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tag.go
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tag.go
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package cbor
import (
"errors"
"math"
"math/big"
"net/url"
"reflect"
"slices"
"time"
)
// TagNumber is a CBOR tag number type.
type TagNumber uint64
const (
tagNumberDatetimeString TagNumber = 0
tagNumberEpochDatetime TagNumber = 1
tagNumberPositiveBignum TagNumber = 2
tagNumberNegativeBignum TagNumber = 3
tagNumberDecimalFraction TagNumber = 4
tagNumberBigfloat TagNumber = 5
tagNumberExpectedBase64URL TagNumber = 21
tagNumberExpectedBase64 TagNumber = 22
tagNumberExpectedBase16 TagNumber = 23
tagNumberEncodedData TagNumber = 24
tagNumberURI TagNumber = 32
tagNumberBase64URL TagNumber = 33
tagNumberBase64 TagNumber = 34
tagNumberSelfDescribe TagNumber = 55799
)
// Tag is a CBOR tag.
type Tag struct {
Number TagNumber
Content any
}
// Decode decodes the tag content.
// The following tags are supported:
//
// - tag number 0: date/time string is decoded as time.Time.
// - tag number 1: epoch-based date/time is decoded as time.Time.
// - tag number 2: positive bignum is decoded as *big.Int.
// - tag number 3: negative bignum is decoded as *big.Int.
// - tag number 4: decimal fraction is not implemented.
// - tag number 5: bigfloat is decoded as *big.Float.
// - tag number 21: expected conversion to base64url is decoded as ExpectedBase64URL.
// - tag number 22: expected conversion to base64 is decoded as ExpectedBase64.
// - tag number 23: expected conversion to base16 is decoded as ExpectedBase16.
// - tag number 24: encoded CBOR data item is decoded as EncodedData.
// - tag number 32: URI is decoded as *url.URL.
// - tag number 33: base64url is decoded as Base64URLString.
// - tag number 34: base64 is decoded as Base64String.
// - tag number 55799: Self-Described CBOR return the content as is.
//
// Other tags returns tag itself.
func (tag Tag) Decode(v any, opts Options) error {
data, err := Marshal(tag.Content)
if err != nil {
return err
}
t := RawTag{Number: tag.Number, Content: data}
return t.Decode(v, opts)
}
type RawTag struct {
Number TagNumber
Content RawMessage
}
// Decode decodes the tag content.
func (tag RawTag) Decode(v any, opts Options) error {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return &InvalidUnmarshalError{reflect.TypeOf(v)}
}
return tag.decodeReflectValue(rv.Elem(), opts)
}
func (tag RawTag) decodeReflectValue(rv reflect.Value, opts Options) error {
firstByte := tag.Content[0]
mt := majorType(firstByte >> 5)
d := newDecodeState(tag.Content)
isNull := firstByte == 0xf6 || firstByte == 0xf7 // null or undefined
u, rv := indirect(rv, isNull)
if u != nil {
return u.UnmarshalCBOR([]byte(tag.Content))
}
switch tag.Number {
// tag number 0: date/time string
case tagNumberDatetimeString:
var s string
if err := d.decode(&s); err != nil {
return wrapSemanticError("cbor: invalid datetime string", err)
}
t, err := time.Parse(time.RFC3339Nano, s)
if err != nil {
return wrapSemanticError("cbor: invalid datetime string", err)
}
if t.Unix() <= minEpoch || t.Unix() >= maxEpoch {
return newSemanticError("cbor: invalid range of datetime")
}
rt := rv.Type()
if rt == timeType {
rv.Set(reflect.ValueOf(t))
return nil
}
if rt.Kind() == reflect.Interface && timeType.Implements(rt) {
rv.Set(reflect.ValueOf(t))
return nil
}
return &UnmarshalTypeError{Value: "datetime", Type: rv.Type()}
// tag number 1: epoch-based date/time
case tagNumberEpochDatetime:
var t time.Time
switch mt {
case majorTypePositiveInt, majorTypeNegativeInt:
var epoch Integer
if err := d.decode(&epoch); err != nil {
return wrapSemanticError("cbor: invalid epoch-based datetime", err)
}
i, err := epoch.Int64()
if err != nil || i <= minEpoch || i >= maxEpoch {
return wrapSemanticError("cbor: invalid range of datetime", err)
}
t = time.Unix(i, 0)
case majorTypeOther:
var epoch float64
if err := d.decode(&epoch); err != nil {
return wrapSemanticError("cbor: invalid epoch-based datetime", err)
}
if !math.IsNaN(epoch) {
if epoch <= minEpoch || epoch >= maxEpoch {
return newSemanticError("cbor: invalid range of datetime")
}
i, f := math.Modf(epoch)
t = time.Unix(int64(i), int64(math.RoundToEven(f*1e9)))
}
default:
return newSemanticError("cbor: invalid epoch-based datetime")
}
rt := rv.Type()
if rt == timeType {
rv.Set(reflect.ValueOf(t))
return nil
}
if rt.Kind() == reflect.Interface {
if rt.NumMethod() == 0 {
if t.IsZero() {
rv.Set(reflect.Zero(rt))
} else {
rv.Set(reflect.ValueOf(t))
}
} else {
return &UnmarshalTypeError{Value: "datetime", Type: rv.Type()}
}
return nil
}
return &UnmarshalTypeError{Value: "datetime", Type: rv.Type()}
// tag number 2: positive bignum
case tagNumberPositiveBignum:
var b []byte
if err := d.decode(&b); err != nil {
return wrapSemanticError("cbor: invalid positive bignum", err)
}
if rv.Type() == bigIntType {
i := rv.Addr().Interface().(*big.Int)
i.SetBytes(b)
return nil
}
i := new(big.Int).SetBytes(b)
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if !i.IsInt64() || rv.OverflowInt(i.Int64()) {
return newSemanticError("cbor: integer overflow")
}
rv.SetInt(i.Int64())
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
if !i.IsUint64() || rv.OverflowUint(i.Uint64()) {
return newSemanticError("cbor: integer overflow")
}
rv.SetUint(i.Uint64())
case reflect.Interface:
if rv.NumMethod() == 0 {
if i.IsInt64() {
rv.Set(reflect.ValueOf(i.Int64()))
} else {
rv.Set(reflect.ValueOf(i))
}
} else if reflect.PointerTo(bigIntType).Implements(rv.Type()) {
rv.Set(reflect.ValueOf(i))
} else {
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
default:
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
// tag number 3: negative bignum
case tagNumberNegativeBignum:
var b []byte
if err := d.decode(&b); err != nil {
return wrapSemanticError("cbor: invalid positive bignum", err)
}
if rv.Type() == bigIntType {
i := rv.Addr().Interface().(*big.Int)
i.SetBytes(b)
i.Sub(minusOne, i)
return nil
}
i := new(big.Int).SetBytes(b)
i.Sub(minusOne, i)
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if !i.IsInt64() || rv.OverflowInt(i.Int64()) {
return newSemanticError("cbor: integer overflow")
}
rv.SetInt(i.Int64())
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return newSemanticError("cbor: integer overflow")
case reflect.Interface:
if rv.NumMethod() == 0 {
if i.IsInt64() {
rv.Set(reflect.ValueOf(i.Int64()))
} else {
rv.Set(reflect.ValueOf(i))
}
} else if reflect.PointerTo(bigIntType).Implements(rv.Type()) {
rv.Set(reflect.ValueOf(i))
} else {
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
default:
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
// tag number 4: decimal fraction
case tagNumberDecimalFraction:
// TODO: implement
return errors.New("TODO: implement")
// tag number 5: bigfloat
case tagNumberBigfloat:
var a []any
if err := d.decode(&a); err != nil {
return wrapSemanticError("cbor: invalid bigfloat", err)
}
if len(a) != 2 {
return newSemanticError("cbor: invalid bigfloat")
}
exp, ok := a[0].(int64)
if !ok {
return newSemanticError("cbor: invalid bigfloat")
}
f := new(big.Float)
switch x := a[1].(type) {
case int64:
f.SetInt64(x)
case Integer:
f.SetInt(x.BigInt())
case *big.Int:
f.SetInt(x)
default:
return &UnmarshalTypeError{Value: "float", Type: rv.Type()}
}
f.SetMantExp(f, int(exp))
if rv.Type() == bigFloatType {
rv.Set(reflect.ValueOf(*f))
return nil
}
switch rv.Kind() {
case reflect.Float32, reflect.Float64:
fv, _ := f.Float64()
if rv.OverflowFloat(fv) {
return newSemanticError("cbor: float overflow")
}
rv.SetFloat(fv)
case reflect.Interface:
if rv.NumMethod() == 0 {
fv, acc := f.Float64()
if acc == big.Exact {
rv.Set(reflect.ValueOf(fv))
} else {
rv.Set(reflect.ValueOf(f))
}
} else if reflect.PointerTo(bigFloatType).Implements(rv.Type()) {
rv.Set(reflect.ValueOf(f))
} else {
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
default:
return &UnmarshalTypeError{Value: "integer", Type: rv.Type()}
}
// tag number 21: expected conversion to base64url
case tagNumberExpectedBase64URL:
opts.set(d)
t := rv.Type()
switch {
case t == expectedBase64URLType:
if err := d.decodeReflectValue(rv.FieldByName("Content")); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base64url", err)
}
case rv.Kind() == reflect.Interface && expectedBase64URLType.Implements(t):
var a any
if err := d.decode(&a); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base64url", err)
}
rv.Set(reflect.ValueOf(ExpectedBase64URL{Content: a}))
default:
return &UnmarshalTypeError{Value: "base64url", Type: rv.Type()}
}
return nil
// tag number 22: expected conversion to base64
case tagNumberExpectedBase64:
opts.set(d)
t := rv.Type()
switch {
case t == expectedBase64Type:
if err := d.decodeReflectValue(rv.FieldByName("Content")); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base64", err)
}
case rv.Kind() == reflect.Interface && expectedBase64Type.Implements(t):
var a any
if err := d.decode(&a); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base64", err)
}
rv.Set(reflect.ValueOf(ExpectedBase64{Content: a}))
default:
return &UnmarshalTypeError{Value: "base64", Type: rv.Type()}
}
return nil
// tag number 23: expected conversion to base16
case tagNumberExpectedBase16:
opts.set(d)
t := rv.Type()
switch {
case t == expectedBase16Type:
if err := d.decodeReflectValue(rv.FieldByName("Content")); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base16", err)
}
case rv.Kind() == reflect.Interface && expectedBase16Type.Implements(t):
var a any
if err := d.decode(&a); err != nil {
return wrapSemanticError("cbor: invalid expected conversion to base16", err)
}
rv.Set(reflect.ValueOf(ExpectedBase16{Content: a}))
default:
return &UnmarshalTypeError{Value: "base16", Type: rv.Type()}
}
return nil
// tag number 24: encoded CBOR data item
case tagNumberEncodedData:
t := rv.Type()
if mt != majorTypeBytes {
return newSemanticError("cbor: invalid encoded data")
}
switch {
case t == encodedDataType:
if err := d.decodeReflectValue(rv); err != nil {
return wrapSemanticError("cbor: invalid encoded data", err)
}
case rv.Kind() == reflect.Interface && encodedDataType.Implements(t):
var b []byte
if err := Unmarshal([]byte(tag.Content), &b); err != nil {
return wrapSemanticError("cbor: invalid encoded data", err)
}
rv.Set(reflect.ValueOf(EncodedData(b)))
default:
return &UnmarshalTypeError{Value: "encoded data", Type: rv.Type()}
}
return nil
// tag number 32: URI
case tagNumberURI:
var s string
if err := d.decode(&s); err != nil {
return wrapSemanticError("cbor: invalid URI", err)
}
u, err := url.Parse(s)
if err != nil {
return wrapSemanticError("cbor: invalid URI", err)
}
t := rv.Type()
switch {
case t == urlType:
rv.Set(reflect.ValueOf(*u))
case rv.Kind() == reflect.Interface && reflect.PointerTo(urlType).Implements(t):
rv.Set(reflect.ValueOf(u))
default:
return &UnmarshalTypeError{Value: "uri", Type: rv.Type()}
}
// tag number 33: base64url
case tagNumberBase64URL:
var s string
if err := d.decode(&s); err != nil {
return wrapSemanticError("cbor: invalid base64url", err)
}
_, err := b64url.DecodeString(s)
if err != nil {
return wrapSemanticError("cbor: invalid base64url", err)
}
t := rv.Type()
switch {
case t == base64URLStringType:
rv.SetString(s)
case rv.Kind() == reflect.Interface && base64URLStringType.Implements(t):
rv.Set(reflect.ValueOf(Base64URLString(s)))
default:
return &UnmarshalTypeError{Value: "base64url", Type: rv.Type()}
}
// tag number 34: base64
case tagNumberBase64:
var s string
if err := d.decode(&s); err != nil {
return wrapSemanticError("cbor: invalid base64url", err)
}
_, err := b64.DecodeString(s)
if err != nil {
return wrapSemanticError("cbor: invalid base64url", err)
}
t := rv.Type()
switch {
case t == base64StringType:
rv.SetString(s)
case rv.Kind() == reflect.Interface && base64URLStringType.Implements(t):
rv.Set(reflect.ValueOf(Base64String(s)))
default:
return &UnmarshalTypeError{Value: "base64url", Type: rv.Type()}
}
// tag number 55799 Self-Described CBOR
case tagNumberSelfDescribe:
opts.set(d)
if err := d.decodeReflectValue(rv); err != nil {
return err
}
default:
switch rv.Type() {
case tagType:
rv.FieldByName("Number").SetUint(uint64(tag.Number))
return d.decodeReflectValue(rv.FieldByName("Content"))
case rawTagType:
contentStart := d.off
if err := d.checkWellFormedChild(); err != nil {
return err
}
rv.FieldByName("Number").SetUint(uint64(tag.Number))
rv.FieldByName("Content").SetBytes(slices.Clone(d.data[contentStart:d.off]))
return nil
}
if rv.Kind() == reflect.Interface && rawTagType.Implements(rv.Type()) {
contentStart := d.off
if err := d.checkWellFormedChild(); err != nil {
return err
}
v := RawTag{
Number: tag.Number,
Content: RawMessage(slices.Clone(d.data[contentStart:d.off])),
}
rv.Set(reflect.ValueOf(v))
return nil
}
return &UnmarshalTypeError{Value: "tag", Type: rv.Type()}
}
return nil
}