text: /*
    ==============================================================================
  
     This file is part of the JUCE library.
     Copyright (c) 2020 - Raw Material Software Limited
  
     JUCE is an open source library subject to commercial or open-source
     licensing.
  
     By using JUCE, you agree to the terms of both the JUCE 6 End-User License
     Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).
  
     End User License Agreement: www.juce.com/juce-6-licence
     Privacy Policy: www.juce.com/juce-privacy-policy
  
     Or: You may also use this code under the terms of the GPL v3 (see
     www.gnu.org/licenses).
  
     JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
     EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
     DISCLAIMED.
  
    ==============================================================================
  */
  
  namespace juce
  {
  
  /**
      Helper functions for managing buffered readers.
  */
  struct Reservoir
  {
      /** Attempts to read the requested range from some kind of input stream,
          with intermediate buffering in a 'reservoir'.
  
          While there are still samples in the requested range left to read, this
          function will check whether the next part of the requested range is
          already loaded into the reservoir. If the range is available, then
          doBufferedRead will call readFromReservoir with the range that should
          be copied to the output buffer. If the range is not available,
          doBufferedRead will call fillReservoir to request that a new region is
          loaded into the reservoir. It will repeat these steps until either the
          entire requested region has been read, or the stream ends.
  
          This will return the range that could not be read successfully, if any.
          An empty range implies that the entire read was successful.
  
          Note that all ranges, including those provided as arguments to the
          callbacks, are relative to the original unbuffered input. That is, if
          getBufferedRange returns the range [200, 300), then readFromReservoir
          might be passed the range [250, 300) in order to copy the final 50
          samples from the reservoir.
  
          @param rangeToRead       the absolute position of the range that should
                                   be read
          @param getBufferedRange  a function void -> Range<Index> that returns
                                   the region currently held in the reservoir
          @param readFromReservoir a function Range<Index> -> void that can be
                                   used to copy samples from the region in the
                                   reservoir specified in the input range
          @param fillReservoir     a function Index -> void that is given a
                                   requested read location, and that should
                                   attempt to fill the reservoir starting at this
                                   location. After this function,
                                   getBufferedRange should return the new region
                                   contained in the managed buffer
      */
      template <typename Index, typename GetBufferedRange, typename ReadFromReservoir, typename FillReservoir>
      static Range<Index> doBufferedRead (Range<Index> rangeToRead,
                                          GetBufferedRange&& getBufferedRange,
                                          ReadFromReservoir&& readFromReservoir,
                                          FillReservoir&& fillReservoir)
      {
          while (! rangeToRead.isEmpty())
          {
              const auto bufferedRange = getBufferedRange();
  
              if (bufferedRange.contains (rangeToRead.getStart()))
              {
                  const auto rangeToReadInBuffer = rangeToRead.getIntersectionWith (getBufferedRange());
                  readFromReservoir (rangeToReadInBuffer);
                  rangeToRead.setStart (rangeToReadInBuffer.getEnd());
              }
              else
              {
                  fillReservoir (rangeToRead.getStart());
  
                  const auto newRange = getBufferedRange();
  
                  if (newRange.isEmpty() || ! newRange.contains (rangeToRead.getStart()))
                      break;
              }
          }
  
          return rangeToRead;
      }
  };
  
  } // namespace juce
  