nimbus-eth1/nimbus/vm/interpreter/utils/utils_numeric.nim

72 lines
2.4 KiB
Nim

# Nimbus
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except according to those terms.
import
strformat, strutils, sequtils, endians, macros,
eth_common/eth_types, rlp,
../../../constants
# some methods based on py-evm utils/numeric
func log2*[bits: static int](value: StUint[bits]): Natural {.inline.}=
(bits - 1) - value.countLeadingZeroBits
func log256*(value: UInt256): Natural {.inline.}=
value.log2 shr 3 # div 8 (= log2(256), Logb x = Loga x/Loga b)
func ceil32*(value: Natural): Natural {.inline.}=
# Round input to the nearest bigger multiple of 32
result = value
let remainder = result and 31 # equivalent to modulo 32
if remainder != 0:
return value + 32 - remainder
func wordCount*(length: Natural): Natural {.inline.}=
# Returns the number of EVM words corresponding to a specific size.
# EVM words is rounded up
length.ceil32 shr 5 # equivalent to `div 32` (32 = 2^5)
proc flipSign(value: var UInt256) =
# ⚠ Warning: low(Int256) (binary repr 0b1000...0000) cannot be negated, please handle this special case
value = not value
value += 1.u256
proc extractSign*(v: var UInt256, sign: var bool) =
sign = v > INT_256_MAX_AS_UINT256
if sign:
flipSign(v)
proc setSign*(v: var UInt256, sign: bool) {.inline.} =
if sign: flipSign(v)
func cleanMemRef*(x: UInt256): int {.inline.} =
## Sanitize memory addresses, catch negative or impossibly big offsets
# See https://github.com/status-im/nimbus/pull/97 for more info
# For rationale on shr, see https://github.com/status-im/nimbus/pull/101
const upperBound = (high(int32) shr 2).u256
if x > upperBound:
return high(int32) shr 2
return x.toInt
proc rangeToPadded*[T: StUint](x: openarray[byte], first, last: int): T =
## Convert take a slice of a sequence of bytes interpret it as the big endian
## representation of an Uint256. Use padding for sequence shorter than 32 bytes
## including 0-length sequences.
let lo = max(0, first)
let hi = min(x.high, last)
if not(lo <= hi):
return # 0
result = T.fromBytesBE(
x.toOpenArray(lo, hi),
allowPadding = true
)