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package com.oracle.svm.core.os;

import java.util.EnumSet;

import org.graalvm.compiler.api.replacements.Fold;
import org.graalvm.nativeimage.ImageSingletons;
import org.graalvm.nativeimage.c.type.WordPointer;
import org.graalvm.word.Pointer;
import org.graalvm.word.PointerBase;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordFactory;

import com.oracle.svm.core.annotate.Uninterruptible;
import com.oracle.svm.core.c.function.CEntryPointCreateIsolateParameters;
import com.oracle.svm.core.heap.Heap;

A provider of ranges of committed memory, which is virtual memory that is backed by physical
memory or swap space.
/**
 * A provider of ranges of committed memory, which is virtual memory that is backed by physical
 * memory or swap space.
 */
public interface CommittedMemoryProvider {
    
Value for alignment parameters that indicates that no specific alignment is required (other than the granularity usually). /**
     * Value for alignment parameters that indicates that no specific alignment is required (other
     * than the {@linkplain #getGranularity() granularity} usually).
     */
    UnsignedWord UNALIGNED = WordFactory.unsigned(1);

    @Fold
    static CommittedMemoryProvider get() {
        return ImageSingletons.lookup(CommittedMemoryProvider.class);
    }

    
Returns whether this provider will always guarantee a heap address space alignment of Heap.getPreferredAddressSpaceAlignment() at image runtime, which may also depend on ImageHeapProvider.guaranteesHeapPreferredAddressSpaceAlignment(). /**
     * Returns whether this provider will always guarantee a heap address space alignment of
     * {@link Heap#getPreferredAddressSpaceAlignment()} at image runtime, which may also depend on
     * {@link ImageHeapProvider#guaranteesHeapPreferredAddressSpaceAlignment()}.
     */
    @Fold
    boolean guaranteesHeapPreferredAddressSpaceAlignment();

    
Performs initializations for the current isolate, before any other methods of this
interface may be called.
Returns:
zero in case of success, non-zero in case of an error./**
     * Performs initializations <em>for the current isolate</em>, before any other methods of this
     * interface may be called.
     *
     * @return zero in case of success, non-zero in case of an error.
     */
    @Uninterruptible(reason = "Still being initialized.")
    int initialize(WordPointer isolatePointer, CEntryPointCreateIsolateParameters parameters);

    
Tear down for the current isolate. This must be the last method of this interface
that is called in an isolate.
Returns:
zero in case of success, non-zero in case of an error./**
     * Tear down <em>for the current isolate</em>. This must be the last method of this interface
     * that is called in an isolate.
     *
     * @return zero in case of success, non-zero in case of an error.
     */
    @Uninterruptible(reason = "Tear-down in progress.")
    int tearDown();

    
Returns the granularity of committed memory management, which is typically the same as that of virtual memory management. /**
     * Returns the granularity of committed memory management, which is typically the same as that
     * of {@linkplain VirtualMemoryProvider#getGranularity() virtual memory management}.
     */
    @Uninterruptible(reason = "Still being initialized.", mayBeInlined = true)
    default UnsignedWord getGranularity() {
        return VirtualMemoryProvider.get().getGranularity();
    }

    
Allocate a block of committed memory.
Params:
nbytes – The number of bytes to allocate, which is rounded up to the next multiple of the granularity if required.
alignment – The required alignment of the block start, or UNALIGNED.
executable – Whether the block must be executable.
Returns:
The start of the allocated block, or WordFactory.nullPointer() in case of an error./**
     * Allocate a block of committed memory.
     *
     * @param nbytes The number of bytes to allocate, which is rounded up to the next multiple of
     *            the {@linkplain #getGranularity() granularity} if required.
     * @param alignment The required alignment of the block start, or {@link #UNALIGNED}.
     * @param executable Whether the block must be executable.
     * @return The start of the allocated block, or {@link WordFactory#nullPointer()} in case of an
     *         error.
     */
    Pointer allocate(UnsignedWord nbytes, UnsignedWord alignment, boolean executable);

    
Release a block of committed memory that was allocated with allocate, requiring the exact same parameter values that were originally passed to allocate. 
Params:
start – The start of the memory block, as returned by allocate.
nbytes – The originally requested size in bytes.
alignment – The originally requested alignment.
executable – Whether the block was requested to be executable.
Returns:
true on success, or false otherwise./**
     * Release a block of committed memory that was allocated with {@link #allocate}, requiring the
     * exact same parameter values that were originally passed to {@link #allocate}.
     *
     * @param start The start of the memory block, as returned by {@link #allocate}.
     * @param nbytes The originally requested size in bytes.
     * @param alignment The originally requested alignment.
     * @param executable Whether the block was requested to be executable.
     * @return true on success, or false otherwise.
     */
    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
    boolean free(PointerBase start, UnsignedWord nbytes, UnsignedWord alignment, boolean executable);

    
Called by the garbage collector before a collection is started, as an opportunity to perform
lazy operations, sanity checks or clean-ups.
/**
     * Called by the garbage collector before a collection is started, as an opportunity to perform
     * lazy operations, sanity checks or clean-ups.
     */
    default void beforeGarbageCollection() {
    }

    
Called by the garbage collector after a collection has ended, as an opportunity to perform
lazy operations, sanity checks or clean-ups.
Params:
completeCollection – Whether the garbage collector has performed a full collection./**
     * Called by the garbage collector after a collection has ended, as an opportunity to perform
     * lazy operations, sanity checks or clean-ups.
     *
     * @param completeCollection Whether the garbage collector has performed a full collection.
     */
    default void afterGarbageCollection(boolean completeCollection) {
    }

    enum Access {
        READ,
        WRITE,
        EXECUTE
    }

    
Change access permissions for a block of committed memory that was allocated with allocate. 
Params:
start – The start of the address range to be protected, which must be a multiple of the granularity.
nbytes – The size in bytes of the address range to be protected, which will be rounded up to a multiple of the granularity.
access – The modes in which the memory is permitted to be accessed, see Access.
Returns:
true on success, or false otherwise./**
     * Change access permissions for a block of committed memory that was allocated with
     * {@link #allocate}.
     *
     * @param start The start of the address range to be protected, which must be a multiple of the
     *            {@linkplain #getGranularity() granularity}.
     * @param nbytes The size in bytes of the address range to be protected, which will be rounded
     *            up to a multiple of the {@linkplain #getGranularity() granularity}.
     * @param access The modes in which the memory is permitted to be accessed, see {@link Access}.
     * @return true on success, or false otherwise.
     */
    boolean protect(PointerBase start, UnsignedWord nbytes, EnumSet<Access> access);
}