Add shift operators (WIP recursive implementation is slow)

src/private/utils.nim

@@ -1,7 +1,9 @@
 # Copyright (c) 2018 Status Research & Development GmbH
 # Distributed under the MIT License (license terms are at http://opensource.org/licenses/MIT).
 
-import ../uint_type
+import  ../uint_type,
+        macros
+
 
 proc bit_length*[T: BaseUint](n: T): int {.noSideEffect.}=
   ## Calculates how many bits are necessary to represent the number
@@ -51,3 +53,8 @@ proc asDoubleUint*[T: BaseUint](n: T): auto {.noSideEffect, inline.} =
   )
 
   n.asUint.Double
+
+macro getSubType*(T: typedesc): untyped =
+  ## Returns the subtype of a generic type
+  ## MpUint[uint32] --> uint32
+  getTypeInst(T)[1][1]

src/uint_bitwise_ops.nim

@@ -1,7 +1,8 @@
 # Copyright (c) 2018 Status Research & Development GmbH
 # Distributed under the MIT License (license terms are at http://opensource.org/licenses/MIT).
 
-import  uint_type
+import  ./private/utils,
+        uint_type
 
 
 proc `not`*(x: MpUint): MpUint {.noInit, noSideEffect, inline.}=
@@ -23,3 +24,50 @@ proc `xor`*(x, y: MpUint): MpUint {.noInit, noSideEffect, inline.}=
   ## `Bitwise xor` of numbers x and y
   result.lo = x.lo xor y.lo
   result.hi = x.hi xor y.hi
+
+proc `shl`*[T: MpUint](x: T, y: SomeInteger): T {.noInit, noSideEffect.}
+  # Forward declaration
+
+proc `shl`*[T: MpUint](x: T, y: SomeInteger): T {.noInit, noSideEffect.}=
+  ## Compute the `shift left` operation of x and y
+
+  if y == 0:
+    return x
+
+  let # TODO: should be a const - https://github.com/nim-lang/Nim/pull/5664
+    size = (T.sizeof * 8)
+    halfSize = size div 2
+
+  type Sub = getSubType T
+
+  if y > halfSize:
+    result.hi = x.lo shl (y - halfSize)
+    result.lo = 0.Sub
+  elif y < halfSize:
+    result.hi = (x.hi shl y) or (x.lo shr (halfSize - y))
+    result.lo = x.lo shl y
+  else:
+    result.hi = x.lo
+    result.lo = 0.Sub
+
+proc `shr`*[T: MpUint](x: T, y: SomeInteger): T {.noInit, noSideEffect.}=
+  ## Compute the `shift right` operation of x and y
+
+  if y == 0:
+    return x
+
+  let # TODO: should be a const - https://github.com/nim-lang/Nim/pull/5664
+    size = (T.sizeof * 8)
+    halfSize = size div 2
+
+  type Sub = getSubType T
+
+  if y > halfSize:
+    result.hi = x.hi shr (y - halfSize)
+    result.lo = 0.Sub
+  elif y < halfSize:
+    result.lo = (x.lo shr y) or (x.hi shl (halfSize - y))
+    result.hi = x.hi shr y
+  else:
+    result.lo = x.hi
+    result.hi = 0.Sub

tests/test_bitwise.nim

@@ -0,0 +1,34 @@
+# Copyright (c) 2018 Status Research & Development GmbH
+# Distributed under the MIT License (license terms are at http://opensource.org/licenses/MIT).
+
+import ../src/mpint, unittest
+
+suite "Testing bitwise operations":
+  let a = initMpUint(100, uint8)
+
+  let b = a * a
+  let z = 10000'u16
+
+  test "Shift left - by less than half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shl 2) == z shl 2
+
+  test "Shift left - by more than half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shl 10) == z shl 10
+
+  test "Shift left - by half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shl 8) == z shl 8
+
+  test "Shift right - by less than half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shr 2) == z shr 2
+
+  test "Shift right - by more than half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shr 10) == z shr 10
+
+  test "Shift right - by half the size of the integer":
+    check: cast[uint16](b) == z # Sanity check
+    check: cast[uint16](b shr 8) == z shr 8