MemoryStream Class Reference

A low overhead memory stream with O(1) append, low heap fragmentation and a linear memory view. More...

#include <MemoryStream.h>

Collaboration diagram for MemoryStream:

Classes
struct	Chunk
struct	Iterator

Public Types
using	StreamData = std::vector< uint8_t >
using	StreamChunk = std::pair< const void *, size_t >

Public Member Functions
	MemoryStream ()=default
	MemoryStream (MemoryStream &&)=default
void	Clear ()
void	AppendByte (char data)
void	AppendData (const void *data, const size_t length)
const void *	GetData () const
const size_t	GetSize () const noexcept
bool	IsEmpty () const noexcept
Iterator	begin () const
Iterator	end () const

Private Types
using	ChunksList = std::list< Chunk >

Private Attributes
ChunksList	mChunks
StreamData	mLinearData
size_t	mDataSize { 0 }

Static Private Attributes
static constexpr size_t	ChunkSize

Detailed Description

A low overhead memory stream with O(1) append, low heap fragmentation and a linear memory view.

wxMemoryBuffer always appends 1Kb to the end of the buffer, causing severe performance issues and significant heap fragmentation. There is no possibility to control the increment value.

std::vector doubles its memory size which can be problematic for large projects as well. Not as bad as wxMemoryBuffer though.

Definition at line 30 of file lib-utility/memorystream.h.

Member Typedef Documentation

ChunksList

using MemoryStream::ChunksList = std::list<Chunk>

private

Definition at line 51 of file lib-utility/memorystream.h.

StreamChunk

using MemoryStream::StreamChunk = std::pair<const void*, size_t>

Definition at line 34 of file lib-utility/memorystream.h.

StreamData

using MemoryStream::StreamData = std::vector<uint8_t>

Definition at line 33 of file lib-utility/memorystream.h.

Constructor & Destructor Documentation

MemoryStream() [1/2]

MemoryStream::MemoryStream ( )

default

MemoryStream() [2/2]

MemoryStream::MemoryStream ( MemoryStream &&  )

default

Member Function Documentation

AppendByte()

void MemoryStream::AppendByte

(

char

data

)

Definition at line 22 of file lib-utility/memorystream.cpp.

{
   AppendData(&data, 1);
}

References AppendData().

Referenced by ProjectSerializer::EndTag(), ProjectSerializer::ProjectSerializer(), ProjectSerializer::StartTag(), ProjectSerializer::Write(), ProjectSerializer::WriteAttr(), ProjectSerializer::WriteData(), XMLUtf8BufferWriter::WriteEscaped(), and ProjectSerializer::WriteName().

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AppendData()

void MemoryStream::AppendData	(	const void *	data,
		const size_t	length
	)

Definition at line 27 of file lib-utility/memorystream.cpp.

{
   if (mChunks.empty())
      mChunks.emplace_back();
 
   StreamChunk dataView = { data, length };
 
   while (mChunks.back().Append(dataView) > 0)
      mChunks.emplace_back();
 
   mDataSize += length;
}

References mChunks, and mDataSize.

Referenced by AppendByte(), ProjectSerializer::ProjectSerializer(), XMLUtf8BufferWriter::Write(), ProjectSerializer::Write(), ProjectSerializer::WriteAttr(), anonymous_namespace{ProjectSerializer.cpp}::WriteBigEndian(), ProjectSerializer::WriteData(), anonymous_namespace{ProjectSerializer.cpp}::WriteLittleEndian(), and ProjectSerializer::WriteName().

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begin()

MemoryStream::Iterator MemoryStream::begin

(

)

const

Definition at line 105 of file lib-utility/memorystream.cpp.

{
   return Iterator(this, true);
}

Referenced by GetData().

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Clear()

void MemoryStream::Clear

(

)

Definition at line 15 of file lib-utility/memorystream.cpp.

{
   mChunks = {};
   mLinearData = {};
   mDataSize = 0;
}

References mChunks, mDataSize, and mLinearData.

end()

MemoryStream::Iterator MemoryStream::end

(

)

const

Definition at line 110 of file lib-utility/memorystream.cpp.

{
   return Iterator(this, false);
}

Referenced by GetData().

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GetData()

const void * MemoryStream::GetData

(

)

const

Definition at line 40 of file lib-utility/memorystream.cpp.

{
   if (!mChunks.empty())
   {
      const size_t desiredSize = GetSize();
 
      mLinearData.reserve(desiredSize);
 
      for (const Chunk& chunk : mChunks)
      {
         auto begin = chunk.Data.begin();
         auto end = begin + chunk.BytesUsed;
 
         mLinearData.insert(mLinearData.end(), begin, end);
      }
 
      mChunks = {};
   }
 
   return mLinearData.data();
}

References begin(), end(), GetSize(), mChunks, and mLinearData.

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GetSize()

const size_t MemoryStream::GetSize ( ) const

noexcept

Definition at line 62 of file lib-utility/memorystream.cpp.

{
   return mDataSize;
}

References mDataSize.

Referenced by GetData(), ProjectSerializer::IsEmpty(), audacity::cloud::audiocom::sync::ProjectCloudExtension::OnUpdateSaved(), and ProjectFileIO::WriteDoc().

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IsEmpty()

bool MemoryStream::IsEmpty ( ) const

noexcept

Definition at line 100 of file lib-utility/memorystream.cpp.

{
   return mDataSize == 0;
}

References mDataSize.

Member Data Documentation

ChunkSize

constexpr size_t MemoryStream::ChunkSize

staticconstexprprivate

Initial value:

=
      1024 * 1024 - 
      2 * sizeof(void*) - 
      sizeof(size_t)

Definition at line 37 of file lib-utility/memorystream.h.

Referenced by MemoryStream::Chunk::Append().

mChunks

ChunksList MemoryStream::mChunks

mutableprivate

Definition at line 99 of file lib-utility/memorystream.h.

Referenced by AppendData(), Clear(), and GetData().

mDataSize

size_t MemoryStream::mDataSize { 0 }

private

Definition at line 102 of file lib-utility/memorystream.h.

Referenced by AppendData(), Clear(), GetSize(), and IsEmpty().

mLinearData

StreamData MemoryStream::mLinearData

mutableprivate

Definition at line 100 of file lib-utility/memorystream.h.

Referenced by Clear(), and GetData().

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

• lib-utility/memorystream.h
• lib-utility/memorystream.cpp