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Commit f995f9a8 authored by John Reck's avatar John Reck
Browse files

Address API review comments 

Also make it less error-prone to use unmap() incorrectly.
Bug: 64264008
Test: CTS tests pass

Change-Id: I21559676e7a850b76db4b61a31e43833396c6087
parent 6ff61dbc

core/java/android/os/SharedMemory.java

+16 −9
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ import java.io.Closeable; 
import java.io.FileDescriptor;

import java.nio.ByteBuffer;

import java.nio.DirectByteBuffer;

import java.nio.NioUtils;



import sun.misc.Cleaner;
@@ -191,11 +192,16 @@ public final class SharedMemory implements Parcelable, Closeable { 
    }



    /**

     * Creates an mmap of the SharedMemory with the specified prot, offset, and length.

     * Creates an mmap of the SharedMemory with the specified prot, offset, and length. This will

     * always produce a new ByteBuffer window to the backing shared memory region. Every call

     * to map() may be paired with a call to {@link #unmap(ByteBuffer)} when the ByteBuffer

     * returned by map() is no longer needed.

     *

     * @param prot A bitwise-or'd combination of PROT_READ, PROT_WRITE, PROT_EXEC, or PROT_NONE.

     * @param offset The offset into the shared memory to begin mapping

     * @param length The length of the region to map

     * @param offset The offset into the shared memory to begin mapping. Must be >= 0 and less than

     *         getSize().

     * @param length The length of the region to map. Must be > 0 and offset + length must not

     *         exceed getSize().

     * @return A ByteBuffer mapping.

     * @throws ErrnoException if the mmap call failed.

     */
@@ -203,7 +209,7 @@ public final class SharedMemory implements Parcelable, Closeable { 
        checkOpen();

        validateProt(prot);

        if (offset < 0) {

            throw new IllegalArgumentException("Offset must be > 0");

            throw new IllegalArgumentException("Offset must be >= 0");

        }

        if (length <= 0) {

            throw new IllegalArgumentException("Length must be > 0");
@@ -218,15 +224,16 @@ public final class SharedMemory implements Parcelable, Closeable { 
    }



    /**

     * Unmaps a buffer previously returned by {@link #map(int, int, int)}

     * Unmaps a buffer previously returned by {@link #map(int, int, int)}. This will immediately

     * release the backing memory of the ByteBuffer, invalidating all references to it. Only

     * call this method if there are no duplicates of the ByteBuffer in use and don't

     * access the ByteBuffer after calling this method.

     *

     * @param buffer The buffer to unmap

     */

    public static void unmap(@NonNull ByteBuffer buffer) {

        if (buffer instanceof DirectByteBuffer) {

            Cleaner cleaner = ((DirectByteBuffer) buffer).cleaner();

            if (cleaner != null) {

                cleaner.clean();

            }

            NioUtils.freeDirectBuffer(buffer);

        } else {

            throw new IllegalArgumentException(

                    "ByteBuffer wasn't created by #map(int, int, int); can't unmap");