67 lines
2.5 KiB
Nim
67 lines
2.5 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 ./datatypes, ./int_negabs, ./uint_div, ./int_comparison, ./compiletime_helpers
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# Here are the expected signs for division/modulo by opposite signs and both negative numbers
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# in EVM
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# Parity: https://github.com/paritytech/parity/blob/684322cd6f210684b890055c43d56bb1bc8cae15/ethcore/evm/src/interpreter/mod.rs#L729-L756
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# - SDIV is sign(a) xor sign(b)
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# - SMOD is sign(a)
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# Go-Ethereum: https://github.com/ethereum/go-ethereum/blob/ba1030b6b84f810c04a82221a1b1c0a3dbf499a8/core/vm/instructions.go#L76-L104
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# - SDIV is "if same sign, div(abs(a), abs(b)), else -div(abs(a), abs(b))
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# - SMOD is "sign(a)"
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#
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# in Nim
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# echo "10 div 3: " & $(10 div 3) # 3
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# echo "10 mod 3: " & $(10 mod 3) # 1
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# echo '\n'
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# echo "10 div -3: " & $(10 div -3) # -3
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# echo "10 mod -3: " & $(10 mod -3) # 1
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# echo '\n'
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# echo "-10 div 3: " & $(-10 div 3) # -3
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# echo "-10 mod 3: " & $(-10 mod 3) # -1
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# echo '\n'
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# echo "-10 div -3: " & $(-10 div -3) # 3
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# echo "-10 mod -3: " & $(-10 mod -3) # -1
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# echo '\n'
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func divmod*(x, y: SomeSignedInt): tuple[quot, rem: SomeSignedInt] {.inline.}=
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# hopefully the compiler fuse that in a single op
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(x div y, x mod y)
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proc divmod*[T, T2](x, y: IntImpl[T, T2]): tuple[quot, rem: IntImpl[T, T2]] =
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## Divmod operation for multi-precision signed integer
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when nimvm:
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let res = divmod(
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convert[UintImpl[T2]](x.abs),
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convert[UintImpl[T2]](y.abs))
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result.quot = convert[type result.quot](res.quot)
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result.rem = convert[type result.rem](res.rem)
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else:
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result = cast[type result](divmod(
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cast[UintImpl[T2]](x.abs),
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cast[UintImpl[T2]](y.abs)
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))
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if (x.isNegative xor y.isNegative):
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# If opposite signs
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result.quot = -result.quot
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if x.isNegative:
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result.rem = -result.rem
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func `div`*(x, y: IntImpl): IntImpl {.inline.} =
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## Division operation for multi-precision signed integer
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divmod(x,y).quot
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func `mod`*(x, y: IntImpl): IntImpl {.inline.} =
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## Division operation for multi-precision signed integer
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divmod(x,y).rem
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