hopp: Bring some old decoding/encoding functions that worked on []byte back

codec.go

@@ -0,0 +1,47 @@
+package hopp
+
+import "fmt"
+
+type anyInt16 interface { ~uint16 | ~int16 }
+type anyInt64 interface { ~uint64 | ~int64 }
+
+// decodeI16 decodes a 16 bit integer from the given data.
+func decodeI16[T anyInt16](data []byte) (T, error) {
+	if len(data) != 2 { return 0, fmt.Errorf("decoding int16: %w", ErrWrongBufferLength) }
+	return T(data[0]) << 8 | T(data[1]), nil
+}
+
+// encodeI16 encodes a 16 bit integer into the given buffer.
+func encodeI16[T anyInt16](buffer []byte, value T) error {
+	if len(buffer) != 2 { return fmt.Errorf("encoding int16: %w", ErrWrongBufferLength) }
+	buffer[0] = byte(value >> 8)
+	buffer[1] = byte(value)
+	return nil
+}
+
+// decodeI64 decodes a 64 bit integer from the given data.
+func decodeI64[T anyInt64](data []byte) (T, error) {
+	if len(data) != 8 { return 0, fmt.Errorf("decoding int64: %w", ErrWrongBufferLength) }
+	return T(data[0]) << 56 |
+		T(data[1]) << 48 |
+		T(data[2]) << 40 |
+		T(data[3]) << 32 |
+		T(data[4]) << 24 |
+		T(data[5]) << 16 |
+		T(data[6]) <<  8 |
+		T(data[7]), nil
+}
+
+// encodeI64 encodes a 64 bit integer into the given buffer.
+func encodeI64[T anyInt64](buffer []byte, value T) error {
+	if len(buffer) != 8 { return fmt.Errorf("encoding int64: %w", ErrWrongBufferLength) }
+	buffer[0] = byte(value >> 56)
+	buffer[1] = byte(value >> 48)
+	buffer[2] = byte(value >> 40)
+	buffer[3] = byte(value >> 32)
+	buffer[4] = byte(value >> 24)
+	buffer[5] = byte(value >> 16)
+	buffer[6] = byte(value >> 8)
+	buffer[7] = byte(value)
+	return nil
+}

error.go

@@ -9,6 +9,7 @@ type Error string; const (
 	ErrIntegerOverflow    Error = "integer overflow"
 	ErrMessageMalformed   Error = "message is malformed"
 	ErrTablePairMissing   Error = "required table pair is missing"
+	ErrWrongBufferLength  Error = "wrong buffer length"
 )
 
 // Error implements the error interface.