| package eu.mulk.jgvariant.core; |
| |
| import static java.nio.ByteOrder.LITTLE_ENDIAN; |
| |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.RecordComponent; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| import java.nio.charset.Charset; |
| import java.nio.charset.StandardCharsets; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.List; |
| import java.util.Optional; |
| import org.jetbrains.annotations.Nullable; |
| |
| /** |
| * Type class for decodable types. |
| * |
| * <p>Use the {@code of*} family of constructor methods to acquire a suitable {@link Decoder} for |
| * the type you wish to decode. |
| * |
| * <p><strong>Example</strong> |
| * |
| * <p>To parse a GVariant of type {@code "a(si)"}, which is an array of pairs of {@link String} and |
| * {@code int}, you can use the following code: |
| * |
| * <pre>{@code |
| * record ExampleRecord(String s, int i) {} |
| * |
| * var decoder = |
| * Decoder.ofArray( |
| * Decoder.ofStructure( |
| * ExampleRecord.class, |
| * Decoder.ofString(UTF_8), |
| * Decoder.ofInt().withByteOrder(LITTLE_ENDIAN))); |
| * |
| * byte[] bytes = ...; |
| * List<ExampleRecord> example = decoder.decode(ByteBuffer.wrap(bytes)); |
| * }</pre> |
| * |
| * @param <T> the type that the {@link Decoder} can decode. |
| */ |
| @SuppressWarnings("java:S1610") |
| public abstract class Decoder<T> { |
| |
| private Decoder() {} |
| |
| /** |
| * @throws java.nio.BufferUnderflowException if the byte buffer is shorter than the requested |
| * data. |
| */ |
| public abstract T decode(ByteBuffer byteSlice); |
| |
| abstract byte alignment(); |
| |
| @Nullable |
| abstract Integer fixedSize(); |
| |
| final boolean hasFixedSize() { |
| return fixedSize() != null; |
| } |
| |
| /** |
| * Switches the input {@link ByteBuffer} to a given {@link ByteOrder} before reading from it. |
| * |
| * @param byteOrder the byte order to use. |
| * @return a new, decorated {@link Decoder}. |
| */ |
| public Decoder<T> withByteOrder(ByteOrder byteOrder) { |
| var delegate = this; |
| |
| return new Decoder<>() { |
| @Override |
| public byte alignment() { |
| return delegate.alignment(); |
| } |
| |
| @Override |
| public @Nullable Integer fixedSize() { |
| return delegate.fixedSize(); |
| } |
| |
| @Override |
| public T decode(ByteBuffer byteSlice) { |
| byteSlice.order(byteOrder); |
| return delegate.decode(byteSlice); |
| } |
| }; |
| } |
| |
| /** |
| * Creates a {@link Decoder} for an {@code Array} type. |
| * |
| * @param elementDecoder a {@link Decoder} for the elements of the array. |
| * @param <U> the element type. |
| * @return a new {@link Decoder}. |
| */ |
| public static <U> Decoder<List<U>> ofArray(Decoder<U> elementDecoder) { |
| return new ArrayDecoder<>(elementDecoder); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for a {@code Maybe} type. |
| * |
| * @param elementDecoder a {@link Decoder} for the contained element. |
| * @param <U> the element type. |
| * @return a new {@link Decoder}. |
| */ |
| public static <U> Decoder<Optional<U>> ofMaybe(Decoder<U> elementDecoder) { |
| return new MaybeDecoder<>(elementDecoder); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for a {@code Structure} type, decoding into a {@link Record}. |
| * |
| * @param recordType the {@link Record} type that represents the components of the structure. |
| * @param componentDecoders a {@link Decoder} for each component of the structure. |
| * @param <U> the {@link Record} type that represents the components of the structure. |
| * @return a new {@link Decoder}. |
| */ |
| public static <U extends Record> Decoder<U> ofStructure( |
| Class<U> recordType, Decoder<?>... componentDecoders) { |
| return new StructureDecoder<>(recordType, componentDecoders); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for a {@code Structure} type, decoding into a {@link List}. |
| * |
| * <p>Prefer {@link #ofStructure(Class, Decoder[])} if possible, which is both more type-safe and |
| * more convenient. |
| * |
| * @param componentDecoders a {@link Decoder} for each component of the structure. |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Object[]> ofStructure(Decoder<?>... componentDecoders) { |
| return new TupleDecoder(componentDecoders); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the {@code Variant} type. |
| * |
| * <p>The returned {@link Object} can be of one of the following types: |
| * |
| * <ul> |
| * <li>{@link Boolean} |
| * <li>{@link Byte} |
| * <li>{@link Short} |
| * <li>{@link Integer} |
| * <li>{@link Long} |
| * <li>{@link String} |
| * <li>{@link Optional} (a GVariant {@code Maybe} type) |
| * <li>{@link List} (a GVariant array) |
| * <li>{@link Object[]} (a GVariant structure) |
| * </ul> |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Object> ofVariant() { |
| return new VariantDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the {@code Boolean} type. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Boolean> ofBoolean() { |
| return new BooleanDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the 8-bit {@code byte} type. |
| * |
| * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| * result of this method. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Byte> ofByte() { |
| return new ByteDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the 16-bit {@code short} type. |
| * |
| * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| * result of this method. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Short> ofShort() { |
| return new ShortDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the 32-bit {@code int} type. |
| * |
| * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| * result of this method. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Integer> ofInt() { |
| return new IntegerDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the 64-bit {@code long} type. |
| * |
| * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| * result of this method. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Long> ofLong() { |
| return new LongDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the {@code double} type. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<Double> ofDouble() { |
| return new DoubleDecoder(); |
| } |
| |
| /** |
| * Creates a {@link Decoder} for the {@link String} type. |
| * |
| * <p><strong>Note:</strong> While GVariant does not prescribe any particular encoding, {@link |
| * java.nio.charset.StandardCharsets#UTF_8} is the most common choice. |
| * |
| * @return a new {@link Decoder}. |
| */ |
| public static Decoder<String> ofString(Charset charset) { |
| return new StringDecoder(charset); |
| } |
| |
| private static int align(int offset, byte alignment) { |
| return offset % alignment == 0 ? offset : offset + alignment - (offset % alignment); |
| } |
| |
| private static int getIntN(ByteBuffer byteSlice) { |
| var intBytes = new byte[4]; |
| byteSlice.get(intBytes, 0, Math.min(4, byteSlice.limit())); |
| return ByteBuffer.wrap(intBytes).order(LITTLE_ENDIAN).getInt(); |
| } |
| |
| @SuppressWarnings("java:S3358") |
| private static int byteCount(int n) { |
| return n < (1 << 8) ? 1 : n < (1 << 16) ? 2 : 4; |
| } |
| |
| private static class ArrayDecoder<U> extends Decoder<List<U>> { |
| |
| private final Decoder<U> elementDecoder; |
| |
| ArrayDecoder(Decoder<U> elementDecoder) { |
| this.elementDecoder = elementDecoder; |
| } |
| |
| @Override |
| public byte alignment() { |
| return elementDecoder.alignment(); |
| } |
| |
| @Override |
| @Nullable |
| Integer fixedSize() { |
| return null; |
| } |
| |
| @Override |
| public List<U> decode(ByteBuffer byteSlice) { |
| List<U> elements; |
| |
| var elementSize = elementDecoder.fixedSize(); |
| if (elementSize != null) { |
| // A simple C-style array. |
| elements = new ArrayList<>(byteSlice.limit() / elementSize); |
| for (int i = 0; i < byteSlice.limit(); i += elementSize) { |
| var element = elementDecoder.decode(byteSlice.slice(i, elementSize)); |
| elements.add(element); |
| } |
| } else { |
| // An array with aligned elements and a vector of framing offsets in the end. |
| int framingOffsetSize = byteCount(byteSlice.limit()); |
| int lastFramingOffset = |
| getIntN(byteSlice.slice(byteSlice.limit() - framingOffsetSize, framingOffsetSize)); |
| int elementCount = (byteSlice.limit() - lastFramingOffset) / framingOffsetSize; |
| |
| elements = new ArrayList<>(elementCount); |
| int position = 0; |
| for (int i = 0; i < elementCount; i++) { |
| int framingOffset = |
| getIntN( |
| byteSlice.slice(lastFramingOffset + i * framingOffsetSize, framingOffsetSize)); |
| elements.add(elementDecoder.decode(byteSlice.slice(position, framingOffset - position))); |
| position = align(framingOffset, alignment()); |
| } |
| } |
| |
| return elements; |
| } |
| } |
| |
| private static class MaybeDecoder<U> extends Decoder<Optional<U>> { |
| |
| private final Decoder<U> elementDecoder; |
| |
| MaybeDecoder(Decoder<U> elementDecoder) { |
| this.elementDecoder = elementDecoder; |
| } |
| |
| @Override |
| public byte alignment() { |
| return elementDecoder.alignment(); |
| } |
| |
| @Override |
| @Nullable |
| Integer fixedSize() { |
| return null; |
| } |
| |
| @Override |
| public Optional<U> decode(ByteBuffer byteSlice) { |
| if (!byteSlice.hasRemaining()) { |
| return Optional.empty(); |
| } else { |
| if (!elementDecoder.hasFixedSize()) { |
| // Remove trailing zero byte. |
| byteSlice.limit(byteSlice.limit() - 1); |
| } |
| |
| return Optional.of(elementDecoder.decode(byteSlice)); |
| } |
| } |
| } |
| |
| private static class StructureDecoder<U extends Record> extends Decoder<U> { |
| |
| private final Class<U> recordType; |
| private final TupleDecoder tupleDecoder; |
| |
| StructureDecoder(Class<U> recordType, Decoder<?>... componentDecoders) { |
| var recordComponents = recordType.getRecordComponents(); |
| if (componentDecoders.length != recordComponents.length) { |
| throw new IllegalArgumentException( |
| "number of decoders (%d) does not match number of structure components (%d)" |
| .formatted(componentDecoders.length, recordComponents.length)); |
| } |
| |
| this.recordType = recordType; |
| this.tupleDecoder = new TupleDecoder(componentDecoders); |
| } |
| |
| @Override |
| public byte alignment() { |
| return tupleDecoder.alignment(); |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return tupleDecoder.fixedSize(); |
| } |
| |
| @Override |
| public U decode(ByteBuffer byteSlice) { |
| Object[] recordConstructorArguments = tupleDecoder.decode(byteSlice); |
| |
| try { |
| var recordComponentTypes = |
| Arrays.stream(recordType.getRecordComponents()) |
| .map(RecordComponent::getType) |
| .toArray(Class<?>[]::new); |
| var recordConstructor = recordType.getDeclaredConstructor(recordComponentTypes); |
| return recordConstructor.newInstance(recordConstructorArguments); |
| } catch (NoSuchMethodException |
| | InstantiationException |
| | IllegalAccessException |
| | InvocationTargetException e) { |
| throw new IllegalStateException(e); |
| } |
| } |
| } |
| |
| private static class TupleDecoder extends Decoder<Object[]> { |
| |
| private final Decoder<?>[] componentDecoders; |
| |
| TupleDecoder(Decoder<?>... componentDecoders) { |
| this.componentDecoders = componentDecoders; |
| } |
| |
| @Override |
| public byte alignment() { |
| return (byte) Arrays.stream(componentDecoders).mapToInt(Decoder::alignment).max().orElse(1); |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| int position = 0; |
| for (var componentDecoder : componentDecoders) { |
| var fixedComponentSize = componentDecoder.fixedSize(); |
| if (fixedComponentSize == null) { |
| return null; |
| } |
| |
| position = align(position, componentDecoder.alignment()); |
| position += fixedComponentSize; |
| } |
| |
| if (position == 0) { |
| return 1; |
| } |
| |
| return align(position, alignment()); |
| } |
| |
| @Override |
| public Object[] decode(ByteBuffer byteSlice) { |
| int framingOffsetSize = byteCount(byteSlice.limit()); |
| |
| var objects = new Object[componentDecoders.length]; |
| |
| int position = 0; |
| int framingOffsetIndex = 0; |
| int componentIndex = 0; |
| for (var componentDecoder : componentDecoders) { |
| position = align(position, componentDecoder.alignment()); |
| |
| var fixedComponentSize = componentDecoder.fixedSize(); |
| if (fixedComponentSize != null) { |
| objects[componentIndex] = |
| componentDecoder.decode(byteSlice.slice(position, fixedComponentSize)); |
| position += fixedComponentSize; |
| } else { |
| if (componentIndex == componentDecoders.length - 1) { |
| // The last component never has a framing offset. |
| int endPosition = byteSlice.limit() - framingOffsetIndex * framingOffsetSize; |
| objects[componentIndex] = |
| componentDecoder.decode(byteSlice.slice(position, endPosition - position)); |
| position = endPosition; |
| } else { |
| int framingOffset = |
| getIntN( |
| byteSlice.slice( |
| byteSlice.limit() - (1 + framingOffsetIndex) * framingOffsetSize, |
| framingOffsetSize)); |
| objects[componentIndex] = |
| componentDecoder.decode(byteSlice.slice(position, framingOffset - position)); |
| position = framingOffset; |
| ++framingOffsetIndex; |
| } |
| } |
| |
| ++componentIndex; |
| } |
| |
| return objects; |
| } |
| } |
| |
| private static class VariantDecoder extends Decoder<Object> { |
| |
| @Override |
| public byte alignment() { |
| return 8; |
| } |
| |
| @Override |
| @Nullable |
| Integer fixedSize() { |
| return null; |
| } |
| |
| @Override |
| public Object decode(ByteBuffer byteSlice) { |
| for (int i = byteSlice.limit() - 1; i >= 0; --i) { |
| if (byteSlice.get(i) != 0) { |
| continue; |
| } |
| |
| var data = byteSlice.slice(0, i); |
| var signature = byteSlice.slice(i + 1, byteSlice.limit() - (i + 1)); |
| |
| Decoder<?> decoder = parseSignature(signature); |
| return decoder.decode(data); |
| } |
| |
| throw new IllegalArgumentException("variant signature not found"); |
| } |
| |
| private static Decoder<?> parseSignature(ByteBuffer signature) { |
| char c = (char) signature.get(); |
| return switch (c) { |
| case 'b' -> Decoder.ofBoolean(); |
| case 'y' -> Decoder.ofByte(); |
| case 'n', 'q' -> Decoder.ofShort(); |
| case 'i', 'u' -> Decoder.ofInt(); |
| case 'x', 't' -> Decoder.ofLong(); |
| case 'd' -> Decoder.ofDouble(); |
| case 's', 'o', 'g' -> Decoder.ofString(StandardCharsets.UTF_8); |
| case 'v' -> Decoder.ofVariant(); |
| case 'm' -> Decoder.ofMaybe(parseSignature(signature)); |
| case 'a' -> Decoder.ofArray(parseSignature(signature)); |
| case '(', '{' -> Decoder.ofStructure(parseTupleTypes(signature).toArray(new Decoder<?>[0])); |
| default -> throw new IllegalArgumentException( |
| String.format("encountered unknown signature byte '%c'", c)); |
| }; |
| } |
| |
| private static List<Decoder<?>> parseTupleTypes(ByteBuffer signature) { |
| List<Decoder<?>> decoders = new ArrayList<>(); |
| |
| while (true) { |
| char c = (char) signature.get(signature.position()); |
| if (c == ')' || c == '}') { |
| signature.get(); |
| break; |
| } |
| |
| decoders.add(parseSignature(signature)); |
| } |
| |
| return decoders; |
| } |
| } |
| |
| private static class BooleanDecoder extends Decoder<Boolean> { |
| |
| @Override |
| public byte alignment() { |
| return 1; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 1; |
| } |
| |
| @Override |
| public Boolean decode(ByteBuffer byteSlice) { |
| return byteSlice.get() != 0; |
| } |
| } |
| |
| private static class ByteDecoder extends Decoder<Byte> { |
| |
| @Override |
| public byte alignment() { |
| return 1; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 1; |
| } |
| |
| @Override |
| public Byte decode(ByteBuffer byteSlice) { |
| return byteSlice.get(); |
| } |
| } |
| |
| private static class ShortDecoder extends Decoder<Short> { |
| |
| @Override |
| public byte alignment() { |
| return 2; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 2; |
| } |
| |
| @Override |
| public Short decode(ByteBuffer byteSlice) { |
| return byteSlice.getShort(); |
| } |
| } |
| |
| private static class IntegerDecoder extends Decoder<Integer> { |
| |
| @Override |
| public byte alignment() { |
| return 4; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 4; |
| } |
| |
| @Override |
| public Integer decode(ByteBuffer byteSlice) { |
| return byteSlice.getInt(); |
| } |
| } |
| |
| private static class LongDecoder extends Decoder<Long> { |
| |
| @Override |
| public byte alignment() { |
| return 8; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 8; |
| } |
| |
| @Override |
| public Long decode(ByteBuffer byteSlice) { |
| return byteSlice.getLong(); |
| } |
| } |
| |
| private static class DoubleDecoder extends Decoder<Double> { |
| |
| @Override |
| public byte alignment() { |
| return 8; |
| } |
| |
| @Override |
| public Integer fixedSize() { |
| return 8; |
| } |
| |
| @Override |
| public Double decode(ByteBuffer byteSlice) { |
| return byteSlice.getDouble(); |
| } |
| } |
| |
| private static class StringDecoder extends Decoder<String> { |
| |
| private final Charset charset; |
| |
| public StringDecoder(Charset charset) { |
| this.charset = charset; |
| } |
| |
| @Override |
| public byte alignment() { |
| return 1; |
| } |
| |
| @Override |
| @Nullable |
| Integer fixedSize() { |
| return null; |
| } |
| |
| @Override |
| public String decode(ByteBuffer byteSlice) { |
| byteSlice.limit(byteSlice.limit() - 1); |
| return charset.decode(byteSlice).toString(); |
| } |
| } |
| } |