op-service: Add nice reader & writer functions

op-service/solabi/util.go

+package solabi
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// These are empty padding values. They should be zero'd & not modified at all.
+var (
+	addressEmptyPadding [12]byte = [12]byte{}
+	uint64EmptyPadding  [24]byte = [24]byte{}
+)
+
+func ReadSignature(r io.Reader) ([]byte, error) {
+	sig := make([]byte, 4)
+	_, err := io.ReadFull(r, sig)
+	fmt.Println(sig)
+	return sig, err
+}
+
+func ReadAndValidateSignature(r io.Reader, expectedSignature []byte) ([]byte, error) {
+	sig := make([]byte, 4)
+	if _, err := io.ReadFull(r, sig); err != nil {
+		return nil, err
+	}
+	if !bytes.Equal(sig, expectedSignature) {
+		return nil, errors.New("invalid function signature")
+	}
+	return sig, nil
+}
+
+func ReadHash(r io.Reader) (common.Hash, error) {
+	var h common.Hash
+	_, err := io.ReadFull(r, h[:])
+	return h, err
+}
+
+func ReadEthBytes32(r io.Reader) (eth.Bytes32, error) {
+	var b eth.Bytes32
+	_, err := io.ReadFull(r, b[:])
+	return b, err
+}
+
+func ReadAddress(r io.Reader) (common.Address, error) {
+	var padding, readPadding [12]byte
+	var a common.Address
+	if _, err := io.ReadFull(r, readPadding[:]); err != nil || !bytes.Equal(readPadding[:], padding[:]) {
+		return a, fmt.Errorf("address padding was not empty: %x", readPadding[:])
+	}
+	_, err := io.ReadFull(r, a[:])
+	return a, err
+}
+
+// ReadUint64 reads a big endian uint64 from a 32 byte word
+func ReadUint64(r io.Reader) (uint64, error) {
+	var padding, readPadding [24]byte
+	var n uint64
+	if _, err := io.ReadFull(r, readPadding[:]); err != nil || !bytes.Equal(readPadding[:], padding[:]) {
+		return 0, fmt.Errorf("number exceeds uint64 bounds: %x", readPadding[:])
+	}
+	if err := binary.Read(r, binary.BigEndian, &n); err != nil {
+		return 0, fmt.Errorf("expected number length to be 8 bytes")
+	}
+	return n, nil
+}
+
+func ReadUint256(r io.Reader) (*big.Int, error) {
+	var n [32]byte
+	if _, err := io.ReadFull(r, n[:]); err != nil {
+		return nil, err
+	}
+	return new(big.Int).SetBytes(n[:]), nil
+}
+
+func WriteSignature(w io.Writer, sig []byte) error {
+	_, err := w.Write(sig)
+	return err
+}
+
+func WriteHash(w io.Writer, h common.Hash) error {
+	_, err := w.Write(h[:])
+	return err
+}
+
+func WriteEthBytes32(w io.Writer, b eth.Bytes32) error {
+	_, err := w.Write(b[:])
+	return err
+}
+
+func WriteAddress(w io.Writer, a common.Address) error {
+	if _, err := w.Write(addressEmptyPadding[:]); err != nil {
+		return err
+	}
+	if _, err := w.Write(a[:]); err != nil {
+		return err
+	}
+	return nil
+}
+
+func WriteUint256(w io.Writer, n *big.Int) error {
+	if n.BitLen() > 256 {
+		return fmt.Errorf("big int exceeds 256 bits: %d", n)
+	}
+	arr := make([]byte, 32)
+	n.FillBytes(arr)
+	_, err := w.Write(arr)
+	return err
+}
+
+func WriteUint64(w io.Writer, n uint64) error {
+	if _, err := w.Write(uint64EmptyPadding[:]); err != nil {
+		return err
+	}
+	if err := binary.Write(w, binary.BigEndian, n); err != nil {
+		return err
+	}
+	return nil
+}