20060303a

1 files changed, 45 insertions, 0 deletions

diff --git a/appl/lib/crc.b b/appl/lib/crc.b
new file mode 100644
index 00000000..d25eeec2
--- /dev/null
+++ b/appl/lib/crc.b
@@ -0,0 +1,45 @@
+implement Crc;
+
+include "crc.m";
+
+init(poly : int, reg : int) : ref CRCstate
+{
+	if (poly == 0)
+		poly = int 16redb88320;
+	tab := 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;
+		}
+		tab[i] = crc;
+	}
+	crcs := ref CRCstate;
+	crcs.crc = 0;
+	crcs.crctab = tab;
+	crcs.reg = reg;
+	return crcs;
+}
+
+crc(crcs : ref CRCstate, buf : array of byte, nb : int) : int
+{
+	n := nb;
+	if (n > len buf)
+		n = len buf;
+	crc := crcs.crc;
+	tab := crcs.crctab;
+	crc ^= crcs.reg;
+	for (i := 0; i < n; i++)
+		crc = tab[int(byte crc ^ buf[i])] ^ ((crc >> 8) & 16r00ffffff);
+	crc ^= crcs.reg;
+	crcs.crc = crc;
+	return crc;
+}
+
+reset(crcs : ref CRCstate)
+{
+	crcs.crc = 0;
+}