#include <stdlib.h>
#include <stdio.h>
#include <hdf5.h>
#include <time.h>
#include <unistd.h>

#define NX 1024
#define NY 2048
#define NTOT NX*NY
#define NCX 1
#define NCY 4

typedef unsigned short data_type;

//-----------------------------------------------------------------------------
hid_t create_dataset(hid_t parent,const char *name,hid_t type_id,hid_t
        space_id,hsize_t *chunk)
{
    //setup the creation property list for the dataset
    hid_t cplist = H5Pcreate(H5P_DATASET_CREATE);
    H5Pset_layout(cplist,H5D_CHUNKED);
    H5Pset_chunk(cplist,2,chunk);
    hid_t dset_id;

    if(chunk!=NULL)
    {
        fprintf(stdout,"Create dataset with chunks ...\n");
        dset_id = H5Dcreate(parent,name,type_id,space_id,H5P_DEFAULT,cplist,
                              H5P_DEFAULT);
    }
    else 
    {
        fprintf(stdout,"Create dataset without chunks ...\n");
        dset_id = H5Dcreate(parent,name,type_id,space_id,H5P_DEFAULT,H5P_DEFAULT,
                              H5P_DEFAULT);
    }

    H5Pclose(cplist);
    return dset_id;
}

//-----------------------------------------------------------------------------
void test(int gbcollect,int rewrite_first)
{

    hsize_t shape[2] = {NX,NY};    //shape of the dataset 
    hsize_t chunk[2] = {NCX,NCY};  //stupid chunk shape for the dataset

    //create a new file
    hid_t fid = H5Fcreate("test2.h5",H5F_ACC_TRUNC,H5P_DEFAULT,H5P_DEFAULT);

    //create type and data space
    hid_t type_id = H5Tcopy(H5T_NATIVE_USHORT);
    hid_t space_id = H5Screate_simple(2,shape,shape);
    hid_t dset_id = create_dataset(fid,"test",type_id,space_id,chunk);

    //generate data
    unsigned short *data = malloc(sizeof(data_type)*NTOT);
    for(size_t i=0;i<NTOT;++i) data[i] = 123;

    //write data to disk
    H5Dwrite(dset_id,type_id,H5S_ALL,H5S_ALL,H5P_DEFAULT,data);

    if(gbcollect)
    {
        fprintf(stdout,"Running garbage collector ...\n");
        H5garbage_collect();
    }

    if(rewrite_first)
    {
        hsize_t start[2]  = {0,0};
        hsize_t count[2]  = {1,1};
        H5Sselect_hyperslab(space_id,H5S_SELECT_SET,start,NULL,count,NULL);
        data_type buffer = 1;
        H5Dwrite(dset_id,type_id,H5S_ALL,space_id,H5P_DEFAULT,&buffer);
    }

    //close everything and release memory
    H5Dclose(dset_id);
    H5Tclose(type_id);
    H5Sclose(space_id);
    H5Fflush(fid,H5F_SCOPE_GLOBAL);
    H5Fclose(fid);
    free(data);
}

//-----------------------------------------------------------------------------
void check()
{
    //read the programs statm file from the proc file system
    FILE *f = fopen("/proc/self/statm","r");
    size_t size,resident,share;
    fscanf(f,"%lu %lu %lu",&size,&resident,&share);
    fclose(f);

    long page_size_kb = sysconf(_SC_PAGE_SIZE) / 1024; 
    double rss = resident * page_size_kb;
    fprintf(stdout,"RSS            - %e kB\n",rss);

    double shared_mem = share * page_size_kb;
    fprintf(stdout,"Shared Memory  - %e kB\n",shared_mem);
    fprintf(stdout,"Private Memory - %e kB\n",rss - shared_mem);
}

//-----------------------------------------------------------------------------
int main(int argc,char **argv)
{
    fprintf(stdout,"Startup ...\n"); 
    check();
#ifdef GARBAGE_COLLECT
    test(1,0);
#else
    test(0,1);
#endif
    fprintf(stdout,"\nAfter first write ...\n");
    check();
#ifdef GARBAGE_COLLECT
    test(1,0);
#else
    test(0,1);
#endif
    fprintf(stdout,"\nAfter second write ...\n");
    check();

    return 0;
}