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build out tests
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@lucix-aws
lucix-aws committed Feb 5, 2024
1 parent 77f9154 commit 0879dad
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255 changes: 33 additions & 222 deletions encoding/cbor/cbor.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,57 +14,21 @@
// variations of encoded containers.
package cbor

import (
"encoding/binary"
"math"
)

// MajorType enumerates CBOR major types.
type MajorType byte

// Enumeration of CBOR major types
const (
MajorTypeUint MajorType = iota
MajorTypeNegInt
MajorTypeSlice
MajorTypeString
MajorTypeList
MajorTypeMap
MajorTypeTag
MajorType7
)

// Encode returns a byte slice that encodes the given Value.
func Encode(v Value) []byte {
p := make([]byte, v.len())
v.encode(p)
return p
}

// Decode returns the Value encoded in the given byte slice.
func Decode(p []byte) (Value, error) {
v, _, err := decode(p)
if err != nil {
return nil, err
}
return v, nil
}

// Value describes a CBOR data item.
//
// The following structures implement Value:
// The following types implement Value:
// - Uint
// - NegInt
// - Slice
// - String
// - List
// - Map
// - Tag
// - Major7Bool
// - Major7Nil
// - Major7Undefined
// - Major7Float32
// - Major7Float64
// - Bool
// - Nil
// - Undefined
// - Float32
// - Float64
type Value interface {
len() int
encode(p []byte) int
Expand All @@ -78,225 +42,72 @@ var (
_ Value = List(nil)
_ Value = Map(nil)
_ Value = (*Tag)(nil)
_ Value = Major7Bool(false)
_ Value = (*Major7Nil)(nil)
_ Value = (*Major7Undefined)(nil)
_ Value = Major7Float32(0)
_ Value = Major7Float64(0)
_ Value = Bool(false)
_ Value = (*Nil)(nil)
_ Value = (*Undefined)(nil)
_ Value = Float32(0)
_ Value = Float64(0)
)

// UInt describes a CBOR uint (major type 0).
// Uint describes a CBOR uint (major type 0).
type Uint uint64

func (i Uint) len() int {
return getLen(int(i))
}

func (i Uint) encode(p []byte) int {
return encodeLen(MajorTypeUint, int(i), p)
}

// NegInt describes a CBOR negative int (major type 1).
type NegInt uint64

func (i NegInt) len() int {
return getLen(int(int(i) - 1))
}

func (i NegInt) encode(p []byte) int {
return encodeLen(MajorTypeNegInt, int(int(i)-1), p)
}

// Slice describes a CBOR byte slice (major type 2).
type Slice []byte

func (s Slice) len() int {
return getLen(len(s)) + len(s)
}

func (s Slice) encode(p []byte) int {
off := encodeLen(MajorTypeSlice, len(s), p)
copy(p[off:], []byte(s))
return off + len(s)
}

// String describes a CBOR text string (major type 3).
type String string

func (s String) len() int {
return getLen(len(s)) + len(s)
}

func (s String) encode(p []byte) int {
off := encodeLen(MajorTypeString, len(s), p)
copy(p[off:], []byte(s))
return off + len(s)
}

// List describes a CBOR list (major type 4).
type List []Value

func (l List) len() int {
total := getLen(len(l))
for _, v := range l {
total += v.len()
}
return total
}

func (l List) encode(p []byte) int {
off := encodeLen(MajorTypeList, len(l), p)
for _, v := range l {
off += v.encode(p[off:])
}
return off
}

// Map describes a CBOR map (major type 5).
//
// The type signature of the map's key is restricted to string as it is in
// Smithy.
type Map map[string]Value

func (m Map) len() int {
total := getLen(len(m))
for k, v := range m {
total += String(k).len() + v.len()
}
return total
}

func (m Map) encode(p []byte) int {
off := encodeLen(MajorTypeMap, len(m), p)
for k, v := range m {
off += String(k).encode(p[off:])
off += v.encode(p[off:])
}
return off
}

// Tag describes a CBOR-tagged value (major type 6).
type Tag struct {
ID uint64
Value Value
}

func (t Tag) len() int {
return getLen(int(t.ID)) + t.Value.len()
}

func (t Tag) encode(p []byte) int {
off := encodeLen(MajorTypeTag, int(t.ID), p)
return off + t.Value.encode(p[off:])
}

// Major7Byte describes a boolean value (major type 7, argument 20/21).
type Major7Bool bool

func (b Major7Bool) len() int {
return 1
}

func (b Major7Bool) encode(p []byte) int {
if b {
p[0] = compose(MajorType7, major7True)
} else {
p[0] = compose(MajorType7, major7False)
}
return 1
}

// Major7Nil is the `nil` / `null` literal (major type 7, argument 22).
type Major7Nil struct{}
// Bool describes a boolean value (major type 7, argument 20/21).
type Bool bool

func (*Major7Nil) len() int {
return 1
}

func (*Major7Nil) encode(p []byte) int {
p[0] = 0b_111_10110
return 1
}
// Nil is the `nil` / `null` literal (major type 7, argument 22).
type Nil struct{}

// Major7Undefined is the `undefined` literal (major type 7, argument 23).
type Major7Undefined struct{}
// Undefined is the `undefined` literal (major type 7, argument 23).
type Undefined struct{}

func (*Major7Undefined) len() int {
return 1
}

func (*Major7Undefined) encode(p []byte) int {
p[0] = 0b_111_10111
return 1
}

// Major7Float32 describes an IEEE 754 single-precision floating-point number
// Float32 describes an IEEE 754 single-precision floating-point number
// (major type 7, argument 26).
//
// Go does not natively support float16, all values encoded as such (major type
// 7, argument 25) must be represented by this variant instead.
type Major7Float32 float32

func (f Major7Float32) len() int {
return 5
}

func (f Major7Float32) encode(p []byte) int {
p[0] = 0b_111_11010
binary.BigEndian.PutUint32(p[1:], math.Float32bits(float32(f)))
return 5
}
type Float32 float32

// Major7Float64 describes an IEEE 754 double-precision floating-point number
// Float64 describes an IEEE 754 double-precision floating-point number
// (major type 7, argument 27).
type Major7Float64 float64
type Float64 float64

func (f Major7Float64) len() int {
return 9
}

func (f Major7Float64) encode(p []byte) int {
p[0] = 0b_111_11011
binary.BigEndian.PutUint64(p[1:], math.Float64bits(float64(f)))
return 5
}

func encodeLen(t MajorType, ln int, p []byte) int {
if ln < 24 {
p[0] = byte(t)<<5 | byte(ln)
return 1 // type and len in single byte
} else if ln < 0x1_00 {
p[0] = byte(t)<<5 | 24
p[1] = byte(ln)
return 2 // type + 1-byte len
} else if ln < 0x1_00_00 {
p[0] = byte(t)<<5 | 25
binary.BigEndian.PutUint16(p[1:], uint16(ln))
return 3 // type + 2-byte len
} else if ln < 0x1_00_00_00_00 {
p[0] = byte(t)<<5 | 26
binary.BigEndian.PutUint32(p[1:], uint32(ln))
return 5 // type + 4-byte len
}

p[0] = byte(t)<<5 | 27
binary.BigEndian.PutUint64(p[1:], uint64(ln))
return 9 // type + 8-byte len
// Encode returns a byte slice that encodes the given Value.
func Encode(v Value) []byte {
p := make([]byte, v.len())
v.encode(p)
return p
}

func getLen(ln int) int {
if ln < 24 {
return 1 // type and len in single byte
} else if ln < 0x1_00 {
return 2 // type + 1-byte len
} else if ln < 0x1_00_00 {
return 3 // type + 2-byte len
} else if ln < 0x1_00_00_00_00 {
return 5 // type + 4-byte len
// Decode returns the Value encoded in the given byte slice.
func Decode(p []byte) (Value, error) {
v, _, err := decode(p)
if err != nil {
return nil, err
}
return 9 // type + 8-byte len
}

func compose(major MajorType, minor byte) byte {
return byte(major)<<5 | minor
return v, nil
}
45 changes: 45 additions & 0 deletions encoding/cbor/const.go
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
package cbor

// major type in LSB position
type majorType byte

const (
majorTypeUint majorType = iota
majorTypeNegInt
majorTypeSlice
majorTypeString
majorTypeList
majorTypeMap
majorTypeTag
majorType7
)

// masks for major/minor component in encoded head
const (
maskMajor = 0b111 << 5
maskMinor = 0b11111
)

// minor value encodings to represent arg bit length (and indefinite)
const (
minorArg1 = 24
minorArg2 = 25
minorArg4 = 26
minorArg8 = 27
minorIndefinite = 31
)

// minor sentinels for everything in major 7
const (
major7False = 20
major7True = 21
major7Nil = 22
major7Undefined = 23
major7Float16 = minorArg2
major7Float32 = minorArg4
major7Float64 = minorArg8
)

// we allocate for 256 items in containers to start at most to prevent huge
// arguments from blowing up memory
const maxAlloc = 0xff
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