Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 1 | package eu.mulk.jgvariant.core; |
| 2 | |
| 3 | import static java.nio.ByteOrder.LITTLE_ENDIAN; |
| 4 | |
| 5 | import eu.mulk.jgvariant.core.Value.Array; |
| 6 | import eu.mulk.jgvariant.core.Value.Bool; |
| 7 | import eu.mulk.jgvariant.core.Value.Float64; |
| 8 | import eu.mulk.jgvariant.core.Value.Int16; |
| 9 | import eu.mulk.jgvariant.core.Value.Int32; |
| 10 | import eu.mulk.jgvariant.core.Value.Int64; |
| 11 | import eu.mulk.jgvariant.core.Value.Int8; |
| 12 | import eu.mulk.jgvariant.core.Value.Maybe; |
| 13 | import eu.mulk.jgvariant.core.Value.Str; |
| 14 | import eu.mulk.jgvariant.core.Value.Structure; |
| 15 | import eu.mulk.jgvariant.core.Value.Variant; |
| 16 | import java.lang.reflect.InvocationTargetException; |
| 17 | import java.lang.reflect.RecordComponent; |
| 18 | import java.nio.ByteBuffer; |
| 19 | import java.nio.ByteOrder; |
| 20 | import java.nio.charset.Charset; |
| 21 | import java.util.ArrayList; |
| 22 | import java.util.Arrays; |
| 23 | import java.util.List; |
| 24 | import java.util.Optional; |
| 25 | import org.jetbrains.annotations.Nullable; |
| 26 | |
| 27 | /** |
| 28 | * Type class for decodable {@link Value} types. |
| 29 | * |
| 30 | * <p>Use the {@code of*} family of constructor methods to acquire a suitable {@link Decoder} for |
| 31 | * the type you wish to decode. |
| 32 | * |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 33 | * <p><strong>Example</strong> |
| 34 | * |
| 35 | * <p>To parse a GVariant of type {@code "a(si)"}, which is an array of pairs of {@link String} and |
| 36 | * {@code int}, you can use the following code: |
| 37 | * |
| 38 | * <pre>{@code |
| 39 | * record ExampleRecord(Value.Str s, Value.Int32 i) {} |
| 40 | * |
| 41 | * var decoder = |
| 42 | * Decoder.ofArray( |
| 43 | * Decoder.ofStructure( |
| 44 | * ExampleRecord.class, |
| 45 | * Decoder.ofStr(UTF_8), |
| 46 | * Decoder.ofInt32().withByteOrder(LITTLE_ENDIAN))); |
| 47 | * |
| 48 | * byte[] bytes = ...; |
| 49 | * Value.Array<Value.Structure<ExampleRecord>> example = decoder.decode(ByteBuffer.wrap(bytes)); |
| 50 | * }</pre> |
| 51 | * |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 52 | * @param <T> the type that the {@link Decoder} can decode. |
| 53 | */ |
| 54 | @SuppressWarnings("java:S1610") |
| 55 | public abstract class Decoder<T extends Value> { |
| 56 | |
| 57 | private Decoder() {} |
| 58 | |
| 59 | /** |
| 60 | * @throws java.nio.BufferUnderflowException if the byte buffer is shorter than the requested |
| 61 | * data. |
| 62 | */ |
| 63 | public abstract T decode(ByteBuffer byteSlice); |
| 64 | |
| 65 | abstract byte alignment(); |
| 66 | |
| 67 | @Nullable |
| 68 | abstract Integer fixedSize(); |
| 69 | |
| 70 | final boolean hasFixedSize() { |
| 71 | return fixedSize() != null; |
| 72 | } |
| 73 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 74 | /** |
| 75 | * Switches the input {@link ByteBuffer} to a given {@link ByteOrder} before reading from it. |
| 76 | * |
| 77 | * @param byteOrder the byte order to use. |
| 78 | * @return a new, decorated {@link Decoder}. |
| 79 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 80 | public Decoder<T> withByteOrder(ByteOrder byteOrder) { |
| 81 | var delegate = this; |
| 82 | |
| 83 | return new Decoder<>() { |
| 84 | @Override |
| 85 | public byte alignment() { |
| 86 | return delegate.alignment(); |
| 87 | } |
| 88 | |
| 89 | @Override |
| 90 | public @Nullable Integer fixedSize() { |
| 91 | return delegate.fixedSize(); |
| 92 | } |
| 93 | |
| 94 | @Override |
| 95 | public T decode(ByteBuffer byteSlice) { |
| 96 | byteSlice.order(byteOrder); |
| 97 | return delegate.decode(byteSlice); |
| 98 | } |
| 99 | }; |
| 100 | } |
| 101 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 102 | /** |
| 103 | * Creates a {@link Decoder} for an {@link Array} type. |
| 104 | * |
| 105 | * @param elementDecoder a {@link Decoder} for the elements of the array. |
| 106 | * @param <U> the element type. |
| 107 | * @return a new {@link Decoder}. |
| 108 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 109 | public static <U extends Value> Decoder<Array<U>> ofArray(Decoder<U> elementDecoder) { |
| 110 | return new Decoder<>() { |
| 111 | @Override |
| 112 | public byte alignment() { |
| 113 | return elementDecoder.alignment(); |
| 114 | } |
| 115 | |
| 116 | @Override |
| 117 | @Nullable |
| 118 | Integer fixedSize() { |
| 119 | return null; |
| 120 | } |
| 121 | |
| 122 | @Override |
| 123 | public Array<U> decode(ByteBuffer byteSlice) { |
| 124 | List<U> elements; |
| 125 | |
| 126 | var elementSize = elementDecoder.fixedSize(); |
| 127 | if (elementSize != null) { |
| 128 | // A simple C-style array. |
| 129 | elements = new ArrayList<>(byteSlice.limit() / elementSize); |
| 130 | for (int i = 0; i < byteSlice.limit(); i += elementSize) { |
| 131 | var element = elementDecoder.decode(byteSlice.slice(i, elementSize)); |
| 132 | elements.add(element); |
| 133 | } |
| 134 | } else { |
| 135 | // An array with aligned elements and a vector of framing offsets in the end. |
| 136 | int framingOffsetSize = byteCount(byteSlice.limit()); |
| 137 | int lastFramingOffset = |
| 138 | getIntN(byteSlice.slice(byteSlice.limit() - framingOffsetSize, framingOffsetSize)); |
| 139 | int elementCount = (byteSlice.limit() - lastFramingOffset) / framingOffsetSize; |
| 140 | |
| 141 | elements = new ArrayList<>(elementCount); |
| 142 | int position = 0; |
| 143 | for (int i = 0; i < elementCount; i++) { |
| 144 | int framingOffset = |
| 145 | getIntN( |
| 146 | byteSlice.slice(lastFramingOffset + i * framingOffsetSize, framingOffsetSize)); |
| 147 | elements.add( |
| 148 | elementDecoder.decode(byteSlice.slice(position, framingOffset - position))); |
| 149 | position = align(framingOffset, alignment()); |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | return new Array<>(elements); |
| 154 | } |
| 155 | }; |
| 156 | } |
| 157 | |
| 158 | private static int align(int offset, byte alignment) { |
| 159 | return offset % alignment == 0 ? offset : offset + alignment - (offset % alignment); |
| 160 | } |
| 161 | |
| 162 | private static int getIntN(ByteBuffer byteSlice) { |
| 163 | var intBytes = new byte[4]; |
| 164 | byteSlice.get(intBytes, 0, Math.min(4, byteSlice.limit())); |
| 165 | return ByteBuffer.wrap(intBytes).order(LITTLE_ENDIAN).getInt(); |
| 166 | } |
| 167 | |
| 168 | @SuppressWarnings("java:S3358") |
| 169 | private static int byteCount(int n) { |
| 170 | return n < (1 << 8) ? 1 : n < (1 << 16) ? 2 : 4; |
| 171 | } |
| 172 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 173 | /** |
| 174 | * Creates a {@link Decoder} for a {@link Maybe} type. |
| 175 | * |
| 176 | * @param elementDecoder a {@link Decoder} for the contained element. |
| 177 | * @param <U> the element type. |
| 178 | * @return a new {@link Decoder}. |
| 179 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 180 | public static <U extends Value> Decoder<Maybe<U>> ofMaybe(Decoder<U> elementDecoder) { |
| 181 | return new Decoder<>() { |
| 182 | @Override |
| 183 | public byte alignment() { |
| 184 | return elementDecoder.alignment(); |
| 185 | } |
| 186 | |
| 187 | @Override |
| 188 | @Nullable |
| 189 | Integer fixedSize() { |
| 190 | return null; |
| 191 | } |
| 192 | |
| 193 | @Override |
| 194 | public Maybe<U> decode(ByteBuffer byteSlice) { |
| 195 | if (!byteSlice.hasRemaining()) { |
| 196 | return new Maybe<>(Optional.empty()); |
| 197 | } else { |
| 198 | if (!elementDecoder.hasFixedSize()) { |
| 199 | // Remove trailing zero byte. |
| 200 | byteSlice.limit(byteSlice.limit() - 1); |
| 201 | } |
| 202 | |
| 203 | return new Maybe<>(Optional.of(elementDecoder.decode(byteSlice))); |
| 204 | } |
| 205 | } |
| 206 | }; |
| 207 | } |
| 208 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 209 | /** |
| 210 | * Creates a {@link Decoder} for a {@link Structure} type. |
| 211 | * |
| 212 | * @param recordType the {@link Record} type that represents the components of the structure. |
| 213 | * @param componentDecoders a {@link Decoder} for each component of the structure. |
| 214 | * @param <U> the {@link Record} type that represents the components of the structure. |
| 215 | * @return a new {@link Decoder}. |
| 216 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 217 | @SafeVarargs |
| 218 | public static <U extends Record> Decoder<Structure<U>> ofStructure( |
| 219 | Class<U> recordType, Decoder<? extends Value>... componentDecoders) { |
| 220 | var recordComponents = recordType.getRecordComponents(); |
| 221 | if (componentDecoders.length != recordComponents.length) { |
| 222 | throw new IllegalArgumentException( |
| 223 | "number of decoders (%d) does not match number of structure components (%d)" |
| 224 | .formatted(componentDecoders.length, recordComponents.length)); |
| 225 | } |
| 226 | |
| 227 | return new Decoder<>() { |
| 228 | @Override |
| 229 | public byte alignment() { |
| 230 | return (byte) Arrays.stream(componentDecoders).mapToInt(Decoder::alignment).max().orElse(1); |
| 231 | } |
| 232 | |
| 233 | @Override |
| 234 | public Integer fixedSize() { |
| 235 | int position = 0; |
| 236 | for (var componentDecoder : componentDecoders) { |
| 237 | var fixedComponentSize = componentDecoder.fixedSize(); |
| 238 | if (fixedComponentSize == null) { |
| 239 | return null; |
| 240 | } |
| 241 | |
| 242 | position = align(position, componentDecoder.alignment()); |
| 243 | position += fixedComponentSize; |
| 244 | } |
| 245 | |
| 246 | if (position == 0) { |
| 247 | return 1; |
| 248 | } |
| 249 | |
| 250 | return align(position, alignment()); |
| 251 | } |
| 252 | |
| 253 | @Override |
| 254 | public Structure<U> decode(ByteBuffer byteSlice) { |
| 255 | int framingOffsetSize = byteCount(byteSlice.limit()); |
| 256 | |
| 257 | var recordConstructorArguments = new Object[recordComponents.length]; |
| 258 | |
| 259 | int position = 0; |
| 260 | int framingOffsetIndex = 0; |
| 261 | int componentIndex = 0; |
| 262 | for (var componentDecoder : componentDecoders) { |
| 263 | position = align(position, componentDecoder.alignment()); |
| 264 | |
| 265 | var fixedComponentSize = componentDecoder.fixedSize(); |
| 266 | if (fixedComponentSize != null) { |
| 267 | recordConstructorArguments[componentIndex] = |
| 268 | componentDecoder.decode(byteSlice.slice(position, fixedComponentSize)); |
| 269 | position += fixedComponentSize; |
| 270 | } else { |
| 271 | if (componentIndex == recordComponents.length - 1) { |
| 272 | // The last component never has a framing offset. |
| 273 | int endPosition = byteSlice.limit() - framingOffsetIndex * framingOffsetSize; |
| 274 | recordConstructorArguments[componentIndex] = |
| 275 | componentDecoder.decode(byteSlice.slice(position, endPosition - position)); |
| 276 | position = endPosition; |
| 277 | } else { |
| 278 | int framingOffset = |
| 279 | getIntN( |
| 280 | byteSlice.slice( |
| 281 | byteSlice.limit() - (1 + framingOffsetIndex) * framingOffsetSize, |
| 282 | framingOffsetSize)); |
| 283 | recordConstructorArguments[componentIndex] = |
| 284 | componentDecoder.decode(byteSlice.slice(position, framingOffset - position)); |
| 285 | position = framingOffset; |
| 286 | ++framingOffsetIndex; |
| 287 | } |
| 288 | } |
| 289 | |
| 290 | ++componentIndex; |
| 291 | } |
| 292 | |
| 293 | try { |
| 294 | var recordComponentTypes = |
| 295 | Arrays.stream(recordType.getRecordComponents()) |
| 296 | .map(RecordComponent::getType) |
| 297 | .toArray(Class<?>[]::new); |
| 298 | var recordConstructor = recordType.getDeclaredConstructor(recordComponentTypes); |
| 299 | return new Structure<>(recordConstructor.newInstance(recordConstructorArguments)); |
| 300 | } catch (NoSuchMethodException |
| 301 | | InstantiationException |
| 302 | | IllegalAccessException |
| 303 | | InvocationTargetException e) { |
| 304 | throw new IllegalStateException(e); |
| 305 | } |
| 306 | } |
| 307 | }; |
| 308 | } |
| 309 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 310 | /** |
| 311 | * Creates a {@link Decoder} for the {@link Variant} type. |
| 312 | * |
| 313 | * @return a new {@link Decoder}. |
| 314 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 315 | public static Decoder<Variant> ofVariant() { |
| 316 | return new Decoder<>() { |
| 317 | @Override |
| 318 | public byte alignment() { |
| 319 | return 8; |
| 320 | } |
| 321 | |
| 322 | @Override |
| 323 | @Nullable |
| 324 | Integer fixedSize() { |
| 325 | return null; |
| 326 | } |
| 327 | |
| 328 | @Override |
| 329 | public Variant decode(ByteBuffer byteSlice) { |
| 330 | // TODO |
| 331 | throw new UnsupportedOperationException("not implemented"); |
| 332 | } |
| 333 | }; |
| 334 | } |
| 335 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 336 | /** |
| 337 | * Creates a {@link Decoder} for the {@link Bool} type. |
| 338 | * |
| 339 | * @return a new {@link Decoder}. |
| 340 | */ |
| 341 | public static Decoder<Bool> ofBool() { |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 342 | return new Decoder<>() { |
| 343 | @Override |
| 344 | public byte alignment() { |
| 345 | return 1; |
| 346 | } |
| 347 | |
| 348 | @Override |
| 349 | public Integer fixedSize() { |
| 350 | return 1; |
| 351 | } |
| 352 | |
| 353 | @Override |
| 354 | public Bool decode(ByteBuffer byteSlice) { |
| 355 | return new Bool(byteSlice.get() != 0); |
| 356 | } |
| 357 | }; |
| 358 | } |
| 359 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 360 | /** |
| 361 | * Creates a {@link Decoder} for the {@link Int8} type. |
| 362 | * |
| 363 | * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| 364 | * result of this method. |
| 365 | * |
| 366 | * @return a new {@link Decoder}. |
| 367 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 368 | public static Decoder<Int8> ofInt8() { |
| 369 | return new Decoder<>() { |
| 370 | @Override |
| 371 | public byte alignment() { |
| 372 | return 1; |
| 373 | } |
| 374 | |
| 375 | @Override |
| 376 | public Integer fixedSize() { |
| 377 | return 1; |
| 378 | } |
| 379 | |
| 380 | @Override |
| 381 | public Int8 decode(ByteBuffer byteSlice) { |
| 382 | return new Int8(byteSlice.get()); |
| 383 | } |
| 384 | }; |
| 385 | } |
| 386 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 387 | /** |
| 388 | * Creates a {@link Decoder} for the {@link Int16} type. |
| 389 | * |
| 390 | * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| 391 | * result of this method. |
| 392 | * |
| 393 | * @return a new {@link Decoder}. |
| 394 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 395 | public static Decoder<Int16> ofInt16() { |
| 396 | return new Decoder<>() { |
| 397 | @Override |
| 398 | public byte alignment() { |
| 399 | return 2; |
| 400 | } |
| 401 | |
| 402 | @Override |
| 403 | public Integer fixedSize() { |
| 404 | return 2; |
| 405 | } |
| 406 | |
| 407 | @Override |
| 408 | public Int16 decode(ByteBuffer byteSlice) { |
| 409 | return new Int16(byteSlice.getShort()); |
| 410 | } |
| 411 | }; |
| 412 | } |
| 413 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 414 | /** |
| 415 | * Creates a {@link Decoder} for the {@link Int32} type. |
| 416 | * |
| 417 | * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| 418 | * result of this method. |
| 419 | * |
| 420 | * @return a new {@link Decoder}. |
| 421 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 422 | public static Decoder<Int32> ofInt32() { |
| 423 | return new Decoder<>() { |
| 424 | @Override |
| 425 | public byte alignment() { |
| 426 | return 4; |
| 427 | } |
| 428 | |
| 429 | @Override |
| 430 | public Integer fixedSize() { |
| 431 | return 4; |
| 432 | } |
| 433 | |
| 434 | @Override |
| 435 | public Int32 decode(ByteBuffer byteSlice) { |
| 436 | return new Int32(byteSlice.getInt()); |
| 437 | } |
| 438 | }; |
| 439 | } |
| 440 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 441 | /** |
| 442 | * Creates a {@link Decoder} for the {@link Int64} type. |
| 443 | * |
| 444 | * <p><strong>Note:</strong> It is often useful to apply {@link #withByteOrder(ByteOrder)} to the |
| 445 | * result of this method. |
| 446 | * |
| 447 | * @return a new {@link Decoder}. |
| 448 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 449 | public static Decoder<Int64> ofInt64() { |
| 450 | return new Decoder<>() { |
| 451 | @Override |
| 452 | public byte alignment() { |
| 453 | return 8; |
| 454 | } |
| 455 | |
| 456 | @Override |
| 457 | public Integer fixedSize() { |
| 458 | return 8; |
| 459 | } |
| 460 | |
| 461 | @Override |
| 462 | public Int64 decode(ByteBuffer byteSlice) { |
| 463 | return new Int64(byteSlice.getLong()); |
| 464 | } |
| 465 | }; |
| 466 | } |
| 467 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 468 | /** |
| 469 | * Creates a {@link Decoder} for the {@link Float64} type. |
| 470 | * |
| 471 | * @return a new {@link Decoder}. |
| 472 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 473 | public static Decoder<Float64> ofFloat64() { |
| 474 | return new Decoder<>() { |
| 475 | @Override |
| 476 | public byte alignment() { |
| 477 | return 8; |
| 478 | } |
| 479 | |
| 480 | @Override |
| 481 | public Integer fixedSize() { |
| 482 | return 8; |
| 483 | } |
| 484 | |
| 485 | @Override |
| 486 | public Float64 decode(ByteBuffer byteSlice) { |
| 487 | return new Float64(byteSlice.getDouble()); |
| 488 | } |
| 489 | }; |
| 490 | } |
| 491 | |
Matthias Andreas Benkard | 4c32c39 | 2021-12-12 21:23:53 +0100 | [diff] [blame^] | 492 | /** |
| 493 | * Creates a {@link Decoder} for the {@link Str} type. |
| 494 | * |
| 495 | * <p><strong>Note:</strong> While GVariant does not prescribe any particular encoding, {@link |
| 496 | * java.nio.charset.StandardCharsets#UTF_8} is the most common choice. |
| 497 | * |
| 498 | * @return a new {@link Decoder}. |
| 499 | */ |
Matthias Andreas Benkard | 261532a | 2021-12-12 20:09:27 +0100 | [diff] [blame] | 500 | public static Decoder<Str> ofStr(Charset charset) { |
| 501 | return new Decoder<>() { |
| 502 | @Override |
| 503 | public byte alignment() { |
| 504 | return 1; |
| 505 | } |
| 506 | |
| 507 | @Override |
| 508 | @Nullable |
| 509 | Integer fixedSize() { |
| 510 | return null; |
| 511 | } |
| 512 | |
| 513 | @Override |
| 514 | public Str decode(ByteBuffer byteSlice) { |
| 515 | byteSlice.limit(byteSlice.limit() - 1); |
| 516 | return new Str(charset.decode(byteSlice).toString()); |
| 517 | } |
| 518 | }; |
| 519 | } |
| 520 | } |