juce_MemoryMappedAudioFormatReader.h

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/*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - 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 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-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
{
 
//==============================================================================
class JUCE_API  MemoryMappedAudioFormatReader  : public AudioFormatReader
{
protected:
    //==============================================================================
    MemoryMappedAudioFormatReader (const File& file, const AudioFormatReader& details,
                                   int64 dataChunkStart, int64 dataChunkLength, int bytesPerFrame);
 
public:
    const File& getFile() const noexcept                    { return file; }

    bool mapEntireFile();

    virtual bool mapSectionOfFile (Range<int64> samplesToMap);

    Range<int64> getMappedSection() const noexcept          { return mappedSection; }

    void touchSample (int64 sample) const noexcept;

    virtual void getSample (int64 sampleIndex, float* result) const noexcept = 0;

    size_t getNumBytesUsed() const                          { return map != nullptr ? map->getSize() : 0; }
 
protected:
    File file;
    Range<int64> mappedSection;
    std::unique_ptr<MemoryMappedFile> map;
    int64 dataChunkStart, dataLength;
    int bytesPerFrame;

    inline int64 sampleToFilePos (int64 sample) const noexcept       { return dataChunkStart + sample * bytesPerFrame; }

    inline int64 filePosToSample (int64 filePos) const noexcept      { return (filePos - dataChunkStart) / bytesPerFrame; }

    inline const void* sampleToPointer (int64 sample) const noexcept { return addBytesToPointer (map->getData(), sampleToFilePos (sample) - map->getRange().getStart()); }

    template <typename SampleType, typename Endianness>
    Range<float> scanMinAndMaxInterleaved (int channel, int64 startSampleInFile, int64 numSamples) const noexcept
    {
        using SourceType = AudioData::Pointer <SampleType, Endianness, AudioData::Interleaved, AudioData::Const>;
 
        return SourceType (addBytesToPointer (sampleToPointer (startSampleInFile), ((int) bitsPerSample / 8) * channel), (int) numChannels)
                .findMinAndMax ((size_t) numSamples);
    }
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MemoryMappedAudioFormatReader)
};
 
} // namespace juce