JUCE: MemoryMappedAudioFormatReader Class Reference

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Public Member Functions | Protected Member Functions | Protected Attributes | List of all members
MemoryMappedAudioFormatReader Class Referenceabstract
juce_audio_formats » format

A specialised type of AudioFormatReader that uses a MemoryMappedFile to read directly from an audio file. More...

`#include <juce_MemoryMappedAudioFormatReader.h>`

Inheritance diagram for MemoryMappedAudioFormatReader:

## Public Member Functions
const File & | getFile () const noexcept
| Returns the file that is being mapped.
bool | mapEntireFile ()
| Attempts to map the entire file into memory.
virtual bool | mapSectionOfFile (Range< int64 > samplesToMap)
| Attempts to map a section of the file into memory.
Range< int64 > | getMappedSection () const noexcept
| Returns the sample range that's currently memory-mapped and available for reading.
void | touchSample (int64 sample) const noexcept
| Touches the memory for the given sample, to force it to be loaded into active memory.
virtual void | getSample (int64 sampleIndex, float *result) const noexcept=0
| Returns the samples for all channels at a given sample position.
size_t | getNumBytesUsed () const
| Returns the number of bytes currently being mapped.
Public Member Functions inherited from AudioFormatReader
virtual | ~AudioFormatReader ()
| Destructor.
const String & | getFormatName () const noexcept
| Returns a description of what type of format this is.
bool | read (float *const *destChannels, int numDestChannels, int64 startSampleInSource, int numSamplesToRead)
| Reads samples from the stream.
bool | read (int *const *destChannels, int numDestChannels, int64 startSampleInSource, int numSamplesToRead, bool fillLeftoverChannelsWithCopies)
| Reads samples from the stream.
bool | read (AudioBuffer< float > *buffer, int startSampleInDestBuffer, int numSamples, int64 readerStartSample, bool useReaderLeftChan, bool useReaderRightChan)
| Fills a section of an AudioBuffer from this reader.
virtual void | readMaxLevels (int64 startSample, int64 numSamples, Range< float > *results, int numChannelsToRead)
| Finds the highest and lowest sample levels from a section of the audio stream.
virtual void | readMaxLevels (int64 startSample, int64 numSamples, float &lowestLeft, float &highestLeft, float &lowestRight, float &highestRight)
| Finds the highest and lowest sample levels from a section of the audio stream.
int64 | searchForLevel (int64 startSample, int64 numSamplesToSearch, double magnitudeRangeMinimum, double magnitudeRangeMaximum, int minimumConsecutiveSamples)
| Scans the source looking for a sample whose magnitude is in a specified range.
virtual AudioChannelSet | getChannelLayout ()
| Get the channel layout of the audio stream.
virtual bool | readSamples (int *const *destChannels, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int numSamples)=0
| Subclasses must implement this method to perform the low-level read operation.

## Protected Member Functions
| MemoryMappedAudioFormatReader (const File &file, const AudioFormatReader &details, int64 dataChunkStart, int64 dataChunkLength, int bytesPerFrame)
| Creates an MemoryMappedAudioFormatReader object.
int64 | sampleToFilePos (int64 sample) const noexcept
| Converts a sample index to a byte position in the file.
int64 | filePosToSample (int64 filePos) const noexcept
| Converts a byte position in the file to a sample index.
const void * | sampleToPointer (int64 sample) const noexcept
| Converts a sample index to a pointer to the mapped file memory.
template<typename SampleType , typename Endianness >
Range< float > | scanMinAndMaxInterleaved (int channel, int64 startSampleInFile, int64 numSamples) const noexcept
| Used by AudioFormatReader subclasses to scan for min/max ranges in interleaved data.
Protected Member Functions inherited from AudioFormatReader
| AudioFormatReader (InputStream *sourceStream, const String &formatName)
| Creates an AudioFormatReader object.

## Protected Attributes
File | file
Range< int64 > | mappedSection
std::unique_ptr< MemoryMappedFile > | map
int64 | dataChunkStart
int64 | dataLength
int | bytesPerFrame

## Additional Inherited Members
Public Attributes inherited from AudioFormatReader
double | sampleRate = 0
| The sample-rate of the stream.
unsigned int | bitsPerSample = 0
| The number of bits per sample, e.g.
int64 | lengthInSamples = 0
| The total number of samples in the audio stream.
unsigned int | numChannels = 0
| The total number of channels in the audio stream.
bool | usesFloatingPointData = false
| Indicates whether the data is floating-point or fixed.
StringPairArray | metadataValues
| A set of metadata values that the reader has pulled out of the stream.
InputStream * | input
| The input stream, for use by subclasses.
Static Protected Member Functions inherited from AudioFormatReader
static void | clearSamplesBeyondAvailableLength (int *const *destChannels, int numDestChannels, int startOffsetInDestBuffer, int64 startSampleInFile, int &numSamples, int64 fileLengthInSamples)
| Used by AudioFormatReader subclasses to clear any parts of the data blocks that lie beyond the end of their available length.

## Detailed Description

A specialised type of AudioFormatReader that uses a MemoryMappedFile to read directly from an audio file.

This allows for incredibly fast random-access to sample data in the mapped region of the file, but not all audio formats support it - see AudioFormat::createMemoryMappedReader().

Note that before reading samples from a MemoryMappedAudioFormatReader, you must first call mapEntireFile() or mapSectionOfFile() to ensure that the region you want to read has been mapped.

See also
  AudioFormat::createMemoryMappedReader, AudioFormatReader

## Constructor & Destructor Documentation

## ◆ MemoryMappedAudioFormatReader()

MemoryMappedAudioFormatReader::MemoryMappedAudioFormatReader | ( | const File & | file,
|  | const AudioFormatReader & | details,
|  | int64 | dataChunkStart,
|  | int64 | dataChunkLength,
|  | int | bytesPerFrame )
| protected

Creates an MemoryMappedAudioFormatReader object.

Note that before attempting to read any data, you must call mapEntireFile() or mapSectionOfFile() to ensure that the region you want to read has been mapped.

## Member Function Documentation

## ◆ getFile()

const File & MemoryMappedAudioFormatReader::getFile | ( |  | ) | const
| noexcept

Returns the file that is being mapped.

## ◆ mapEntireFile()

bool MemoryMappedAudioFormatReader::mapEntireFile | ( |  | ) |

Attempts to map the entire file into memory.

## ◆ mapSectionOfFile()

virtual bool MemoryMappedAudioFormatReader::mapSectionOfFile | ( | Range< int64 > | samplesToMap | ) |
| virtual

Attempts to map a section of the file into memory.

## ◆ getMappedSection()

Range< int64 > MemoryMappedAudioFormatReader::getMappedSection | ( |  | ) | const
| noexcept

Returns the sample range that's currently memory-mapped and available for reading.

## ◆ touchSample()

void MemoryMappedAudioFormatReader::touchSample | ( | int64 | sample | ) | const
| noexcept

Touches the memory for the given sample, to force it to be loaded into active memory.

## ◆ getSample()

virtual void MemoryMappedAudioFormatReader::getSample | ( | int64 | sampleIndex,
|  | float * | result ) const
| pure virtualnoexcept

Returns the samples for all channels at a given sample position.

The result array must be large enough to hold a value for each channel that this reader contains.

## ◆ getNumBytesUsed()

size_t MemoryMappedAudioFormatReader::getNumBytesUsed | ( |  | ) | const

Returns the number of bytes currently being mapped.

## ◆ sampleToFilePos()

int64 MemoryMappedAudioFormatReader::sampleToFilePos | ( | int64 | sample | ) | const
| protectednoexcept

Converts a sample index to a byte position in the file.

## ◆ filePosToSample()

int64 MemoryMappedAudioFormatReader::filePosToSample | ( | int64 | filePos | ) | const
| protectednoexcept

Converts a byte position in the file to a sample index.

## ◆ sampleToPointer()

const void * MemoryMappedAudioFormatReader::sampleToPointer | ( | int64 | sample | ) | const
| protectednoexcept

Converts a sample index to a pointer to the mapped file memory.

References addBytesToPointer().

## ◆ scanMinAndMaxInterleaved()

template<typename SampleType , typename Endianness >

Range< float > MemoryMappedAudioFormatReader::scanMinAndMaxInterleaved | ( | int | channel,
|  | int64 | startSampleInFile,
|  | int64 | numSamples ) const
| protectednoexcept

Used by AudioFormatReader subclasses to scan for min/max ranges in interleaved data.

References addBytesToPointer(), and Range< ValueType >::findMinAndMax().

## Member Data Documentation

## ◆ file

File MemoryMappedAudioFormatReader::file
| protected

## ◆ mappedSection

Range<int64> MemoryMappedAudioFormatReader::mappedSection
| protected

## ◆ map

std::unique_ptr<MemoryMappedFile> MemoryMappedAudioFormatReader::map
| protected

## ◆ dataChunkStart

int64 MemoryMappedAudioFormatReader::dataChunkStart
| protected

## ◆ dataLength

int64 MemoryMappedAudioFormatReader::dataLength
| protected

## ◆ bytesPerFrame

int MemoryMappedAudioFormatReader::bytesPerFrame
| protected

The documentation for this class was generated from the following file:

- juce_MemoryMappedAudioFormatReader.h