2d encoder base

this is just a copy of the 1d RS encoder

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>

codex/erasure/backends/leopard2d.nim

@@ -0,0 +1,86 @@
+## Nim-Codex
+## Copyright (c) 2022 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.
+
+import std/options
+
+import pkg/leopard
+import pkg/stew/results
+
+import ../backend
+
+type
+  LeoEncoderBackend* = ref object of EncoderBackend
+    encoder*: Option[LeoEncoder]
+
+  LeoDecoderBackend* = ref object of DecoderBackend
+    decoder*: Option[LeoDecoder]
+
+method encode*(
+  self: LeoEncoderBackend,
+  data,
+  parity: var openArray[seq[byte]]): Result[void, cstring] =
+
+  if parity.len == 0:
+    return ok()
+
+  var encoder = if self.encoder.isNone:
+      self.encoder = (? LeoEncoder.init(
+        self.blockSize,
+        self.buffers,
+        self.parity)).some
+      self.encoder.get()
+    else:
+      self.encoder.get()
+
+  encoder.encode(data, parity)
+
+method decode*(
+  self: LeoDecoderBackend,
+  data,
+  parity,
+  recovered: var openArray[seq[byte]]): Result[void, cstring] =
+
+  var decoder = if self.decoder.isNone:
+      self.decoder = (? LeoDecoder.init(
+        self.blockSize,
+        self.buffers,
+        self.parity)).some
+      self.decoder.get()
+    else:
+      self.decoder.get()
+
+  decoder.decode(data, parity, recovered)
+
+method release*(self: LeoEncoderBackend) =
+  if self.encoder.isSome:
+    self.encoder.get().free()
+
+method release*(self: LeoDecoderBackend) =
+  if self.decoder.isSome:
+    self.decoder.get().free()
+
+func new*(
+  T: type LeoEncoderBackend,
+  blockSize,
+  buffers,
+  parity: int): T =
+  T(
+    blockSize: blockSize,
+    buffers: buffers,
+    parity: parity)
+
+func new*(
+  T: type LeoDecoderBackend,
+  blockSize,
+  buffers,
+  parity: int): T =
+  T(
+    blockSize: blockSize,
+    buffers: buffers,
+    parity: parity)