sliding_shard(stripedio * iomgr, std::string _filename_edata, std::string _filename_adj, vid_t _range_st, vid_t _range_en, size_t _blocksize, metrics &_m,
                      bool _disable_writes=false, bool onlyadj = false) :
        iomgr(iomgr),
        filename_edata(_filename_edata),
        filename_adj(_filename_adj),
        range_st(_range_st),
        range_end(_range_en),
        blocksize(_blocksize),
        m(_m),
        disable_writes(_disable_writes) {
            curvid = 0;
            adjoffset = 0;
            edataoffset = 0;
            disable_writes = false;
            only_adjacency = onlyadj;
            curblock = NULL;
            curadjblock = NULL;
            window_start_edataoffset = 0;
            disable_async_writes = false;
            
            while(blocksize % sizeof(int) != 0) blocksize++;
            assert(blocksize % sizeof(int)==0);
            
            adjfilesize = get_filesize(filename_adj);
            edatafilesize = get_shard_edata_filesize<int>(filename_edata);
            if (!only_adjacency) {
                logstream(LOG_DEBUG) << "Total edge data size: " << edatafilesize << std::endl;
            } else {
                // Nothing
            }
            
            adjfile_session = iomgr->open_session(filename_adj, true);
            save_offset();
            
            async_edata_loading = false; // With dynamic edge data size, do not load

        }

 void commit(bool all) {
     if (edgedata == NULL || only_adjacency) return; 
     assert(is_loaded);
     metrics_entry cm = m.start_time();
     
     /**
       * This is an optimization that is relevant only if memory shard
       * has been used in a case where only out-edges are considered.
       * Out-edges are in a continuous "window", while in-edges are 
       * scattered all over the shard
       */
     if (all) {
         iomgr->managed_pwritea_now(edata_iosession, &edgedata, edatafilesize, 0);
     } else {
         size_t last = streaming_offset_edge_ptr;
         if (last == 0){
             // rollback
             last = edatafilesize;
         }   
         char * bufp = ((char*)edgedata + range_start_edge_ptr);
         iomgr->managed_pwritea_now(edata_iosession, &bufp, last - range_start_edge_ptr, range_start_edge_ptr);
         
     }
     m.stop_time(cm, "memshard_commit");
     
     iomgr->managed_release(adj_session, &adjdata);
     iomgr->managed_release(edata_iosession, &edgedata);
     is_loaded = false;
 }

 inline void check_curblock(size_t toread) {
     if (curblock == NULL || curblock->end < edataoffset+toread) {
         if (curblock != NULL) {
             if (!curblock->active) {
                 curblock->release(iomgr);
             }
         }
         // Load next
         std::string blockfilename = filename_shard_edata_block(filename_edata, (int) (edataoffset / blocksize), blocksize);
         int edata_session = iomgr->open_session(blockfilename, false, true);
         sblock<ET> newblock(edata_session, edata_session, true, blockfilename);
         
         // We align blocks always to the blocksize, even if that requires
         // allocating and reading some unnecessary data.
         newblock.offset = (edataoffset / blocksize) * blocksize; // Align
         size_t correction = edataoffset - newblock.offset;
         newblock.end = std::min(edatafilesize, newblock.offset + blocksize);
         assert(newblock.end >= newblock.offset);
         int realsize = get_block_uncompressed_size(blockfilename, newblock.end - newblock.offset);
         iomgr->managed_malloc(edata_session, &newblock.data, realsize, newblock.offset);
         newblock.ptr = newblock.data + correction;
         activeblocks.push_back(newblock);
         curblock = &activeblocks[activeblocks.size()-1];
         curblock->active = true;
         curblock->read_now(iomgr);
     }
 }

 void releaseblocks() {
     for(int i=0; i < (int)loadedblocks.size(); i++) {
         delete(loadedblocks[i].dblock);
         iomgr->managed_release(loadedblocks[i].fd, &loadedblocks[i].data);
         iomgr->close_session(loadedblocks[i].fd);
         loadedblocks[i].data = NULL;
         loadedblocks[i].dblock = NULL;
     }
     loadedblocks.clear();
 }

        ~memory_shard() {

            if (edata_iosession >= 0) {
                if (edgedata != NULL) iomgr->managed_release(edata_iosession, &edgedata);
                iomgr->close_session(edata_iosession);
            }
            if (adj_session >= 0) {
                if (adjdata != NULL) iomgr->managed_release(adj_session, &adjdata);
                iomgr->close_session(adj_session);
            }
        }

 vdblock load_block(int blockid) {
     vdblock db(blockid);
     
     std::string blockfname = blockfilename(blockid);
     db.fd = iomgr->open_session(blockfname, false, true);
     int realsize = get_block_uncompressed_size(blockfname, -1);
     assert(realsize > 0);
     
     iomgr->managed_malloc(db.fd, &db.data, realsize, 0);
     iomgr->managed_preada_now(db.fd, &db.data, realsize, 0);
     db.dblock = new dynamicdata_block<VertexDataType>(verticesperblock, (uint8_t *)db.data, realsize);
     return db;
 }

 virtual void open_file(std::string base_filename) {
     filename = filename_degree_data(base_filename);
     modified = false;
     if (!use_mmap) {
         iomgr->allow_preloading(filename);
         filedesc = iomgr->open_session(filename.c_str(), false);
     } else {
         mmap_length = get_filesize(filename);
         filedesc = open(filename.c_str(), O_RDWR);
         mmap_file = (degree *) mmap(NULL, mmap_length, PROT_READ | PROT_WRITE, MAP_SHARED, filedesc, 0);
         assert(mmap_file);
     }
 }

 virtual ~degree_data() {
     if (!use_mmap) {
         if (loaded_chunk != NULL) {
             iomgr->managed_release(filedesc, &loaded_chunk);
         }        
         iomgr->close_session(filedesc);
     } else {
         if (modified) {
             msync(mmap_file, mmap_length, MS_SYNC);
         }
         munmap(mmap_file, mmap_length);
         close(filedesc);
     }
 }

 /**
   * Saves the current chunk of vertex values
   */
 virtual void save(bool async=false) {
     if (!use_mmap) {
         assert(loaded_chunk != NULL); 
         size_t datasize = (vertex_en - vertex_st + 1) * sizeof(VertexDataType);
         size_t datastart = vertex_st * sizeof(VertexDataType);
         if (async) {
             iomgr->managed_pwritea_async(filedesc, &loaded_chunk, datasize, datastart, false);
         } else {
             iomgr->managed_pwritea_now(filedesc, &loaded_chunk, datasize, datastart);
         }
     } else {
         // do nothing
     }
 }

 virtual ~vertex_data_store() {
     if (!use_mmap) {
         iomgr->close_session(filedesc);
         iomgr->wait_for_writes();
         if (loaded_chunk != NULL) {
             iomgr->managed_release(filedesc, &loaded_chunk);
         }
     } else {
         logstream(LOG_INFO) << "Syncing vertex data..." << std::endl;
         msync(mmap_file, mmap_length, MS_SYNC);
         munmap(mmap_file, mmap_length);
         close(filedesc);
     }
 }

 /**
   * Loads a chunk of vertex degrees
   * @param vertex_st first vertex id
   * @param vertex_en last vertex id, inclusive
   */
 virtual void load(vid_t _vertex_st, vid_t _vertex_en) {
     assert(_vertex_en >= _vertex_st);
     vertex_st = _vertex_st;
     vertex_en = _vertex_en;
     
     size_t datasize = (vertex_en - vertex_st + 1) * sizeof(degree);
     size_t datastart = vertex_st * sizeof(degree);
     
     if (loaded_chunk != NULL) {
         iomgr->managed_release(filedesc, &loaded_chunk);
     }
     
     iomgr->managed_malloc(filedesc, &loaded_chunk, datasize, datastart);
     iomgr->managed_preada_now(filedesc, &loaded_chunk, datasize, datastart);
 }

 void save() {
     if (!use_mmap) {
         size_t datasize = (vertex_en - vertex_st + 1) * sizeof(degree);
         size_t datastart = vertex_st * sizeof(degree);
         iomgr->managed_pwritea_now(filedesc, &loaded_chunk, datasize, datastart);
     }
 }

 void write_block(vdblock &block) {
     int realsize;
     uint8_t * outdata;
     block.dblock->write(&outdata, realsize);
     std::string blockfname = blockfilename(block.blockid);
     iomgr->managed_pwritea_now(block.fd, &outdata, realsize, 0); /* Need to write whole block in the compressed regime */
     write_block_uncompressed_size(blockfname, realsize);
 }

        // TODO: recycle ptr!
        void load() {
            is_loaded = true;
            adjfilesize = get_filesize(filename_adj);
            edatafilesize = get_filesize(filename_edata);
            
            bool async_inedgedata_loading = !svertex_t().computational_edges();
            
#ifdef SUPPORT_DELETIONS
            async_inedgedata_loading = false;  // Currently we encode the deleted status of an edge into the edge value (should be changed!),
                                               // so we need the edge data while loading
#endif
                        
            //preada(adjf, adjdata, adjfilesize, 0);
            
            adj_session = iomgr->open_session(filename_adj, true);
            iomgr->managed_malloc(adj_session, &adjdata, adjfilesize, 0);
            adj_stream_session = streaming_task(iomgr, adj_session, adjfilesize, (char**) &adjdata);
            
            iomgr->launch_stream_reader(&adj_stream_session);            
            /* Initialize edge data asynchonous reading */
            if (!only_adjacency) {
                edata_iosession = iomgr->open_session(filename_edata, false);
                
                iomgr->managed_malloc(edata_iosession, &edgedata, edatafilesize, 0);
                if (async_inedgedata_loading) {
                    iomgr->managed_preada_async(edata_iosession, &edgedata, edatafilesize, 0);
                } else {
                    iomgr->managed_preada_now(edata_iosession, &edgedata, edatafilesize, 0);
                }
            }
        }

 void ensure_size(vid_t maxid) {
     if (!use_mmap) {
         iomgr->truncate(filedesc, (1 + maxid) * sizeof(degree));
     } else {
         munmap(mmap_file, mmap_length);
         ftruncate(filedesc, (1 + maxid) * sizeof(degree));
         close(filedesc);
         open_file(base_filename);
     }
 }

 virtual void open_file() {
     if (!use_mmap) {
         filedesc = iomgr->open_session(filename.c_str(), false);
     } else {
         mmap_length = get_filesize(filename);
         filedesc = open(filename.c_str(), O_RDWR);
         mmap_file = (VertexDataType *) mmap(NULL, mmap_length, PROT_WRITE | PROT_READ, MAP_SHARED, filedesc, 0);
         assert(mmap_file);
     }
 }

        /**
         * Loads a chunk of vertex values
         * @param vertex_st first vertex id
         * @param vertex_en last vertex id, inclusive
         */
        virtual void load(vid_t _vertex_st, vid_t _vertex_en) {
            if (!use_mmap) {
                assert(_vertex_en >= _vertex_st);
                vertex_st = _vertex_st;
                vertex_en = _vertex_en;
                
                size_t datasize = (vertex_en - vertex_st + 1)* sizeof(VertexDataType);
                size_t datastart = vertex_st * sizeof(VertexDataType);
                
                if (loaded_chunk != NULL) {
                    iomgr->managed_release(filedesc, &loaded_chunk);
                }
                
                iomgr->managed_malloc(filedesc, &loaded_chunk, datasize, datastart);
                iomgr->managed_preada_now(filedesc, &loaded_chunk, datasize, datastart);
            } else {
                // Do nothing
            }

        }

 inline void check_adjblock(size_t toread) {
     if (curadjblock == NULL || curadjblock->end <= adjoffset + toread) {
         if (curadjblock != NULL) {
             curadjblock->release(iomgr);
             delete curadjblock;
             curadjblock = NULL;
         }
         sblock<ET> * newblock = new sblock<ET>(0, adjfile_session);
         newblock->offset = adjoffset;
         newblock->end = std::min(adjfilesize, adjoffset+blocksize);
         assert(newblock->end > 0);
         assert(newblock->end >= newblock->offset);
         iomgr->managed_malloc(adjfile_session, &newblock->data, newblock->end - newblock->offset, adjoffset);
         newblock->ptr = newblock->data;
         metrics_entry me = m.start_time();
         iomgr->managed_preada_now(adjfile_session, &newblock->data, newblock->end - newblock->offset, adjoffset);
         m.stop_time(me, "blockload");
         curadjblock = newblock;
     }
 }

 ~sliding_shard() {
     release_prior_to_offset(true);
     if (curblock != NULL) {
         curblock->release(iomgr);
         delete curblock;
         curblock = NULL;
     }
     if (curadjblock != NULL) {
         curadjblock->release(iomgr);
         delete curadjblock;
         curadjblock = NULL;
     }
     
     
     iomgr->close_session(adjfile_session);
 }

 virtual ~degree_data() {
     if (loaded_chunk != NULL) {
         iomgr->managed_release(filedesc, &loaded_chunk);
     }        
     iomgr->close_session(filedesc);
 }