+/* Functions and types for CRC checks.
+ *
+ * Generated on Wed Sep 21 22:30:11 2011,
+ * by pycrc v0.7.8, http://www.tty1.net/pycrc/
+ * using the configuration:
+ * Width = 15
+ * Poly = 0x4599
+ * XorIn = 0x0000
+ * ReflectIn = False
+ * XorOut = 0x0000
+ * ReflectOut = False
+ * Algorithm = table-driven
+ *****************************************************************************/
+typedef uint16_t crc_t;
+
+static const crc_t crc_table[2] = {
+ 0x0000, 0x4599
+};
+
+crc_t crc_update(crc_t crc, uint32_t data, size_t bit_len)
+{
+ unsigned int tbl_idx;
+/* crc_t bc = crc; */
+/* uint32_t bd = data; */
+/* size_t bl = bit_len; */
+
+ while (bit_len--) {
+ tbl_idx = (crc >> 14) ^ (data >> 31);
+ crc = crc_table[tbl_idx & 0x01] ^ (crc << 1);
+ data <<= 1;
+ }
+ crc = crc & 0x7fff;
+/* printf("crc: 0x%04x -> 0x%04x data: 0x%08x len: %d\n", */
+/* bc, crc, bd, bl); */
+ return crc;
+}
+
+uint32_t calc_bitmap_crc(uint32_t *bitmap, unsigned start, unsigned end)
+{
+ crc_t crc = 0;
+ crc = crc_update(crc, bitmap[0] << start, 32 - start);
+ crc = crc_update(crc, bitmap[1], 32);
+ crc = crc_update(crc, bitmap[2], end - 64 > 32 ? 32 : end - 64); /* FIXME: This seems to be broken for end < 64 */
+ crc = crc_update(crc, bitmap[3], end > 96 ? end - 96 : 0);
+ return crc << 17;
+}
+
+unsigned calc_stuff_bits(struct can_frame *frame) {
+ uint32_t bitmap[4];
+ unsigned start = 0, end;
+ uint32_t mask, ones = 0, basemask = 0xf8000000;
+ unsigned stuffed = 0;
+ memset(bitmap, 0, sizeof(bitmap));
+ uint32_t crc;
+
+/* char received[64]; */
+/* sprint_canframe(received, frame, true); */
+/* printf("Frame: %s\n", received); */
+
+ if (frame->can_id & CAN_EFF_FLAG) {
+ // bit 31 0
+ // [0] |...........................sBBBB| s = SOF, B = Base ID (11 bits)
+ // [1] |BBBBBBBSIEEEEEEEEEEEEEEEEEER10DLC4| S = SRR, I = IDE, E = Extended ID (18 bits), DLC4 = DLC
+ // [2] |00000000111111112222222233333333| Data bytes, MSB first
+ // [3] |44444444555555556666666677777777|
+ bitmap[0] =
+ ((frame->can_id & CAN_EFF_MASK) >> 25);
+ bitmap[1] =
+ ((frame->can_id & CAN_EFF_MASK) >> 18) << 25 |
+ 3 << 23 |
+ ((frame->can_id & CAN_EFF_MASK) & 0x3ffff) << 7 |
+ (!!(frame->can_id & CAN_RTR_FLAG)) << 6 |
+ 0 << 4 |
+ frame->can_dlc & 0xf;
+ memcpy(&bitmap[2], &frame->data, frame->can_dlc);
+ start = 27;
+ end = 64 + 8*frame->can_dlc;
+ } else {
+ // bit 31 0
+ // [0] |.............sIIIIIIIIIIIRE0DLC4| s = SOF, I = ID (11 bits), R = RTR, E = IDE, DLC4 = DLC
+ // [1] |00000000111111112222222233333333| Data bytes, MSB first
+ // [2] |44444444555555556666666677777777|
+ bitmap[0] =
+ (frame->can_id << 7) |
+ (!!(frame->can_id & CAN_RTR_FLAG)) << 6 |
+ 0 << 4 |
+ frame->can_dlc & 0xf;
+ memcpy(&bitmap[1], &frame->data, frame->can_dlc);
+ start = 13;
+ end = 32 + 8*frame->can_dlc;
+ }
+ crc = calc_bitmap_crc(bitmap, start, end);
+ uint32_t crc_be = htons(crc << 17);
+ memcpy((char*)bitmap + end/8, &crc_be, 2); /* end is guaranteed to be divisible by 8 */
+ end += 15;
+
+ while (start < end) {
+ mask = basemask >> (start & 0x1f);
+ while (1) {
+ ones = ones ? mask : 0;
+ uint32_t chunk = (bitmap[start >> 5] & mask) ^ ones;
+ //printf("start=%d bitmap=0x%08x mask=0x%08x ones=0x%08x chunk=0x%08x\n", start, bitmap[start >> 5], mask, ones, chunk);
+ if (chunk) {
+ unsigned change = __builtin_clz(chunk);
+ start = start & ~0x1f | change;
+ basemask = 0xf8000000;
+ } else {
+ unsigned oldstart = start;
+ start += __builtin_popcount(mask);
+ mask = (oldstart & 0x1f) ? basemask << (-oldstart & 0x1f) : 0;
+ //printf("oldstart=%d shl=%d mask=0x%08x\n", oldstart, -oldstart & 0x1f, mask);
+ if (mask && start < end)
+ continue;
+ if (start <= end && !mask) {
+ stuffed++;
+ basemask = 0xf0000000;
+ //printf("stuffed %d\n", !ones);
+ }
+ }
+ break;
+ }
+ ones = !ones;
+ }
+ //printf ("STUFFED %d BITS\n", stuffed);
+ return stuffed;
+}
+
+unsigned calc_frame_txtime_us(struct can_frame *frame) {
+ return calc_stuff_bits(frame) +
+ 1 + /* SOF */
+ 11 + /* ID A */
+ ((frame->can_id & CAN_EFF_FLAG) ?
+ 1 + /* SRR */
+ 1 + /* IDE */
+ 18 + /* ID B */
+ 1 + /* RTR */
+ 2 /* r1, r0 */
+ :
+ 1 + /* rtr */
+ 2) + /* ide, r0 */
+ 4 + /* dlc */
+ 8*frame->can_dlc +
+ 15 + /* CRC */
+ 3 + /* CRC del, ACK, ACK del */
+ 7; /* EOF */
+}
+