Livt.Net

src/tftp/TftpUploadBuffer.lvt

namespace Livt.Net

using Livt.IO

/**
 * Owns one RAM containing disjoint filename and upload-data regions. Scheduled
 * access follows ITftpUploadBuffer; no initialization or payload reset is required.
 * STYLE selects default backing. B may replace it with any owned IRam providing
 * at least 576 bytes, including ArrayRam. One caller serializes reads and writes.
 */
component TftpUploadBuffer<STYLE: MemoryStyle = MemoryStyle.Block,
	B: IRam<byte> & new() = Ram<byte, 576, STYLE>> : ITftpUploadBuffer
{
	// Region geometry keeps filename bytes intact while data chunks are replaced.
	public const NAME_CAPACITY: int = 64
	public const DATA_CAPACITY: int = 512

	// Owned byte storage in the inherited clock/reset context.
	storage: B

	/**
	 * Creates storage; callers must stage every byte before reading a prefix.
	 */
	new()
	{
		storage = new B()
	}

	/**
	 * Stages one filename byte without touching the payload region.
	 */
	override fn SetNameByte(index: int, value: byte) bool
	{
		if (index < 0 || index >= NAME_CAPACITY) {
			return false
		}

		storage.Write(index, value)
		return true
	}

	/**
	 * Reads a staged filename byte, or zero for an invalid index.
	 */
	override fn GetNameByte(index: int) byte
	{
		if (index < 0 || index >= NAME_CAPACITY) {
			return 0
		}

		return storage.Read(index)
	}

	/**
	 * Stages one payload byte without touching the retained filename.
	 */
	override fn SetDataByte(index: int, value: byte) bool
	{
		if (index < 0 || index >= DATA_CAPACITY) {
			return false
		}

		storage.Write(NAME_CAPACITY + index, value)
		return true
	}

	/**
	 * Reads a staged payload byte, or zero for an invalid index.
	 */
	override fn GetDataByte(index: int) byte
	{
		if (index < 0 || index >= DATA_CAPACITY) {
			return 0
		}

		return storage.Read(NAME_CAPACITY + index)
	}
}