old_contents: '''Virtual datasets: The 'Eiger' use case
  
  https://support.hdfgroup.org/HDF5/docNewFeatures/VDS/HDF5-VDS-requirements-use-cases-2014-12-10.pdf
  '''
  
  import h5py
  import numpy as np
  
  
  files = ['1.h5', '2.h5', '3.h5', '4.h5', '5.h5']
  entry_key = 'data' # where the data is inside of the source files.
  sh = h5py.File(files[0], 'r')[entry_key].shape # get the first ones shape.
  
  layout = h5py.VirtualLayout(shape=(len(files) * sh[0], ) + sh[1:], dtype=np.float64)
  M_start = 0
  for i, filename in enumerate(files):
      M_end = M_start + sh[0]
      vsource = h5py.VirtualSource(filename, entry_key, shape=sh)
      layout[M_start:M_end:1, :, :] = vsource
      M_start = M_end
  
  with h5py.File("eiger_vds.h5", 'w', libver='latest') as f:
      f.create_virtual_dataset('data', layout, fillvalue=0)
  
new_contents: '''Virtual datasets: The 'Eiger' use case
  
  https://support.hdfgroup.org/HDF5/docNewFeatures/VDS/HDF5-VDS-requirements-use-cases-2014-12-10.pdf
  '''
  
  import h5py
  import numpy as np
  
  # create files: 7 images each, (120,130) pixels
  for i in range(1,6): 
      data = np.random.randint(0,1<<16,(7,120,130) ) 
      with h5py.File(str(i)+".h5","w") as h:
          h["/data"]=data 
  
  
  files = ['1.h5', '2.h5', '3.h5', '4.h5', '5.h5']
  entry_key = 'data' # where the data is inside of the source files.
  sh = h5py.File(files[0], 'r')[entry_key].shape # get the first ones shape.
  
  layout = h5py.VirtualLayout(shape=(len(files) * sh[0], ) + sh[1:], dtype=np.float64)
  M_start = 0
  for i, filename in enumerate(files):
      M_end = M_start + sh[0]
      vsource = h5py.VirtualSource(filename, entry_key, shape=sh)
      layout[M_start:M_end:1, :, :] = vsource
      M_start = M_end
  
  with h5py.File("eiger_vds.h5", 'w', libver='latest') as f:
      f.create_virtual_dataset('data', layout, fillvalue=0)
  
subject: Update eiger_use_case.py