add decode functions for info and data packets

internal/decoders/chunk.go

@@ -0,0 +1,43 @@
+package decoders
+
+import (
+	"encoding/binary"
+)
+
+type ChunkHeader struct {
+	Id           uint16
+	DataLen      uint16
+	HasSubchunks bool
+}
+
+type Chunk struct {
+	Header    ChunkHeader
+	ChunkData []byte
+}
+
+func DecodeChunk(bytes []byte) Chunk {
+	id := binary.LittleEndian.Uint16(bytes[0:2])
+	lengthAndFlag := binary.LittleEndian.Uint16(bytes[2:4])
+
+	data_len := lengthAndFlag
+
+	has_subchunks := lengthAndFlag > 32768
+
+	if has_subchunks {
+		data_len = data_len - 32768
+	}
+
+	header := ChunkHeader{
+		Id:           id,
+		DataLen:      data_len,
+		HasSubchunks: has_subchunks,
+	}
+
+	chunk_data := bytes[4 : 4+header.DataLen]
+
+	return Chunk{
+		Header:    header,
+		ChunkData: chunk_data,
+	}
+
+}