generalise python wave writer

common/riffwriter.py

@@ -0,0 +1,37 @@
+from abc import ABC, abstractmethod
+from typing import BinaryIO, List
+
+
+class AbstractRiffChunk(ABC):
+	@abstractmethod
+	def fourcc(self) -> bytes: raise NotImplementedError
+
+	@abstractmethod
+	def size(self) -> int: raise NotImplementedError
+
+	@abstractmethod
+	def write(self, f: BinaryIO): raise NotImplementedError
+
+
+class RiffFile(AbstractRiffChunk):
+	def fourcc(self) -> bytes: return b"RIFF"
+
+	def size(self) -> int: return 4 + sum(8 + c.size() for c in self._chunks)
+
+	def __init__(self, type: bytes, chunks: List[AbstractRiffChunk]):
+		self._chunks = chunks
+		if len(type) != 4: raise ValueError
+		self._type = type
+
+	def write(self, f: BinaryIO):
+		f.writelines([
+			self.fourcc(),
+			self.size().to_bytes(4, "little", signed=False),
+			self._type])
+		for chunk in self._chunks:
+			size = chunk.size()
+			if size & 0x3: raise AssertionError("Unaligned chunks will produce malformed riff files")
+			f.writelines([
+				chunk.fourcc(),
+				size.to_bytes(4, "little", signed=False)])
+			chunk.write(f)