initial definition of a MemRange type

LICENSE

@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright [yyyy] [name of copyright owner]
+   Copyright 2018 Status Research & Development GmbH
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

ranges.nim

@@ -0,0 +1,6 @@
+import
+  ranges/memranges
+
+export
+  memranges
+

ranges.nimble

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+mode = ScriptMode.Verbose
+
+packageName   = "ranges"
+version       = "0.0.1"
+author        = "Status Research & Development GmbH"
+description   = "Exploration of various implementations of memory range types"
+license       = "Apache2"
+skipDirs      = @["tests"]
+
+requires "nim >= 0.17.0"
+
+proc configForTests() =
+  --hints: off
+  --debuginfo
+  --path: "."
+  --run
+
+task test, "run CPU tests":
+  configForTests()
+  setCommand "c", "tests/all.nim"
+

ranges/memranges.nim

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+import
+  ptr_arith
+
+type
+  MemRange* = object
+    start: pointer
+    size: csize
+
+template len*(mr: MemRange): int = mr.size
+template `[]`*(mr: MemRange, idx: int): byte = (cast[ptr byte](shift(mr.start, idx)))[]
+proc baseAddr*(mr: MemRange): pointer = mr.start
+
+when false:
+  # XXX: Alternative definition that crashes the compiler. Investigate
+  type
+    MemRange* = distinct (pointer, csize)
+
+  template len*(mr: MemRange): int = mr[1]
+  template `[]`*(mr: MemRange, idx: int): byte = (cast[ptr byte](shift(mr[0], idx)))[]
+  proc baseAddr*(mr: MemRange): pointer = mr[0]
+
+proc makeMemRange*(start: pointer, size: csize): MemRange =
+  result.start = start
+  result.size = size
+