From 136af483e104cc39eb53c41baa09f45ee8064ebe Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Sat, 9 Jun 2001 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2001-06-09

---
 pc/memory.c        | 13 +++----
 port/devloopback.c |  1 +
 port/thwack.c      | 36 +++++++++---------
 port/unthwack.c    | 95 ++++++++++++++++++++++++++++++++++------------
 4 files changed, 93 insertions(+), 52 deletions(-)

diff --git a/pc/memory.c b/pc/memory.c
index fa881c66e9870e65bc1371fc9b63db6cb4c83e3f..e48539460bdb09121eaa7994018724ce1c0b7ea7 100644
--- a/pc/memory.c
+++ b/pc/memory.c
@@ -225,14 +225,11 @@ umbscan(void)
 	 */
 	p = KADDR(0xC0000);
 	while(p < (uchar*)KADDR(0xE0000)){
-		/*
-		 * Test for 0x55 AA before poking obtrusively,
-		 * some machines (e.g. Thinkpad X20) seem to map
-		 * something dynamic here (cardbus?) causing weird
-		 * problems if it is changed.
-		 */
-		if(p[0] == 0x55 && p[1] == 0xAA){
-			p += p[2]*512;
+		if (p[0] == 0x55 && p[1] == 0xAA) {
+			/* Skip p[2] chunks of 512 bytes.  Test for 0x55 AA before
+			     poking obtrusively, or else the Thinkpad X20 dies when
+			     setting up the cardbus (PB) */
+			p += p[2] * 512;
 			continue;
 		}
 
diff --git a/port/devloopback.c b/port/devloopback.c
index 84c002aadf5e497754b9f94fb811c118061a0475..b1f039a663be877466aceb3dd8537fc62f5d987a 100644
--- a/port/devloopback.c
+++ b/port/devloopback.c
@@ -551,6 +551,7 @@ loopbackwrite(Chan *c, void *va, long n, vlong off)
 			iunlock(link);
 		}else
 			error("unknown control request");
+		poperror();
 		free(cb);
 		break;
 	default:
diff --git a/port/thwack.c b/port/thwack.c
index b3af49b3e802b21631334356d01f1132eb76d215..2b48de67181c3d850193c8d14c6f9bb6ecf8e19e 100644
--- a/port/thwack.c
+++ b/port/thwack.c
@@ -74,17 +74,15 @@ thwackack(Thwack *tw, ulong seq, ulong mask)
 
 	slot = tw->slot;
 	for(;;){
-		for(;;){
-			slot--;
-			if(slot < 0)
-				slot += EWinBlocks;
-			if(slot == tw->slot)
-				return;
-			if(tw->blocks[slot].seq == seq){
-				tw->blocks[slot].acked = 1;
-				break;
-			}
-		}
+		slot--;
+		if(slot < 0)
+			slot += EWinBlocks;
+		if(slot == tw->slot)
+			break;
+		if(tw->blocks[slot].seq != seq)
+			continue;
+
+		tw->blocks[slot].acked = 1;
 
 		if(mask == 0)
 			break;
@@ -250,7 +248,7 @@ thwack(Thwack *tw, uchar *dst, uchar *src, int n, ulong seq, ulong stats[ThwStat
 		}
 		if(len < MinMatch){
 			toff = *s;
-			lithist = (lithist << 1) | toff < 32 | toff > 127;
+			lithist = (lithist << 1) | (toff < 32) | (toff > 127);
 			if(lithist & 0x1e){
 				twbits = (twbits << 9) | toff;
 				twnbits += 9;
@@ -355,13 +353,6 @@ thwack(Thwack *tw, uchar *dst, uchar *src, int n, ulong seq, ulong stats[ThwStat
 		}
 	}
 
-	stats[StatBytes] += blocks->maxoff;
-	stats[StatLits] += lits;
-	stats[StatMatches] += matches;
-	stats[StatOffBits] += offbits;
-	stats[StatLenBits] += lenbits;
-	stats[StatDelay] = stats[StatDelay]*7/8 + dst[0];
-	stats[StatHist] = stats[StatHist]*7/8 + nhist;
 
 	if(twnbits & 7){
 		twbits <<= 8 - (twnbits & 7);
@@ -377,6 +368,13 @@ thwack(Thwack *tw, uchar *dst, uchar *src, int n, ulong seq, ulong stats[ThwStat
 	if(tw->slot >= EWinBlocks)
 		tw->slot = 0;
 
+	stats[StatBytes] += blocks->maxoff;
+	stats[StatLits] += lits;
+	stats[StatMatches] += matches;
+	stats[StatOffBits] += offbits;
+	stats[StatLenBits] += lenbits;
+	stats[StatDelay] = stats[StatDelay]*7/8 + dst[0];
+	stats[StatHist] = stats[StatHist]*7/8 + nhist;
 	stats[StatOutBytes] += twdst - dst;
 
 	return twdst - dst;
diff --git a/port/unthwack.c b/port/unthwack.c
index 4ea74af18be783ac1bb1aad47cdfc2f8cf7e37fd..3c8f40f5c1a3415309590a171e3c7d26703ea69e 100644
--- a/port/unthwack.c
+++ b/port/unthwack.c
@@ -59,39 +59,86 @@ unthwackinit(Unthwack *ut)
 		ut->blocks[i].data = ut->data[i];
 }
 
-int
-unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
+ulong
+unthwackstate(Unthwack *ut, uchar *mask)
 {
-	UnthwBlock blocks[CompBlocks], *b, *eblocks;
-	uchar *s, *d, *dmax, *smax, lit;
-	ulong cmask, cseq, bseq, utbits, lithist;
-	int i, off, len, bits, slot, tslot, use, code, utnbits, overbits;
+	ulong bseq, seq;
+	int slot, m;
 
-	if(nsrc < 4 || nsrc > ThwMaxBlock)
-		return -1;
+	seq = ~0UL;
+	m = 0;
+	slot = ut->slot;
+	for(;;){
+		slot--;
+		if(slot < 0)
+			slot += DWinBlocks;
+		if(slot == ut->slot)
+			break;
+		if(ut->blocks[slot].maxoff == 0)
+			continue;
+		bseq = ut->blocks[slot].seq;
+		if(seq == ~0UL)
+			seq = bseq;
+		else if(seq - bseq > MaxSeqMask)
+			break;
+		else
+			m |= 1 << (seq - bseq - 1);
+	}
+	*mask = m;
+	return seq;
+}
+
+/*
+ * insert this block in it's correct sequence number order.
+ * replace the oldest block, which is always pointed to by ut->slot.
+ * the encoder doesn't use a history at wraparound,
+ * so don't worry about that case.
+ */
+static int
+unthwackinsert(Unthwack *ut, int len, ulong seq)
+{
+	uchar *d;
+	int slot, tslot;
 
-	/*
-	 * insert this block in it's correct sequence number order.
-	 * replace the oldest block, which is always pointed to by ut->slot.
-	 * the encoder doesn't use a history at wraparound,
-	 * so don't worry about that case.
-	 */
 	tslot = ut->slot;
 	for(;;){
 		slot = tslot - 1;
 		if(slot < 0)
 			slot += DWinBlocks;
-		if(ut->blocks[slot].seq <= seq)
+		if(ut->blocks[slot].seq <= seq || ut->blocks[slot].maxoff == 0)
 			break;
 		d = ut->blocks[tslot].data;
 		ut->blocks[tslot] = ut->blocks[slot];
 		ut->blocks[slot].data = d;
 		tslot = slot;
 	}
-	b = blocks;
 	ut->blocks[tslot].seq = seq;
-	ut->blocks[tslot].maxoff = 0;
-	*b = ut->blocks[tslot];
+	ut->blocks[tslot].maxoff = len;
+
+	ut->slot++;
+	if(ut->slot >= DWinBlocks)
+		ut->slot = 0;
+
+	ut->blocks[ut->slot].seq = ~0UL;
+	ut->blocks[ut->slot].maxoff = 0;
+
+	return tslot;
+}
+
+int
+unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
+{
+	UnthwBlock blocks[CompBlocks], *b, *eblocks;
+	uchar *s, *d, *dmax, *smax, lit;
+	ulong cmask, cseq, bseq, utbits;
+	int i, off, len, bits, slot, use, code, utnbits, overbits, lithist;
+
+	if(nsrc < 4 || nsrc > ThwMaxBlock)
+		return -1;
+
+	slot = ut->slot;
+	b = blocks;
+	*b = ut->blocks[slot];
 	d = b->data;
 	dmax = d + ndst;
 
@@ -101,7 +148,6 @@ unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
 	cseq = seq - src[0];
 	cmask = src[1];
 	b++;
-	slot = tslot;
 	while(cseq != seq && b < blocks + CompBlocks){
 		slot--;
 		if(slot < 0)
@@ -125,8 +171,8 @@ unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
 	}
 	eblocks = b;
 	if(cseq != seq){
-		print("blocks not in decompression window: cseq=%ld seq=%ld cmask=%lx nb=%ld\n", cseq, seq, cmask, eblocks - blocks);
-		return -1;
+		print("blocks dropped: seq=%ld cseq=%ld %d cmask=%#lx %#x\n", seq, cseq, src[0], cmask, src[1]);
+		return -2;
 	}
 
 	smax = src + nsrc;
@@ -168,6 +214,8 @@ unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
 					lit = (lit - 64) & 0xff;
 				}
 			}
+			if(d >= dmax)
+				return -1;
 			*d++ = lit;
 			lithist = (lithist << 1) | (lit < 32) | (lit > 127);
 			blocks->maxoff++;
@@ -242,11 +290,8 @@ unthwack(Unthwack *ut, uchar *dst, int ndst, uchar *src, int nsrc, ulong seq)
 
 	len = d - blocks->data;
 	memmove(dst, blocks->data, len);
-	ut->blocks[tslot].maxoff = len;
 
-	ut->slot++;
-	if(ut->slot >= DWinBlocks)
-		ut->slot = 0;
+	unthwackinsert(ut, len, seq);
 
 	return len;
 }