2.10.0
Freundlich's C++ toolkit
Classes | Functions
fcppt.container.buffer

Description

A special buffer class for uninitialized memory.

Ordinary arrays in C++ are not default-initialized, which is mostly for performance reasons. This helps in situations where you have to call functions that write into a buffer handed to them, e.g. when reading from a file. If you need a dynamically sized array instead, you could use a std::vector. However, std::vector default-initializes its values.

fcppt::container::buffer::object instead manages a partially uninitialized block of memory: It contains

Consider the following example in which the user wants to read 1024 integers from a file stream, using binary I/O. We have to hand a raw buffer to the ifstream::read function that counts sizeof(int) * 1024 bytes. After reading has been done, we check if it succeeded and if it has, we increase the read area size appropriately.

typedef
int
>
buffer_type;
buffer_type raw_chars{
1024
};
"test_file",
std::ios_base::binary
};
if(
file.read(
// Hand the beginning of the write area to the read function.
char *
>(
raw_chars.write_data()
),
std::streamsize
>(
raw_chars.write_size()
*
sizeof(int)
)
)
)
)
// If reading succeeded, we have read gcount bytes and therefore
// gcount / sizeof(int) integers.
raw_chars.written(
>(
file.gcount()
)
)
/
sizeof(int)
);
<< "Integers read: ";
for(
int const value
:
raw_chars
)
<< value << ", ";
<< '\n';

A buffer can be converted into an fcppt::container::raw_vector::object using fcppt::container::buffer::to_raw_vector. A raw vector acts more like a standard container and is similar to std::vector.

Classes

class  fcppt::container::buffer::object< T, A >
 A contiguous container for uninitialized data that contains a write and a read area. More...
 

Functions

template<typename T , typename A , typename Function >
fcppt::container::buffer::object< T, A > fcppt::container::buffer::append_from (fcppt::container::buffer::object< T, A > &&_buffer, typename fcppt::container::buffer::object< T, A >::size_type const _size, Function const &_function)
 Appends to a buffer using a function. More...
 
template<typename T , typename A , typename Function >
fcppt::optional::object< fcppt::container::buffer::object< T, A >> fcppt::container::buffer::append_from_opt (fcppt::container::buffer::object< T, A > &&_buffer, typename fcppt::container::buffer::object< T, A >::size_type const _size, Function const &_function)
 Appends to a buffer using a function which may fail. More...
 
template<typename Buffer , typename Function >
Buffer fcppt::container::buffer::read_from (typename Buffer::size_type const _size, Function const &_function)
 Reads into a buffer using a function. More...
 
template<typename Buffer , typename Function >
fcppt::optional::object< Buffer > fcppt::container::buffer::read_from_opt (typename Buffer::size_type const _size, Function const &_function)
 Reads into a buffer using a function which may fail. More...
 
template<typename T , typename A >
fcppt::container::raw_vector::object< T, A > fcppt::container::buffer::to_raw_vector (fcppt::container::buffer::object< T, A > &&_buffer) noexcept
 Convert a buffer into a raw_vector. More...
 

Function Documentation

◆ append_from()

template<typename T , typename A , typename Function >
fcppt::container::buffer::object< T, A> fcppt::container::buffer::append_from ( fcppt::container::buffer::object< T, A > &&  _buffer,
typename fcppt::container::buffer::object< T, A >::size_type const  _size,
Function const &  _function 
)

Appends to a buffer using a function.

Allocates a write area for _buffer of size _size and then calls _function(_buffer.write_data(),_size). The result of the function is used to expand _buffer's read area size.

Template Parameters
FunctionA function callable as size_type (pointer, size_type).

◆ append_from_opt()

template<typename T , typename A , typename Function >
fcppt::optional::object< fcppt::container::buffer::object< T, A >> fcppt::container::buffer::append_from_opt ( fcppt::container::buffer::object< T, A > &&  _buffer,
typename fcppt::container::buffer::object< T, A >::size_type const  _size,
Function const &  _function 
)

Appends to a buffer using a function which may fail.

Allocates a buffer buf of size _size and then calls _function(buf.write_data(),_size). If the result of the function is nothing, then nothing is returned. Otherwise, The result of the function is used to set buf's read area size.

Template Parameters
FunctionA function callable as fcppt::optional::object<size_type> (pointer, size_type).

◆ read_from()

template<typename Buffer , typename Function >
Buffer fcppt::container::buffer::read_from ( typename Buffer::size_type const  _size,
Function const &  _function 
)
inline

Reads into a buffer using a function.

Allocates a buffer buf of size _size and then calls _function(buf.write_data(),_size). The result of the function is used to set buf's read area size.

Template Parameters
BufferAn fcppt::container::buffer::object.
FunctionA function callable as size_type (pointer, size_type).

◆ read_from_opt()

template<typename Buffer , typename Function >
fcppt::optional::object< Buffer> fcppt::container::buffer::read_from_opt ( typename Buffer::size_type const  _size,
Function const &  _function 
)

Reads into a buffer using a function which may fail.

Allocates a buffer buf of size _size and then calls _function(buf.write_data(),_size). If the result of the function is nothing, then nothing is returned. Otherwise, The result of the function is used to set buf's read area size.

Template Parameters
BufferAn fcppt::container::buffer::object.
FunctionA function callable as fcppt::optional::object<size_type> (pointer, size_type).

◆ to_raw_vector()

template<typename T , typename A >
fcppt::container::raw_vector::object< T, A> fcppt::container::buffer::to_raw_vector ( fcppt::container::buffer::object< T, A > &&  _buffer)
noexcept

Convert a buffer into a raw_vector.