From 04b0bc6d90ee30fd60585dffe6862e2723dd5662 Mon Sep 17 00:00:00 2001
From: charles <charles>
Date: Tue, 20 May 2003 22:59:15 +0000
Subject: [PATCH] *** empty log message ***

---
 utils/gen-ecc.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 utils/gen-ecc.c

diff --git a/utils/gen-ecc.c b/utils/gen-ecc.c
new file mode 100644
index 0000000..ee9b9be
--- /dev/null
+++ b/utils/gen-ecc.c
@@ -0,0 +1,68 @@
+// Program to generate a  column parity table for yaffs_ecc.c
+
+
+
+// Generate a column parity byte for a byte.
+// This byte is already aligned for the ecc.
+// The output byte has the form:
+// bit 7: p4
+// bit 6: p4'
+// bit 5: p2
+// bit 4: p2'
+// bit 3: p1
+// bit 2: p1'
+// bit 1: unused.
+// bit 0 of the output byte holds the line parity.
+unsigned char entry(unsigned char x)
+{
+	unsigned char b0, b1, b2, b3, b4, b5, b6, b7;
+	unsigned char p4, p2, p1, p4p, p2p, p1p;
+	unsigned char linep;
+	unsigned char result;
+	
+	b0 = (x & 0x01) ? 1 : 0;
+	b1 = (x & 0x02) ? 1 : 0;
+	b2 = (x & 0x04) ? 1 : 0;
+	b3 = (x & 0x08) ? 1 : 0;
+	b4 = (x & 0x10) ? 1 : 0;
+	b5 = (x & 0x20) ? 1 : 0;
+	b6 = (x & 0x40) ? 1 : 0;
+	b7 = (x & 0x80) ? 1 : 0;
+	
+	p4 = b7 ^ b6 ^ b5 ^ b4;     p4p = b3 ^ b2 ^ b1 ^ b0;
+	p2 = b7 ^ b6 ^ b3 ^ b2;     p2p = b5 ^ b4 ^ b1 ^ b0;
+	p1 = b7 ^ b5 ^ b3 ^ b1;     p1p = b6 ^ b4 ^ b2 ^ b0;
+	
+	linep = p1 ^ p1p;
+	
+	result = 0;
+	if(p4)    result |= 0x80;
+	if(p4p)   result |= 0x40;
+	if(p2)    result |= 0x20;
+	if(p2p)   result |= 0x10;
+	if(p1)    result |= 0x08;
+	if(p1p)   result |= 0x04;
+	if(linep) result |= 0x01;
+	
+	//result >>= 2;
+	//if(linep) result |= 0x40;
+	
+	return result;
+	
+}
+
+
+int main(int argc, char *argv[])
+{
+	unsigned i;
+	
+	printf("const unsigned char column_parity_table[] = {");
+	for(i = 0; i < 256; i++)
+	{
+		if((i & 0xf) == 0) printf("\n");
+		printf("0x%02x, ",entry((unsigned char) i));
+	}
+	printf("\n};\n");
+}
+
+
-- 
2.30.2