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// Copyright (c) Faye Amacker. All rights reserved.
// Licensed under the MIT License. See LICENSE in the project root for license information.
package cbor
import (
"fmt"
"io"
"strconv"
)
type cborType uint8
const (
cborTypePositiveInt cborType = 0x00
cborTypeNegativeInt cborType = 0x20
cborTypeByteString cborType = 0x40
cborTypeTextString cborType = 0x60
cborTypeArray cborType = 0x80
cborTypeMap cborType = 0xa0
cborTypeTag cborType = 0xc0
cborTypePrimitives cborType = 0xe0
)
func (t cborType) String() string {
switch t {
case cborTypePositiveInt:
return "positive integer"
case cborTypeNegativeInt:
return "negative integer"
case cborTypeByteString:
return "byte string"
case cborTypeTextString:
return "UTF-8 text string"
case cborTypeArray:
return "array"
case cborTypeMap:
return "map"
case cborTypeTag:
return "tag"
case cborTypePrimitives:
return "primitives"
default:
return "Invalid type " + strconv.Itoa(int(t))
}
}
type additionalInformation uint8
const (
maxAdditionalInformationWithoutArgument = 23
additionalInformationWith1ByteArgument = 24
additionalInformationWith2ByteArgument = 25
additionalInformationWith4ByteArgument = 26
additionalInformationWith8ByteArgument = 27
// For major type 7.
additionalInformationAsFalse = 20
additionalInformationAsTrue = 21
additionalInformationAsNull = 22
additionalInformationAsUndefined = 23
additionalInformationAsFloat16 = 25
additionalInformationAsFloat32 = 26
additionalInformationAsFloat64 = 27
// For major type 2, 3, 4, 5.
additionalInformationAsIndefiniteLengthFlag = 31
)
const (
maxSimpleValueInAdditionalInformation = 23
minSimpleValueIn1ByteArgument = 32
)
func (ai additionalInformation) isIndefiniteLength() bool {
return ai == additionalInformationAsIndefiniteLengthFlag
}
const (
// From RFC 8949 Section 3:
// "The initial byte of each encoded data item contains both information about the major type
// (the high-order 3 bits, described in Section 3.1) and additional information
// (the low-order 5 bits)."
// typeMask is used to extract major type in initial byte of encoded data item.
typeMask = 0xe0
// additionalInformationMask is used to extract additional information in initial byte of encoded data item.
additionalInformationMask = 0x1f
)
func getType(raw byte) cborType {
return cborType(raw & typeMask)
}
func getAdditionalInformation(raw byte) byte {
return raw & additionalInformationMask
}
func isBreakFlag(raw byte) bool {
return raw == cborBreakFlag
}
func parseInitialByte(b byte) (t cborType, ai byte) {
return getType(b), getAdditionalInformation(b)
}
const (
tagNumRFC3339Time = 0
tagNumEpochTime = 1
tagNumUnsignedBignum = 2
tagNumNegativeBignum = 3
tagNumExpectedLaterEncodingBase64URL = 21
tagNumExpectedLaterEncodingBase64 = 22
tagNumExpectedLaterEncodingBase16 = 23
tagNumSelfDescribedCBOR = 55799
)
const (
cborBreakFlag = byte(0xff)
cborByteStringWithIndefiniteLengthHead = byte(0x5f)
cborTextStringWithIndefiniteLengthHead = byte(0x7f)
cborArrayWithIndefiniteLengthHead = byte(0x9f)
cborMapWithIndefiniteLengthHead = byte(0xbf)
)
var (
cborFalse = []byte{0xf4}
cborTrue = []byte{0xf5}
cborNil = []byte{0xf6}
cborNaN = []byte{0xf9, 0x7e, 0x00}
cborPositiveInfinity = []byte{0xf9, 0x7c, 0x00}
cborNegativeInfinity = []byte{0xf9, 0xfc, 0x00}
)
// validBuiltinTag checks that supported built-in tag numbers are followed by expected content types.
func validBuiltinTag(tagNum uint64, contentHead byte) error {
t := getType(contentHead)
switch tagNum {
case tagNumRFC3339Time:
// Tag content (date/time text string in RFC 3339 format) must be string type.
if t != cborTypeTextString {
return newInadmissibleTagContentTypeError(
tagNumRFC3339Time,
"text string",
t.String())
}
return nil
case tagNumEpochTime:
// Tag content (epoch date/time) must be uint, int, or float type.
if t != cborTypePositiveInt && t != cborTypeNegativeInt && (contentHead < 0xf9 || contentHead > 0xfb) {
return newInadmissibleTagContentTypeError(
tagNumEpochTime,
"integer or floating-point number",
t.String())
}
return nil
case tagNumUnsignedBignum, tagNumNegativeBignum:
// Tag content (bignum) must be byte type.
if t != cborTypeByteString {
return newInadmissibleTagContentTypeErrorf(
fmt.Sprintf(
"tag number %d or %d must be followed by byte string, got %s",
tagNumUnsignedBignum,
tagNumNegativeBignum,
t.String(),
))
}
return nil
case tagNumExpectedLaterEncodingBase64URL, tagNumExpectedLaterEncodingBase64, tagNumExpectedLaterEncodingBase16:
// From RFC 8949 3.4.5.2:
// The data item tagged can be a byte string or any other data item. In the latter
// case, the tag applies to all of the byte string data items contained in the data
// item, except for those contained in a nested data item tagged with an expected
// conversion.
return nil
}
return nil
}
// Transcoder is a scheme for transcoding a single CBOR encoded data item to or from a different
// data format.
type Transcoder interface {
// Transcode reads the data item in its source format from a Reader and writes a
// corresponding representation in its destination format to a Writer.
Transcode(dst io.Writer, src io.Reader) error
}
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