include/core/SkTRegistry.h

/*
 * Copyright 2009, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef SkTRegistry_DEFINED
#define SkTRegistry_DEFINED

#include "SkTypes.h"

/** Template class that registers itself (in the constructor) into a linked-list
    and provides a function-pointer. This can be used to auto-register a set of
    services, e.g. a set of image codecs.
 */
template <typename T, typename P> class SkTRegistry : SkNoncopyable {
public:
    typedef T (*Factory)(P);

    SkTRegistry(Factory fact) {
#ifdef ANDROID
        // work-around for double-initialization bug
        {
            SkTRegistry* reg = gHead;
            while (reg) {
                if (reg == this) {
                    return;
                }
                reg = reg->fChain;
            }
        }
#endif
        fFact = fact;
        fChain = gHead;
        gHead = this;
    }

    static const SkTRegistry* Head() { return gHead; }

    const SkTRegistry* next() const { return fChain; }
    Factory factory() const { return fFact; }

private:
    Factory      fFact;
    SkTRegistry* fChain;

    static SkTRegistry* gHead;
};

// The caller still needs to declare an instance of this somewhere
template <typename T, typename P> SkTRegistry<T, P>* SkTRegistry<T, P>::gHead;

#endif