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use LambdaMetafactory to generate Supplier<Checksum> for java.util.zip.CRC32C instances #595

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merged 1 commit into from
Sep 10, 2024
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use LambdaMetafactory to generate Supplier<Checksum> for java.util.zip.CRC32C instances #595

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37 changes: 22 additions & 15 deletions src/main/java/org/xerial/snappy/SnappyFramed.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
package org.xerial.snappy;

import java.io.IOException;
import java.lang.invoke.LambdaMetafactory;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
Expand Down Expand Up @@ -37,21 +38,27 @@ final class SnappyFramed
Supplier<Checksum> supplier = null;
try
{
final Class crc32cClazz = Class.forName("java.util.zip.CRC32C");
final MethodHandles.Lookup lookup = MethodHandles.publicLookup();

final MethodHandle conHandle = lookup.findConstructor(crc32cClazz, MethodType.methodType(void.class))
.asType(MethodType.methodType(Checksum.class));
supplier = () -> {
try
{
return (Checksum) conHandle.invokeExact();
}
catch (Throwable e)
{
throw new IllegalStateException(e);
}
};
final Class<?> crc32cClazz = Class.forName("java.util.zip.CRC32C");
// using LambdaMetafactory requires a caller sensitive lookup
final MethodHandles.Lookup lookup = MethodHandles.lookup();
final MethodHandle conHandle = lookup.findConstructor(crc32cClazz, MethodType.methodType(void.class));

// use LambdaMetafactory to generate an implementation of Supplier<Checksum> which invokes
// the java.util.zip.CRC32C default constructor
supplier = (Supplier<Checksum>) LambdaMetafactory.metafactory(lookup,
// method name on Supplier
"get",
// functional interface to be created by factory
MethodType.methodType(Supplier.class),
// type of the functional interface
// uses a generic, so erasure to Object
MethodType.methodType(Object.class),
// the method handle to call
conHandle,
// type as used at call site
MethodType.methodType(Checksum.class))
.getTarget()
.invoke();
}
catch(Throwable t)
{
Expand Down
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