Merge "Add template class StateQueue"

#   AudioResamplerSinc.cpp.arm

#   AudioResamplerCubic.cpp.arm

LOCAL_SRC_FILES += StateQueue.cpp

LOCAL_C_INCLUDES := \

    $(call include-path-for, audio-effects) \

    $(call include-path-for, audio-utils)

/*

 * Copyright (C) 2012 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.

 */

#define LOG_TAG "StateQueue"

//#define LOG_NDEBUG 0

#include <time.h>

#include <cutils/atomic.h>

#include <utils/Log.h>

#include "StateQueue.h"

namespace android {

// Constructor and destructor

template<typename T> StateQueue<T>::StateQueue() :

    mNext(NULL), mAck(NULL), mCurrent(NULL),

    mMutating(&mStates[0]), mExpecting(NULL),

    mInMutation(false), mIsDirty(false), mIsInitialized(false)

{

}

template<typename T> StateQueue<T>::~StateQueue()

{

}

// Observer APIs

template<typename T> const T* StateQueue<T>::poll()

{

    const T *next = (const T *) android_atomic_acquire_load((volatile int32_t *) &mNext);

    if (next != mCurrent) {

        mAck = next;    // no additional barrier needed

        mCurrent = next;

    }

    return next;

}

// Mutator APIs

template<typename T> T* StateQueue<T>::begin()

{

    ALOG_ASSERT(!mInMutation, "begin() called when in a mutation");

    mInMutation = true;

    return mMutating;

}

template<typename T> void StateQueue<T>::end(bool didModify)

{

    ALOG_ASSERT(mInMutation, "end() called when not in a mutation");

    ALOG_ASSERT(mIsInitialized || didModify, "first end() must modify for initialization");

    if (didModify) {

        mIsDirty = true;

        mIsInitialized = true;

    }

    mInMutation = false;

}

template<typename T> bool StateQueue<T>::push(StateQueue<T>::block_t block)

{

#define PUSH_BLOCK_ACK_NS    3000000L   // 3 ms: time between checks for ack in push()

                                        //       FIXME should be configurable

    static const struct timespec req = {0, PUSH_BLOCK_ACK_NS};

    ALOG_ASSERT(!mInMutation, "push() called when in a mutation");

    if (mIsDirty) {

        // wait for prior push to be acknowledged

        if (mExpecting != NULL) {

            for (;;) {

                const T *ack = (const T *) mAck;    // no additional barrier needed

                if (ack == mExpecting) {

                    // unnecessary as we're about to rewrite

                    //mExpecting = NULL;

                    break;

                }

                if (block == BLOCK_NEVER) {

                    return false;

                }

                nanosleep(&req, NULL);

            }

        }

        // publish

        android_atomic_release_store((int32_t) mMutating, (volatile int32_t *) &mNext);

        mExpecting = mMutating;

        // copy with circular wraparound

        if (++mMutating >= &mStates[kN]) {

            mMutating = &mStates[0];

        }

        *mMutating = *mExpecting;

        mIsDirty = false;

    }

    // optionally wait for this push or a prior push to be acknowledged

    if (block == BLOCK_UNTIL_ACKED) {

        if (mExpecting != NULL) {

            for (;;) {

                const T *ack = (const T *) mAck;    // no additional barrier needed

                if (ack == mExpecting) {

                    mExpecting = NULL;

                    break;

                }

                nanosleep(&req, NULL);

            }

        }

    }

    return true;

}

}   // namespace android

// hack for gcc

#ifdef STATE_QUEUE_INSTANTIATIONS

#include STATE_QUEUE_INSTANTIATIONS

#endif

/*

 * Copyright (C) 2012 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 ANDROID_AUDIO_STATE_QUEUE_H

#define ANDROID_AUDIO_STATE_QUEUE_H

namespace android {

// manages a FIFO queue of states

template<typename T> class StateQueue {

public:

            StateQueue();

    virtual ~StateQueue();

    // Observer APIs

    // Poll for a state change.  Returns a pointer to a read-only state,

    // or NULL if the state has not been initialized yet.

    // If a new state has not pushed by mutator since the previous poll,

    // then the returned pointer will be unchanged.

    // The previous state pointer is guaranteed to still be valid;

    // this allows the observer to diff the previous and new states.

    const T* poll();

    // Mutator APIs

    // Begin a mutation.  Returns a pointer to a read/write state, except the

    // first time it is called the state is write-only and _must_ be initialized.

    // Mutations cannot be nested.

    // If the state is dirty and has not been pushed onto the state queue yet, then

    // this new mutation will be squashed together with the previous one.

    T*      begin();

    // End the current mutation and indicate whether caller modified the state.

    // If didModify is true, then the state is marked dirty (in need of pushing).

    // There is no rollback option because modifications are done in place.

    // Does not automatically push the new state onto the state queue.

    void    end(bool didModify = true);

    // Push a new state, if any, out to the observer via the state queue.

    // For BLOCK_NEVER, returns:

    //      true if not dirty, or dirty and pushed successfully

    //      false if dirty and not pushed because that would block; remains dirty

    // For BLOCK_UNTIL_PUSHED and BLOCK_UNTIL_ACKED, always returns true.

    // No-op if there are no pending modifications (not dirty), except

    //      for BLOCK_UNTIL_ACKED it will wait until a prior push has been acknowledged.

    // Must not be called in the middle of a mutation.

    enum block_t {

        BLOCK_NEVER,        // do not block

        BLOCK_UNTIL_PUSHED, // block until there's a slot available for the push

        BLOCK_UNTIL_ACKED,  // also block until the push is acknowledged by the observer

    };

    bool    push(block_t block = BLOCK_NEVER);

    // Return whether the current state is dirty (modified and not pushed).

    bool    isDirty() const { return mIsDirty; }

private:

    static const unsigned kN = 4;       // values != 4 are not supported by this code

    T                 mStates[kN];      // written by mutator, read by observer

    // "volatile" is meaningless with SMP, but here it indicates that we're using atomic ops

    volatile const T* mNext; // written by mutator to advance next, read by observer

    volatile const T* mAck;  // written by observer to acknowledge advance of next, read by mutator

    // only used by observer

    const T*          mCurrent;         // most recent value returned by poll()

    // only used by mutator

    T*                mMutating;        // where updates by mutator are done in place

    const T*          mExpecting;       // what the mutator expects mAck to be set to

    bool              mInMutation;      // whether we're currently in the middle of a mutation

    bool              mIsDirty;         // whether mutating state has been modified since last push

    bool              mIsInitialized;   // whether mutating state has been initialized yet

};  // class StateQueue

}   // namespace android

#endif  // ANDROID_AUDIO_STATE_QUEUE_H