vrs::FileFormat::FileHeader Struct Reference

Every file starts with this header, which may grow but not shrink! More...

#include <FileFormat.h>

Public Member Functions
void	init ()
	Initialize the structure's fixed values with default values for a regular VRS file.
void	init (uint32_t magic1, uint32_t magic2, uint32_t magic3, uint32_t formatVersion)
	Initialize the structure's fixed values, with configuration options.
bool	looksLikeAVRSFile () const
bool	looksLikeOurFiles (uint32_t magic1, uint32_t magic2, uint32_t magic3) const
bool	isFormatSupported () const
void	enableFrontIndexRecordSupport ()
int64_t	getEndOfUserRecordsOffset (int64_t fileSize) const

Public Attributes
LittleEndian< uint32_t >	magicHeader1
	magic value #1
LittleEndian< uint32_t >	magicHeader2
	magic value #2
LittleEndian< uint64_t >	creationId
	A timestamp, hopefully unique, to match files (future).
LittleEndian< uint32_t >	fileHeaderSize
	This header size, in bytes.
LittleEndian< uint32_t >	recordHeaderSize
	Record headers' size, in bytes (same for all).
LittleEndian< int64_t >	indexRecordOffset
	Index record offset in the whole file.
LittleEndian< int64_t >	descriptionRecordOffset
	Description record offset in the whole file.
LittleEndian< int64_t >	firstUserRecordOffset
LittleEndian< uint64_t >	future2
	For future use.
LittleEndian< uint64_t >	future3
	For future use.
LittleEndian< uint64_t >	future4
	For future use.
LittleEndian< uint32_t >	magicHeader3
	magic value #3
LittleEndian< uint32_t >	fileFormatVersion
	file format version.

Detailed Description

Every file starts with this header, which may grow but not shrink!

Member Function Documentation

enableFrontIndexRecordSupport()

void vrs::FileFormat::FileHeader::enableFrontIndexRecordSupport

(

)

By default, the index record is written at the end of the file (original behavior), and the first user record is just after the description record. You can reserve space for the index record between the description record and the first user record, so that it is possible the read the file forward only, for streaming. But if you do that, the VRS file can only be read by a newer version of VRS, so you must bump the file version number by calling this method.

getEndOfUserRecordsOffset()

int64_t vrs::FileFormat::FileHeader::getEndOfUserRecordsOffset

(

int64_t

fileSize

)

const

Get a best guess as to where user records end. If the file has no index, this value may be inaccurate, but a sensible estimation will be returned (probably the end of the file). Only call this methods for file headers read from an actual VRS file.

Parameters

fileSize

the size of the VRS file, value returned if no better estimate can be made, or when the file's index is at the start of the file (in which case it is the right answer).

Returns

The index of the first byte after the last user record.

isFormatSupported()

bool vrs::FileFormat::FileHeader::isFormatSupported

(

)

const

Check if the file format is supported. Might fail if the file was written by a recent version of VRS that changed the file format.

looksLikeAVRSFile()

bool vrs::FileFormat::FileHeader::looksLikeAVRSFile

(

)

const

Check the sanity of the file header.

Returns

True if the header looks valid for a VRS file, false otherwise.

looksLikeOurFiles()

bool vrs::FileFormat::FileHeader::looksLikeOurFiles	(	uint32_t	magic1,
		uint32_t	magic2,
		uint32_t	magic3
	)		const

Check the sanity of the file header.

Returns

True if the header looks valid a header we might have created, false otherwise.

Member Data Documentation

firstUserRecordOffset

LittleEndian<int64_t> vrs::FileFormat::FileHeader::firstUserRecordOffset

Offset of the first user record in the file. If 0, the first record is just after the description record (original behavior)

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

• vrs/FileFormat.h
• vrs/FileFormat.cpp