/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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.
   */
  
  package io.netty.buffer;
  
  
  import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
  
  import io.netty.buffer.PoolArena.SizeClass;
  import io.netty.util.Recycler.EnhancedHandle;
  import io.netty.util.internal.MathUtil;
  import io.netty.util.internal.ObjectPool;
  import io.netty.util.internal.ObjectPool.Handle;
  import io.netty.util.internal.ObjectPool.ObjectCreator;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.nio.ByteBuffer;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Queue;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * Acts a Thread cache for allocations. This implementation is moduled after
   * <a href="https://people.freebsd.org/~jasone/jemalloc/bsdcan2006/jemalloc.pdf">jemalloc</a> and the descripted
   * technics of
   * <a href="https://www.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919">
   * Scalable memory allocation using jemalloc</a>.
   */
  final class PoolThreadCache {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(PoolThreadCache.class);
      private static final int INTEGER_SIZE_MINUS_ONE = Integer.SIZE - 1;
  
      final PoolArena<byte[]> heapArena;
      final PoolArena<ByteBuffer> directArena;
  
      // Hold the caches for the different size classes, which are small and normal.
      private final MemoryRegionCache<byte[]>[] smallSubPageHeapCaches;
      private final MemoryRegionCache<ByteBuffer>[] smallSubPageDirectCaches;
      private final MemoryRegionCache<byte[]>[] normalHeapCaches;
      private final MemoryRegionCache<ByteBuffer>[] normalDirectCaches;
  
      private final int freeSweepAllocationThreshold;
      private final AtomicBoolean freed = new AtomicBoolean();
      @SuppressWarnings("unused") // Field is only here for the finalizer.
      private final FreeOnFinalize freeOnFinalize;
  
      private int allocations;
  
      // TODO: Test if adding padding helps under contention
      //private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
  
      PoolThreadCache(PoolArena<byte[]> heapArena, PoolArena<ByteBuffer> directArena,
                      int smallCacheSize, int normalCacheSize, int maxCachedBufferCapacity,
                      int freeSweepAllocationThreshold, boolean useFinalizer) {
          checkPositiveOrZero(maxCachedBufferCapacity, "maxCachedBufferCapacity");
          this.freeSweepAllocationThreshold = freeSweepAllocationThreshold;
          this.heapArena = heapArena;
          this.directArena = directArena;
          if (directArena != null) {
              smallSubPageDirectCaches = createSubPageCaches(smallCacheSize, directArena.sizeClass.nSubpages);
              normalDirectCaches = createNormalCaches(normalCacheSize, maxCachedBufferCapacity, directArena);
              directArena.numThreadCaches.getAndIncrement();
          } else {
              // No directArea is configured so just null out all caches
              smallSubPageDirectCaches = null;
              normalDirectCaches = null;
          }
          if (heapArena != null) {
              // Create the caches for the heap allocations
              smallSubPageHeapCaches = createSubPageCaches(smallCacheSize, heapArena.sizeClass.nSubpages);
              normalHeapCaches = createNormalCaches(normalCacheSize, maxCachedBufferCapacity, heapArena);
              heapArena.numThreadCaches.getAndIncrement();
          } else {
              // No heapArea is configured so just null out all caches
              smallSubPageHeapCaches = null;
              normalHeapCaches = null;
          }
  
          // Only check if there are caches in use.
          if ((smallSubPageDirectCaches != null || normalDirectCaches != null
                  || smallSubPageHeapCaches != null || normalHeapCaches != null)
                  && freeSweepAllocationThreshold < 1) {
             throw new IllegalArgumentException("freeSweepAllocationThreshold: "
                     + freeSweepAllocationThreshold + " (expected: > 0)");
         }
         freeOnFinalize = useFinalizer ? new FreeOnFinalize(this) : null;
     }
 
     private static <T> MemoryRegionCache<T>[] createSubPageCaches(
             int cacheSize, int numCaches) {
         if (cacheSize > 0 && numCaches > 0) {
             @SuppressWarnings("unchecked")
             MemoryRegionCache<T>[] cache = new MemoryRegionCache[numCaches];
             for (int i = 0; i < cache.length; i++) {
                 // TODO: maybe use cacheSize / cache.length
                 cache[i] = new SubPageMemoryRegionCache<T>(cacheSize);
             }
             return cache;
         } else {
             return null;
         }
     }
 
     @SuppressWarnings("unchecked")
     private static <T> MemoryRegionCache<T>[] createNormalCaches(
             int cacheSize, int maxCachedBufferCapacity, PoolArena<T> area) {
         if (cacheSize > 0 && maxCachedBufferCapacity > 0) {
             int max = Math.min(area.sizeClass.chunkSize, maxCachedBufferCapacity);
             // Create as many normal caches as we support based on how many sizeIdx we have and what the upper
             // bound is that we want to cache in general.
             List<MemoryRegionCache<T>> cache = new ArrayList<MemoryRegionCache<T>>() ;
             for (int idx = area.sizeClass.nSubpages; idx < area.sizeClass.nSizes &&
                     area.sizeClass.sizeIdx2size(idx) <= max; idx++) {
                 cache.add(new NormalMemoryRegionCache<T>(cacheSize));
             }
             return cache.toArray(new MemoryRegionCache[0]);
         } else {
             return null;
         }
     }
 
     // val > 0
     static int log2(int val) {
         return INTEGER_SIZE_MINUS_ONE - Integer.numberOfLeadingZeros(val);
     }
 
     /**
      * Try to allocate a small buffer out of the cache. Returns {@code true} if successful {@code false} otherwise
      */
     boolean allocateSmall(PoolArena<?> area, PooledByteBuf<?> buf, int reqCapacity, int sizeIdx) {
         return allocate(cacheForSmall(area, sizeIdx), buf, reqCapacity);
     }
 
     /**
      * Try to allocate a normal buffer out of the cache. Returns {@code true} if successful {@code false} otherwise
      */
     boolean allocateNormal(PoolArena<?> area, PooledByteBuf<?> buf, int reqCapacity, int sizeIdx) {
         return allocate(cacheForNormal(area, sizeIdx), buf, reqCapacity);
     }
 
     @SuppressWarnings({ "unchecked", "rawtypes" })
     private boolean allocate(MemoryRegionCache<?> cache, PooledByteBuf buf, int reqCapacity) {
         if (cache == null) {
             // no cache found so just return false here
             return false;
         }
         boolean allocated = cache.allocate(buf, reqCapacity, this);
         if (++ allocations >= freeSweepAllocationThreshold) {
             allocations = 0;
             trim();
         }
         return allocated;
     }
 
     /**
      * Add {@link PoolChunk} and {@code handle} to the cache if there is enough room.
      * Returns {@code true} if it fit into the cache {@code false} otherwise.
      */
     @SuppressWarnings({ "unchecked", "rawtypes" })
     boolean add(PoolArena<?> area, PoolChunk chunk, ByteBuffer nioBuffer,
                 long handle, int normCapacity, SizeClass sizeClass) {
         int sizeIdx = area.sizeClass.size2SizeIdx(normCapacity);
         MemoryRegionCache<?> cache = cache(area, sizeIdx, sizeClass);
         if (cache == null) {
             return false;
         }
         if (freed.get()) {
             return false;
         }
         return cache.add(chunk, nioBuffer, handle, normCapacity);
     }
 
     private MemoryRegionCache<?> cache(PoolArena<?> area, int sizeIdx, SizeClass sizeClass) {
         switch (sizeClass) {
         case Normal:
             return cacheForNormal(area, sizeIdx);
         case Small:
             return cacheForSmall(area, sizeIdx);
         default:
             throw new Error();
         }
     }
 
     /**
      *  Should be called if the Thread that uses this cache is about to exit to release resources out of the cache
      */
     void free(boolean finalizer) {
         // As free() may be called either by the finalizer or by FastThreadLocal.onRemoval(...) we need to ensure
         // we only call this one time.
         if (freed.compareAndSet(false, true)) {
             if (freeOnFinalize != null) {
                 // Help GC: this can race with a finalizer thread, but will be null out regardless
                 freeOnFinalize.cache = null;
             }
             int numFreed = free(smallSubPageDirectCaches, finalizer) +
                            free(normalDirectCaches, finalizer) +
                            free(smallSubPageHeapCaches, finalizer) +
                            free(normalHeapCaches, finalizer);
 
             if (numFreed > 0 && logger.isDebugEnabled()) {
                 logger.debug("Freed {} thread-local buffer(s) from thread: {}", numFreed,
                              Thread.currentThread().getName());
             }
 
             if (directArena != null) {
                 directArena.numThreadCaches.getAndDecrement();
             }
 
             if (heapArena != null) {
                 heapArena.numThreadCaches.getAndDecrement();
             }
         }
     }
 
     private static int free(MemoryRegionCache<?>[] caches, boolean finalizer) {
         if (caches == null) {
             return 0;
         }
 
         int numFreed = 0;
         for (MemoryRegionCache<?> c: caches) {
             numFreed += free(c, finalizer);
         }
         return numFreed;
     }
 
     private static int free(MemoryRegionCache<?> cache, boolean finalizer) {
         if (cache == null) {
             return 0;
         }
         return cache.free(finalizer);
     }
 
     void trim() {
         trim(smallSubPageDirectCaches);
         trim(normalDirectCaches);
         trim(smallSubPageHeapCaches);
         trim(normalHeapCaches);
     }
 
     private static void trim(MemoryRegionCache<?>[] caches) {
         if (caches == null) {
             return;
         }
         for (MemoryRegionCache<?> c: caches) {
             trim(c);
         }
     }
 
     private static void trim(MemoryRegionCache<?> cache) {
         if (cache == null) {
             return;
         }
         cache.trim();
     }
 
     private MemoryRegionCache<?> cacheForSmall(PoolArena<?> area, int sizeIdx) {
         if (area.isDirect()) {
             return cache(smallSubPageDirectCaches, sizeIdx);
         }
         return cache(smallSubPageHeapCaches, sizeIdx);
     }
 
     private MemoryRegionCache<?> cacheForNormal(PoolArena<?> area, int sizeIdx) {
         // We need to subtract area.sizeClass.nSubpages as sizeIdx is the overall index for all sizes.
         int idx = sizeIdx - area.sizeClass.nSubpages;
         if (area.isDirect()) {
             return cache(normalDirectCaches, idx);
         }
         return cache(normalHeapCaches, idx);
     }
 
     private static <T> MemoryRegionCache<T> cache(MemoryRegionCache<T>[] cache, int sizeIdx) {
         if (cache == null || sizeIdx > cache.length - 1) {
             return null;
         }
         return cache[sizeIdx];
     }
 
     /**
      * Cache used for buffers which are backed by TINY or SMALL size.
      */
     private static final class SubPageMemoryRegionCache<T> extends MemoryRegionCache<T> {
         SubPageMemoryRegionCache(int size) {
             super(size, SizeClass.Small);
         }
 
         @Override
         protected void initBuf(
                 PoolChunk<T> chunk, ByteBuffer nioBuffer, long handle, PooledByteBuf<T> buf, int reqCapacity,
                 PoolThreadCache threadCache) {
             chunk.initBufWithSubpage(buf, nioBuffer, handle, reqCapacity, threadCache);
         }
     }
 
     /**
      * Cache used for buffers which are backed by NORMAL size.
      */
     private static final class NormalMemoryRegionCache<T> extends MemoryRegionCache<T> {
         NormalMemoryRegionCache(int size) {
             super(size, SizeClass.Normal);
         }
 
         @Override
         protected void initBuf(
                 PoolChunk<T> chunk, ByteBuffer nioBuffer, long handle, PooledByteBuf<T> buf, int reqCapacity,
                 PoolThreadCache threadCache) {
             chunk.initBuf(buf, nioBuffer, handle, reqCapacity, threadCache);
         }
     }
 
     private abstract static class MemoryRegionCache<T> {
         private final int size;
         private final Queue<Entry<T>> queue;
         private final SizeClass sizeClass;
         private int allocations;
 
         MemoryRegionCache(int size, SizeClass sizeClass) {
             this.size = MathUtil.safeFindNextPositivePowerOfTwo(size);
             queue = PlatformDependent.newFixedMpscUnpaddedQueue(this.size);
             this.sizeClass = sizeClass;
         }
 
         /**
          * Init the {@link PooledByteBuf} using the provided chunk and handle with the capacity restrictions.
          */
         protected abstract void initBuf(PoolChunk<T> chunk, ByteBuffer nioBuffer, long handle,
                                         PooledByteBuf<T> buf, int reqCapacity, PoolThreadCache threadCache);
 
         /**
          * Add to cache if not already full.
          */
         @SuppressWarnings("unchecked")
         public final boolean add(PoolChunk<T> chunk, ByteBuffer nioBuffer, long handle, int normCapacity) {
             Entry<T> entry = newEntry(chunk, nioBuffer, handle, normCapacity);
             boolean queued = queue.offer(entry);
             if (!queued) {
                 // If it was not possible to cache the chunk, immediately recycle the entry
                 entry.unguardedRecycle();
             }
 
             return queued;
         }
 
         /**
          * Allocate something out of the cache if possible and remove the entry from the cache.
          */
         public final boolean allocate(PooledByteBuf<T> buf, int reqCapacity, PoolThreadCache threadCache) {
             Entry<T> entry = queue.poll();
             if (entry == null) {
                 return false;
             }
             initBuf(entry.chunk, entry.nioBuffer, entry.handle, buf, reqCapacity, threadCache);
             entry.unguardedRecycle();
 
             // allocations is not thread-safe which is fine as this is only called from the same thread all time.
             ++ allocations;
             return true;
         }
 
         /**
          * Clear out this cache and free up all previous cached {@link PoolChunk}s and {@code handle}s.
          */
         public final int free(boolean finalizer) {
             return free(Integer.MAX_VALUE, finalizer);
         }
 
         private int free(int max, boolean finalizer) {
             int numFreed = 0;
             for (; numFreed < max; numFreed++) {
                 Entry<T> entry = queue.poll();
                 if (entry != null) {
                     freeEntry(entry, finalizer);
                 } else {
                     // all cleared
                     return numFreed;
                 }
             }
             return numFreed;
         }
 
         /**
          * Free up cached {@link PoolChunk}s if not allocated frequently enough.
          */
         public final void trim() {
             int free = size - allocations;
             allocations = 0;
 
             // We not even allocated all the number that are
             if (free > 0) {
                 free(free, false);
             }
         }
 
         @SuppressWarnings({ "unchecked", "rawtypes" })
         private  void freeEntry(Entry entry, boolean finalizer) {
             // Capture entry state before we recycle the entry object.
             PoolChunk chunk = entry.chunk;
             long handle = entry.handle;
             ByteBuffer nioBuffer = entry.nioBuffer;
             int normCapacity = entry.normCapacity;
 
             if (!finalizer) {
                 // recycle now so PoolChunk can be GC'ed. This will only be done if this is not freed because of
                 // a finalizer.
                 entry.recycle();
             }
 
             chunk.arena.freeChunk(chunk, handle, normCapacity, sizeClass, nioBuffer, finalizer);
         }
 
         static final class Entry<T> {
             final EnhancedHandle<Entry<?>> recyclerHandle;
             PoolChunk<T> chunk;
             ByteBuffer nioBuffer;
             long handle = -1;
             int normCapacity;
 
             Entry(Handle<Entry<?>> recyclerHandle) {
                 this.recyclerHandle = (EnhancedHandle<Entry<?>>) recyclerHandle;
             }
 
             void recycle() {
                 chunk = null;
                 nioBuffer = null;
                 handle = -1;
                 recyclerHandle.recycle(this);
             }
 
             void unguardedRecycle() {
                 chunk = null;
                 nioBuffer = null;
                 handle = -1;
                 recyclerHandle.unguardedRecycle(this);
             }
         }
 
         @SuppressWarnings("rawtypes")
         private static Entry newEntry(PoolChunk<?> chunk, ByteBuffer nioBuffer, long handle, int normCapacity) {
             Entry entry = RECYCLER.get();
             entry.chunk = chunk;
             entry.nioBuffer = nioBuffer;
             entry.handle = handle;
             entry.normCapacity = normCapacity;
             return entry;
         }
 
         @SuppressWarnings("rawtypes")
         private static final ObjectPool<Entry> RECYCLER = ObjectPool.newPool(new ObjectCreator<Entry>() {
             @SuppressWarnings("unchecked")
             @Override
             public Entry newObject(Handle<Entry> handle) {
                 return new Entry(handle);
             }
         });
     }
 
     private static final class FreeOnFinalize {
 
         private volatile PoolThreadCache cache;
 
         private FreeOnFinalize(PoolThreadCache cache) {
             this.cache = cache;
         }
 
         /// TODO: In the future when we move to Java9+ we should use java.lang.ref.Cleaner.
         @SuppressWarnings({"FinalizeDeclaration", "deprecation"})
         @Override
         protected void finalize() throws Throwable {
             try {
                 super.finalize();
             } finally {
                 PoolThreadCache cache = this.cache;
                 // this can race with a non-finalizer thread calling free: regardless who wins, the cache will be
                 // null out
                 this.cache = null;
                 if (cache != null) {
                     cache.free(true);
                 }
             }
         }
     }
 }