Livt.Net

src/ethernet/EthernetFrameBuilder.lvt

namespace Livt.Net

/**
 * Pure Ethernet II header encoding from explicit endpoint addresses.
 * It neither reads a request frame nor owns protocol state.
 */
class EthernetFrameBuilder
{
	/**
	 * Returns bytes 0..13: destination MAC, source MAC, then EtherType.
	 * etherType is 1536..65535. Out-of-header indices return zero.
	 */
	public static inline fn GetByte[](
		index: int, sourceMac: byte[6], destinationMac: byte[6], etherType: int) byte
	{
		if (index < 0) {
			return 0x00
		}

		if (index < 6) {
			return destinationMac[index]
		}

		if (index < 12) {
			return sourceMac[index - 6]
		}

		if (index == 12) {
			return NetworkOrder.HighByte(etherType)
		}

		if (index == 13) {
			return NetworkOrder.LowByte(etherType)
		}

		return 0x00
	}
}