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comparing CRC with table driven CRC.

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This commit is contained in:
skarg
2007-06-29 21:39:24 +00:00
parent 250cc92e00
commit 0543daa828
1 changed files with 55 additions and 6 deletions
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bacnet-stack/ports/linux/rx_fsm.c
+55 -6
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@@ -53,7 +53,7 @@
/* local port data - shared with RS-485 */
volatile struct mstp_port_struct_t MSTP_Port;
void *milliseconds_task(void *pArg)
{
struct timespec timeOut,remains;
@@ -86,7 +86,56 @@ uint16_t dlmstp_put_receive(
return 0;
}
static uint8_t calculate_header_CRC(volatile struct mstp_port_struct_t *mstp_port)
static const uint8_t CRC_Table[256] =
{
0000, 0xfe, 0xff, 0x01, 0xfd, 0x03, 0x02, 0xfc,
0xf9, 0x07, 0x06, 0xf8, 0x04, 0xfa, 0xfb, 0x05,
0xf1, 0x0f, 0x0e, 0xf0, 0x0c, 0xf2, 0xf3, 0x0d,
0x08, 0xf6, 0xf7, 0x09, 0xf5, 0x0b, 0x0a, 0xf4,
0xe1, 0x1f, 0x1e, 0xe0, 0x1c, 0xe2, 0xe3, 0x1d,
0x18, 0xe6, 0xe7, 0x19, 0xe5, 0x1b, 0x1a, 0xe4,
0x10, 0xee, 0xef, 0x11, 0xed, 0x13, 0x12, 0xec,
0xe9, 0x17, 0x16, 0xe8, 0x14, 0xea, 0xeb, 0x15,
0xc1, 0x3f, 0x3e, 0xc0, 0x3c, 0xc2, 0xc3, 0x3d,
0x38, 0xc6, 0xc7, 0x39, 0xc5, 0x3b, 0x3a, 0xc4,
0x30, 0xce, 0xcf, 0x31, 0xcd, 0x33, 0x32, 0xcc,
0xc9, 0x37, 0x36, 0xc8, 0x34, 0xca, 0xcb, 0x35,
0x20, 0xde, 0xdf, 0x21, 0xdd, 0x23, 0x22, 0xdc,
0xd9, 0x27, 0x26, 0xd8, 0x24, 0xda, 0xdb, 0x25,
0xd1, 0x2f, 0x2e, 0xd0, 0x2c, 0xd2, 0xd3, 0x2d,
0x28, 0xd6, 0xd7, 0x29, 0xd5, 0x2b, 0x2a, 0xd4,
0x81, 0x7f, 0x7e, 0x80, 0x7c, 0x82, 0x83, 0x7d,
0x78, 0x86, 0x87, 0x79, 0x85, 0x7b, 0x7a, 0x84,
0x70, 0x8e, 0x8f, 0x71, 0x8d, 0x73, 0x72, 0x8c,
0x89, 0x77, 0x76, 0x88, 0x74, 0x8a, 0x8b, 0x75,
0x60, 0x9e, 0x9f, 0x61, 0x9d, 0x63, 0x62, 0x9c,
0x99, 0x67, 0x66, 0x98, 0x64, 0x9a, 0x9b, 0x65,
0x91, 0x6f, 0x6e, 0x90, 0x6c, 0x92, 0x93, 0x6d,
0x68, 0x96, 0x97, 0x69, 0x95, 0x6b, 0x6a, 0x94,
0x40, 0xbe, 0xbf, 0x41, 0xbd, 0x43, 0x42, 0xbc,
0xb9, 0x47, 0x46, 0xb8, 0x44, 0xba, 0xbb, 0x45,
0xb1, 0x4f, 0x4e, 0xb0, 0x4c, 0xb2, 0xb3, 0x4d,
0x48, 0xb6, 0xb7, 0x49, 0xb5, 0x4b, 0x4a, 0xb4,
0xa1, 0x5f, 0x5e, 0xa0, 0x5c, 0xa2, 0xa3, 0x5d,
0x58, 0xa6, 0xa7, 0x59, 0xa5, 0x5b, 0x5a, 0xa4,
0x50, 0xae, 0xaf, 0x51, 0xad, 0x53, 0x52, 0xac,
0xa9, 0x57, 0x56, 0xa8, 0x54, 0xaa, 0xab, 0x55
};
static uint8_t calculate_header_CRC_table(
volatile struct mstp_port_struct_t *mstp_port)
{
uint8_t crc8 = 0xFF; /* used to calculate the crc value */
crc8 = CRC_Table[mstp_port->FrameType ^ crc8];
crc8 = CRC_Table[mstp_port->DestinationAddress ^ crc8];
crc8 = CRC_Table[mstp_port->SourceAddress ^ crc8];
crc8 = CRC_Table[HI_BYTE(mstp_port->DataLength) ^ crc8];
crc8 = CRC_Table[LO_BYTE(mstp_port->DataLength) ^ crc8];
}
static uint8_t calculate_header_CRC(
volatile struct mstp_port_struct_t *mstp_port)
{
uint8_t crc8 = 0xFF; /* used to calculate the crc value */
@@ -116,7 +165,6 @@ static void print_received_packet(
/* Data CRC: (present only if Length is non-zero) two octets, */
/* least significant octet first */
/* (pad): (optional) at most one octet of padding: X'FF' */
crc8 = calculate_header_CRC(mstp_port);
fprintf(stderr,
"55 FF %02X %02X %02X %02X %02X %02X ",
mstp_port->FrameType,
@@ -126,9 +174,10 @@ static void print_received_packet(
LO_BYTE(mstp_port->DataLength),
mstp_port->HeaderCRCActual);
if (print_crc_flag) {
fprintf(stderr,
"[%02X] ",
crc8);
crc8 = calculate_header_CRC(mstp_port);
fprintf(stderr, "[%02X] ", crc8);
crc8 = calculate_header_CRC_table(mstp_port);
fprintf(stderr, "[%02X] ", crc8);
}
if (mstp_port->DataLength) {
for (i = 0; i < mstp_port->DataLength; i++) {