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// Copyright 2009 The Go 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 gc
import (
"fmt"
"math/big"
)
// implements integer arithmetic
// Mpint represents an integer constant.
type Mpint struct {
Val big.Int
Ovf bool // set if Val overflowed compiler limit (sticky)
Rune bool // set if syntax indicates default type rune
}
func (a *Mpint) SetOverflow() {
a.Val.SetUint64(1) // avoid spurious div-zero errors
a.Ovf = true
}
func (a *Mpint) checkOverflow(extra int) bool {
// We don't need to be precise here, any reasonable upper limit would do.
// For now, use existing limit so we pass all the tests unchanged.
if a.Val.BitLen()+extra > Mpprec {
a.SetOverflow()
}
return a.Ovf
}
func (a *Mpint) Set(b *Mpint) {
a.Val.Set(&b.Val)
}
func (a *Mpint) SetFloat(b *Mpflt) int {
// avoid converting huge floating-point numbers to integers
// (2*Mpprec is large enough to permit all tests to pass)
if b.Val.MantExp(nil) > 2*Mpprec {
return -1
}
if _, acc := b.Val.Int(&a.Val); acc == big.Exact {
return 0
}
const delta = 16 // a reasonably small number of bits > 0
var t big.Float
t.SetPrec(Mpprec - delta)
// try rounding down a little
t.SetMode(big.ToZero)
t.Set(&b.Val)
if _, acc := t.Int(&a.Val); acc == big.Exact {
return 0
}
// try rounding up a little
t.SetMode(big.AwayFromZero)
t.Set(&b.Val)
if _, acc := t.Int(&a.Val); acc == big.Exact {
return 0
}
return -1
}
func (a *Mpint) Add(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Add")
}
a.SetOverflow()
return
}
a.Val.Add(&a.Val, &b.Val)
if a.checkOverflow(0) {
yyerror("constant addition overflow")
}
}
func (a *Mpint) Sub(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Sub")
}
a.SetOverflow()
return
}
a.Val.Sub(&a.Val, &b.Val)
if a.checkOverflow(0) {
yyerror("constant subtraction overflow")
}
}
func (a *Mpint) Mul(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Mul")
}
a.SetOverflow()
return
}
a.Val.Mul(&a.Val, &b.Val)
if a.checkOverflow(0) {
yyerror("constant multiplication overflow")
}
}
func (a *Mpint) Quo(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Quo")
}
a.SetOverflow()
return
}
a.Val.Quo(&a.Val, &b.Val)
if a.checkOverflow(0) {
// can only happen for div-0 which should be checked elsewhere
yyerror("constant division overflow")
}
}
func (a *Mpint) Rem(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Rem")
}
a.SetOverflow()
return
}
a.Val.Rem(&a.Val, &b.Val)
if a.checkOverflow(0) {
// should never happen
yyerror("constant modulo overflow")
}
}
func (a *Mpint) Or(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Or")
}
a.SetOverflow()
return
}
a.Val.Or(&a.Val, &b.Val)
}
func (a *Mpint) And(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint And")
}
a.SetOverflow()
return
}
a.Val.And(&a.Val, &b.Val)
}
func (a *Mpint) AndNot(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint AndNot")
}
a.SetOverflow()
return
}
a.Val.AndNot(&a.Val, &b.Val)
}
func (a *Mpint) Xor(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Xor")
}
a.SetOverflow()
return
}
a.Val.Xor(&a.Val, &b.Val)
}
func (a *Mpint) Lsh(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Lsh")
}
a.SetOverflow()
return
}
s := b.Int64()
if s < 0 || s >= Mpprec {
msg := "shift count too large"
if s < 0 {
msg = "invalid negative shift count"
}
yyerror("%s: %d", msg, s)
a.SetInt64(0)
return
}
if a.checkOverflow(int(s)) {
yyerror("constant shift overflow")
return
}
a.Val.Lsh(&a.Val, uint(s))
}
func (a *Mpint) Rsh(b *Mpint) {
if a.Ovf || b.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("ovf in Mpint Rsh")
}
a.SetOverflow()
return
}
s := b.Int64()
if s < 0 {
yyerror("invalid negative shift count: %d", s)
if a.Val.Sign() < 0 {
a.SetInt64(-1)
} else {
a.SetInt64(0)
}
return
}
a.Val.Rsh(&a.Val, uint(s))
}
func (a *Mpint) Cmp(b *Mpint) int {
return a.Val.Cmp(&b.Val)
}
func (a *Mpint) CmpInt64(c int64) int {
if c == 0 {
return a.Val.Sign() // common case shortcut
}
return a.Val.Cmp(big.NewInt(c))
}
func (a *Mpint) Neg() {
a.Val.Neg(&a.Val)
}
func (a *Mpint) Int64() int64 {
if a.Ovf {
if nsavederrors+nerrors == 0 {
yyerror("constant overflow")
}
return 0
}
return a.Val.Int64()
}
func (a *Mpint) SetInt64(c int64) {
a.Val.SetInt64(c)
}
func (a *Mpint) SetString(as string) {
_, ok := a.Val.SetString(as, 0)
if !ok {
// required syntax is [+-][0[x]]d*
// At the moment we lose precise error cause;
// the old code distinguished between:
// - malformed hex constant
// - malformed octal constant
// - malformed decimal constant
// TODO(gri) use different conversion function
yyerror("malformed integer constant: %s", as)
a.Val.SetUint64(0)
return
}
if a.checkOverflow(0) {
yyerror("constant too large: %s", as)
}
}
func (x *Mpint) String() string {
return bconv(x, 0)
}
func bconv(xval *Mpint, flag FmtFlag) string {
if flag&FmtSharp != 0 {
return fmt.Sprintf("%#x", &xval.Val)
}
return xval.Val.String()
}