[nixio] implement dow_crc8 in C

mote/v2/openwrt/package/flukso/luasrc/flukso/spi.lua

@@ -31,27 +31,6 @@ local getfenv, setmetatable, tonumber =
 module (...)
 local modenv = getfenv()
 
--- private
-local function dow_crc(sequence, crc)
-	crc = crc or 0x00
-
-	local r1 = { 0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83,
-                     0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41 }
-
-	local r2 = { 0x00, 0x9d, 0x23, 0xbe, 0x46, 0xdb, 0x65, 0xf8,
-                     0x8c, 0x11, 0xaf, 0x32, 0xca, 0x57, 0xe9, 0x74 }
-
-	local first_char = sequence:sub(1, 1)
-
-	if first_char ~= '' then
-		local i = nixio.bit.band(nixio.bit.bxor(first_char:byte(), crc), 0xff)
-		crc = nixio.bit.bxor(r1[nixio.bit.band(i, 0xf) + 1], r2[nixio.bit.rshift(i, 4) + 1])
-		return dow_crc(sequence:sub(2, -1), crc)
-	else
-		return nixio.bin.hexlify(string.char(crc))
-	end
-end
-
 --- Create a new spi message object.
 --
 -- Attributes:
@@ -153,7 +132,7 @@ function rx(msg, cdev)
 		msg.received.crc = msg.received.l:sub(-2, -1)
 		msg.received.l   = msg.received.l:sub(1, -3)
 
-		if dow_crc(msg.received.l) ~= msg.received.crc then
+		if nixio.bin.dow_crc(msg.received.l) ~= tonumber(BinDecHex.Hex2Dec(msg.received.crc)) then
 			--> TODO implement crc error counter
 			msg.received.l = ''
 		end

mote/v2/openwrt/package/luci/libs/nixio/src/binary.c

@@ -94,6 +94,41 @@ static const uint32_t nixio__crc32_tbl[] = {
 	0x2d02ef8dU
 };
 
+static const uint8_t nixio__dow_crc_tbl[] = {
+	0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83, 
+	0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41, 
+	0x9d, 0xc3, 0x21, 0x7f, 0xfc, 0xa2, 0x40, 0x1e, 
+	0x5f, 0x01, 0xe3, 0xbd, 0x3e, 0x60, 0x82, 0xdc, 
+	0x23, 0x7d, 0x9f, 0xc1, 0x42, 0x1c, 0xfe, 0xa0, 
+	0xe1, 0xbf, 0x5d, 0x03, 0x80, 0xde, 0x3c, 0x62, 
+	0xbe, 0xe0, 0x02, 0x5c, 0xdf, 0x81, 0x63, 0x3d, 
+	0x7c, 0x22, 0xc0, 0x9e, 0x1d, 0x43, 0xa1, 0xff, 
+	0x46, 0x18, 0xfa, 0xa4, 0x27, 0x79, 0x9b, 0xc5, 
+	0x84, 0xda, 0x38, 0x66, 0xe5, 0xbb, 0x59, 0x07, 
+	0xdb, 0x85, 0x67, 0x39, 0xba, 0xe4, 0x06, 0x58, 
+	0x19, 0x47, 0xa5, 0xfb, 0x78, 0x26, 0xc4, 0x9a, 
+	0x65, 0x3b, 0xd9, 0x87, 0x04, 0x5a, 0xb8, 0xe6, 
+	0xa7, 0xf9, 0x1b, 0x45, 0xc6, 0x98, 0x7a, 0x24, 
+	0xf8, 0xa6, 0x44, 0x1a, 0x99, 0xc7, 0x25, 0x7b, 
+	0x3a, 0x64, 0x86, 0xd8, 0x5b, 0x05, 0xe7, 0xb9, 
+	0x8c, 0xd2, 0x30, 0x6e, 0xed, 0xb3, 0x51, 0x0f, 
+	0x4e, 0x10, 0xf2, 0xac, 0x2f, 0x71, 0x93, 0xcd, 
+	0x11, 0x4f, 0xad, 0xf3, 0x70, 0x2e, 0xcc, 0x92, 
+	0xd3, 0x8d, 0x6f, 0x31, 0xb2, 0xec, 0x0e, 0x50, 
+	0xaf, 0xf1, 0x13, 0x4d, 0xce, 0x90, 0x72, 0x2c, 
+	0x6d, 0x33, 0xd1, 0x8f, 0x0c, 0x52, 0xb0, 0xee, 
+	0x32, 0x6c, 0x8e, 0xd0, 0x53, 0x0d, 0xef, 0xb1, 
+	0xf0, 0xae, 0x4c, 0x12, 0x91, 0xcf, 0x2d, 0x73, 
+	0xca, 0x94, 0x76, 0x28, 0xab, 0xf5, 0x17, 0x49, 
+	0x08, 0x56, 0xb4, 0xea, 0x69, 0x37, 0xd5, 0x8b, 
+	0x57, 0x09, 0xeb, 0xb5, 0x36, 0x68, 0x8a, 0xd4, 
+	0x95, 0xcb, 0x29, 0x77, 0xf4, 0xaa, 0x48, 0x16, 
+	0xe9, 0xb7, 0x55, 0x0b, 0x88, 0xd6, 0x34, 0x6a, 
+	0x2b, 0x75, 0x97, 0xc9, 0x4a, 0x14, 0xf6, 0xa8, 
+	0x74, 0x2a, 0xc8, 0x96, 0x15, 0x4b, 0xa9, 0xf7, 
+	0xb6, 0xe8, 0x0a, 0x54, 0xd7, 0x89, 0x6b, 0x35, 
+};
+
 static int nixio_bin_crc32(lua_State *L) {
 	size_t len;
 	const char *buffer = luaL_checklstring(L, 1, &len);
@@ -108,6 +143,19 @@ static int nixio_bin_crc32(lua_State *L) {
 	return 1;
 }
 
+static int nixio_bin_dow_crc(lua_State *L) {
+	size_t len;
+	const char *buffer = luaL_checklstring(L, 1, &len);
+	uint8_t value = (uint8_t)luaL_optinteger(L, 2, 0);
+
+	for (size_t i=0; i<len; i++) {
+		value = nixio__dow_crc_tbl[(value ^ buffer[i]) & 0xff];
+	}
+
+	lua_pushinteger(L, (int)value);
+	return 1;
+}
+
 static int nixio_bin_hexlify(lua_State *L) {
 	size_t len, lenout;
 	luaL_checktype(L, 1, LUA_TSTRING);
@@ -300,6 +348,7 @@ static const luaL_reg R[] = {
 	{"hexlify",		nixio_bin_hexlify},
 	{"unhexlify",		nixio_bin_unhexlify},
 	{"crc32",		nixio_bin_crc32},
+	{"dow_crc",		nixio_bin_dow_crc},
 	{"b64encode",		nixio_bin_b64encode},
 	{"b64decode",		nixio_bin_b64decode},
 	{NULL,			NULL}