lnd.xprv/tlv/record.go
2019-08-07 15:03:43 -07:00

154 lines
3.5 KiB
Go

package tlv
import (
"io"
"github.com/btcsuite/btcd/btcec"
)
// Type is an 64-bit identifier for a TLV Record.
type Type uint64
// Encoder is a signature for methods that can encode TLV values. An error
// should be returned if the Encoder cannot support the underlying type of val.
// The provided scratch buffer must be non-nil.
type Encoder func(w io.Writer, val interface{}, buf *[8]byte) error
// Decoder is a signature for methods that can decode TLV values. An error
// should be returned if the Decoder cannot support the underlying type of val.
// The provided scratch buffer must be non-nil.
type Decoder func(r io.Reader, val interface{}, buf *[8]byte, l uint64) error
// ENOP is an encoder that doesn't modify the io.Writer and never fails.
func ENOP(io.Writer, interface{}, *[8]byte) error { return nil }
// DNOP is an encoder that doesn't modify the io.Reader and never fails.
func DNOP(io.Reader, interface{}, *[8]byte, uint64) error { return nil }
// SizeFunc is a function that can compute the length of a given field. Since
// the size of the underlying field can change, this allows the size of the
// field to be evaluated at the time of encoding.
type SizeFunc func() uint64
// SizeVarBytes returns a SizeFunc that can compute the length of a byte slice.
func SizeVarBytes(e *[]byte) SizeFunc {
return func() uint64 {
return uint64(len(*e))
}
}
// Record holds the required information to encode or decode a TLV record.
type Record struct {
value interface{}
typ Type
staticSize uint64
sizeFunc SizeFunc
encoder Encoder
decoder Decoder
}
// Size returns the size of the Record's value. If no static size is known, the
// dynamic size will be evaluated.
func (f *Record) Size() uint64 {
if f.sizeFunc == nil {
return f.staticSize
}
return f.sizeFunc()
}
// MakePrimitiveRecord creates a record for common types.
func MakePrimitiveRecord(typ Type, val interface{}) Record {
var (
staticSize uint64
sizeFunc SizeFunc
encoder Encoder
decoder Decoder
)
switch e := val.(type) {
case *uint8:
staticSize = 1
encoder = EUint8
decoder = DUint8
case *uint16:
staticSize = 2
encoder = EUint16
decoder = DUint16
case *uint32:
staticSize = 4
encoder = EUint32
decoder = DUint32
case *uint64:
staticSize = 8
encoder = EUint64
decoder = DUint64
case *[32]byte:
staticSize = 32
encoder = EBytes32
decoder = DBytes32
case *[33]byte:
staticSize = 33
encoder = EBytes33
decoder = DBytes33
case **btcec.PublicKey:
staticSize = 33
encoder = EPubKey
decoder = DPubKey
case *[64]byte:
staticSize = 64
encoder = EBytes64
decoder = DBytes64
case *[]byte:
sizeFunc = SizeVarBytes(e)
encoder = EVarBytes
decoder = DVarBytes
default:
panic("unknown primitive type")
}
return Record{
value: val,
typ: typ,
staticSize: staticSize,
sizeFunc: sizeFunc,
encoder: encoder,
decoder: decoder,
}
}
// MakeStaticRecord creates a record for a field of fixed-size
func MakeStaticRecord(typ Type, val interface{}, size uint64, encoder Encoder,
decoder Decoder) Record {
return Record{
value: val,
typ: typ,
staticSize: size,
encoder: encoder,
decoder: decoder,
}
}
// MakeDynamicRecord creates a record whose size may vary, and will be
// determined at the time of encoding via sizeFunc.
func MakeDynamicRecord(typ Type, val interface{}, sizeFunc SizeFunc,
encoder Encoder, decoder Decoder) Record {
return Record{
value: val,
typ: typ,
sizeFunc: sizeFunc,
encoder: encoder,
decoder: decoder,
}
}