Add big.Int and integer utilities from geth/common/math

- big.go: BigPow, ParseBig256, U256, U256Bytes, PaddedBigBytes, etc.
- integer.go: HexOrDecimal64, ParseUint64, SafeAdd/Sub/Mul

Consolidating math utilities into luxfi/math to eliminate
geth/common/math dependency.

math/big.go

@@ -0,0 +1,173 @@
+// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package math
+
+import (
+	"fmt"
+	"math/big"
+)
+
+// Various big integer limit values.
+var (
+	tt256     = BigPow(2, 256)
+	tt256m1   = new(big.Int).Sub(tt256, big.NewInt(1))
+	MaxBig256 = new(big.Int).Set(tt256m1)
+)
+
+const (
+	// number of bits in a big.Word
+	wordBits = 32 << (uint64(^big.Word(0)) >> 63)
+	// number of bytes in a big.Word
+	wordBytes = wordBits / 8
+)
+
+// HexOrDecimal256 marshals big.Int as hex or decimal.
+type HexOrDecimal256 big.Int
+
+// NewHexOrDecimal256 creates a new HexOrDecimal256
+func NewHexOrDecimal256(x int64) *HexOrDecimal256 {
+	b := big.NewInt(x)
+	h := HexOrDecimal256(*b)
+	return &h
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (i *HexOrDecimal256) UnmarshalJSON(input []byte) error {
+	if len(input) > 1 && input[0] == '"' {
+		input = input[1 : len(input)-1]
+	}
+	return i.UnmarshalText(input)
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (i *HexOrDecimal256) UnmarshalText(input []byte) error {
+	bigint, ok := ParseBig256(string(input))
+	if !ok {
+		return fmt.Errorf("invalid hex or decimal integer %q", input)
+	}
+	*i = HexOrDecimal256(*bigint)
+	return nil
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (i *HexOrDecimal256) MarshalText() ([]byte, error) {
+	if i == nil {
+		return []byte("0x0"), nil
+	}
+	return fmt.Appendf(nil, "%#x", (*big.Int)(i)), nil
+}
+
+// Decimal256 unmarshals big.Int as a decimal string.
+type Decimal256 big.Int
+
+// NewDecimal256 creates a new Decimal256
+func NewDecimal256(x int64) *Decimal256 {
+	b := big.NewInt(x)
+	d := Decimal256(*b)
+	return &d
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (i *Decimal256) UnmarshalText(input []byte) error {
+	bigint, ok := ParseBig256(string(input))
+	if !ok {
+		return fmt.Errorf("invalid hex or decimal integer %q", input)
+	}
+	*i = Decimal256(*bigint)
+	return nil
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (i *Decimal256) MarshalText() ([]byte, error) {
+	return []byte(i.String()), nil
+}
+
+// String implements Stringer.
+func (i *Decimal256) String() string {
+	if i == nil {
+		return "0"
+	}
+	return fmt.Sprintf("%#d", (*big.Int)(i))
+}
+
+// ParseBig256 parses s as a 256 bit integer in decimal or hexadecimal syntax.
+func ParseBig256(s string) (*big.Int, bool) {
+	if s == "" {
+		return new(big.Int), true
+	}
+	var bigint *big.Int
+	var ok bool
+	if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
+		bigint, ok = new(big.Int).SetString(s[2:], 16)
+	} else {
+		bigint, ok = new(big.Int).SetString(s, 10)
+	}
+	if ok && bigint.BitLen() > 256 {
+		bigint, ok = nil, false
+	}
+	return bigint, ok
+}
+
+// MustParseBig256 parses s as a 256 bit big integer and panics if invalid.
+func MustParseBig256(s string) *big.Int {
+	v, ok := ParseBig256(s)
+	if !ok {
+		panic("invalid 256 bit integer: " + s)
+	}
+	return v
+}
+
+// BigPow returns a ** b as a big integer.
+func BigPow(a, b int64) *big.Int {
+	r := big.NewInt(a)
+	return r.Exp(r, big.NewInt(b), nil)
+}
+
+// BigMax returns the larger of x or y.
+func BigMax(x, y *big.Int) *big.Int {
+	if x.Cmp(y) < 0 {
+		return y
+	}
+	return x
+}
+
+// BigMin returns the smaller of x or y.
+func BigMin(x, y *big.Int) *big.Int {
+	if x.Cmp(y) > 0 {
+		return y
+	}
+	return x
+}
+
+// PaddedBigBytes encodes a big integer as big-endian bytes with padding.
+func PaddedBigBytes(bigint *big.Int, n int) []byte {
+	if bigint.BitLen()/8 >= n {
+		return bigint.Bytes()
+	}
+	ret := make([]byte, n)
+	ReadBits(bigint, ret)
+	return ret
+}
+
+// ReadBits encodes the absolute value of bigint as big-endian bytes.
+func ReadBits(bigint *big.Int, buf []byte) {
+	i := len(buf)
+	for _, d := range bigint.Bits() {
+		for j := 0; j < wordBytes && i > 0; j++ {
+			i--
+			buf[i] = byte(d)
+			d >>= 8
+		}
+	}
+}
+
+// U256 encodes x as a 256 bit two's complement number. Destructive.
+func U256(x *big.Int) *big.Int {
+	return x.And(x, tt256m1)
+}
+
+// U256Bytes converts a big Int into a 256bit EVM number. Destructive.
+func U256Bytes(n *big.Int) []byte {
+	return PaddedBigBytes(U256(n), 32)
+}

math/integer.go

@@ -0,0 +1,76 @@
+// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package math
+
+import (
+	"fmt"
+	"math/bits"
+	"strconv"
+)
+
+// HexOrDecimal64 marshals uint64 as hex or decimal.
+type HexOrDecimal64 uint64
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (i *HexOrDecimal64) UnmarshalJSON(input []byte) error {
+	if len(input) > 1 && input[0] == '"' {
+		input = input[1 : len(input)-1]
+	}
+	return i.UnmarshalText(input)
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (i *HexOrDecimal64) UnmarshalText(input []byte) error {
+	n, ok := ParseUint64(string(input))
+	if !ok {
+		return fmt.Errorf("invalid hex or decimal integer %q", input)
+	}
+	*i = HexOrDecimal64(n)
+	return nil
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (i HexOrDecimal64) MarshalText() ([]byte, error) {
+	return fmt.Appendf(nil, "%#x", uint64(i)), nil
+}
+
+// ParseUint64 parses s as an integer in decimal or hexadecimal syntax.
+func ParseUint64(s string) (uint64, bool) {
+	if s == "" {
+		return 0, true
+	}
+	if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
+		v, err := strconv.ParseUint(s[2:], 16, 64)
+		return v, err == nil
+	}
+	v, err := strconv.ParseUint(s, 10, 64)
+	return v, err == nil
+}
+
+// MustParseUint64 parses s as an integer and panics if invalid.
+func MustParseUint64(s string) uint64 {
+	v, ok := ParseUint64(s)
+	if !ok {
+		panic("invalid unsigned 64 bit integer: " + s)
+	}
+	return v
+}
+
+// SafeSub returns x-y and checks for overflow.
+func SafeSub(x, y uint64) (uint64, bool) {
+	diff, borrowOut := bits.Sub64(x, y, 0)
+	return diff, borrowOut != 0
+}
+
+// SafeAdd returns x+y and checks for overflow.
+func SafeAdd(x, y uint64) (uint64, bool) {
+	sum, carryOut := bits.Add64(x, y, 0)
+	return sum, carryOut != 0
+}
+
+// SafeMul returns x*y and checks for overflow.
+func SafeMul(x, y uint64) (uint64, bool) {
+	hi, lo := bits.Mul64(x, y)
+	return lo, hi != 0
+}