+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));
+ crc_t crc = 0;
+ uint32_t crcx;
+
+/* char received[64]; */
+/* sprint_canframe(received, frame, true); */
+/* printf("Frame: %s\n", received); */
+
+ if (frame->can_id & CAN_EFF_FLAG) {
+ 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;
+ bitmap[2] = htonl(((uint32_t*)frame->data)[0]);
+ bitmap[3] = htonl(((uint32_t*)frame->data)[1]);
+ start = 27;
+ end = 64 + 8*frame->can_dlc;
+ 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);
+ crc = crc_update(crc, bitmap[3], end > 96 ? end - 96 : 0);
+ crcx = (uint32_t)htons(crc) << 17;
+ if (frame->can_dlc < 4)
+ bitmap[2] |= crcx >> (frame->can_dlc*8);
+ if (frame->can_dlc = 3)
+ bitmap[3] |= crcx << 8;
+ if (frame->can_dlc >= 4)
+ bitmap[3] |= crcx >> (frame->can_dlc*8);
+ } else {
+ bitmap[0] =
+ (frame->can_id << 7) |
+ (!!(frame->can_id & CAN_RTR_FLAG)) << 6 |
+ 0 << 4 |
+ frame->can_dlc & 0xf;
+ bitmap[1] = htonl(((uint32_t*)frame->data)[0]);
+ bitmap[2] = htonl(((uint32_t*)frame->data)[1]);
+ start = 13;
+ end = 32 + 8*frame->can_dlc;
+ }
+ /* TODO: Calc stuff bits in CRC */
+ 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;
+}