Refactor kafka to pure Go (franz-go), fix DBC stubs, update Dockerfile

pkg/can-go/internal/reinterpret/reinterpret.go

@@ -0,0 +1,50 @@
+// Package reinterpret provides primitives for reinterpreting arbitrary-length values as signed or unsigned.
+package reinterpret
+
+// AsSigned reinterprets the provided unsigned value as a signed value.
+func AsSigned(unsigned uint64, bits uint8) int64 {
+	switch bits {
+	case 8:
+		return int64(int8(uint8(unsigned)))
+	case 16:
+		return int64(int16(uint16(unsigned)))
+	case 32:
+		return int64(int32(uint32(unsigned)))
+	case 64:
+		return int64(unsigned)
+	default:
+		// calculate bit mask for sign bit
+		signBitMask := uint64(1 << (bits - 1))
+		// check if sign bit is set
+		isNegative := unsigned&signBitMask > 0
+		if !isNegative {
+			// sign bit not set means we can reinterpret the value as-is
+			return int64(unsigned)
+		}
+		// calculate bit mask for extracting value bits (all bits except the sign bit)
+		valueBitMask := signBitMask - 1
+		// calculate two's complement of the value bits
+		value := ((^unsigned) & valueBitMask) + 1
+		// result is the negative value of the two's complement
+		return -1 * int64(value)
+	}
+}
+
+// AsUnsigned reinterprets the provided signed value as an unsigned value.
+func AsUnsigned(signed int64, bits uint8) uint64 {
+	switch bits {
+	case 8:
+		return uint64(uint8(int8(signed)))
+	case 16:
+		return uint64(uint16(int16(signed)))
+	case 32:
+		return uint64(uint32(int32(signed)))
+	case 64:
+		return uint64(signed)
+	default:
+		// calculate bit mask for extracting relevant bits
+		valueBitMask := uint64(1<<bits) - 1
+		// extract relevant bits
+		return uint64(signed) & valueBitMask
+	}
+}