + nb2 - bits);
n = nb1 + nb2 - bits;
s.reg = s.svreg >> (s.svn - n);
s.nbits += n;
}
return l2[code].decode;
}
#
# uncompress a block that was encoded with dynamic huffman codes
# RFC 1951, section 3.2.7
#
dynhuff(s: ref State)
{
hlit := getn(s, 5, 0) + 257;
hdist := getn(s, 5, 0) + 1;
hclen := getn(s, 4, 0) + 4;
if(hlit > Nlitlen || hlit < 257 || hdist > Noff)
fatal(s, "corrupt data");
runlentab := array[Nclen] of { * => Huff(0, 0) };
count := array[RunlenBits+1] of { * => 0 };
for(i := 0; i < hclen; i++) {
nb := getn(s, 3, 0);
if(nb) {
runlentab[clenorder[i]].bits = nb;
count[nb]++;
}
}
hufftabinit(runlentab, Nclen, count, RunlenBits);
runlendec := decodeinit(runlentab, Nclen, RunlenBits, 0);
if(runlendec == nil)
fatal(s, "corrupt data");
lengths := decodelen(s, runlendec, hlit+hdist);
if(lengths == nil)
fatal(s, "corrupt length table");
dlitlendec := decodedyn(s, lengths[0:hlit], hlit, 9);
doffdec := decodedyn(s, lengths[hlit:], hdist, 5);
decodeblock(s, dlitlendec, doffdec);
}
#
# return the decoded combined length table for literal and distance alphabets
#
decodelen(s: ref State, runlendec: ref DeHuff, nlen: int): array of int
{
lengths := array[nlen] of int;
for(n := 0; n < nlen;) {
nb := decodesym(s, runlendec);
nr := 1;
case nb {
0 to 15 =>
;
16 =>
nr = getn(s, 2, 0) + 3;
if(n == 0)
return nil;
nb = lengths[n-1];
17 =>
nr = getn(s, 3, 0) + 3;
nb = 0;
18 =>
nr = getn(s, 7, 0) + 11;
nb = 0;
* =>
return nil;
}
if(n+nr > nlen)
return nil;
while(--nr >= 0)
lengths[n++] = nb;
}
return lengths;
}
#
# (1) read a dynamic huffman code from the input stream
# (2) decode it using the run-length huffman code
# (3) return the decode table for the dynamic huffman code
#
decodedyn(s: ref State, lengths: array of int, nlen, nb1: int): ref DeHuff
{
hufftab := array[nlen] of Huff;
count := array[MaxHuffBits+1] of { * => 0 };
maxnb := 0;
for(n := 0; n < nlen; n++) {
c := lengths[n];
if(c) {
hufftab[n].bits = c;
count[c]++;
if(c > maxnb)
maxnb = c;
}else
hufftab[n].bits = 0;
hufftab[n].encode = 0;
}
hufftabinit(hufftab, nlen, count, maxnb);
nb2 := 0;
if(maxnb > nb1)
nb2 = maxnb - nb1;
d := decodeinit(hufftab, nlen, nb1, nb2);
if (d == nil)
fatal(s, "decodeinit failed");
return d;
}
#
# RFC 1951, section 3.2.2
#
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;
# differences from Deflate module:
# (1) leave huffman code right-justified in encode
# (2) don't reverse it
if(bits != 0)
tab[i].encode = nc[bits]++;
}
}
#
# convert 'array of Huff' produced by hufftabinit()
# into 2-level lookup table for decoding
#
# nb1(nb2): number of bits handled by first(second)-level table
#
decodeinit(tab: array of Huff, n, nb1, nb2: int): ref DeHuff
{
i, j, k, d: int;
dehuff := ref DeHuff(array[1<<nb1] of { * => L1(0, 0, nil) }, nb1, nb2);
l1 := dehuff.l1;
for(i = 0; i < n; i++) {
bits := tab[i].bits;
if(bits == 0)
continue;
l1x := tab[i].encode;
if(l1x >= (1 << bits))
return nil;
if(bits <= nb1) {
d = nb1 - bits;
l1x <<= d;
k = l1x + mask[d];
for(j = l1x; j <= k; j++) {
l1[j].decode = i;
l1[j].bits = bits;
}
continue;
}
# advance to second-level table
d = bits - nb1;
l2x := l1x & mask[d];
l1x >>= d;
if(l1[l1x].l2 == nil)
l1[l1x].l2 = array[1<<nb2] of { * => L2(0, 0) };
l2 := l1[l1x].l2;
d = (nb1 + nb2) - bits;
l2x <<= d;
k = l2x + mask[d];
for(j = l2x; j <= k; j++) {
l2[j].decode = i;
l2[j].bits = bits;
}
}
return dehuff;
}
#
# get next byte from reg
# assumptions:
# (1) flushbits() has been called
# (2) ungetn() won't be called after a getb()
#
getb(s: ref State): int
{
if(s.nbits < 8)
need(s, 8);
b := byte s.reg;
s.reg >>= 8;
s.nbits -= 8;
return int b;
}
#
# get next n bits from reg; if r != 0, reverse the bits
#
getn(s: ref State, n, r: int): int
{
if(s.nbits < n)
need(s, n);
s.svreg = s.reg;
s.svn = n;
i := s.reg & mask[n];
s.reg >>= n;
s.nbits -= n;
if(r) {
if(n <= 8) {
i = int revtab[i];
i >>= 8 - n;
} else {
i = ((int revtab[i & 16rff]) << 8)
| (int revtab[i >> 8]);
i >>= 16 - n;
}
}
return i;
}
#
# ensure that at least n bits are available in reg
#
need(s: ref State, n: int)
{
while(s.nbits < n) {
if(s.in >= s.ein) {
s.c <-= ref Rq.Fill(s.ibuf, s.rc);
s.ein = <- s.rc;
if (s.ein < 0)
exit;
if (s.ein == 0)
fatal(s, "premature end of stream");
s.in = 0;
}
s.reg = ((int s.ibuf[s.in++]) << s.nbits) | s.reg;
s.nbits += 8;
}
}
#
# if partial byte consumed from reg, dispose of remaining bits
#
flushbits(s: ref State)
{
drek := s.nbits % 8;
if(drek) {
s.reg >>= drek;
s.nbits -= drek;
}
}
#
# output buffer is full, so flush it
#
flushout(s: ref State)
{
outblock(s);
s.c <-= ref Rq.Result(s.obuf[0:s.out], s.rc);
flag := <- s.rc;
if (flag == -1)
exit;
buf := s.hist;
s.hist = s.obuf;
s.usehist = 1;
s.obuf = buf;
s.out = 0;
}
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;
}
outblockgzip(s: ref State)
{
buf := s.obuf;
n := s.out;
crc := s.crc;
crc ^= int 16rffffffff;
for(i := 0; i < n; i++)
crc = s.crctab[int(byte crc ^ buf[i])] ^ ((crc >> 8) & 16r00ffffff);
s.crc = crc ^ int 16rffffffff;
s.tot += n;
}
outblockzlib(s: ref State)
{
ZLADLERBASE: con big 65521;
buf := s.obuf;
n := s.out;
s1 := s.sum & big 16rffff;
s2 := (s.sum>>16) & big 16rffff;
for(i := 0; i < n; i++) {
s1 = (s1 + big buf[i]) % ZLADLERBASE;
s2 = (s2 + s1) % ZLADLERBASE;
}
s.sum = (s2<<16) + s1;
}
outblock(s: ref State)
{
case s.headers {
Hgzip => outblockgzip(s);
Hzlib => outblockzlib(s);
}
}
#
# irrecoverable error; invariably denotes data corruption
#
fatal(s: ref State, e: string)
{
s.c <-= ref Rq.Error(e);
exit;
}