ChunkedSampleTableStore< T, ChunkSize > Class Template Reference

RAM-backed like RamSampleTableStore, but grows by allocating additional fixed-size chunks instead of reallocating and copying one single growing array. More...

#include <SampleTableStore.h>

Inheritance diagram for ChunkedSampleTableStore< T, ChunkSize >:

Public Member Functions
	~ChunkedSampleTableStore ()
void	append (T value) override
	Appends one entry - call in file order, once per table entry.
void	clear () override
	Resets to empty - call once per begin()/track.
T	get (size_t index) override
	Reads back entry 'index' - index must be < size().
virtual void	setNextEntryOffset (uint64_t fileOffset)
virtual void	setOnDiskEntrySize (size_t bytes)
size_t	size () override
	Number of entries appended so far.

Protected Attributes
Vector< T * >	chunks
size_t	count = 0

Detailed Description

template<typename T, size_t ChunkSize = 4096>
class audio_tools::ChunkedSampleTableStore< T, ChunkSize >

RAM-backed like RamSampleTableStore, but grows by allocating additional fixed-size chunks instead of reallocating and copying one single growing array.

This project's Vector<T>::push_back() (AudioBasic/Collections/Vector.h) allocates exactly the new size on every growth, with no spare capacity

• once the array is full, every single push_back() reallocates and copies everything already in it. For the hundreds of thousands of entries a feature-length movie's stsz/stco tables need, that's O(N) work per append, O(N^2) total, which is real, measured wall-clock time spent before a single frame can play.

This store sidesteps that by keeping a Vector of chunk pointers rather than a Vector of T directly: growing by one chunk means appending one more pointer (cheap - the pointer vector itself stays tiny, e.g. ~70 pointers for 288K entries at the default chunk size) and allocating a fresh fixed-size block, without ever touching or copying any previously-appended data. Same total memory as RamSampleTableStore, but O(1) amortized append instead of O(N) - the same idea behind this project's DynamicMultiBuffer (AudioTools/Sandbox/DynamicMultiBuffer.h), reimplemented directly here rather than wrapped: that class's public API is a sequential read()/write() cursor, not the indexed get() ChunkedSampleTableStore needs, and as Sandbox-status code it's not something to take a hard dependency on from a container decoder.

Constructor & Destructor Documentation

~ChunkedSampleTableStore()

template<typename T , size_t ChunkSize = 4096>

~ChunkedSampleTableStore ( )

inline

Member Function Documentation

append()

template<typename T , size_t ChunkSize = 4096>

void append ( T  value )

inlineoverridevirtual

Appends one entry - call in file order, once per table entry.

Implements SampleTableStore< T >.

clear()

template<typename T , size_t ChunkSize = 4096>

void clear ( )

inlineoverridevirtual

Resets to empty - call once per begin()/track.

Implements SampleTableStore< T >.

get()

template<typename T , size_t ChunkSize = 4096>

T get ( size_t  index )

inlineoverridevirtual

Reads back entry 'index' - index must be < size().

Implements SampleTableStore< T >.

setNextEntryOffset()

template<typename T >

virtual void setNextEntryOffset ( uint64_t  fileOffset )

inlinevirtualinherited

Only meaningful for SourceSeekSampleTableStore: the absolute byte offset (from the start of the original MP4 file) of the entry about to be appended next. Default no-op - other implementations ignore it, so callers can always call this unconditionally before append() without needing to know which implementation is active.

Reimplemented in SourceSeekSampleTableStore< T >.

setOnDiskEntrySize()

template<typename T >

virtual void setOnDiskEntrySize ( size_t  bytes )

inlinevirtualinherited

Only meaningful for SourceSeekSampleTableStore, and only for tables whose on-disk width isn't a fixed sizeof(T) - see its comment. Default no-op.

Reimplemented in SourceSeekSampleTableStore< T >.

size()

template<typename T , size_t ChunkSize = 4096>

size_t size ( )

inlineoverridevirtual

Number of entries appended so far.

Implements SampleTableStore< T >.

Member Data Documentation

chunks

template<typename T , size_t ChunkSize = 4096>

Vector<T*> chunks

protected

count

template<typename T , size_t ChunkSize = 4096>

size_t count = 0

protected

---

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

• src/AudioTools/AudioCodecs/SampleTableStore.h