Add package pkg/io and pkg/safecast

pkg/io/io.go

@@ -0,0 +1,41 @@
+//  Copyright 2021 PolyCrypt GmbH
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package io
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/perun-network/perun-cosmwasm-backend/pkg/safecast"
+	pio "perun.network/go-perun/pkg/io"
+)
+
+// WriteBytesUint16 writes the uint16-length-encoded byte slice to the stream.
+func WriteBytesUint16(w io.Writer, a []byte) error {
+	l := safecast.Uint16FromInt(len(a))
+	return pio.Encode(w, l, a)
+}
+
+// ReadBytesUint16 reads an uint16-length-encoded byte slice from the stream.
+func ReadBytesUint16(r io.Reader, a *[]byte) error {
+	var l uint16
+	err := pio.Decode(r, &l)
+	if err != nil {
+		return fmt.Errorf("reading length: %w", err)
+	}
+
+	*a = make([]byte, l)
+	return pio.Decode(r, a)
+}

pkg/io/io_test.go

@@ -0,0 +1,49 @@
+//  Copyright 2021 PolyCrypt GmbH
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package io_test
+
+import (
+	"bytes"
+	"math/rand"
+	"testing"
+
+	"github.com/perun-network/perun-cosmwasm-backend/pkg/io"
+)
+
+func TestReadWriteBytesUint16(t *testing.T) {
+	// Generate random byte slice with uint16 length.
+	l := rand.Intn(1 << 16)
+	b := make([]byte, l)
+	_, err := rand.Read(b)
+	if err != nil {
+		panic(err)
+	}
+
+	var buf bytes.Buffer
+	err = io.WriteBytesUint16(&buf, b)
+	if err != nil {
+		t.Fatalf("writing: %v", err)
+	}
+
+	_b := make([]byte, len(b))
+	err = io.ReadBytesUint16(&buf, &_b)
+	if err != nil {
+		t.Fatalf("reading: %v", err)
+	}
+
+	if !bytes.Equal(b, _b) {
+		t.Errorf("no equal: %v, %v", b, _b)
+	}
+}

pkg/safecast/safecast.go

@@ -0,0 +1,33 @@
+//  Copyright 2021 PolyCrypt GmbH
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package safecast
+
+// Uint16FromInt converts an int into an uint16 and panics if the value overflows.
+func Uint16FromInt(a int) uint16 {
+	b := uint16(a)
+	if a != int(b) {
+		panic("unsafe")
+	}
+	return b
+}
+
+// Int64FromUint64 converts an uint64 into an int64 and panics if the value overflows.
+func Int64FromUint64(a uint64) int64 {
+	b := int64(a)
+	if b < 0 {
+		panic("unsafe")
+	}
+	return b
+}

pkg/safecast/safecast_test.go

@@ -0,0 +1,80 @@
+//  Copyright 2021 PolyCrypt GmbH
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+package safecast_test
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/perun-network/perun-cosmwasm-backend/pkg/safecast"
+)
+
+func TestUint16FromInt(t *testing.T) {
+	// Test valid input: Correct result, no panic.
+	func() {
+		defer func() {
+			if err := recover(); err != nil {
+				t.Errorf("casting valid value should not panic: %v", err)
+			}
+		}()
+
+		i := rand.Intn(1 << 16)
+		_i := safecast.Uint16FromInt(i)
+		if i != int(_i) {
+			t.Errorf("values should be equal: %v, %v", i, _i)
+		}
+	}()
+
+	// Test invalid input: Panic.
+	func() {
+		defer func() {
+			if err := recover(); err == nil {
+				t.Errorf("casting invalid value should panic")
+			}
+		}()
+
+		i := 1 << 16
+		_ = safecast.Uint16FromInt(i)
+	}()
+}
+
+func TestInt64FromUint64(t *testing.T) {
+	// Test valid input: Correct result, no panic.
+	func() {
+		defer func() {
+			if err := recover(); err != nil {
+				t.Errorf("casting valid value should not panic: %v", err)
+			}
+		}()
+
+		i := uint64(rand.Int63())
+		_i := safecast.Int64FromUint64(i)
+		if i != uint64(_i) {
+			t.Errorf("values should be equal: %v, %v", i, _i)
+		}
+	}()
+
+	// Test invalid input: Panic.
+	func() {
+		defer func() {
+			if err := recover(); err == nil {
+				t.Errorf("casting invalid value should panic")
+			}
+		}()
+
+		i := uint64(1<<63) + 1
+		_ = safecast.Int64FromUint64(i)
+	}()
+}