Release v0.3.0

vendor/github.com/lightningnetwork/lnd/tlv/truncated.go

@@ -0,0 +1,207 @@
+package tlv
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+// ErrTUintNotMinimal signals that decoding a truncated uint failed because the
+// value was not minimally encoded.
+var ErrTUintNotMinimal = errors.New("truncated uint not minimally encoded")
+
+// numLeadingZeroBytes16 computes the number of leading zeros for a uint16.
+func numLeadingZeroBytes16(v uint16) uint64 {
+	switch {
+	case v == 0:
+		return 2
+	case v&0xff00 == 0:
+		return 1
+	default:
+		return 0
+	}
+}
+
+// SizeTUint16 returns the number of bytes remaining in a uint16 after
+// truncating the leading zeros.
+func SizeTUint16(v uint16) uint64 {
+	return 2 - numLeadingZeroBytes16(v)
+}
+
+// ETUint16 is an Encoder for truncated uint16 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint16.
+func ETUint16(w io.Writer, val interface{}, buf *[8]byte) error {
+	if t, ok := val.(*uint16); ok {
+		binary.BigEndian.PutUint16(buf[:2], *t)
+		numZeros := numLeadingZeroBytes16(*t)
+		_, err := w.Write(buf[numZeros:2])
+		return err
+	}
+	return NewTypeForEncodingErr(val, "uint16")
+}
+
+// ETUint16T is an Encoder for truncated uint16 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint16.
+func ETUint16T(w io.Writer, val uint16, buf *[8]byte) error {
+	binary.BigEndian.PutUint16(buf[:2], val)
+	numZeros := numLeadingZeroBytes16(val)
+	_, err := w.Write(buf[numZeros:2])
+	return err
+}
+
+// DTUint16 is an Decoder for truncated uint16 values, where leading zeros will
+// be resurrected. An error is returned if val is not a *uint16.
+func DTUint16(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
+	if t, ok := val.(*uint16); ok && l <= 2 {
+		_, err := io.ReadFull(r, buf[2-l:2])
+		if err != nil {
+			return err
+		}
+		zero(buf[:2-l])
+		*t = binary.BigEndian.Uint16(buf[:2])
+		if 2-numLeadingZeroBytes16(*t) != l {
+			return ErrTUintNotMinimal
+		}
+		return nil
+	}
+	return NewTypeForDecodingErr(val, "uint16", l, 2)
+}
+
+// numLeadingZeroBytes16 computes the number of leading zeros for a uint32.
+func numLeadingZeroBytes32(v uint32) uint64 {
+	switch {
+	case v == 0:
+		return 4
+	case v&0xffffff00 == 0:
+		return 3
+	case v&0xffff0000 == 0:
+		return 2
+	case v&0xff000000 == 0:
+		return 1
+	default:
+		return 0
+	}
+}
+
+// SizeTUint32 returns the number of bytes remaining in a uint32 after
+// truncating the leading zeros.
+func SizeTUint32(v uint32) uint64 {
+	return 4 - numLeadingZeroBytes32(v)
+}
+
+// ETUint32 is an Encoder for truncated uint32 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint32.
+func ETUint32(w io.Writer, val interface{}, buf *[8]byte) error {
+	if t, ok := val.(*uint32); ok {
+		binary.BigEndian.PutUint32(buf[:4], *t)
+		numZeros := numLeadingZeroBytes32(*t)
+		_, err := w.Write(buf[numZeros:4])
+		return err
+	}
+	return NewTypeForEncodingErr(val, "uint32")
+}
+
+// ETUint32T is an Encoder for truncated uint32 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint32.
+func ETUint32T(w io.Writer, val uint32, buf *[8]byte) error {
+	binary.BigEndian.PutUint32(buf[:4], val)
+	numZeros := numLeadingZeroBytes32(val)
+	_, err := w.Write(buf[numZeros:4])
+	return err
+}
+
+// DTUint32 is an Decoder for truncated uint32 values, where leading zeros will
+// be resurrected. An error is returned if val is not a *uint32.
+func DTUint32(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
+	if t, ok := val.(*uint32); ok && l <= 4 {
+		_, err := io.ReadFull(r, buf[4-l:4])
+		if err != nil {
+			return err
+		}
+		zero(buf[:4-l])
+		*t = binary.BigEndian.Uint32(buf[:4])
+		if 4-numLeadingZeroBytes32(*t) != l {
+			return ErrTUintNotMinimal
+		}
+		return nil
+	}
+	return NewTypeForDecodingErr(val, "uint32", l, 4)
+}
+
+// numLeadingZeroBytes64 computes the number of leading zeros for a uint32.
+//
+// TODO(conner): optimize using unrolled binary search
+func numLeadingZeroBytes64(v uint64) uint64 {
+	switch {
+	case v == 0:
+		return 8
+	case v&0xffffffffffffff00 == 0:
+		return 7
+	case v&0xffffffffffff0000 == 0:
+		return 6
+	case v&0xffffffffff000000 == 0:
+		return 5
+	case v&0xffffffff00000000 == 0:
+		return 4
+	case v&0xffffff0000000000 == 0:
+		return 3
+	case v&0xffff000000000000 == 0:
+		return 2
+	case v&0xff00000000000000 == 0:
+		return 1
+	default:
+		return 0
+	}
+}
+
+// SizeTUint64 returns the number of bytes remaining in a uint64 after
+// truncating the leading zeros.
+func SizeTUint64(v uint64) uint64 {
+	return 8 - numLeadingZeroBytes64(v)
+}
+
+// ETUint64 is an Encoder for truncated uint64 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint64.
+func ETUint64(w io.Writer, val interface{}, buf *[8]byte) error {
+	if t, ok := val.(*uint64); ok {
+		binary.BigEndian.PutUint64(buf[:], *t)
+		numZeros := numLeadingZeroBytes64(*t)
+		_, err := w.Write(buf[numZeros:])
+		return err
+	}
+	return NewTypeForEncodingErr(val, "uint64")
+}
+
+// ETUint64T is an Encoder for truncated uint64 values, where leading zeros will
+// be omitted. An error is returned if val is not a *uint64.
+func ETUint64T(w io.Writer, val uint64, buf *[8]byte) error {
+	binary.BigEndian.PutUint64(buf[:], val)
+	numZeros := numLeadingZeroBytes64(val)
+	_, err := w.Write(buf[numZeros:])
+	return err
+}
+
+// DTUint64 is an Decoder for truncated uint64 values, where leading zeros will
+// be resurrected. An error is returned if val is not a *uint64.
+func DTUint64(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
+	if t, ok := val.(*uint64); ok && l <= 8 {
+		_, err := io.ReadFull(r, buf[8-l:])
+		if err != nil {
+			return err
+		}
+		zero(buf[:8-l])
+		*t = binary.BigEndian.Uint64(buf[:])
+		if 8-numLeadingZeroBytes64(*t) != l {
+			return ErrTUintNotMinimal
+		}
+		return nil
+	}
+	return NewTypeForDecodingErr(val, "uint64", l, 8)
+}
+
+// zero clears the passed byte slice.
+func zero(b []byte) {
+	for i := range b {
+		b[i] = 0x00
+	}
+}