/*
 * Copyright (c) 2008-2018 the MRtrix3 contributors.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, you can obtain one at http://mozilla.org/MPL/2.0/
 *
 * MRtrix3 is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * For more details, see http://www.mrtrix.org/
 */


#include "header.h"
#include "image_io/sparse.h"



namespace MR
{
  namespace ImageIO
  {



    void SparseLegacy::load (const Header& header, size_t)
    {

      Default::load (header,0);

      std::fstream stream (file.name.c_str(), std::ios_base::in | std::ios_base::binary);
      stream.seekg (0, std::ios::end);
      const uint64_t file_size = stream.tellg();
      stream.close();
      const uint64_t current_sparse_data_size = file_size - file.start;

      if (current_sparse_data_size) {

        mmap.reset (new File::MMap (file, is_image_readwrite(), true, current_sparse_data_size));
        data_end = current_sparse_data_size;

      } else if (is_image_readwrite()) {

        //CONF option: SparseDataInitialSize
        //CONF default: 16777216
        //CONF Initial buffer size for data in MRtrix sparse image format file (in bytes).

        // Default = initialise 16MB, this is enough to store whole-brain fixel data at 2.5mm resolution
        const uint64_t init_sparse_data_size = File::Config::get_int ("SparseDataInitialSize", 16777216);
        const size_t new_file_size = file.start + init_sparse_data_size;
        DEBUG ("Initialising output sparse data file " + file.name + ": new file size " + str(new_file_size) 
            + " (" + str(init_sparse_data_size) + " of which is initial sparse data buffer)");
        File::resize (file.name, new_file_size);
        mmap.reset (new File::MMap (file, is_image_readwrite(), false, init_sparse_data_size));

        // Writes a single uint32_t(0) to the start of the sparse data region
        // Any voxel that has its value initialised to 0 will point here, and therefore dereferencing of any
        //   such voxel will yield a Fixel::Value with zero elements
        memset (off2mem (0), 0x00, sizeof (uint32_t));

        data_end = sizeof(uint32_t);

      }

      // If this is the formation of a new image, want to explicitly zero all of the
      //   raw image data - otherwise any random data could be misinterpreted as a large
      //   pointer offset from the start of the sparse image data
      if (is_image_new()) {
        for (auto& i : mmaps) 
          memset (i->address(), 0x00, i->size());
      }

    }



    void SparseLegacy::unload (const Header& header)
    {

      Default::unload (header);

      const uint64_t truncate_file_size = (data_end == size()) ? 0 : file.start + data_end;
      // Null the excess data before closing the memory map to prevent std::ofstream from giving an error
      //   (writing uninitialised values)
      memset (off2mem(data_end), 0x00, size() - data_end);
      mmap.reset();

      if (truncate_file_size) {
        DEBUG ("truncating sparse image data file " + file.name + " to " + str(truncate_file_size) + " bytes");
        File::resize (file.name, truncate_file_size);
      }

    }









    uint64_t SparseLegacy::set_numel (const uint64_t old_offset, const uint32_t numel)
    {
      assert (is_image_readwrite());

      // Before allocating new memory, verify that the current offset does not point to
      //   a voxel that has more elements than is required
      if (old_offset) {

        assert (old_offset < data_end);

        const uint32_t existing_numel = get_numel (old_offset);
        if (existing_numel >= numel) {

          // Set the new number of elements, clear the unwanted data, and return
          memcpy (off2mem(old_offset), &numel, sizeof(uint32_t));
          memset (off2mem(old_offset) + sizeof(uint32_t) + (numel * class_size), 0x00, ((existing_numel - numel) * class_size));
          // If this voxel is being cleared (i.e. no elements), rather than returning a pointer to a voxel with
          //   zero elements, instead return a pointer to the start of the sparse data, where there's a single
          //   uint32_t(0) which can be used for any and all voxels with zero elements
          return numel ? old_offset : 0;

        } else {

          // Existing memory allocation for this voxel is not sufficient; erase it
          // Note that the handler makes no attempt at re-using this memory later; new data is just concatenated
          //   to the end of the buffer
          memset (off2mem(old_offset), 0x00, sizeof(uint32_t) + (existing_numel * class_size));

        }
      }

      // Don't allocate memory for voxels with no sparse data; just point them all to the start of the
      //   sparse data where theres a single uint32_t(0)
      if (!numel)
        return 0;

      const int64_t requested_size = sizeof (uint32_t) + (numel * class_size);
      if (data_end + requested_size > size()) {

        // size() should never be empty if data is being written...
        assert (size());
        uint64_t new_sparse_data_size = 2 * size();

        // Cover rare case where a huge memory request occurs early
        while (new_sparse_data_size < data_end + requested_size)
          new_sparse_data_size *= 2;

        // Memory error arises due to the uninitialised data between the end of the sparse data and the end
        //   of the file at its current size being written using std::ofstream
        // Therefore, explicitly null all data that hasn't already been written
        //   (this does not prohibit the use of this memory for subsequent sparse data though)
        memset (off2mem(data_end), 0x00, size() - data_end);

        mmap.reset();

        const size_t new_file_size = file.start + new_sparse_data_size;
        DEBUG ("Resizing sparse data file " + file.name + ": new file size " + str(new_file_size) + " (" + str(new_sparse_data_size) + " of which is for sparse data)");
        File::resize (file.name, new_file_size);
        mmap.reset (new File::MMap (file, Base::writable, true, new_sparse_data_size));

      }

      // Write the uint32_t indicating the number of elements in this voxel
      memcpy (off2mem(data_end), &numel, sizeof(uint32_t));

      // The return value is the offset from the beginning of the sparse data
      const uint64_t ret = data_end;
      data_end += requested_size;

      return ret;
    }







  }
}


