jruby/core/src/main/java/org/jruby/FlagRegistry.java at master · jruby/jruby · GitHub

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package org.jruby;

import java.util.BitSet;

import java.util.HashMap;

import java.util.Map;

/**

* This class serves as a registry of all bit flags we use on JRuby objects.

* In order to maximally use our bit flags and prevent overlap between ancestors and dependents,

* this class registers flags on a first-come, first-served basis using previous flags registered

* for ancestor classes as a base line for new flags in a descendant.

* Because of the first-come, first-served nature, the most general types will need to register

* their flags first. This guarantees all bit flags from the progenitor on down will be packed

* tightly while avoiding overlaps.

public class FlagRegistry {

private final Map<Class, Integer> currentShift = new HashMap<>();

private final Map<Class, BitSet> registry = new HashMap<>();

/**

* Register a new flag for the given class.

* The bit index for the new flag will be calculated at runtime, by walking parent classes

* and looking for previously-registered flags. Ancestors should register all their flags

* before descendants (which means they should not be registered in a static initializer

* unless the parent is known to have fully run its own static initializers).

* @param klass the class for which to register a new flag

* @return an integer with the new flag bit set

public synchronized int newFlag(Class klass) {

Class currentKlass = klass;

Integer shift = null;

while (currentKlass != null &&

(shift = currentShift.get(currentKlass)) == null) {

currentKlass = currentKlass.getSuperclass();

}

if (shift == null) shift = 0;

BitSet flags = registry.get(klass);

if (flags == null) {

flags = new BitSet();

registry.put(klass, flags);

}

flags.set(shift);

assert flagsAreValid(klass, shift);

currentShift.put(klass, shift + 1);

return 1 << shift++;

}

public synchronized void printFlags() {

System.out.println(registry);

}

private boolean flagsAreValid(Class klass, int bitIndex) {

BitSet gathered = new BitSet();

Class currentKlass = klass;

while (currentKlass != null) {

BitSet flags = registry.get(klass);

if (flags != null) {

if (flags.intersects(gathered)) {

throw new AssertionError(klass.getName() + " uses flag " + bitIndex + " that overlaps with " + currentKlass);

}

gathered.and(flags);

}

currentKlass = currentKlass.getSuperclass();

}

return true;

}

jruby/core/src/main/java/org/jruby/FlagRegistry.java at master · jruby/jruby · GitHub

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jruby/core/src/main/java/org/jruby/FlagRegistry.java at master · jruby/jruby · GitHub

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