file.hpp File Reference

Cross platform file management functions and classes. More...

#include <cstdint>
#include <ctime>
#include <functional>
#include "pstore/adt/error_or.hpp"
#include "pstore/support/array_elements.hpp"
#include "pstore/support/error.hpp"
#include "file_posix.hpp"

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Classes
class	pstore::file::system_error
class	pstore::file::file_base
	An abstract file class. Provides the interface for file access. More...
class	pstore::file::range_lock
	A synchronization object that can be used to protect data in a file from being simultaneously accessed by multiple processes. More...
class	pstore::file::in_memory
	Implements an in-memory file which provides a file-like API to a chunk of pre-allocated memory. More...
class	pstore::file::file_handle
	Implements a portable file access API. More...
struct	pstore::file::file_handle::unique
	unique is an empty class type used to disambiguate the overloads of creating a file. More...
struct	pstore::file::file_handle::temporary
	temporary is an empty class type used to disambiguate the overloads of creating a file. More...
class	pstore::file::deleter_base
	A class which, on destruction, will delete a file whose name is passed to the constructor. More...

Namespaces
	pstore::file
	The 'file' namespace contains all of the database file management functions and classes .

Functions
template<typename RandomGenerator >
std::string	pstore::file::details::name_from_template (std::string const &tmpl, RandomGenerator rng)
	The name_from_template() function takes the given file name template and returns a string in which a portion of the template is overwritten to create a file name. More...
template<typename WidthType , typename PointeeType , typename Function >
std::size_t	pstore::file::details::split (PointeeType *buffer, std::size_t size, Function const &function)
	Unfortunately, the Win32 ReadFile() and WriteFile() functions accept size parameters whose type is DWORD whereas our API uses std::size_t. More...
template<typename WidthType , typename Function >
std::size_t	pstore::file::details::split (void *const buffer, std::size_t const size, Function const &function)
template<typename WidthType , typename Function >
std::size_t	pstore::file::details::split (void const *const buffer, std::size_t const size, Function const &function)
std::ostream &	pstore::file::operator<< (std::ostream &os, file_handle const &fh)
bool	pstore::file::exists (std::string const &path)
	Returns true if the file system contains an object at the location given by path. More...
void	pstore::file::unlink (std::string const &path, bool allow_noent=false)
	Deletes the file system object at the location given by path. More...

Detailed Description

Cross platform file management functions and classes.

Function Documentation

name_from_template()

template<typename RandomGenerator >

std::string pstore::file::details::name_from_template	(	std::string const &	tmpl,
		RandomGenerator	rng
	)

The name_from_template() function takes the given file name template and returns a string in which a portion of the template is overwritten to create a file name.

The template may be any file name with some number of `Xs' appended to it, for example /tmp/temp.XXXXXX. The trailing `Xs' are replaced with a unique alphanumeric combination. The number of unique file names mktemp() can return depends on the number of `Xs' provided.

Template Parameters

RandomGenerator

A Callable object with the signature equivalent to std::function<unsigned(unsigned)>. The function's result must be in the range 0 to the value given by the single parameter.

Parameters

tmpl	A template string which forms the basis for the result string. Any trailing X characters are replaced by characters derived from the result of the rng function.
rng	A random number generator function which should return a value in the range [0,max).

Returns

A string derived from the tmpl argument but with trailing 'X's replaced by random characters from an internal alphabet.

Note

This function is used on platforms that don't have a native implementation of the mkstemp() function.

split()

template<typename WidthType , typename PointeeType , typename Function >

std::size_t pstore::file::details::split	(	PointeeType *	buffer,
		std::size_t	size,
		Function const &	function
	)

Unfortunately, the Win32 ReadFile() and WriteFile() functions accept size parameters whose type is DWORD whereas our API uses std::size_t.

std::size_t is obviously 64-bits on a 64-bit host, but DWORD is always 32-bit. This function splits up the request into chunks which are no larger than the WidthType max value.

Template Parameters

WidthType	The integer type whose largest value determines the largest 'chunk' into which the size parameter can be split.
PointeeType	The type of the elements of the buffer array.
Function	A callable whose signature whose be equivalent to std::function<std::size_t(PointeeType*,WidthType)>. It is called for each chunk into which size is divided. The return value should be the number of bytes processed; the first argument is the first value to process; the second element is the number of contiguous elements to be processed.

Parameters

buffer	The base address of the buffer to be processed by the provided callback.
size	The total number of bytes to be processed.
function	This function is called repeatedly to operate on each portion of the buffer.

Returns

The sum of the values returned by function.