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* amend * building * build * userprompt * imports * build val * gaz * io file Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>
115 lines
2.6 KiB
Go
115 lines
2.6 KiB
Go
// Package math includes important helpers for Ethereum such as fast integer square roots.
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package math
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import (
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"errors"
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stdmath "math"
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"math/bits"
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"github.com/thomaso-mirodin/intmath/u64"
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)
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// Common square root values.
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var squareRootTable = map[uint64]uint64{
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4: 2,
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16: 4,
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64: 8,
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256: 16,
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1024: 32,
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4096: 64,
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16384: 128,
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65536: 256,
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262144: 512,
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1048576: 1024,
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4194304: 2048,
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}
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// IntegerSquareRoot defines a function that returns the
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// largest possible integer root of a number using go's standard library.
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func IntegerSquareRoot(n uint64) uint64 {
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if v, ok := squareRootTable[n]; ok {
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return v
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}
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// Golang floating point precision may be lost above 52 bits, so we use a
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// non floating point method. u64.Sqrt is about x2.5 slower than math.Sqrt.
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if n >= 1<<52 {
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return u64.Sqrt(n)
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}
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return uint64(stdmath.Sqrt(float64(n)))
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}
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// CeilDiv8 divides the input number by 8
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// and takes the ceiling of that number.
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func CeilDiv8(n int) int {
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ret := n / 8
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if n%8 > 0 {
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ret++
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}
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return ret
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}
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// IsPowerOf2 returns true if n is an
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// exact power of two. False otherwise.
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func IsPowerOf2(n uint64) bool {
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return n != 0 && (n&(n-1)) == 0
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}
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// PowerOf2 returns an integer that is the provided
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// exponent of 2. Can only return powers of 2 till 63,
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// after that it overflows
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func PowerOf2(n uint64) uint64 {
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if n >= 64 {
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panic("integer overflow")
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}
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return 1 << n
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}
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// Max returns the larger integer of the two
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// given ones.This is used over the Max function
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// in the standard math library because that max function
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// has to check for some special floating point cases
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// making it slower by a magnitude of 10.
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func Max(a, b uint64) uint64 {
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if a > b {
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return a
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}
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return b
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}
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// Min returns the smaller integer of the two
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// given ones. This is used over the Min function
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// in the standard math library because that min function
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// has to check for some special floating point cases
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// making it slower by a magnitude of 10.
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func Min(a, b uint64) uint64 {
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if a < b {
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return a
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}
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return b
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}
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// Mul64 multiples 2 64-bit unsigned integers and checks if they
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// lead to an overflow. If they do not, it returns the result
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// without an error.
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func Mul64(a, b uint64) (uint64, error) {
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overflows, val := bits.Mul64(a, b)
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if overflows > 0 {
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return 0, errors.New("multiplication overflows")
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}
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return val, nil
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}
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// Add64 adds 2 64-bit unsigned integers and checks if they
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// lead to an overflow. If they do not, it returns the result
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// without an error.
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func Add64(a, b uint64) (uint64, error) {
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res, carry := bits.Add64(a, b, 0 /* carry */)
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if carry > 0 {
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return 0, errors.New("addition overflows")
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}
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return res, nil
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}
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