file_header.hpp File Reference

The file header and footer member functions. More...

#include <atomic>
#include "pstore/core/address.hpp"
#include "pstore/core/uuid.hpp"
#include "pstore/serialize/types.hpp"

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Classes
struct	pstore::serialize::serializer< extent< T > >
	A specialization which teaches the serialization framework how to read and write instances of extent. More...
class	pstore::header
	The data store file header. More...
struct	pstore::header::body
	Represents the portion of the header structure which is covered by the computed CRC value. More...
struct	pstore::lock_block
	The lock-block is a small struct placed immediately after the file header which is used by the transaction lock. More...
struct	pstore::trailer
	The transaction footer structure. More...
struct	pstore::trailer::body
	Represents the portion of the trailer structure which is covered by the computed CRC value. More...

Macros
#define	PSTORE_INDICES
#define	X(a)   a,

Functions
	pstore::PSTORE_STATIC_ASSERT (offsetof(header::body, signature1)==0)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header::body, signature2)==4)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header::body, version)==8)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header::body, header_size)==12)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header::body, id)==16)
	pstore::PSTORE_STATIC_ASSERT (sizeof(header::body)==32)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header, a)==0)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header, crc)==32)
	pstore::PSTORE_STATIC_ASSERT (offsetof(header, footer_pos)==40)
	pstore::PSTORE_STATIC_ASSERT (alignof(header)==8)
	pstore::PSTORE_STATIC_ASSERT (sizeof(header)==48)
	pstore::PSTORE_STATIC_ASSERT (offsetof(lock_block, vacuum_lock)==0)
	pstore::PSTORE_STATIC_ASSERT (offsetof(lock_block, transaction_lock)==8)
	pstore::PSTORE_STATIC_ASSERT (alignof(lock_block)==8)
	pstore::PSTORE_STATIC_ASSERT (sizeof(lock_block)==16)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, signature1)==0)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, generation)==8)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, unused1)==12)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, size)==16)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, time)==24)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, prev_generation)==32)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, index_records)==40)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, unused2)==88)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer::body, unused3)==92)
	pstore::PSTORE_STATIC_ASSERT (alignof(trailer::body)==8)
	pstore::PSTORE_STATIC_ASSERT (sizeof(trailer::body)==96)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer, a)==0)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer, crc)==96)
	pstore::PSTORE_STATIC_ASSERT (offsetof(trailer, signature2)==104)
	pstore::PSTORE_STATIC_ASSERT (alignof(trailer)==8)
	pstore::PSTORE_STATIC_ASSERT (sizeof(trailer)==112)

Variables
constexpr auto	pstore::leader_size = sizeof (header) + sizeof (lock_block)

Detailed Description

The file header and footer member functions.

The capacity of an individual segment is defined by offset_number_bits (i.e. the largest offset that we can encode before we need to start again with a new segment). This is 4Mb, which is considerably smaller than I'd like because of the fact that the Windows virtual memory system resizes the underlying file to match to ....

The initial state of the file is shown below. The file simply contains its header structure an an inital (empty) transaction (t₀).

The header and footer types are pstore::header and pstore::trailer repectively. The state of the file after the first transaction (t₁) has been committed:

A thread connecting to the data store uses the pstore::header::footer_pos value to find the most recent completed transaction; this is an instance of pstore::trailer and marks the end of the data associated with that transaction.

Macro Definition Documentation

PSTORE_INDICES

#define PSTORE_INDICES

Value:

X (compilation)                                                                                \
    X (debug_line_header)                                                                          \
    X (fragment)                                                                                   \
    X (name)                                                                                       \
    X (path)                                                                                       \
    X (write)