decimal/decimal_msgpack.go

94 lines
1.8 KiB
Go

package decimal
import (
"errors"
)
var (
errShortBytes = errors.New("msgp: too few bytes left to read object")
)
// MarshalMsg implements msgp.Marshaler
// Note: limit to 31 digits, if d.IntPart size large than 31, will be lose.
func (d Decimal) MarshalMsg(b []byte) ([]byte, error) {
o := require(b, d.Msgsize())
str := d.String()
sz := len(str)
// limit to 31 digits
// note, if d.IntPart size large than 3, will be lose.
if sz > 31 {
sz = 31
// if last char is '.' then limit to 30 digits
if str[30] == '.' {
sz = 30
}
str = str[:sz]
}
o, n := ensure(o, 1+sz)
o[n] = byte(0xa0 | sz)
n++
return o[:n+copy(o[n:], str)], nil
}
// UnmarshalMsg implements msgp.Unmarshaler
func (d *Decimal) UnmarshalMsg(b []byte) ([]byte, error) {
o, err := b, errShortBytes
l := len(b)
if l < 1 {
return o, err
}
sz := int(b[0] & 0x1f)
if len(b[1:]) < sz {
return o, err
}
if *d, err = NewFromString(string(b[1 : sz+1])); err == nil {
o = b[sz:]
}
return o, err
}
// Msgsize returns an upper bound estimate of the number of bytes occupied by the serialized message
func (d Decimal) Msgsize() int {
return 32
}
// Require ensures that cap(old)-len(old) >= extra.
func require(old []byte, extra int) []byte {
l := len(old)
c := cap(old)
r := l + extra
if c >= r {
return old
} else if l == 0 {
return make([]byte, 0, extra)
}
// the new size is the greater
// of double the old capacity
// and the sum of the old length
// and the number of new bytes
// necessary.
c <<= 1
if c < r {
c = r
}
n := make([]byte, l, c)
copy(n, old)
return n
}
// ensure 'sz' extra bytes in 'b' btw len(b) and cap(b)
func ensure(b []byte, sz int) ([]byte, int) {
l := len(b)
c := cap(b)
if c-l < sz {
o := make([]byte, (2*c)+sz) // exponential growth
n := copy(o, b)
return o[:n+sz], n
}
return b[:l+sz], l
}