src/java.base/share/classes/java/lang/foreign/ValueLayout.java

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package java.lang.foreign;

import jdk.internal.foreign.layout.ValueLayouts;

import java.lang.invoke.VarHandle;
import java.nio.ByteOrder;

/**
 * A layout that models values of basic data types. Examples of values modeled by
 * a value layout are <em>integral</em> values (either signed or unsigned),
 * <em>floating-point</em> values and <em>address</em> values.
 * <p>
 * Each value layout has a size, an alignment (both expressed in bytes),
 * a {@linkplain ByteOrder byte order}, and a <em>carrier</em>, that is, the Java type
 * that should be used when {@linkplain MemorySegment#get(OfInt, long) accessing} a
 * region of memory using the value layout.
 * <p>

 * This class defines useful value layout constants for Java primitive types and
 * addresses.
 *
 * @apiNote Some characteristics of the Java layout constants are platform-dependent.
 *          For instance, the byte order of these constants is set to the
 *          {@linkplain ByteOrder#nativeOrder() native byte order}, thus making it easy
 *          to work with other APIs, such as arrays and {@link java.nio.ByteBuffer}.
 *
 * @implSpec implementing classes and subclasses are immutable, thread-safe and
 * <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>.
 *
 * @sealedGraph
 * @since 22
 */
public sealed interface ValueLayout extends MemoryLayout
        permits ValueLayout.OfBoolean, ValueLayout.OfByte, ValueLayout.OfChar,
        ValueLayout.OfShort, ValueLayout.OfInt,  ValueLayout.OfFloat,
        ValueLayout.OfLong, ValueLayout.OfDouble, AddressLayout {

    /**
     * {@return the value's byte order}
     */
    ByteOrder order();

    /**
     * {@return a value layout with the same characteristics as this layout, but with the given byte order}
     *
     * @param order the desired byte order
     */
    ValueLayout withOrder(ByteOrder order);

    /**
     * {@inheritDoc}
     */
    @Override
    ValueLayout withoutName();

    /**
     * {@return the carrier associated with this value layout}
     */
    Class<?> carrier();

    /**
     * {@inheritDoc}
     */
    @Override
    ValueLayout withName(String name);

    /**
     * {@inheritDoc}
     *
     * @throws IllegalArgumentException {@inheritDoc}
     */
    @Override
    ValueLayout withByteAlignment(long byteAlignment);

    /**
     * {@return a var handle which can be used to access values described by this value
     *          layout, in a given memory segment}
     * <p>
     * The returned var handle's {@linkplain VarHandle#varType() var type} is the
     * {@linkplain ValueLayout#carrier() carrier type} of this value layout, and the
     * list of coordinate types is {@code (MemorySegment, long)}, where the
     * memory segment coordinate corresponds to the memory segment to be accessed, and
     * the {@code long} coordinate corresponds to the byte offset into the accessed
     * memory segment at which the access occurs.
     * <p>
     * The returned var handle checks that accesses are aligned according to
     * this value layout's {@linkplain MemoryLayout#byteAlignment() alignment constraint}.
     *
     * @apiNote This method is similar, but more efficient than calling
     *          {@code MemoryLayout#varHandle(PathElement...)} with an empty path
     *          element array, as it avoids the creation of the var args array.
     *
     * @apiNote The returned var handle features certain
     *          <a href="MemoryLayout.html#access-mode-restrictions">access mode restrictions</a>
     *          common to all memory access var handles derived from memory layouts.
     *
     * @see MemoryLayout#varHandle(PathElement...)
     */
    VarHandle varHandle();

    /**
     * A value layout whose carrier is {@code boolean.class}.
     *
     * @see #JAVA_BOOLEAN
     * @since 22
     */
        sealed interface OfBoolean extends ValueLayout permits ValueLayouts.OfBooleanImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfBoolean withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfBoolean withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfBoolean withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfBoolean withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code byte.class}.
     *
     * @see #JAVA_BYTE
     * @since 22
     */
        sealed interface OfByte extends ValueLayout permits ValueLayouts.OfByteImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfByte withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfByte withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfByte withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfByte withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code char.class}.
     *
     * @see #JAVA_CHAR
     * @see #JAVA_CHAR_UNALIGNED
     * @since 22
     */
        sealed interface OfChar extends ValueLayout permits ValueLayouts.OfCharImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfChar withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfChar withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfChar withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfChar withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code short.class}.
     *
     * @see #JAVA_SHORT
     * @see #JAVA_SHORT_UNALIGNED
     * @since 22
     */
        sealed interface OfShort extends ValueLayout permits ValueLayouts.OfShortImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfShort withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfShort withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfShort withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfShort withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code int.class}.
     *
     * @see #JAVA_INT
     * @see #JAVA_INT_UNALIGNED
     * @since 22
     */
        sealed interface OfInt extends ValueLayout permits ValueLayouts.OfIntImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfInt withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfInt withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfInt withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfInt withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code float.class}.
     *
     * @see #JAVA_FLOAT
     * @see #JAVA_FLOAT_UNALIGNED
     * @since 22
     */
        sealed interface OfFloat extends ValueLayout permits ValueLayouts.OfFloatImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfFloat withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfFloat withoutName();

        /**
         * {@inheritDoc}
         */
        @Override
        OfFloat withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfFloat withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code long.class}.
     *
     * @see #JAVA_LONG
     * @see #JAVA_LONG_UNALIGNED
     * @since 22
     */
        sealed interface OfLong extends ValueLayout permits ValueLayouts.OfLongImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfLong withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfLong withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfLong withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfLong withOrder(ByteOrder order);

    }

    /**
     * A value layout whose carrier is {@code double.class}.
     *
     * @see #JAVA_DOUBLE
     * @see #JAVA_DOUBLE_UNALIGNED
     * @since 22
     */
        sealed interface OfDouble extends ValueLayout permits ValueLayouts.OfDoubleImpl {

        /**
         * {@inheritDoc}
         */
        @Override
        OfDouble withName(String name);

        /**
         * {@inheritDoc}
         */
        @Override
        OfDouble withoutName();

        /**
         * {@inheritDoc}
         * @throws IllegalArgumentException {@inheritDoc}
         */
        @Override
        OfDouble withByteAlignment(long byteAlignment);

        /**
         * {@inheritDoc}
         */
        @Override
        OfDouble withOrder(ByteOrder order);

    }

    /**
     * An address layout constant whose size is the same as that of a
     * machine address ({@code size_t}), byte alignment set to {@code sizeof(size_t)},
     * byte order set to {@link ByteOrder#nativeOrder()}.
     */
    AddressLayout ADDRESS = ValueLayouts.OfAddressImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code byte},
     * byte alignment set to 1, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfByte JAVA_BYTE = ValueLayouts.OfByteImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code boolean},
     * byte alignment set to 1, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfBoolean JAVA_BOOLEAN = ValueLayouts.OfBooleanImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code char},
     * byte alignment set to 2, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfChar JAVA_CHAR = ValueLayouts.OfCharImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code short},
     * byte alignment set to 2, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfShort JAVA_SHORT = ValueLayouts.OfShortImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code int},
     * byte alignment set to 4, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfInt JAVA_INT = ValueLayouts.OfIntImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code long},
     * byte alignment set to 8, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfLong JAVA_LONG = ValueLayouts.OfLongImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code float},
     * byte alignment set to 4, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfFloat JAVA_FLOAT = ValueLayouts.OfFloatImpl.of(ByteOrder.nativeOrder());

    /**
     * A value layout constant whose size is the same as that of a Java {@code double},
     * byte alignment set to 8, and byte order set to {@link ByteOrder#nativeOrder()}.
     */
    OfDouble JAVA_DOUBLE = ValueLayouts.OfDoubleImpl.of(ByteOrder.nativeOrder());

    /**
     * An unaligned address layout constant whose size is the same as that of a
     * machine address ({@code size_t}), and byte order set to
     * {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * ADDRESS.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    AddressLayout ADDRESS_UNALIGNED = ADDRESS.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code char}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_CHAR.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfChar JAVA_CHAR_UNALIGNED = JAVA_CHAR.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code short}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_SHORT.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfShort JAVA_SHORT_UNALIGNED = JAVA_SHORT.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code int}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_INT.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfInt JAVA_INT_UNALIGNED = JAVA_INT.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code long}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_LONG.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfLong JAVA_LONG_UNALIGNED = JAVA_LONG.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code float}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_FLOAT.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfFloat JAVA_FLOAT_UNALIGNED = JAVA_FLOAT.withByteAlignment(1);

    /**
     * An unaligned value layout constant whose size is the same as that of a Java {@code double}
     * and byte order set to {@link ByteOrder#nativeOrder()}.
     * Equivalent to the following code:
     * {@snippet lang=java :
     * JAVA_DOUBLE.withByteAlignment(1);
     * }
     * @apiNote Care should be taken when using unaligned value layouts as they may
     *          induce performance and portability issues.
     */
    OfDouble JAVA_DOUBLE_UNALIGNED = JAVA_DOUBLE.withByteAlignment(1);

}