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|
package ber
import (
"bytes"
"errors"
"fmt"
"math"
"strconv"
"strings"
)
func encodeFloat(v float64) []byte {
switch {
case math.IsInf(v, 1):
return []byte{0x40}
case math.IsInf(v, -1):
return []byte{0x41}
case math.IsNaN(v):
return []byte{0x42}
case v == 0.0:
if math.Signbit(v) {
return []byte{0x43}
}
return []byte{}
default:
// we take the easy part ;-)
value := []byte(strconv.FormatFloat(v, 'G', -1, 64))
var ret []byte
if bytes.Contains(value, []byte{'E'}) {
ret = []byte{0x03}
} else {
ret = []byte{0x02}
}
ret = append(ret, value...)
return ret
}
}
func ParseReal(v []byte) (val float64, err error) {
if len(v) == 0 {
return 0.0, nil
}
switch {
case v[0]&0x80 == 0x80:
val, err = parseBinaryFloat(v)
case v[0]&0xC0 == 0x40:
val, err = parseSpecialFloat(v)
case v[0]&0xC0 == 0x0:
val, err = parseDecimalFloat(v)
default:
return 0.0, fmt.Errorf("invalid info block")
}
if err != nil {
return 0.0, err
}
if val == 0.0 && !math.Signbit(val) {
return 0.0, errors.New("REAL value +0 must be encoded with zero-length value block")
}
return val, nil
}
func parseBinaryFloat(v []byte) (float64, error) {
var info byte
var buf []byte
info, v = v[0], v[1:]
var base int
switch info & 0x30 {
case 0x00:
base = 2
case 0x10:
base = 8
case 0x20:
base = 16
case 0x30:
return 0.0, errors.New("bits 6 and 5 of information octet for REAL are equal to 11")
}
scale := uint((info & 0x0c) >> 2)
var expLen int
switch info & 0x03 {
case 0x00:
expLen = 1
case 0x01:
expLen = 2
case 0x02:
expLen = 3
case 0x03:
expLen = int(v[0])
if expLen > 8 {
return 0.0, errors.New("too big value of exponent")
}
v = v[1:]
}
buf, v = v[:expLen], v[expLen:]
exponent, err := ParseInt64(buf)
if err != nil {
return 0.0, err
}
if len(v) > 8 {
return 0.0, errors.New("too big value of mantissa")
}
mant, err := ParseInt64(v)
if err != nil {
return 0.0, err
}
mantissa := mant << scale
if info&0x40 == 0x40 {
mantissa = -mantissa
}
return float64(mantissa) * math.Pow(float64(base), float64(exponent)), nil
}
func parseDecimalFloat(v []byte) (val float64, err error) {
switch v[0] & 0x3F {
case 0x01: // NR form 1
var iVal int64
iVal, err = strconv.ParseInt(strings.TrimLeft(string(v[1:]), " "), 10, 64)
val = float64(iVal)
case 0x02, 0x03: // NR form 2, 3
val, err = strconv.ParseFloat(strings.Replace(strings.TrimLeft(string(v[1:]), " "), ",", ".", -1), 64)
default:
err = errors.New("incorrect NR form")
}
if err != nil {
return 0.0, err
}
if val == 0.0 && math.Signbit(val) {
return 0.0, errors.New("REAL value -0 must be encoded as a special value")
}
return val, nil
}
func parseSpecialFloat(v []byte) (float64, error) {
if len(v) != 1 {
return 0.0, errors.New(`encoding of "special value" must not contain exponent and mantissa`)
}
switch v[0] {
case 0x40:
return math.Inf(1), nil
case 0x41:
return math.Inf(-1), nil
case 0x42:
return math.NaN(), nil
case 0x43:
return math.Copysign(0, -1), nil
}
return 0.0, errors.New(`encoding of "special value" not from ASN.1 standard`)
}
|
