Add shift operators (WIP recursive implementation is slow)

This commit is contained in:
mratsim 2018-02-16 13:54:38 +01:00
parent cec8a752fb
commit 35e80263a3
3 changed files with 93 additions and 4 deletions

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@ -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
@ -50,4 +52,9 @@ proc asDoubleUint*[T: BaseUint](n: T): auto {.noSideEffect, inline.} =
else: uint16
)
n.asUint.Double
n.asUint.Double
macro getSubType*(T: typedesc): untyped =
## Returns the subtype of a generic type
## MpUint[uint32] --> uint32
getTypeInst(T)[1][1]

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@ -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.}=
@ -22,4 +23,51 @@ proc `and`*(x, y: MpUint): MpUint {.noInit, noSideEffect, inline.}=
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
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

34
tests/test_bitwise.nim Normal file
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@ -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