add block stream abstraction

dagger/chunkedblockstream.nim

@@ -0,0 +1,28 @@
+## Nim-Dagger
+## Copyright (c) 2021 Status Research & Development GmbH
+## Licensed under either of
+##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+## at your option.
+## This file may not be copied, modified, or distributed except according to
+## those terms.
+
+{.push raises: [Defect].}
+
+import pkg/questionable
+import pkg/questionable/results
+
+import ./blockstream
+import ./chunker
+
+type
+  ChunkedBlockStreamRef* = ref object of BlockStreamRef
+    chunker*: Chunker
+
+method nextBlock*(c: ChunkedBlockStreamRef): ?!Block =
+  let data: seq[byte] = c.chunker.getBytes()
+  if data.len > 0:
+    return success Block.new(data)
+
+proc new*(T: type ChunkedBlockStreamRef, chunker: Chunker): T =
+  T(chunker: chunker)