feat(framing): framing done

refactor(framing): re-name hamming codec to 7,4 to reflect algorithm used

framing.py

@@ -0,0 +1,46 @@
+from header import Onbeat_Header, PROTOCOL_IDENTIFIER
+from reedsolo import RSCodec
+import numpy as np
+
+PROTOCOL_V1_NOFEC = 1
+PROTOCOL_V1_FEC = 2
+RSC = RSCodec(255-223,255)
+
+def decode_packet(packet: list[int]) -> tuple[Onbeat_Header, list[int]]:
+    if len(packet) < 32:
+        raise OverflowError(f"Packet is too small to be valid, len: {len(packet)}")
+    header_raw = packet[0:32]
+    header = Onbeat_Header(0, 0, "", 0, 0)
+    if header.decode(header_raw) != True:
+        raise RuntimeError("invalid CRC")
+    if header.protocol_id != PROTOCOL_IDENTIFIER:
+        raise ValueError(f"Protocol ID mismatch, got{header.protocol_id}, expected {PROTOCOL_IDENTIFIER}")
+    if header.pkt_len > len(packet) - 32:
+        raise OverflowError(f"Header not fully captured, len:{header.pkt_len}, maximal: {len(packet) - 32}")
+    elif header.pkt_len == 0:
+        return header, []
+    payload = packet[32:32+header.pkt_len]
+    if header.protocol_configuration == PROTOCOL_V1_FEC:
+        payload_decoded = np.empty((4, min(len(payload)//4-32, 255)), dtype=int)
+        for i in range(0,4):
+            payload_decoded[i] = RSC.decode(bytearray(payload[i::4]))[0]
+        payload = payload_decoded.flatten(order='F').tolist()
+    elif header.protocol_configuration == PROTOCOL_V1_NOFEC:
+        pass
+    else:
+        raise ValueError(f"Unknown protocol configuration: {header.protocol_configuration}")
+    return header, payload
+
+def encode_packet(payload: list[int], callsign: str, sequence: int, rs_coding: bool = False) -> list[int]:
+    protocol_configuration = PROTOCOL_V1_NOFEC
+    if rs_coding == True:
+        protocol_configuration = PROTOCOL_V1_FEC
+        if len(payload) != 0:
+            for _ in range(0, len(payload)%4):
+                payload.append(0)
+            payload_encoded = np.empty((4, min((len(payload))//4+32, 255)), dtype=int)
+            for i in range(0,4):
+                payload_encoded[i] = RSC.encode(bytearray(payload[i::4]))
+            payload = payload_encoded.flatten(order='F').tolist()
+    header = Onbeat_Header(0, protocol_configuration, callsign, len(payload), sequence)
+    return header.encode() + payload