org.github.jamm.string.PlainReflectionStringMeter Maven / Gradle / Ivy

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Jamm provides MemoryMeter, a java agent to measure actual object memory use including JVM overhead.

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package org.github.jamm.string;

import java.lang.invoke.MethodHandle;

import org.github.jamm.CannotAccessFieldException;
import org.github.jamm.MemoryMeterStrategy;

/**
 * {@code StringMeter} used to measure Java 9+ strings where the {@code String} value is a {@code byte} array.
 *
 */
final class PlainReflectionStringMeter extends StringMeter {

    /**
     * The method handle used to access the value field.
     */
    private final MethodHandle valueMH;

    public PlainReflectionStringMeter(MethodHandle valueMH) {
        this.valueMH = valueMH;
    }

    @Override
    public long measureStringValue(MemoryMeterStrategy strategy, String s) {
        try {
            return strategy.measureArray((byte[]) valueMH.invoke(s));
        }  catch (Throwable e) {
            throw new CannotAccessFieldException("The value of the value field from java.lang.String cannot be retrieved", e);
        }
    }
}