[do not merge] Rlp package

rlp/decoder.go

@@ -0,0 +1,277 @@
+package rlp
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+type Decoder struct {
+	buf *buf
+}
+
+func NewDecoder(buf []byte) *Decoder {
+	return &Decoder{
+		buf: newBuf(buf, 0),
+	}
+}
+
+func (d *Decoder) String() string {
+	return fmt.Sprintf(`left=%x pos=%d`, d.buf.Bytes(), d.buf.off)
+}
+
+func (d *Decoder) Consumed() []byte {
+	return d.buf.u[:d.buf.off]
+}
+
+func (d *Decoder) Underlying() []byte {
+	return d.buf.Underlying()
+}
+
+func (d *Decoder) Empty() bool {
+	return d.buf.empty()
+}
+
+func (d *Decoder) Offset() int {
+	return d.buf.Offset()
+}
+
+func (d *Decoder) Bytes() []byte {
+	return d.buf.Bytes()
+}
+
+func (d *Decoder) ReadByte() (n byte, err error) {
+	return d.buf.ReadByte()
+}
+
+func (d *Decoder) PeekByte() (n byte, err error) {
+	return d.buf.PeekByte()
+}
+
+func (d *Decoder) Rebase() {
+	d.buf.u = d.Bytes()
+	d.buf.off = 0
+}
+func (d *Decoder) Fork() *Decoder {
+	return &Decoder{
+		buf: newBuf(d.buf.u, d.buf.off),
+	}
+}
+
+func (d *Decoder) PeekToken() (Token, error) {
+	prefix, err := d.PeekByte()
+	if err != nil {
+		return TokenUnknown, err
+	}
+	return identifyToken(prefix), nil
+}
+
+func (d *Decoder) ElemDec() (*Decoder, Token, error) {
+	a, t, err := d.Elem()
+	return NewDecoder(a), t, err
+}
+
+func (d *Decoder) RawElemDec() (*Decoder, Token, error) {
+	a, t, err := d.RawElem()
+	return NewDecoder(a), t, err
+}
+
+func (d *Decoder) RawElem() ([]byte, Token, error) {
+	w := d.buf
+	start := w.Offset()
+	// figure out what we are reading
+	prefix, err := w.ReadByte()
+	if err != nil {
+		return nil, TokenUnknown, err
+	}
+	token := identifyToken(prefix)
+
+	var (
+		sz    int
+		lenSz int
+	)
+	// switch on the token
+	switch token {
+	case TokenDecimal:
+		// in this case, the value is just the byte itself
+	case TokenShortList:
+		sz = int(token.Diff(prefix))
+		_, err = nextFull(w, sz)
+	case TokenLongList:
+		lenSz = int(token.Diff(prefix))
+		sz, err = nextBeInt(w, lenSz)
+		if err != nil {
+			return nil, token, err
+		}
+		_, err = nextFull(w, sz)
+	case TokenShortBlob:
+		sz := int(token.Diff(prefix))
+		_, err = nextFull(w, sz)
+	case TokenLongBlob:
+		lenSz := int(token.Diff(prefix))
+		sz, err = nextBeInt(w, lenSz)
+		if err != nil {
+			return nil, token, err
+		}
+		_, err = nextFull(w, sz)
+	default:
+		return nil, token, fmt.Errorf("%w: unknown token", ErrDecode)
+	}
+	stop := w.Offset()
+	//log.Printf("%x %s\n", buf, token)
+	if err != nil {
+		return nil, token, err
+	}
+	return w.Underlying()[start:stop], token, nil
+}
+
+func (d *Decoder) Elem() ([]byte, Token, error) {
+	w := d.buf
+	// figure out what we are reading
+	prefix, err := w.ReadByte()
+	if err != nil {
+		return nil, TokenUnknown, err
+	}
+	token := identifyToken(prefix)
+
+	var (
+		buf   []byte
+		sz    int
+		lenSz int
+	)
+	// switch on the token
+	switch token {
+	case TokenDecimal:
+		// in this case, the value is just the byte itself
+		buf = []byte{prefix}
+	case TokenShortList:
+		sz = int(token.Diff(prefix))
+		buf, err = nextFull(w, sz)
+	case TokenLongList:
+		lenSz = int(token.Diff(prefix))
+		sz, err = nextBeInt(w, lenSz)
+		if err != nil {
+			return nil, token, err
+		}
+		buf, err = nextFull(w, sz)
+	case TokenShortBlob:
+		sz := int(token.Diff(prefix))
+		buf, err = nextFull(w, sz)
+	case TokenLongBlob:
+		lenSz := int(token.Diff(prefix))
+		sz, err = nextBeInt(w, lenSz)
+		if err != nil {
+			return nil, token, err
+		}
+		buf, err = nextFull(w, sz)
+	default:
+		return nil, token, fmt.Errorf("%w: unknown token", ErrDecode)
+	}
+	//log.Printf("%x %s\n", buf, token)
+	if err != nil {
+		return nil, token, fmt.Errorf("read data: %w", err)
+	}
+	return buf, token, nil
+}
+
+func ReadElem[T any](d *Decoder, fn func(*T, []byte) error, receiver *T) error {
+	buf, token, err := d.Elem()
+	if err != nil {
+		return err
+	}
+	switch token {
+	case TokenDecimal,
+		TokenShortBlob,
+		TokenLongBlob,
+		TokenShortList,
+		TokenLongList:
+		return fn(receiver, buf)
+	default:
+		return fmt.Errorf("%w: ReadElem found unexpected token", ErrDecode)
+	}
+}
+
+func (d *Decoder) ForList(fn func(*Decoder) error) error {
+	// grab the list bytes
+	buf, token, err := d.Elem()
+	if err != nil {
+		return err
+	}
+	switch token {
+	case TokenShortList, TokenLongList:
+		dec := NewDecoder(buf)
+		for {
+			if dec.buf.Len() == 0 {
+				return nil
+			}
+			err := fn(dec)
+			if errors.Is(err, io.EOF) {
+				return nil
+			}
+			if err != nil {
+				return err
+			}
+			// reset the byte
+			dec = NewDecoder(dec.Bytes())
+		}
+	default:
+		return fmt.Errorf("%w: ForList on non-list", ErrDecode)
+	}
+}
+
+type buf struct {
+	u   []byte
+	off int
+}
+
+func newBuf(u []byte, off int) *buf {
+	return &buf{u: u, off: off}
+}
+
+func (b *buf) empty() bool { return len(b.u) <= b.off }
+
+func (b *buf) PeekByte() (n byte, err error) {
+	if len(b.u) <= b.off {
+		return 0, io.EOF
+	}
+	return b.u[b.off], nil
+}
+func (b *buf) ReadByte() (n byte, err error) {
+	if len(b.u) <= b.off {
+		return 0, io.EOF
+	}
+	b.off++
+	return b.u[b.off-1], nil
+}
+
+func (b *buf) Next(n int) (xs []byte) {
+	m := b.Len()
+	if n > m {
+		n = m
+	}
+	data := b.u[b.off : b.off+n]
+	b.off += n
+	return data
+}
+
+func (b *buf) Offset() int {
+	return b.off
+}
+
+func (b *buf) Bytes() []byte {
+	return b.u[b.off:]
+}
+
+func (b *buf) String() string {
+	if b == nil {
+		// Special case, useful in debugging.
+		return "<nil>"
+	}
+	return string(b.u[b.off:])
+}
+
+func (b *buf) Len() int { return len(b.u) - b.off }
+
+func (b *buf) Underlying() []byte {
+	return b.u
+}