Package io.flutter.plugin.common

Class StandardMessageCodec

  • All Implemented Interfaces:
    MessageCodec<Object>
    public class StandardMessageCodec
extends Object
implements MessageCodec<Object>
    MessageCodec using the Flutter standard binary encoding.

    This codec is guaranteed to be compatible with the corresponding StandardMessageCodec on the Dart side. These parts of the Flutter SDK are evolved synchronously.

    Supported messages are acyclic values of these forms:

    • null
    • Booleans
    • Bytes, Shorts, Integers, Longs
    • BigIntegers (see below)
    • Floats, Doubles
    • Strings
    • byte[], int[], long[], float[], double[]
    • Lists of supported values
    • Maps with supported keys and values

    On the Dart side, these values are represented as follows:

    • null: null
    • Boolean: bool
    • Byte, Short, Integer, Long: int
    • Float, Double: double
    • String: String
    • byte[]: Uint8List
    • int[]: Int32List
    • long[]: Int64List
    • float[]: Float32List
    • double[]: Float64List
    • List: List
    • Map: Map

    BigIntegers are represented in Dart as strings with the hexadecimal representation of the integer's value.

    To extend the codec, overwrite the writeValue and readValueOfType methods.

    • Constructor Detail

      • StandardMessageCodec

        public StandardMessageCodec()

    • Method Detail

      • encodeMessage

        @Nullable
public ByteBuffer encodeMessage​(@Nullable
                                Object message)
        Description copied from interface: MessageCodec
        Encodes the specified message into binary.
        Specified by:
        encodeMessage in interface MessageCodec<Object>
        Parameters:
        message - the T message, possibly null.
        Returns:
        a ByteBuffer containing the encoding between position 0 and the current position, or null, if message is null.

      • decodeMessage

        @Nullable
public Object decodeMessage​(@Nullable
                            ByteBuffer message)
        Description copied from interface: MessageCodec
        Decodes the specified message from binary.

        Warning: The ByteBuffer is "direct" and it won't be valid beyond this call. Storing the ByteBuffer and using it later and will lead to a java.nio.BufferUnderflowException. If you want to retain the data you'll need to copy it.

        Specified by:
        decodeMessage in interface MessageCodec<Object>
        Parameters:
        message - the ByteBuffer message, possibly null.
        Returns:
        a T value representation of the bytes between the given buffer's current position and its limit, or null, if message is null.

      • writeSize

        protected static final void writeSize​(@NonNull
                                      ByteArrayOutputStream stream,
                                      int value)
        Writes an int representing a size to the specified stream. Uses an expanding code of 1 to 5 bytes to optimize for small values.

      • writeChar

        protected static final void writeChar​(@NonNull
                                      ByteArrayOutputStream stream,
                                      int value)
        Writes the least significant two bytes of the specified int to the specified stream.

      • writeInt

        protected static final void writeInt​(@NonNull
                                     ByteArrayOutputStream stream,
                                     int value)
        Writes the specified int as 4 bytes to the specified stream.

      • writeLong

        protected static final void writeLong​(@NonNull
                                      ByteArrayOutputStream stream,
                                      long value)
        Writes the specified long as 8 bytes to the specified stream.

      • writeFloat

        protected static final void writeFloat​(@NonNull
                                       ByteArrayOutputStream stream,
                                       float value)
        Writes the specified double as 4 bytes to the specified stream

      • writeDouble

        protected static final void writeDouble​(@NonNull
                                        ByteArrayOutputStream stream,
                                        double value)
        Writes the specified double as 8 bytes to the specified stream.

      • writeBytes

        protected static final void writeBytes​(@NonNull
                                       ByteArrayOutputStream stream,
                                       @NonNull
                                       byte[] bytes)
        Writes the length and then the actual bytes of the specified array to the specified stream.

      • writeAlignment

        protected static final void writeAlignment​(@NonNull
                                           ByteArrayOutputStream stream,
                                           int alignment)
        Writes a number of padding bytes to the specified stream to ensure that the next value is aligned to a whole multiple of the specified alignment. An example usage with alignment = 8 is to ensure doubles are word-aligned in the stream.

      • writeValue

        protected void writeValue​(@NonNull
                          ByteArrayOutputStream stream,
                          @Nullable
                          Object value)
        Writes a type discriminator byte and then a byte serialization of the specified value to the specified stream.

        Subclasses can extend the codec by overriding this method, calling super for values that the extension does not handle.

      • readSize

        protected static final int readSize​(@NonNull
                                    ByteBuffer buffer)
        Reads an int representing a size as written by writeSize.

      • readBytes

        @NonNull
protected static final byte[] readBytes​(@NonNull
                                        ByteBuffer buffer)
        Reads a byte array as written by writeBytes.

      • readAlignment

        protected static final void readAlignment​(@NonNull
                                          ByteBuffer buffer,
                                          int alignment)
        Reads alignment padding bytes as written by writeAlignment.

      • readValue

        @NonNull
protected final Object readValue​(@NonNull
                                 ByteBuffer buffer)
        Reads a value as written by writeValue.

      • readValueOfType

        @Nullable
protected Object readValueOfType​(byte type,
                                 @NonNull
                                 ByteBuffer buffer)
        Reads a value of the specified type.

        Subclasses may extend the codec by overriding this method, calling super for types that the extension does not handle.