mirror of
https://github.com/42wim/matterbridge.git
synced 2024-12-11 19:52:04 -08:00
158 lines
3.1 KiB
Go
158 lines
3.1 KiB
Go
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package ber
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import (
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"bytes"
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"errors"
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"fmt"
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"math"
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"strconv"
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"strings"
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)
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func encodeFloat(v float64) []byte {
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switch {
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case math.IsInf(v, 1):
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return []byte{0x40}
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case math.IsInf(v, -1):
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return []byte{0x41}
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case math.IsNaN(v):
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return []byte{0x42}
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case v == 0.0:
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if math.Signbit(v) {
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return []byte{0x43}
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}
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return []byte{}
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default:
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// we take the easy part ;-)
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value := []byte(strconv.FormatFloat(v, 'G', -1, 64))
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var ret []byte
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if bytes.Contains(value, []byte{'E'}) {
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ret = []byte{0x03}
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} else {
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ret = []byte{0x02}
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}
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ret = append(ret, value...)
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return ret
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}
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}
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func ParseReal(v []byte) (val float64, err error) {
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if len(v) == 0 {
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return 0.0, nil
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}
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switch {
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case v[0]&0x80 == 0x80:
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val, err = parseBinaryFloat(v)
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case v[0]&0xC0 == 0x40:
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val, err = parseSpecialFloat(v)
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case v[0]&0xC0 == 0x0:
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val, err = parseDecimalFloat(v)
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default:
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return 0.0, fmt.Errorf("invalid info block")
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}
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if err != nil {
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return 0.0, err
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}
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if val == 0.0 && !math.Signbit(val) {
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return 0.0, errors.New("REAL value +0 must be encoded with zero-length value block")
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}
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return val, nil
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}
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func parseBinaryFloat(v []byte) (float64, error) {
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var info byte
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var buf []byte
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info, v = v[0], v[1:]
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var base int
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switch info & 0x30 {
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case 0x00:
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base = 2
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case 0x10:
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base = 8
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case 0x20:
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base = 16
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case 0x30:
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return 0.0, errors.New("bits 6 and 5 of information octet for REAL are equal to 11")
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}
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scale := uint((info & 0x0c) >> 2)
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var expLen int
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switch info & 0x03 {
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case 0x00:
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expLen = 1
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case 0x01:
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expLen = 2
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case 0x02:
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expLen = 3
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case 0x03:
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expLen = int(v[0])
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if expLen > 8 {
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return 0.0, errors.New("too big value of exponent")
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}
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v = v[1:]
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}
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buf, v = v[:expLen], v[expLen:]
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exponent, err := ParseInt64(buf)
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if err != nil {
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return 0.0, err
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}
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if len(v) > 8 {
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return 0.0, errors.New("too big value of mantissa")
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}
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mant, err := ParseInt64(v)
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if err != nil {
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return 0.0, err
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}
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mantissa := mant << scale
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if info&0x40 == 0x40 {
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mantissa = -mantissa
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}
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return float64(mantissa) * math.Pow(float64(base), float64(exponent)), nil
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}
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func parseDecimalFloat(v []byte) (val float64, err error) {
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switch v[0] & 0x3F {
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case 0x01: // NR form 1
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var iVal int64
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iVal, err = strconv.ParseInt(strings.TrimLeft(string(v[1:]), " "), 10, 64)
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val = float64(iVal)
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case 0x02, 0x03: // NR form 2, 3
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val, err = strconv.ParseFloat(strings.Replace(strings.TrimLeft(string(v[1:]), " "), ",", ".", -1), 64)
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default:
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err = errors.New("incorrect NR form")
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}
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if err != nil {
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return 0.0, err
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}
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if val == 0.0 && math.Signbit(val) {
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return 0.0, errors.New("REAL value -0 must be encoded as a special value")
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}
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return val, nil
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}
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func parseSpecialFloat(v []byte) (float64, error) {
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if len(v) != 1 {
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return 0.0, errors.New(`encoding of "special value" must not contain exponent and mantissa`)
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}
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switch v[0] {
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case 0x40:
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return math.Inf(1), nil
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case 0x41:
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return math.Inf(-1), nil
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case 0x42:
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return math.NaN(), nil
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case 0x43:
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return math.Copysign(0, -1), nil
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}
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return 0.0, errors.New(`encoding of "special value" not from ASN.1 standard`)
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}
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