From 74a4d8c26dd3c1e9febcb717cfd6cb6512991a7a Mon Sep 17 00:00:00 2001
From: "Charles.Forsyth" <devnull@localhost>
Date: Fri, 22 Dec 2006 21:39:35 +0000
Subject: 20060303

---
 os/ip/ptclbsum.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 os/ip/ptclbsum.c

(limited to 'os/ip/ptclbsum.c')

diff --git a/os/ip/ptclbsum.c b/os/ip/ptclbsum.c
new file mode 100644
index 00000000..4b895ecf
--- /dev/null
+++ b/os/ip/ptclbsum.c
@@ -0,0 +1,72 @@
+#include	"u.h"
+#include	"../port/lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"../port/error.h"
+#include	"ip.h"
+
+static	short	endian	= 1;
+static	uchar*	aendian	= (uchar*)&endian;
+#define	LITTLE	*aendian
+
+ushort
+ptclbsum(uchar *addr, int len)
+{
+	ulong losum, hisum, mdsum, x;
+	ulong t1, t2;
+
+	losum = 0;
+	hisum = 0;
+	mdsum = 0;
+
+	x = 0;
+	if((ulong)addr & 1) {
+		if(len) {
+			hisum += addr[0];
+			len--;
+			addr++;
+		}
+		x = 1;
+	}
+	while(len >= 16) {
+		t1 = *(ushort*)(addr+0);
+		t2 = *(ushort*)(addr+2);	mdsum += t1;
+		t1 = *(ushort*)(addr+4);	mdsum += t2;
+		t2 = *(ushort*)(addr+6);	mdsum += t1;
+		t1 = *(ushort*)(addr+8);	mdsum += t2;
+		t2 = *(ushort*)(addr+10);	mdsum += t1;
+		t1 = *(ushort*)(addr+12);	mdsum += t2;
+		t2 = *(ushort*)(addr+14);	mdsum += t1;
+		mdsum += t2;
+		len -= 16;
+		addr += 16;
+	}
+	while(len >= 2) {
+		mdsum += *(ushort*)addr;
+		len -= 2;
+		addr += 2;
+	}
+	if(x) {
+		if(len)
+			losum += addr[0];
+		if(LITTLE)
+			losum += mdsum;
+		else
+			hisum += mdsum;
+	} else {
+		if(len)
+			hisum += addr[0];
+		if(LITTLE)
+			hisum += mdsum;
+		else
+			losum += mdsum;
+	}
+
+	losum += hisum >> 8;
+	losum += (hisum & 0xff) << 8;
+	while(hisum = losum>>16)
+		losum = hisum + (losum & 0xffff);
+
+	return losum & 0xffff;
+}
-- 
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