Record Class BytePtr

java.lang.Object
java.lang.Record
club.doki7.ffm.ptr.BytePtr
All Implemented Interfaces:
IPointer, Iterable<Byte>
@ValueBasedCandidate @UnsafeConstructor public record BytePtr(@NotNull MemorySegment segment) extends Record implements IPointer, Iterable<Byte>

Represents a pointer to byte(s) in native memory.

The property segment() should always be not-null (segment != NULL && !segment.equals(MemorySegment.NULL)). To represent null pointer, you may use a Java null instead. See the documentation of IPointer.segment() for more details.

The constructor of this class is marked as UnsafeConstructor, because it does not perform any runtime check. The constructor can be useful for automatic code generators. For normal users, checked(MemorySegment) is a good safe alternative.

  • Constructor Details

    • BytePtr

      public BytePtr(@NotNull @NotNull MemorySegment segment)
      Creates an instance of a BytePtr record class.
      Parameters:
      segment - the value for the segment record component

  • Method Details

    • size

      public long size()

    • read

      public byte read()

    • write

      public void write(byte value)

    • read

      public byte read(long index)

    • write

      public void write(long index, byte value)

    • write

      public void write(byte @NotNull [] bytes)

    • writeV

      public void writeV(byte value0, byte @NotNull ... values)

    • writeString

      public void writeString(@NotNull @NotNull String s)

    • readStringSafe

      @NotNull public @NotNull String readStringSafe()

      Assume the BytePtr is a null-terminated string, reads the string from the beginning of the underlying memory segment, until the first NUL byte is encountered.

      This function requires the size of the underlying memory segment to be set correctly. If the size is not known in advance and correctly set (for example, the BytePtr or the underlying MemorySegment is returned from some C API), you may use readString() (note that it is Unsafe) instead.

    • readString

      @Unsafe @NotNull public @NotNull String readString()

      Assumes the BytePtr is a null-terminated string, reads the string from the beginning of the underlying memory segment, until the first NUL byte is encountered.

      This function is Unsafe because it does not check the size of the underlying memory segment. This function is suitable for the cases that the size of the underlying memory segment is not known in advance and correctly set (for example, the BytePtr or the underlying MemorySegment is returned from some C API). If the size is correctly set, you may use readStringSafe() instead.

    • reinterpret

      @Unsafe @NotNull public @NotNull BytePtr reinterpret(long newSize)

      Assume the BytePtr is capable of holding at least newSize bytes, create a new view BytePtr that uses the same backing storage as this BytePtr, but with the new size. Since there is actually no way to really check whether the new size is valid, while buffer overflow is undefined behavior, this method is marked as Unsafe.

      This method could be useful when handling data returned from some C API, where the size of data is not known in advance.

      If the size of the underlying segment is actually known in advance and correctly set, and you want to create a shrunk view, you may use slice(long) (with validation) instead.

    • offset

      @NotNull public @NotNull BytePtr offset(long offset)

    • slice

      @NotNull public @NotNull BytePtr slice(long start, long end)
      Note that this function uses the List.subList(int, int) semantics (left inclusive, right exclusive interval), not MemorySegment.asSlice(long, long) semantics (offset + newSize). Be careful with the difference.

    • slice

      @NotNull public @NotNull BytePtr slice(long end)

    • iterator

      @NotNull public @NotNull Iterator<Byte> iterator()
      Specified by:
      iterator in interface Iterable<Byte>

    • checked

      @Nullable public static @Nullable BytePtr checked(@NotNull @NotNull MemorySegment segment)

      Create a new BytePtr using segment as backing storage, with argument validation.

      If segment is not big enough to hold at least one byte, that segment is simply considered "empty". See the documentation of IPointer.segment() for more details.

      Parameters:
      segment - the MemorySegment to use as the backing storage
      Returns:
      null if segment is MemorySegment.NULL, otherwise a new BytePtr that uses segment as backing storage
      Throws:
      IllegalArgumentException - if segment is not native

    • checked

      @NotNull public static @NotNull BytePtr checked(@NotNull @NotNull ByteBuffer buffer)

      Create a new BytePtr using the same backing storage as buffer, with argument validation.

      The main difference between this static method and the allocate(Arena, ByteBuffer) method is that this method does not copy the contents of buffer into a newly allocated MemorySegment. Instead, the newly created BytePtr will use the same backing storage as buffer. Thus, modifications from one side will be visible on the other side.

      Be careful with java.nio buffer types' Buffer.position() property: only the "remaining" (from Buffer.position() to Buffer.limit()) part of buffer will be referred. If you have ever read from buffer, and you want all the contents of buffer to be referred, you may want to call Buffer.rewind().

      Parameters:
      buffer - the ByteBuffer to use as the backing storage
      Returns:
      a new BytePtr that uses buffer as its backing storage
      Throws:
      IllegalArgumentException - if buffer is not direct

    • from

      @NotNull public static @NotNull BytePtr from(@NotNull @NotNull IPointer ptr)

    • allocate

      @NotNull public static @NotNull BytePtr allocate(@NotNull @NotNull Arena arena)

    • allocate

      @NotNull public static @NotNull BytePtr allocate(@NotNull @NotNull Arena arena, long size)

    • allocate

      @NotNull public static @NotNull BytePtr allocate(@NotNull @NotNull Arena arena, byte @NotNull [] bytes)

    • allocate

      @NotNull public static @NotNull BytePtr allocate(@NotNull @NotNull Arena arena, Collection<Byte> bytes)

    • allocateV

      @NotNull public static @NotNull BytePtr allocateV(@NotNull @NotNull Arena arena, byte value0, byte... values)

    • allocate

      @NotNull public static @NotNull BytePtr allocate(@NotNull @NotNull Arena arena, @NotNull @NotNull ByteBuffer buffer)

      Allocate a new BytePtr in arena and copy the contents of buffer into the newly allocated BytePtr.

      Be careful with java.nio buffer types' Buffer.position() property: only the "remaining" (from Buffer.position() to Buffer.limit()) part of buffer will be copied. If you have ever read from buffer, and you want all the contents of buffer to be copied, you may want to call Buffer.rewind().

      Parameters:
      arena - the Arena to allocate the new BytePtr in
      buffer - the ByteBuffer to copy the contents from
      Returns:
      a new BytePtr that contains the contents of buffer

    • allocateAligned

      @NotNull public static @NotNull BytePtr allocateAligned(@NotNull @NotNull Arena arena, long size, long alignment)

    • allocateString

      @NotNull public static @NotNull BytePtr allocateString(@NotNull @NotNull Arena arena, @NotNull @NotNull String s)

    • toString

      public final String toString()
      Returns a string representation of this record class. The representation contains the name of the class, followed by the name and value of each of the record components.
      Specified by:
      toString in class Record
      Returns:
      a string representation of this object

    • hashCode

      public final int hashCode()
      Returns a hash code value for this object. The value is derived from the hash code of each of the record components.
      Specified by:
      hashCode in class Record
      Returns:
      a hash code value for this object

    • equals

      public final boolean equals(Object o)
      Indicates whether some other object is "equal to" this one. The objects are equal if the other object is of the same class and if all the record components are equal. All components in this record class are compared with Objects::equals(Object,Object).
      Specified by:
      equals in class Record
      Parameters:
      o - the object with which to compare
      Returns:
      true if this object is the same as the o argument; false otherwise.

    • segment

      @NotNull public @NotNull MemorySegment segment()
      Returns the value of the segment record component.
      Specified by:
      segment in interface IPointer
      Returns:
      the value of the segment record component