12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.nio;
27
28 import jdk.internal.misc.JavaNioAccess;
29 import jdk.internal.misc.SharedSecrets;
30 import jdk.internal.misc.Unsafe;
31 import jdk.internal.misc.VM;
32 import jdk.internal.ref.CleanerFactory;
33
34 import java.util.concurrent.atomic.AtomicLong;
35 import java.util.function.BooleanSupplier;
36
37 /**
38 * Access to bits, native and otherwise.
39 */
40
41 class Bits { // package-private
42
43 private Bits() { }
44
45
46 // -- Swapping --
47
48 static short swap(short x) {
49 return Short.reverseBytes(x);
50 }
51
52 static char swap(char x) {
53 return Character.reverseBytes(x);
54 }
55
590
591 static boolean unaligned() {
592 return unaligned;
593 }
594
595
596 // -- Direct memory management --
597
598 // A user-settable upper limit on the maximum amount of allocatable
599 // direct buffer memory. This value may be changed during VM
600 // initialization if it is launched with "-XX:MaxDirectMemorySize=<size>".
601 private static volatile long maxMemory = VM.maxDirectMemory();
602 private static final AtomicLong reservedMemory = new AtomicLong();
603 private static final AtomicLong totalCapacity = new AtomicLong();
604 private static final AtomicLong count = new AtomicLong();
605 private static volatile boolean memoryLimitSet;
606
607 // These methods should be called whenever direct memory is allocated or
608 // freed. They allow the user to control the amount of direct memory
609 // which a process may access. All sizes are specified in bytes.
610 static void reserveMemory(long size, int cap) {
611
612 if (!memoryLimitSet && VM.initLevel() >= 1) {
613 maxMemory = VM.maxDirectMemory();
614 memoryLimitSet = true;
615 }
616
617 if (!CleanerFactory.dbbCleaner().retryWhileHelpingClean(
618 new BooleanSupplier() {
619 @Override
620 public boolean getAsBoolean() {
621 return tryReserveMemory(size, cap);
622 }
623 })) {
624 // no luck
625 throw new OutOfMemoryError("Direct buffer memory");
626 }
627 }
628
629 private static boolean tryReserveMemory(long size, int cap) {
630
631 // -XX:MaxDirectMemorySize limits the total capacity rather than the
632 // actual memory usage, which will differ when buffers are page
633 // aligned.
634 long totalCap;
635 while (cap <= maxMemory - (totalCap = totalCapacity.get())) {
636 if (totalCapacity.compareAndSet(totalCap, totalCap + cap)) {
637 reservedMemory.addAndGet(size);
638 count.incrementAndGet();
639 return true;
640 }
641 }
642
643 return false;
644 }
645
646
647 static void unreserveMemory(long size, int cap) {
648 long cnt = count.decrementAndGet();
649 long reservedMem = reservedMemory.addAndGet(-size);
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.nio;
27
28 import jdk.internal.misc.JavaNioAccess;
29 import jdk.internal.misc.SharedSecrets;
30 import jdk.internal.misc.Unsafe;
31 import jdk.internal.misc.VM;
32
33 import java.util.concurrent.atomic.AtomicLong;
34
35 /**
36 * Access to bits, native and otherwise.
37 */
38
39 class Bits { // package-private
40
41 private Bits() { }
42
43
44 // -- Swapping --
45
46 static short swap(short x) {
47 return Short.reverseBytes(x);
48 }
49
50 static char swap(char x) {
51 return Character.reverseBytes(x);
52 }
53
588
589 static boolean unaligned() {
590 return unaligned;
591 }
592
593
594 // -- Direct memory management --
595
596 // A user-settable upper limit on the maximum amount of allocatable
597 // direct buffer memory. This value may be changed during VM
598 // initialization if it is launched with "-XX:MaxDirectMemorySize=<size>".
599 private static volatile long maxMemory = VM.maxDirectMemory();
600 private static final AtomicLong reservedMemory = new AtomicLong();
601 private static final AtomicLong totalCapacity = new AtomicLong();
602 private static final AtomicLong count = new AtomicLong();
603 private static volatile boolean memoryLimitSet;
604
605 // These methods should be called whenever direct memory is allocated or
606 // freed. They allow the user to control the amount of direct memory
607 // which a process may access. All sizes are specified in bytes.
608 static boolean tryReserveMemory(long size, int cap) {
609
610 if (!memoryLimitSet && VM.initLevel() >= 1) {
611 maxMemory = VM.maxDirectMemory();
612 memoryLimitSet = true;
613 }
614
615 // -XX:MaxDirectMemorySize limits the total capacity rather than the
616 // actual memory usage, which will differ when buffers are page
617 // aligned.
618 long totalCap;
619 while (cap <= maxMemory - (totalCap = totalCapacity.get())) {
620 if (totalCapacity.compareAndSet(totalCap, totalCap + cap)) {
621 reservedMemory.addAndGet(size);
622 count.incrementAndGet();
623 return true;
624 }
625 }
626
627 return false;
628 }
629
630
631 static void unreserveMemory(long size, int cap) {
632 long cnt = count.decrementAndGet();
633 long reservedMem = reservedMemory.addAndGet(-size);
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