public static WritableMemory wrapMap()

in src/main/java/org/apache/datasketches/memory/internal/WritableMemoryImpl.java [169:208]

36 lines of code
9 McCabe index (conditional complexity)


  public static WritableMemory wrapMap(
      final File file,
      final long fileOffsetBytes,
      final long capacityBytes,
      final ByteOrder byteOrder,
      final boolean localReadOnly,
      final Arena arena)
          throws IllegalArgumentException, IOException {
    Objects.requireNonNull(arena, "Arena must be non-null.");
    Objects.requireNonNull(file, "File must be non-null.");
    Objects.requireNonNull(byteOrder, "ByteOrder must be non-null.");
    final FileChannel.MapMode mapMode;
    final boolean fileCanRead = file.canRead();
    if (localReadOnly) {
      if (fileCanRead) { mapMode = READ_ONLY; }
      else { throw new IllegalArgumentException("File must be readable."); }
    } else { //!localReadOnly
      if (fileCanRead && file.canWrite()) { mapMode = READ_WRITE; }
      else {
        throw new IllegalArgumentException("File must be readable and writable.");
      }
    }

    final Set<OpenOption> openOptions = READ_WRITE.equals(mapMode)
      ? Set.of(StandardOpenOption.READ, StandardOpenOption.WRITE)
      : Set.of(StandardOpenOption.READ);

    final boolean nativeBOType = byteOrder == ByteOrder.nativeOrder();
    final int type = MEMORY | MAP | DIRECT
          | (localReadOnly ? READONLY : 0)
          | (nativeBOType ? NATIVE_BO : NONNATIVE_BO);

    try (final FileChannel fileChannel = FileChannel.open(file.toPath(), openOptions)) {
      final MemorySegment seg = fileChannel.map(mapMode, fileOffsetBytes, capacityBytes, arena);

      return nativeBOType
          ? new NativeWritableMemoryImpl(seg, type, null, arena)
          : new NonNativeWritableMemoryImpl(seg, type, null, arena);
    }
  }