GoToSocial/vendor/modernc.org/mathutil/int.go
kim ed46224573
Add SQLite support, fix un-thread-safe DB caches, small performance f… (#172)
* Add SQLite support, fix un-thread-safe DB caches, small performance fixes

Signed-off-by: kim (grufwub) <grufwub@gmail.com>

* add SQLite licenses to README

Signed-off-by: kim (grufwub) <grufwub@gmail.com>

* appease the linter, and fix my dumbass-ery

Signed-off-by: kim (grufwub) <grufwub@gmail.com>

* make requested changes

Signed-off-by: kim (grufwub) <grufwub@gmail.com>

* add back comment

Signed-off-by: kim (grufwub) <grufwub@gmail.com>
2021-08-29 16:41:41 +02:00

280 lines
5.8 KiB
Go

// Copyright (c) 2018 The mathutil Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package mathutil // import "modernc.org/mathutil"
import (
"fmt"
"math"
"math/big"
)
var (
// MaxInt128 represents the maximun Int128 value as big.Int
MaxInt128 *big.Int
// MinInt128 represents the minimun Int128 value as big.Int
MinInt128 *big.Int
// MaxUint128 represents the maximun Uint128 value as big.Int
MaxUint128 *big.Int
)
func init() {
var ok bool
MaxInt128, ok = big.NewInt(0).SetString("0x7fffffff_ffffffff_ffffffff_ffffffff", 0)
if !ok {
panic("internal error")
}
MinInt128 = big.NewInt(0).Set(MaxInt128)
MinInt128.Add(MinInt128, _1)
MinInt128.Neg(MinInt128)
MaxUint128, ok = big.NewInt(0).SetString("0xffffffff_ffffffff_ffffffff_ffffffff", 0)
if !ok {
panic("internal error")
}
}
const (
maxInt128 = 1<<127 - 1
maxUint128 = 1<<128 - 1
minInt128 = -maxInt128 - 1
)
// Int128 is an 128 bit signed integer.
type Int128 struct {
Lo int64 // Bits 63..0.
Hi int64 // Bits 127..64.
}
// Add returns the sum of x and y and a carry indication.
func (x Int128) Add(y Int128) (r Int128, cy bool) {
r.Lo = x.Lo + y.Lo
r.Hi = x.Hi + y.Hi
if uint64(r.Lo) < uint64(x.Lo) {
r.Hi++
}
return r, (r.Cmp(x) < 0) == (y.Sign() >= 0)
}
// BigInt returns x in the form of a big.Int.
func (x Int128) BigInt() *big.Int {
r := big.NewInt(x.Hi)
r.Lsh(r, 64)
lo := big.NewInt(0)
lo.SetUint64(uint64(x.Lo))
return r.Add(r, lo)
}
// Cmp compares x and y and returns:
//
// -1 if x < y
// 0 if x == y
// +1 if x > y
func (x Int128) Cmp(y Int128) int {
if x.Hi > y.Hi {
return 1
}
if x.Hi < y.Hi {
return -1
}
if uint64(x.Lo) > uint64(y.Lo) {
return 1
}
if uint64(x.Lo) < uint64(y.Lo) {
return -1
}
return 0
}
// Neg returns -x and an indication that x was not equal to MinInt128.
func (x Int128) Neg() (r Int128, ok bool) {
if x == (Int128{Hi: math.MinInt64}) {
return x, false
}
x.Lo = ^x.Lo
x.Hi = ^x.Hi
r, _ = x.Add(Int128{Lo: 1})
return r, true
}
// SetBigInt sets x to y, returns x and an error, if any.
func (x *Int128) SetBigInt(y *big.Int) (r Int128, err error) {
if y.Cmp(MaxInt128) > 0 {
return *x, fmt.Errorf("%T.SetInt: overflow", x)
}
if y.Cmp(MinInt128) < 0 {
return *x, fmt.Errorf("%T.SetInt: underflow", x)
}
neg := y.Sign() < 0
var z big.Int
z.Set(y)
if neg {
z.Neg(&z)
}
r.Lo = z.Int64()
z.Rsh(&z, 64)
r.Hi = z.Int64()
if neg {
r, _ = r.Neg()
}
*x = r
return r, nil
}
// SetInt64 sets x to y and returns x.
func (x *Int128) SetInt64(y int64) (r Int128) {
r.Lo = y
if y >= 0 {
r.Hi = 0
*x = r
return r
}
r.Hi = -1
*x = r
return r
}
// SetUint64 sets x to y and returns x.
func (x *Int128) SetUint64(y uint64) (r Int128) {
r = Int128{Lo: int64(y)}
*x = r
return r
}
// Sign returns:
//
// -1 if x < 0
// 0 if x == 0
// +1 if x > 0
func (x Int128) Sign() int {
if x.Hi < 0 {
return -1
}
if x.Hi != 0 || x.Lo != 0 {
return 1
}
return 0
}
// String implements fmt.Stringer()
func (x Int128) String() string { return x.BigInt().String() }
// NewInt128FromInt64 return a new Int128 value initialized to n.
func NewInt128FromInt64(n int64) (r Int128) {
r.Lo = n
if n < 0 {
r.Hi = -1
}
return r
}
// NewInt128FromUint64 return a new Int128 value initialized to n.
func NewInt128FromUint64(n uint64) (r Int128) { return Int128{Lo: int64(n)} }
// NewInt128FromFloat32 returns a new Int128 value initialized to n. Result is
// not specified in n does not represent a number within the range of Int128
// values.
func NewInt128FromFloat32(n float32) (r Int128) {
if n >= minInt128 && n <= maxInt128 {
if n >= math.MinInt64 && n <= math.MaxInt64 {
return NewInt128FromInt64(int64(n))
}
f := big.NewFloat(float64(n))
bi, _ := f.Int(nil)
r.SetBigInt(bi)
}
return r
}
// NewInt128FromFloat64 returns a new Int128 value initialized to n. Result is
// not specified in n does not represent a number within the range of Int128
// values.
func NewInt128FromFloat64(n float64) (r Int128) {
if n >= minInt128 && n <= maxInt128 {
if n >= math.MinInt64 && n <= math.MaxInt64 {
return NewInt128FromInt64(int64(n))
}
f := big.NewFloat(n)
bi, _ := f.Int(nil)
r.SetBigInt(bi)
}
return r
}
// Uint128 is an 128 bit unsigned integer.
type Uint128 struct {
Lo uint64 // Bits 63..0.
Hi uint64 // Bits 127..64.
}
// NewUint128FromInt64 return a new Uint128 value initialized to n.
func NewUint128FromInt64(n int64) (r Uint128) {
r.Lo = uint64(n)
if n < 0 {
r.Hi = ^uint64(0)
}
return r
}
// NewUint128FromUint64 return a new Uint128 value initialized to n.
func NewUint128FromUint64(n uint64) (r Uint128) { return Uint128{Lo: n} }
// NewUint128FromFloat32 returns a new Uint128 value initialized to n. Result is
// not specified in n does not represent a number within the range of Uint128
// values.
func NewUint128FromFloat32(n float32) (r Uint128) {
if n >= 0 {
if n <= math.MaxUint64 {
return NewUint128FromUint64(uint64(n))
}
f := big.NewFloat(float64(n))
bi, _ := f.Int(nil)
r.SetBigInt(bi)
}
return r
}
// NewUint128FromFloat64 returns a new Uint128 value initialized to n. Result is
// not specified in n does not represent a number within the range of Uint128
// values.
func NewUint128FromFloat64(n float64) (r Uint128) {
if n >= 0 && n <= maxUint128 {
if n <= math.MaxUint64 {
return NewUint128FromUint64(uint64(n))
}
f := big.NewFloat(n)
bi, _ := f.Int(nil)
r.SetBigInt(bi)
}
return r
}
// SetBigInt sets x to y, returns x and an error, if any.
func (x *Uint128) SetBigInt(y *big.Int) (r Uint128, err error) {
if y.Sign() < 0 || y.Cmp(MaxUint128) > 0 {
return *x, fmt.Errorf("%T.SetInt: overflow", x)
}
var z big.Int
z.Set(y)
r.Lo = z.Uint64()
z.Rsh(&z, 64)
r.Hi = z.Uint64()
*x = r
return r, nil
}