free() — netty Function Reference

Source Code

buffer/src/main/java/io/netty/buffer/PoolChunk.java lines 500–546

    void free(long handle, int normCapacity, ByteBuffer nioBuffer) {
        if (isSubpage(handle)) {
            int sIdx = runOffset(handle);
            PoolSubpage<T> subpage = subpages[sIdx];
            assert subpage != null;
            PoolSubpage<T> head = subpage.chunk.arena.smallSubpagePools[subpage.headIndex];
            // Obtain the head of the PoolSubPage pool that is owned by the PoolArena and synchronize on it.
            // This is need as we may add it back and so alter the linked-list structure.
            head.lock();
            try {
                assert subpage.doNotDestroy;
                if (subpage.free(head, bitmapIdx(handle))) {
                    //the subpage is still used, do not free it
                    return;
                }
                assert !subpage.doNotDestroy;
                // Null out slot in the array as it was freed and we should not use it anymore.
                subpages[sIdx] = null;
            } finally {
                head.unlock();
            }
        }

        int runSize = runSize(pageShifts, handle);
        //start free run
        runsAvailLock.lock();
        try {
            // collapse continuous runs, successfully collapsed runs
            // will be removed from runsAvail and runsAvailMap
            long finalRun = collapseRuns(handle);

            //set run as not used
            finalRun &= ~(1L << IS_USED_SHIFT);
            //if it is a subpage, set it to run
            finalRun &= ~(1L << IS_SUBPAGE_SHIFT);

            insertAvailRun(runOffset(finalRun), runPages(finalRun), finalRun);
            freeBytes += runSize;
        } finally {
            runsAvailLock.unlock();
        }

        if (nioBuffer != null && cachedNioBuffers != null &&
            cachedNioBuffers.size() < PooledByteBufAllocator.DEFAULT_MAX_CACHED_BYTEBUFFERS_PER_CHUNK) {
            cachedNioBuffers.offer(nioBuffer);
        }
    }