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math/big: don't scan past a binary exponent if not accepted syntactically

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TBR adonovan

Change-Id: I842cbc855dbd560f65e76c9a557dff1a22c5d610
Reviewed-on: https://go-review.googlesource.com/4882
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Griesemer 2015-02-12 15:09:56 -08:00
parent ccdbfe3174
commit a809dc7adb
2 changed files with 22 additions and 8 deletions
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7
src/math/big/floatconv.go
View File

@ -46,11 +46,12 @@ func (z *Float) SetString(s string) (*Float, bool) {
// digits = digit { digit } .
// digit = "0" ... "9" | "a" ... "z" | "A" ... "Z" .
//
// The base argument must be 0 or a value between 2 through MaxBase.
// The base argument must be 0, 2, 10, or 16. Providing an invalid base
// argument will lead to a run-time panic.
//
// For base 0, the number prefix determines the actual base: A prefix of
// ``0x'' or ``0X'' selects base 16, and a ``0b'' or ``0B'' prefix selects
// base 2; otherwise, the actual base is 10 and no prefix is permitted.
// base 2; otherwise, the actual base is 10 and no prefix is accepted.
// The octal prefix ``0'' is not supported.
//
// A "p" exponent indicates power of 2 for the exponent; for instance "1.2p3"
@ -75,7 +76,7 @@ func (z *Float) Scan(r io.ByteScanner, base int) (f *Float, b int, err error) {
// exponent
var exp int64
var ebase int
exp, ebase, err = scanExponent(r)
exp, ebase, err = scanExponent(r, true)
if err != nil {
return
}

21
src/math/big/ratconv.go
View File

@ -78,9 +78,8 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
// exponent
var exp int64
var ebase int
exp, ebase, err = scanExponent(r)
if ebase == 2 || err != nil {
exp, _, err = scanExponent(r, false)
if err != nil {
return nil, false
}
@ -115,7 +114,17 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
return z, true
}
func scanExponent(r io.ByteScanner) (exp int64, base int, err error) {
// scanExponent scans the longest possible prefix of r representing a decimal
// ('e', 'E') or binary ('p') exponent, if any. It returns the exponent, the
// exponent base (10 or 2), or a read or syntax error, if any.
//
// exponent = ( "E" | "e" | "p" ) [ sign ] digits .
// sign = "+" | "-" .
// digits = digit { digit } .
// digit = "0" ... "9" .
//
// A binary exponent is only permitted if binExpOk is set.
func scanExponent(r io.ByteScanner, binExpOk bool) (exp int64, base int, err error) {
base = 10
var ch byte
@ -130,7 +139,11 @@ func scanExponent(r io.ByteScanner) (exp int64, base int, err error) {
case 'e', 'E':
// ok
case 'p':
if binExpOk {
base = 2
break // ok
}
fallthrough // binary exponent not permitted
default:
r.UnreadByte()
return // no exponent; same as e0