mirror of git://gcc.gnu.org/git/gcc.git
74 lines
2.0 KiB
Go
74 lines
2.0 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file implements encoding/decoding of Rats.
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package big
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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// Gob codec version. Permits backward-compatible changes to the encoding.
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const ratGobVersion byte = 1
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// GobEncode implements the gob.GobEncoder interface.
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func (x *Rat) GobEncode() ([]byte, error) {
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if x == nil {
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return nil, nil
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}
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buf := make([]byte, 1+4+(len(x.a.abs)+len(x.b.abs))*_S) // extra bytes for version and sign bit (1), and numerator length (4)
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i := x.b.abs.bytes(buf)
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j := x.a.abs.bytes(buf[:i])
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n := i - j
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if int(uint32(n)) != n {
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// this should never happen
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return nil, errors.New("Rat.GobEncode: numerator too large")
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}
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binary.BigEndian.PutUint32(buf[j-4:j], uint32(n))
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j -= 1 + 4
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b := ratGobVersion << 1 // make space for sign bit
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if x.a.neg {
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b |= 1
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}
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buf[j] = b
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return buf[j:], nil
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}
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// GobDecode implements the gob.GobDecoder interface.
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func (z *Rat) GobDecode(buf []byte) error {
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if len(buf) == 0 {
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// Other side sent a nil or default value.
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*z = Rat{}
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return nil
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}
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b := buf[0]
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if b>>1 != ratGobVersion {
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return fmt.Errorf("Rat.GobDecode: encoding version %d not supported", b>>1)
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}
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const j = 1 + 4
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i := j + binary.BigEndian.Uint32(buf[j-4:j])
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z.a.neg = b&1 != 0
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z.a.abs = z.a.abs.setBytes(buf[j:i])
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z.b.abs = z.b.abs.setBytes(buf[i:])
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return nil
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}
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// MarshalText implements the encoding.TextMarshaler interface.
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func (x *Rat) MarshalText() (text []byte, err error) {
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// TODO(gri): get rid of the []byte/string conversion
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return []byte(x.RatString()), nil
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}
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// UnmarshalText implements the encoding.TextUnmarshaler interface.
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func (z *Rat) UnmarshalText(text []byte) error {
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// TODO(gri): get rid of the []byte/string conversion
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if _, ok := z.SetString(string(text)); !ok {
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return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Rat", text)
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}
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return nil
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}
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