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package com.oracle.truffle.llvm.runtime.memory;

Stores constants and provides checking functions for LLVMMemory implementations that support handle objects. /**
 * Stores constants and provides checking functions for {@link LLVMMemory} implementations that
 * support handle objects.
 */
public abstract class LLVMHandleMemoryBase extends LLVMMemory {

    protected static final int HANDLE_OBJECT_SIZE_BITS = 30;
    protected static final long HANDLE_OBJECT_SIZE = 1L << HANDLE_OBJECT_SIZE_BITS; // 0.5 GB
    protected static final int HANDLE_OBJECT_ADDRESS_BITS = Integer.SIZE; // use int cast as mask
    protected static final long HANDLE_HEADER_MASK = -1L << (HANDLE_OBJECT_SIZE_BITS + HANDLE_OBJECT_ADDRESS_BITS);
    protected static final long HANDLE_OFFSET_MASK = HANDLE_OBJECT_SIZE - 1;

    protected static final long HANDLE_SPACE_START = 0x8000000000000000L;
    protected static final long HANDLE_SPACE_END = 0xC000000000000000L;
    protected static final long DEREF_HANDLE_SPACE_START = HANDLE_SPACE_END;
    protected static final long DEREF_HANDLE_SPACE_END = 0x0000000000000000L;

    
A fast bit-check if the provided address is within the handle space.
/**
     * A fast bit-check if the provided address is within the handle space.
     */
    public static boolean isHandleMemory(long address) {
        return (address & HANDLE_SPACE_START) != 0;
    }

    
A fast bit-check if the provided address is within the normal handle space.
/**
     * A fast bit-check if the provided address is within the normal handle space.
     */
    public static boolean isCommonHandleMemory(long address) {
        return ((address & HANDLE_HEADER_MASK) == HANDLE_SPACE_START);
    }

    
A fast bit-check if the provided address is within the auto-deref handle space.
/**
     * A fast bit-check if the provided address is within the auto-deref handle space.
     */
    public static boolean isDerefHandleMemory(long address) {
        return ((address & HANDLE_HEADER_MASK) == DEREF_HANDLE_SPACE_START);
    }
}