add libflate

src/libflate/adler.c

@@ -0,0 +1,72 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+enum
+{
+	ADLERITERS	= 5552,	/* max iters before can overflow 32 bits */
+	ADLERBASE	= 65521 /* largest prime smaller than 65536 */
+};
+
+ulong
+adler32(ulong adler, void *vbuf, int n)
+{
+	ulong s1, s2;
+	uchar *buf, *ebuf;
+	int m;
+
+	buf = vbuf;
+	s1 = adler & 0xffff;
+	s2 = (adler >> 16) & 0xffff;
+	for(; n >= 16; n -= m){
+		m = n;
+		if(m > ADLERITERS)
+			m = ADLERITERS;
+		m &= ~15;
+		for(ebuf = buf + m; buf < ebuf; buf += 16){
+			s1 += buf[0];
+			s2 += s1;
+			s1 += buf[1];
+			s2 += s1;
+			s1 += buf[2];
+			s2 += s1;
+			s1 += buf[3];
+			s2 += s1;
+			s1 += buf[4];
+			s2 += s1;
+			s1 += buf[5];
+			s2 += s1;
+			s1 += buf[6];
+			s2 += s1;
+			s1 += buf[7];
+			s2 += s1;
+			s1 += buf[8];
+			s2 += s1;
+			s1 += buf[9];
+			s2 += s1;
+			s1 += buf[10];
+			s2 += s1;
+			s1 += buf[11];
+			s2 += s1;
+			s1 += buf[12];
+			s2 += s1;
+			s1 += buf[13];
+			s2 += s1;
+			s1 += buf[14];
+			s2 += s1;
+			s1 += buf[15];
+			s2 += s1;
+		}
+		s1 %= ADLERBASE;
+		s2 %= ADLERBASE;
+	}
+	if(n){
+		for(ebuf = buf + n; buf < ebuf; buf++){
+			s1 += buf[0];
+			s2 += s1;
+		}
+		s1 %= ADLERBASE;
+		s2 %= ADLERBASE;
+	}
+	return (s2 << 16) + s1;
+}

src/libflate/crc.c

@@ -0,0 +1,40 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+ulong*
+mkcrctab(ulong poly)
+{
+	ulong *crctab;
+	ulong crc;
+	int i, j;
+
+	crctab = malloc(256 * sizeof(ulong));
+	if(crctab == nil)
+		return nil;
+
+	for(i = 0; i < 256; i++){
+		crc = i;
+		for(j = 0; j < 8; j++){
+			if(crc & 1)
+				crc = (crc >> 1) ^ poly;
+			else
+				crc >>= 1;
+		}
+		crctab[i] = crc;
+	}
+	return crctab;
+}
+
+ulong
+blockcrc(ulong *crctab, ulong crc, void *vbuf, int n)
+{
+	uchar *buf, *ebuf;
+
+	crc ^= 0xffffffff;
+	buf = vbuf;
+	ebuf = buf + n;
+	while(buf < ebuf)
+		crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
+	return crc ^ 0xffffffff;
+}

src/libflate/deflateblock.c

@@ -0,0 +1,56 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+typedef struct Block	Block;
+
+struct Block
+{
+	uchar	*pos;
+	uchar	*limit;
+};
+
+static int
+blread(void *vb, void *buf, int n)
+{
+	Block *b;
+
+	b = vb;
+	if(n > b->limit - b->pos)
+		n = b->limit - b->pos;
+	memmove(buf, b->pos, n);
+	b->pos += n;
+	return n;
+}
+
+static int
+blwrite(void *vb, void *buf, int n)
+{
+	Block *b;
+
+	b = vb;
+
+	if(n > b->limit - b->pos)
+		n = b->limit - b->pos;
+	memmove(b->pos, buf, n);
+	b->pos += n;
+	return n;
+}
+
+int
+deflateblock(uchar *dst, int dsize, uchar *src, int ssize, int level, int debug)
+{
+	Block bd, bs;
+	int ok;
+
+	bs.pos = src;
+	bs.limit = src + ssize;
+
+	bd.pos = dst;
+	bd.limit = dst + dsize;
+
+	ok = deflate(&bd, blwrite, &bs, blread, level, debug);
+	if(ok != FlateOk)
+		return ok;
+	return bd.pos - dst;
+}

src/libflate/deflatezlib.c

@@ -0,0 +1,60 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+#include "zlib.h"
+
+typedef struct ZRead	ZRead;
+
+struct ZRead
+{
+	ulong	adler;
+	void	*rr;
+	int	(*r)(void*, void*, int);
+};
+
+static int
+zlread(void *vzr, void *buf, int n)
+{
+	ZRead *zr;
+
+	zr = vzr;
+	n = (*zr->r)(zr->rr, buf, n);
+	if(n <= 0)
+		return n;
+	zr->adler = adler32(zr->adler, buf, n);
+	return n;
+}
+
+int
+deflatezlib(void *wr, int (*w)(void*, void*, int), void *rr, int (*r)(void*, void*, int), int level, int debug)
+{
+	ZRead zr;
+	uchar buf[4];
+	int ok;
+
+	buf[0] = ZlibDeflate | ZlibWin32k;
+
+	/* bogus zlib encoding of compression level */
+	buf[1] = ((level > 2) + (level > 5) + (level > 8)) << 6;
+
+	/* header check field */
+	buf[1] |= 31 - ((buf[0] << 8) | buf[1]) % 31;
+	if((*w)(wr, buf, 2) != 2)
+		return FlateOutputFail;
+
+	zr.rr = rr;
+	zr.r = r;
+	zr.adler = 1;
+	ok = deflate(wr, w, &zr, zlread, level, debug);
+	if(ok != FlateOk)
+		return ok;
+
+	buf[0] = zr.adler >> 24;
+	buf[1] = zr.adler >> 16;
+	buf[2] = zr.adler >> 8;
+	buf[3] = zr.adler;
+	if((*w)(wr, buf, 4) != 4)
+		return FlateOutputFail;
+
+	return FlateOk;
+}

src/libflate/deflatezlibblock.c

@@ -0,0 +1,34 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+#include "zlib.h"
+
+int
+deflatezlibblock(uchar *dst, int dsize, uchar *src, int ssize, int level, int debug)
+{
+	ulong adler;
+	int n;
+
+	if(dsize < 6)
+		return FlateOutputFail;
+
+	n = deflateblock(dst + 2, dsize - 6, src, ssize, level, debug);
+	if(n < 0)
+		return n;
+
+	dst[0] = ZlibDeflate | ZlibWin32k;
+
+	/* bogus zlib encoding of compression level */
+	dst[1] = ((level > 2) + (level > 5) + (level > 8)) << 6;
+
+	/* header check field */
+	dst[1] |= 31 - ((dst[0] << 8) | dst[1]) % 31;
+
+	adler = adler32(1, src, ssize);
+	dst[n + 2] = adler >> 24;
+	dst[n + 3] = adler >> 16;
+	dst[n + 4] = adler >> 8;
+	dst[n + 5] = adler;
+
+	return n + 6;
+}

src/libflate/flateerr.c

@@ -0,0 +1,23 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+char *
+flateerr(int err)
+{
+	switch(err){
+	case FlateOk:
+		return "no error";
+	case FlateNoMem:
+		return "out of memory";
+	case FlateInputFail:
+		return "input error";
+	case FlateOutputFail:
+		return "output error";
+	case FlateCorrupted:
+		return "corrupted data";
+	case FlateInternal:
+		return "internal error";
+	}
+	return "unknown error";
+}

src/libflate/inflate.c

@@ -0,0 +1,693 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+enum {
+	HistorySize=	32*1024,
+	BufSize=	4*1024,
+	MaxHuffBits=	17,	/* maximum bits in a encoded code */
+	Nlitlen=	288,	/* number of litlen codes */
+	Noff=		32,	/* number of offset codes */
+	Nclen=		19,	/* number of codelen codes */
+	LenShift=	10,	/* code = len<<LenShift|code */
+	LitlenBits=	7,	/* number of bits in litlen decode table */
+	OffBits=	6,	/* number of bits in offset decode table */
+	ClenBits=	6,	/* number of bits in code len decode table */
+	MaxFlatBits=	LitlenBits,
+	MaxLeaf=	Nlitlen
+};
+
+typedef struct Input	Input;
+typedef struct History	History;
+typedef struct Huff	Huff;
+
+struct Input
+{
+	int	error;		/* first error encountered, or FlateOk */
+	void	*wr;
+	int	(*w)(void*, void*, int);
+	void	*getr;
+	int	(*get)(void*);
+	ulong	sreg;
+	int	nbits;
+};
+
+struct History
+{
+	uchar	his[HistorySize];
+	uchar	*cp;		/* current pointer in history */
+	int	full;		/* his has been filled up at least once */
+};
+
+struct Huff
+{
+	int	maxbits;	/* max bits for any code */
+	int	minbits;	/* min bits to get before looking in flat */
+	int	flatmask;	/* bits used in "flat" fast decoding table */
+	ulong	flat[1<<MaxFlatBits];
+	ulong	maxcode[MaxHuffBits];
+	ulong	last[MaxHuffBits];
+	ulong	decode[MaxLeaf];
+};
+
+/* litlen code words 257-285 extra bits */
+static int litlenextra[Nlitlen-257] =
+{
+/* 257 */	0, 0, 0,
+/* 260 */	0, 0, 0, 0, 0, 1, 1, 1, 1, 2,
+/* 270 */	2, 2, 2, 3, 3, 3, 3, 4, 4, 4,
+/* 280 */	4, 5, 5, 5, 5, 0, 0, 0
+};
+
+static int litlenbase[Nlitlen-257];
+
+/* offset code word extra bits */
+static int offextra[Noff] =
+{
+	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,
+};
+static int offbase[Noff];
+
+/* order code lengths */
+static int clenorder[Nclen] =
+{
+        16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
+};
+
+/* for static huffman tables */
+static	Huff	litlentab;
+static	Huff	offtab;
+static	uchar	revtab[256];
+
+static int	uncblock(Input *in, History*);
+static int	fixedblock(Input *in, History*);
+static int	dynamicblock(Input *in, History*);
+static int	sregfill(Input *in, int n);
+static int	sregunget(Input *in);
+static int	decode(Input*, History*, Huff*, Huff*);
+static int	hufftab(Huff*, char*, int, int);
+static int	hdecsym(Input *in, Huff *h, int b);
+
+int
+inflateinit(void)
+{
+	char *len;
+	int i, j, base;
+
+	/* byte reverse table */
+	for(i=0; i<256; i++)
+		for(j=0; j<8; j++)
+			if(i & (1<<j))
+				revtab[i] |= 0x80 >> j;
+
+	for(i=257,base=3; i<Nlitlen; i++) {
+		litlenbase[i-257] = base;
+		base += 1<<litlenextra[i-257];
+	}
+	/* strange table entry in spec... */
+	litlenbase[285-257]--;
+
+	for(i=0,base=1; i<Noff; i++) {
+		offbase[i] = base;
+		base += 1<<offextra[i];
+	}
+
+	len = malloc(MaxLeaf);
+	if(len == nil)
+		return FlateNoMem;
+
+	/* static Litlen bit lengths */
+	for(i=0; i<144; i++)
+		len[i] = 8;
+	for(i=144; i<256; i++)
+		len[i] = 9;
+	for(i=256; i<280; i++)
+		len[i] = 7;
+	for(i=280; i<Nlitlen; i++)
+		len[i] = 8;
+
+	if(!hufftab(&litlentab, len, Nlitlen, MaxFlatBits))
+		return FlateInternal;
+
+	/* static Offset bit lengths */
+	for(i=0; i<Noff; i++)
+		len[i] = 5;
+
+	if(!hufftab(&offtab, len, Noff, MaxFlatBits))
+		return FlateInternal;
+	free(len);
+
+	return FlateOk;
+}
+
+int
+inflate(void *wr, int (*w)(void*, void*, int), void *getr, int (*get)(void*))
+{
+	History *his;
+	Input in;
+	int final, type;
+
+	his = malloc(sizeof(History));
+	if(his == nil)
+		return FlateNoMem;
+	his->cp = his->his;
+	his->full = 0;
+	in.getr = getr;
+	in.get = get;
+	in.wr = wr;
+	in.w = w;
+	in.nbits = 0;
+	in.sreg = 0;
+	in.error = FlateOk;
+
+	do {
+		if(!sregfill(&in, 3))
+			goto bad;
+		final = in.sreg & 0x1;
+		type = (in.sreg>>1) & 0x3;
+		in.sreg >>= 3;
+		in.nbits -= 3;
+		switch(type) {
+		default:
+			in.error = FlateCorrupted;
+			goto bad;
+		case 0:
+			/* uncompressed */
+			if(!uncblock(&in, his))
+				goto bad;
+			break;
+		case 1:
+			/* fixed huffman */
+			if(!fixedblock(&in, his))
+				goto bad;
+			break;
+		case 2:
+			/* dynamic huffman */
+			if(!dynamicblock(&in, his))
+				goto bad;
+			break;
+		}
+	} while(!final);
+
+	if(his->cp != his->his && (*w)(wr, his->his, his->cp - his->his) != his->cp - his->his) {
+		in.error = FlateOutputFail;
+		goto bad;
+	}
+
+	if(!sregunget(&in))
+		goto bad;
+
+	free(his);
+	if(in.error != FlateOk)
+		return FlateInternal;
+	return FlateOk;
+
+bad:
+	free(his);
+	if(in.error == FlateOk)
+		return FlateInternal;
+	return in.error;
+}
+
+static int
+uncblock(Input *in, History *his)
+{
+	int len, nlen, c;
+	uchar *hs, *hp, *he;
+
+	if(!sregunget(in))
+		return 0;
+	len = (*in->get)(in->getr);
+	len |= (*in->get)(in->getr)<<8;
+	nlen = (*in->get)(in->getr);
+	nlen |= (*in->get)(in->getr)<<8;
+	if(len != (~nlen&0xffff)) {
+		in->error = FlateCorrupted;
+		return 0;
+	}
+
+	hp = his->cp;
+	hs = his->his;
+	he = hs + HistorySize;
+
+	while(len > 0) {
+		c = (*in->get)(in->getr);
+		if(c < 0)
+			return 0;
+		*hp++ = c;
+		if(hp == he) {
+			his->full = 1;
+			if((*in->w)(in->wr, hs, HistorySize) != HistorySize) {
+				in->error = FlateOutputFail;
+				return 0;
+			}
+			hp = hs;
+		}
+		len--;
+	}
+
+	his->cp = hp;
+
+	return 1;
+}
+
+static int
+fixedblock(Input *in, History *his)
+{
+	return decode(in, his, &litlentab, &offtab);
+}
+
+static int
+dynamicblock(Input *in, History *his)
+{
+	Huff *lentab, *offtab;
+	char *len;
+	int i, j, n, c, nlit, ndist, nclen, res, nb;
+
+	if(!sregfill(in, 14))
+		return 0;
+	nlit = (in->sreg&0x1f) + 257;
+	ndist = ((in->sreg>>5) & 0x1f) + 1;
+	nclen = ((in->sreg>>10) & 0xf) + 4;
+	in->sreg >>= 14;
+	in->nbits -= 14;
+
+	if(nlit > Nlitlen || ndist > Noff || nlit < 257) {
+		in->error = FlateCorrupted;
+		return 0;
+	}
+
+	/* huff table header */
+	len = malloc(Nlitlen+Noff);
+	lentab = malloc(sizeof(Huff));
+	offtab = malloc(sizeof(Huff));
+	if(len == nil || lentab == nil || offtab == nil){
+		in->error = FlateNoMem;
+		goto bad;
+	}
+	for(i=0; i < Nclen; i++)
+		len[i] = 0;
+	for(i=0; i<nclen; i++) {
+		if(!sregfill(in, 3))
+			goto bad;
+		len[clenorder[i]] = in->sreg & 0x7;
+		in->sreg >>= 3;
+		in->nbits -= 3;
+	}
+
+	if(!hufftab(lentab, len, Nclen, ClenBits)){
+		in->error = FlateCorrupted;
+		goto bad;
+	}
+
+	n = nlit+ndist;
+	for(i=0; i<n;) {
+		nb = lentab->minbits;
+		for(;;){
+			if(in->nbits<nb && !sregfill(in, nb))
+				goto bad;
+			c = lentab->flat[in->sreg & lentab->flatmask];
+			nb = c & 0xff;
+			if(nb > in->nbits){
+				if(nb != 0xff)
+					continue;
+				c = hdecsym(in, lentab, c);
+				if(c < 0)
+					goto bad;
+			}else{
+				c >>= 8;
+				in->sreg >>= nb;
+				in->nbits -= nb;
+			}
+			break;
+		}
+
+		if(c < 16) {
+			j = 1;
+		} else if(c == 16) {
+			if(in->nbits<2 && !sregfill(in, 2))
+				goto bad;
+			j = (in->sreg&0x3)+3;
+			in->sreg >>= 2;
+			in->nbits -= 2;
+			if(i == 0) {
+				in->error = FlateCorrupted;
+				goto bad;
+			}
+			c = len[i-1];
+		} else if(c == 17) {
+			if(in->nbits<3 && !sregfill(in, 3))
+				goto bad;
+			j = (in->sreg&0x7)+3;
+			in->sreg >>= 3;
+			in->nbits -= 3;
+			c = 0;
+		} else if(c == 18) {
+			if(in->nbits<7 && !sregfill(in, 7))
+				goto bad;
+			j = (in->sreg&0x7f)+11;
+			in->sreg >>= 7;
+			in->nbits -= 7;
+			c = 0;
+		} else {
+			in->error = FlateCorrupted;
+			goto bad;
+		}
+
+		if(i+j > n) {
+			in->error = FlateCorrupted;
+			goto bad;
+		}
+
+		while(j) {
+			len[i] = c;
+			i++;
+			j--;
+		}
+	}
+
+	if(!hufftab(lentab, len, nlit, LitlenBits)
+	|| !hufftab(offtab, &len[nlit], ndist, OffBits)){
+		in->error = FlateCorrupted;
+		goto bad;
+	}
+
+	res = decode(in, his, lentab, offtab);
+
+	free(len);
+	free(lentab);
+	free(offtab);
+
+	return res;
+
+bad:
+	free(len);
+	free(lentab);
+	free(offtab);
+	return 0;
+}
+
+static int
+decode(Input *in, History *his, Huff *litlentab, Huff *offtab)
+{
+	int len, off;
+	uchar *hs, *hp, *hq, *he;
+	int c;
+	int nb;
+
+	hs = his->his;
+	he = hs + HistorySize;
+	hp = his->cp;
+
+	for(;;) {
+		nb = litlentab->minbits;
+		for(;;){
+			if(in->nbits<nb && !sregfill(in, nb))
+				return 0;
+			c = litlentab->flat[in->sreg & litlentab->flatmask];
+			nb = c & 0xff;
+			if(nb > in->nbits){
+				if(nb != 0xff)
+					continue;
+				c = hdecsym(in, litlentab, c);
+				if(c < 0)
+					return 0;
+			}else{
+				c >>= 8;
+				in->sreg >>= nb;
+				in->nbits -= nb;
+			}
+			break;
+		}
+
+		if(c < 256) {
+			/* literal */
+			*hp++ = c;
+			if(hp == he) {
+				his->full = 1;
+				if((*in->w)(in->wr, hs, HistorySize) != HistorySize) {
+					in->error = FlateOutputFail;
+					return 0;
+				}
+				hp = hs;
+			}
+			continue;
+		}
+
+		if(c == 256)
+			break;
+
+		if(c > 285) {
+			in->error = FlateCorrupted;
+			return 0;
+		}
+
+		c -= 257;
+		nb = litlenextra[c];
+		if(in->nbits < nb && !sregfill(in, nb))
+			return 0;
+		len = litlenbase[c] + (in->sreg & ((1<<nb)-1));
+		in->sreg >>= nb;
+		in->nbits -= nb;
+
+		/* get offset */
+		nb = offtab->minbits;
+		for(;;){
+			if(in->nbits<nb && !sregfill(in, nb))
+				return 0;
+			c = offtab->flat[in->sreg & offtab->flatmask];
+			nb = c & 0xff;
+			if(nb > in->nbits){
+				if(nb != 0xff)
+					continue;
+				c = hdecsym(in, offtab, c);
+				if(c < 0)
+					return 0;
+			}else{
+				c >>= 8;
+				in->sreg >>= nb;
+				in->nbits -= nb;
+			}
+			break;
+		}
+
+		if(c > 29) {
+			in->error = FlateCorrupted;
+			return 0;
+		}
+
+		nb = offextra[c];
+		if(in->nbits < nb && !sregfill(in, nb))
+			return 0;
+
+		off = offbase[c] + (in->sreg & ((1<<nb)-1));
+		in->sreg >>= nb;
+		in->nbits -= nb;
+
+		hq = hp - off;
+		if(hq < hs) {
+			if(!his->full) {
+				in->error = FlateCorrupted;
+				return 0;
+			}
+			hq += HistorySize;
+		}
+
+		/* slow but correct */
+		while(len) {
+			*hp = *hq;
+			hq++;
+			hp++;
+			if(hq >= he)
+				hq = hs;
+			if(hp == he) {
+				his->full = 1;
+				if((*in->w)(in->wr, hs, HistorySize) != HistorySize) {
+					in->error = FlateOutputFail;
+					return 0;
+				}
+				hp = hs;
+			}
+			len--;
+		}
+
+	}
+
+	his->cp = hp;
+
+	return 1;
+}
+
+static int
+revcode(int c, int b)
+{
+	/* shift encode up so it starts on bit 15 then reverse */
+	c <<= (16-b);
+	c = revtab[c>>8] | (revtab[c&0xff]<<8);
+	return c;
+}
+
+/*
+ * construct the huffman decoding arrays and a fast lookup table.
+ * the fast lookup is a table indexed by the next flatbits bits,
+ * which returns the symbol matched and the number of bits consumed,
+ * or the minimum number of bits needed and 0xff if more than flatbits
+ * bits are needed.
+ *
+ * flatbits can be longer than the smallest huffman code,
+ * because shorter codes are assigned smaller lexical prefixes.
+ * this means assuming zeros for the next few bits will give a
+ * conservative answer, in the sense that it will either give the
+ * correct answer, or return the minimum number of bits which
+ * are needed for an answer.
+ */
+static int
+hufftab(Huff *h, char *hb, int maxleaf, int flatbits)
+{
+	ulong bitcount[MaxHuffBits];
+	ulong c, fc, ec, mincode, code, nc[MaxHuffBits];
+	int i, b, minbits, maxbits;
+
+	for(i = 0; i < MaxHuffBits; i++)
+		bitcount[i] = 0;
+	maxbits = -1;
+	minbits = MaxHuffBits + 1;
+	for(i=0; i < maxleaf; i++){
+		b = hb[i];
+		if(b){
+			bitcount[b]++;
+			if(b < minbits)
+				minbits = b;
+			if(b > maxbits)
+				maxbits = b;
+		}
+	}
+
+	h->maxbits = maxbits;
+	if(maxbits <= 0){
+		h->maxbits = 0;
+		h->minbits = 0;
+		h->flatmask = 0;
+		return 1;
+	}
+	code = 0;
+	c = 0;
+	for(b = 0; b <= maxbits; b++){
+		h->last[b] = c;
+		c += bitcount[b];
+		mincode = code << 1;
+		nc[b] = mincode;
+		code = mincode + bitcount[b];
+		if(code > (1 << b))
+			return 0;
+		h->maxcode[b] = code - 1;
+		h->last[b] += code - 1;
+	}
+
+	if(flatbits > maxbits)
+		flatbits = maxbits;
+	h->flatmask = (1 << flatbits) - 1;
+	if(minbits > flatbits)
+		minbits = flatbits;
+	h->minbits = minbits;
+
+	b = 1 << flatbits;
+	for(i = 0; i < b; i++)
+		h->flat[i] = ~0;
+
+	/*
+	 * initialize the flat table to include the minimum possible
+	 * bit length for each code prefix
+	 */
+	for(b = maxbits; b > flatbits; b--){
+		code = h->maxcode[b];
+		if(code == -1)
+			break;
+		mincode = code + 1 - bitcount[b];
+		mincode >>= b - flatbits;
+		code >>= b - flatbits;
+		for(; mincode <= code; mincode++)
+			h->flat[revcode(mincode, flatbits)] = (b << 8) | 0xff;
+	}
+
+	for(i = 0; i < maxleaf; i++){
+		b = hb[i];
+		if(b <= 0)
+			continue;
+		c = nc[b]++;
+		if(b <= flatbits){
+			code = (i << 8) | b;
+			ec = (c + 1) << (flatbits - b);
+			if(ec > (1<<flatbits))
+				return 0;	/* this is actually an internal error */
+			for(fc = c << (flatbits - b); fc < ec; fc++)
+				h->flat[revcode(fc, flatbits)] = code;
+		}
+		if(b > minbits){
+			c = h->last[b] - c;
+			if(c >= maxleaf)
+				return 0;
+			h->decode[c] = i;
+		}
+	}
+	return 1;
+}
+
+static int
+hdecsym(Input *in, Huff *h, int nb)
+{
+	long c;
+
+	if((nb & 0xff) == 0xff)
+		nb = nb >> 8;
+	else
+		nb = nb & 0xff;
+	for(; nb <= h->maxbits; nb++){
+		if(in->nbits<nb && !sregfill(in, nb))
+			return -1;
+		c = revtab[in->sreg&0xff]<<8;
+		c |= revtab[(in->sreg>>8)&0xff];
+		c >>= (16-nb);
+		if(c <= h->maxcode[nb]){
+			in->sreg >>= nb;
+			in->nbits -= nb;
+			return h->decode[h->last[nb] - c];
+		}
+	}
+	in->error = FlateCorrupted;
+	return -1;
+}
+
+static int
+sregfill(Input *in, int n)
+{
+	int c;
+
+	while(n > in->nbits) {
+		c = (*in->get)(in->getr);
+		if(c < 0){
+			in->error = FlateInputFail;
+			return 0;
+		}
+		in->sreg |= c<<in->nbits;
+		in->nbits += 8;
+	}
+	return 1;
+}
+
+static int
+sregunget(Input *in)
+{
+	if(in->nbits >= 8) {
+		in->error = FlateInternal;
+		return 0;
+	}
+
+	/* throw other bits on the floor */
+	in->nbits = 0;
+	in->sreg = 0;
+	return 1;
+}

src/libflate/inflateblock.c

@@ -0,0 +1,54 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+
+typedef struct Block	Block;
+
+struct Block
+{
+	uchar	*pos;
+	uchar	*limit;
+};
+
+static int
+blgetc(void *vb)
+{
+	Block *b;
+
+	b = vb;
+	if(b->pos >= b->limit)
+		return -1;
+	return *b->pos++;
+}
+
+static int
+blwrite(void *vb, void *buf, int n)
+{
+	Block *b;
+
+	b = vb;
+
+	if(n > b->limit - b->pos)
+		n = b->limit - b->pos;
+	memmove(b->pos, buf, n);
+	b->pos += n;
+	return n;
+}
+
+int
+inflateblock(uchar *dst, int dsize, uchar *src, int ssize)
+{
+	Block bd, bs;
+	int ok;
+
+	bs.pos = src;
+	bs.limit = src + ssize;
+
+	bd.pos = dst;
+	bd.limit = dst + dsize;
+
+	ok = inflate(&bd, blwrite, &bs, blgetc);
+	if(ok != FlateOk)
+		return ok;
+	return bd.pos - dst;
+}

src/libflate/inflatezlib.c

@@ -0,0 +1,66 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+#include "zlib.h"
+
+typedef struct ZWrite	ZWrite;
+
+struct ZWrite
+{
+	ulong	adler;
+	void	*wr;
+	int	(*w)(void*, void*, int);
+};
+
+static int
+zlwrite(void *vzw, void *buf, int n)
+{
+	ZWrite *zw;
+
+	zw = vzw;
+	zw->adler = adler32(zw->adler, buf, n);
+	n = (*zw->w)(zw->wr, buf, n);
+	if(n <= 0)
+		return n;
+	return n;
+}
+
+int
+inflatezlib(void *wr, int (*w)(void*, void*, int), void *getr, int (*get)(void*))
+{
+	ZWrite zw;
+	ulong v;
+	int c, i;
+
+	c = (*get)(getr);
+	if(c < 0)
+		return FlateInputFail;
+	i = (*get)(getr);
+	if(i < 0)
+		return FlateInputFail;
+
+	if(((c << 8) | i) % 31)
+		return FlateCorrupted;
+	if((c & ZlibMeth) != ZlibDeflate
+	|| (c & ZlibCInfo) > ZlibWin32k)
+		return FlateCorrupted;
+
+	zw.wr = wr;
+	zw.w = w;
+	zw.adler = 1;
+	i = inflate(&zw, zlwrite, getr, get);
+	if(i != FlateOk)
+		return i;
+
+	v = 0;
+	for(i = 0; i < 4; i++){
+		c = (*get)(getr);
+		if(c < 0)
+			return FlateInputFail;
+		v = (v << 8) | c;
+	}
+	if(zw.adler != v)
+		return FlateCorrupted;
+
+	return FlateOk;
+}

src/libflate/inflatezlibblock.c

@@ -0,0 +1,68 @@
+#include <u.h>
+#include <libc.h>
+#include <flate.h>
+#include "zlib.h"
+
+typedef struct Block	Block;
+
+struct Block
+{
+	uchar	*pos;
+	uchar	*limit;
+};
+
+static int
+blgetc(void *vb)
+{
+	Block *b;
+
+	b = vb;
+	if(b->pos >= b->limit)
+		return -1;
+	return *b->pos++;
+}
+
+static int
+blwrite(void *vb, void *buf, int n)
+{
+	Block *b;
+
+	b = vb;
+
+	if(n > b->limit - b->pos)
+		n = b->limit - b->pos;
+	memmove(b->pos, buf, n);
+	b->pos += n;
+	return n;
+}
+
+int
+inflatezlibblock(uchar *dst, int dsize, uchar *src, int ssize)
+{
+	Block bd, bs;
+	int ok;
+
+	if(ssize < 6)
+		return FlateInputFail;
+
+	if(((src[0] << 8) | src[1]) % 31)
+		return FlateCorrupted;
+	if((src[0] & ZlibMeth) != ZlibDeflate
+	|| (src[0] & ZlibCInfo) > ZlibWin32k)
+		return FlateCorrupted;
+
+	bs.pos = src + 2;
+	bs.limit = src + ssize - 6;
+
+	bd.pos = dst;
+	bd.limit = dst + dsize;
+
+	ok = inflate(&bd, blwrite, &bs, blgetc);
+	if(ok != FlateOk)
+		return ok;
+
+	if(adler32(1, dst, bs.pos - dst) != ((bs.pos[0] << 24) | (bs.pos[1] << 16) | (bs.pos[2] << 8) | bs.pos[3]))
+		return FlateCorrupted;
+
+	return bd.pos - dst;
+}

src/libflate/mkfile

@@ -0,0 +1,22 @@
+PLAN9=../..
+<$PLAN9/src/mkhdr
+
+LIB=libflate.a
+OFILES=\
+	deflate.$O\
+	deflatezlib.$O\
+	deflateblock.$O\
+	deflatezlibblock.$O\
+	inflate.$O\
+	inflatezlib.$O\
+	inflateblock.$O\
+	inflatezlibblock.$O\
+	flateerr.$O\
+	crc.$O\
+	adler.$O\
+
+HFILES=\
+	$PLAN9/include/flate.h\
+	zlib.h\
+
+<$PLAN9/src/mksyslib

src/libflate/zlib.h

@@ -0,0 +1,11 @@
+/*
+ * zlib header fields
+ */
+enum
+{
+	ZlibMeth	= 0x0f,			/* mask of compression methods */
+	ZlibDeflate	= 0x08,
+
+	ZlibCInfo	= 0xf0,			/* mask of compression aux. info */
+	ZlibWin32k	= 0x70,			/* 32k history window */
+};