Created
October 13, 2021 11:13
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A malloc allocator which doesn't zero memory
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import jdk.incubator.foreign.Addressable; | |
import jdk.incubator.foreign.CLinker; | |
import jdk.incubator.foreign.FunctionDescriptor; | |
import jdk.incubator.foreign.MemoryAddress; | |
import jdk.incubator.foreign.MemorySegment; | |
import jdk.incubator.foreign.ResourceScope; | |
import jdk.incubator.foreign.SegmentAllocator; | |
import jdk.incubator.foreign.ValueLayout; | |
import java.lang.invoke.MethodHandle; | |
class Malloc implements SegmentAllocator { | |
private final ResourceScope scope; | |
public Malloc(ResourceScope scope) { | |
this.scope = scope; | |
} | |
@Override | |
public MemorySegment allocate(long bytesSize, long bytesAlignment) { | |
MemoryAddress ptr = allocateMemory(bytesAlignment, bytesSize); | |
if (ptr.equals(MemoryAddress.NULL)) { | |
throw new IllegalArgumentException(); | |
} | |
try { | |
scope.addCloseAction(() -> freeMemory(ptr)); | |
return MemorySegment.ofAddressNative(ptr, bytesSize, scope); | |
} catch (IllegalStateException ex) { | |
freeMemory(ptr); | |
throw ex; | |
} | |
} | |
private static CLinker LINKER = CLinker.systemCLinker(); | |
private static final MethodHandle FREE = LINKER.downcallHandle( | |
LINKER.lookup("free").get(), FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)); | |
private static final MethodHandle ALIGNED_MALLOC = LINKER.downcallHandle( | |
LINKER.lookup("aligned_alloc").get(), FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.JAVA_LONG, ValueLayout.JAVA_LONG)); | |
private static void freeMemory(Addressable address) { | |
try { | |
FREE.invokeExact(address); | |
} catch (Throwable ex) { | |
throw new IllegalStateException(ex); | |
} | |
} | |
private static MemoryAddress allocateMemory(long alignment, long size) { | |
try { | |
return (MemoryAddress)ALIGNED_MALLOC.invokeExact(alignment, size); | |
} catch (Throwable ex) { | |
throw new IllegalStateException(ex); | |
} | |
} | |
public static void main(String[] args) { | |
MemorySegment segment; | |
try (var scope = ResourceScope.newConfinedScope()) { | |
SegmentAllocator malloc = new Malloc(scope); | |
segment = malloc.allocate(100); | |
System.out.println(segment); | |
} | |
} | |
} |
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