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https://github.com/status-im/nim-stint.git
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ccf87daac1
* implement arithmetic right shift * workaround Nim VM 'cast' limitation * fix high(stint) bug * fix compile time bit shift bug * add test for compile time shift and high(stint) * add tests against ttmath
128 lines
3.5 KiB
Nim
128 lines
3.5 KiB
Nim
# Stint
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# Copyright 2018 Status Research & Development GmbH
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# Licensed under either of
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#
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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#
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import ../stint, unittest
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when defined(cpp):
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import quicktest, ttmath_compat
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func high(T: typedesc[SomeUnsignedInt]): T =
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not T(0)
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suite "Testing signed int bitwise operations":
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const
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hi = high(int64)
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lo = low(int64)
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itercount = 1000
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test "Shift Left":
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var y = 1.u256
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for i in 1..255:
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let x = 1.i256 shl i
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y = y shl 1
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check cast[stint.Uint256](x) == y
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test "Shift Right":
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const leftMost = 1.i256 shl 255
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var y = 1.u256 shl 255
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for i in 1..255:
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let x = leftMost shr i
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y = y shr 1
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check cast[stint.Uint256](x) == y
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test "ashr on positive int":
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const leftMost = 1.i256 shl 254
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var y = 1.u256 shl 254
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for i in 1..255:
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let x = ashr(leftMost, i)
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y = y shr 1
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check x == cast[stint.Int256](y)
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test "ashr on negative int":
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const
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leftMostU = 1.u256 shl 255
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leftMostI = 1.i256 shl 255
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var y = leftMostU
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for i in 1..255:
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let x = ashr(leftMostI, i)
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y = (y shr 1) or leftMostU
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check x == cast[stint.Int256](y)
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test "Compile time shift":
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const
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# set all bits
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x = high(stint.Int256) or (1.i256 shl 255)
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y = not 0.i256
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check x == y
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const
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a = (high(stint.Int256) shl 10) shr 10
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b = (high(stint.Uint256) shl 10) shr 10
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c = ashr(high(stint.Int256) shl 10, 10)
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check a == cast[stint.Int256](b)
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check c != cast[stint.Int256](b)
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check c != a
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when defined(cpp):
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quicktest "signed int `shl` vs ttmath", itercount do(x0: int64(min=lo, max=hi),
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x1: int64(min=0, max=hi),
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x2: int64(min=0, max=hi),
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x3: int64(min=0, max=hi),
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y: int(min=0, max=(255))):
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let
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x = [x0, x1, x2, x3]
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ttm_x = x.asTT
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mp_x = cast[stint.Int256](x)
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let
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ttm_z = ttm_x shl y
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mp_z = mp_x shl y
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check ttm_z.asSt == mp_z
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quicktest "signed int `shr` vs ttmath", itercount do(x0: int64(min=lo, max=hi),
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x1: int64(min=0, max=hi),
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x2: int64(min=0, max=hi),
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x3: int64(min=0, max=hi),
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y: int(min=0, max=(255))):
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let
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x = [cast[uint64](x0), cast[uint64](x1), cast[uint64](x2), cast[uint64](x3)]
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ttm_x = x.asTT
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mp_x = cast[stint.Int256](x)
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let
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ttm_z = ttm_x shr y.uint
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mp_z = mp_x shr y
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check cast[stint.Int256](ttm_z.asSt) == mp_z
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quicktest "arithmetic shift right vs ttmath", itercount do(x0: int64(min=lo, max=hi),
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x1: int64(min=0, max=hi),
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x2: int64(min=0, max=hi),
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x3: int64(min=0, max=hi),
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y: int(min=0, max=(255))):
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let
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x = [x0, x1, x2, x3]
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ttm_x = x.asTT
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mp_x = cast[stint.Int256](x)
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let
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ttm_z = ttm_x shr y # C/CPP usually implement `shr` as `ashr` a.k.a. `sar`
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mp_z = ashr(mp_x, y)
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check ttm_z.asSt == mp_z
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