The data store file header. More...

#include <file_header.hpp>

Collaboration diagram for pstore::header:

Classes
struct	body
	Represents the portion of the header structure which is covered by the computed CRC value. More...

Public Member Functions
bool	is_valid () const noexcept

std::uint32_t	get_crc () const noexcept
	Computes the CRC value for the header.

uuid	id () const noexcept
	Returns the database ID. More...

void	set_id (uuid const &id) noexcept

std::array< std::uint16_t, 2 > const &	version () const noexcept
	Returns the file format version number (major, minor).

Public Attributes
body	a

std::uint32_t	crc = 0
	The fields of the header, up to and including this one, are not modified as the code interacts with the data store; they're effectively read-only. More...

std::uint32_t	unused1 = 0

std::atomic< typed_address< trailer > >	footer_pos
	The file offset of the current (most recent) file footer. More...

Static Public Attributes
static constexpr std::uint16_t	major_version = 1

static constexpr std::uint16_t	minor_version = 12

static std::array< std::uint8_t, 4 > const	file_signature1 {{'p', 'S', 't', 'r'}}

static std::uint32_t const	file_signature2 = 0x0507FFFF

Detailed Description

The data store file header.

Member Function Documentation

◆ id()

uuid pstore::header::id ( ) const

inlinenoexcept

Returns the database ID.

When created, each pstore file has a unique ID number. It is preserved by import/export and strip/merge. External references may use this ID to check that they are referring to the correct database.

Member Data Documentation

◆ crc

std::uint32_t pstore::header::crc = 0

The fields of the header, up to and including this one, are not modified as the code interacts with the data store; they're effectively read-only.

Unfortunately, we can't make them physically read-only – for example by marking the containing memory page as read-only – because the library does need to be able to modify the footer_pos field when a transaction is committed.

This crc is used to ensure that the fields from #signature1 to #sync_name are not modified.

◆ footer_pos

std::atomic<typed_address<trailer> > pstore::header::footer_pos

The file offset of the current (most recent) file footer.

This value is modified as the the very last step of commiting a transaction.

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

include/pstore/core/file_header.hpp
lib/core/file_header.cpp

Classes

Public Member Functions