preimage: extend for example program usage

preimage/filechan.go

+package preimage
+
+import (
+	"io"
+	"os"
+)
+
+// FileChannel is a unidirectional channel for file I/O
+type FileChannel interface {
+	io.ReadWriteCloser
+	// Reader returns the file that is used for reading.
+	Reader() *os.File
+	// Writer returns the file that is used for writing.
+	Writer() *os.File
+}
+
+type ReadWritePair struct {
+	r *os.File
+	w *os.File
+}
+
+// NewReadWritePair creates a new FileChannel that uses the given files
+func NewReadWritePair(r *os.File, w *os.File) *ReadWritePair {
+	return &ReadWritePair{r: r, w: w}
+}
+
+func (rw *ReadWritePair) Read(p []byte) (int, error) {
+	return rw.r.Read(p)
+}
+
+func (rw *ReadWritePair) Write(p []byte) (int, error) {
+	return rw.w.Write(p)
+}
+
+func (rw *ReadWritePair) Reader() *os.File {
+	return rw.r
+}
+
+func (rw *ReadWritePair) Writer() *os.File {
+	return rw.w
+}
+
+func (rw *ReadWritePair) Close() error {
+	if err := rw.r.Close(); err != nil {
+		return err
+	}
+	return rw.w.Close()
+}
+
+// CreateBidirectionalChannel creates a pair of FileChannels that are connected to each other.
+func CreateBidirectionalChannel() (FileChannel, FileChannel, error) {
+	ar, bw, err := os.Pipe()
+	if err != nil {
+		return nil, nil, err
+	}
+	br, aw, err := os.Pipe()
+	if err != nil {
+		return nil, nil, err
+	}
+	return NewReadWritePair(ar, aw), NewReadWritePair(br, bw), nil
+}
+
+const (
+	HClientRFd = 3
+	HClientWFd = 4
+	PClientRFd = 5
+	PClientWFd = 6
+)
+
+func ClientHinterChannel() FileChannel {
+	r := os.NewFile(HClientRFd, "preimage-hint-read")
+	w := os.NewFile(HClientWFd, "preimage-hint-write")
+	return NewReadWritePair(r, w)
+}
+
+// ClientPreimageChannel returns a FileChannel for the preimage oracle in a detached context
+func ClientPreimageChannel() FileChannel {
+	r := os.NewFile(PClientRFd, "preimage-oracle-read")
+	w := os.NewFile(PClientWFd, "preimage-oracle-write")
+	return NewReadWritePair(r, w)
+}

preimage/hash.go

+package preimage
+
+import "golang.org/x/crypto/sha3"
+
+func Keccak256(v []byte) (out [32]byte) {
+	s := sha3.NewLegacyKeccak256()
+	s.Write(v)
+	s.Sum(out[:0])
+	return
+}

preimage/oracle_test.go

@@ -9,16 +9,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
-	"golang.org/x/crypto/sha3"
 )
 
-func keccak256(v []byte) (out [32]byte) {
-	s := sha3.NewLegacyKeccak256()
-	s.Write(v)
-	s.Sum(out[:0])
-	return
-}
-
 type readWritePair struct {
 	io.Reader
 	io.Writer
@@ -38,11 +30,11 @@ func TestOracle(t *testing.T) {
 
 		preimageByHash := make(map[[32]byte][]byte)
 		for _, p := range preimages {
-			k := Keccak256Key(keccak256(p))
+			k := Keccak256Key(Keccak256(p))
 			preimageByHash[k.PreimageKey()] = p
 		}
 		for _, p := range preimages {
-			k := Keccak256Key(keccak256(p))
+			k := Keccak256Key(Keccak256(p))
 
 			var wg sync.WaitGroup
 			wg.Add(2)