protected ByteBuf newDirectBuffer(int initialCapacity, int maxCapacity) {PoolThreadCache cache = threadCache.get();PoolArena<ByteBuffer> directArena = cache.directArena;ByteBuf buf;if (directArena != null) { buf = directArena.allocate(cache, initialCapacity, maxCapacity);} else {if (PlatformDependent.hasUnsafe()) {buf = UnsafeByteBufUtil.newUnsafeDirectByteBuf(this, initialCapacity, maxCapacity);} else {buf = new UnpooledDirectByteBuf(this, initialCapacity, maxCapacity);}}return toLeakAwareBuffer(buf);
}

PooledByteBuf<T> allocate(PoolThreadCache cache, int reqCapacity, int maxCapacity) { PooledByteBuf<T> buf = newByteBuf(maxCapacity); allocate(cache, buf, reqCapacity);return buf;
}

protected PooledByteBuf<ByteBuffer> newByteBuf(int maxCapacity) { if (HAS_UNSAFE) { return PooledUnsafeDirectByteBuf.newInstance(maxCapacity);} else {return PooledDirectByteBuf.newInstance(maxCapacity);}
}

static PooledUnsafeDirectByteBuf newInstance(int maxCapacity) {PooledUnsafeDirectByteBuf buf = RECYCLER.get();buf.reuse(maxCapacity);return buf;
}

final void reuse(int maxCapacity) {maxCapacity(maxCapacity);setRefCnt(1);setIndex0(0, 0);discardMarks();
}

PooledByteBuf<T> allocate(PoolThreadCache cache, int reqCapacity, int maxCapacity) { PooledByteBuf<T> buf = newByteBuf(maxCapacity); allocate(cache, buf, reqCapacity);return buf;
}

private void allocate(PoolThreadCache cache, PooledByteBuf<T> buf, final int reqCapacity) {//规格化final int normCapacity = normalizeCapacity(reqCapacity);if (isTinyOrSmall(normCapacity)) { int tableIdx;PoolSubpage<T>[] table;//判断是不是tintyboolean tiny = isTiny(normCapacity);if (tiny) { // < 512//缓存分配if (cache.allocateTiny(this, buf, reqCapacity, normCapacity)) {return;}//通过tinyIdx拿到tableIdxtableIdx = tinyIdx(normCapacity);//subpage的数组table = tinySubpagePools;} else {if (cache.allocateSmall(this, buf, reqCapacity, normCapacity)) {return;}tableIdx = smallIdx(normCapacity);table = smallSubpagePools;}//拿到对应的节点final PoolSubpage<T> head = table[tableIdx];synchronized (head) {final PoolSubpage<T> s = head.next;//默认情况下, head的next也是自身if (s != head) {assert s.doNotDestroy && s.elemSize == normCapacity;long handle = s.allocate();assert handle >= 0;s.chunk.initBufWithSubpage(buf, handle, reqCapacity);if (tiny) {allocationsTiny.increment();} else {allocationsSmall.increment();}return;}}allocateNormal(buf, reqCapacity, normCapacity);return;}if (normCapacity <= chunkSize) {//首先在缓存上进行内存分配if (cache.allocateNormal(this, buf, reqCapacity, normCapacity)) {//分配成功, 返回return;}//分配不成功, 做实际的内存分配
        allocateNormal(buf, reqCapacity, normCapacity);} else {//大于这个值, 就不在缓存上分配
        allocateHuge(buf, reqCapacity);}
}