Base class for block headers. More...

#include <BlockHeader.h>

Inheritance diagram for Hypertable::BlockHeader:

Public Member Functions
	BlockHeader (uint16_t version=LatestVersion, const char *magic=0)
	Constructor. More...

virtual	~BlockHeader ()
	Destructor. More...

void	set_magic (const char *magic)
	Sets the "magic" field. More...

const char *	get_magic ()
	Gets a pointer to the "magic" field. More...

bool	check_magic (const char *magic)
	Compares a given character sequence with the magic field. More...

void	set_data_length (uint32_t length)
	Sets the uncompressed data length field. More...

uint32_t	get_data_length ()
	Gets the uncompressed data length field. More...

void	set_data_zlength (uint32_t zlength)
	Sets the compressed data length field. More...

uint32_t	get_data_zlength ()
	Gets the compressed data length field. More...

void	set_data_checksum (uint32_t checksum)
	Sets the checksum field. More...

uint32_t	get_data_checksum ()
	Gets the checksum field. More...

void	set_compression_type (uint16_t type)
	Sets the compression type field. More...

uint16_t	get_compression_type ()
	Gets the compression type field. More...

void	set_flags (uint16_t flags)
	Sets the flags field. More...

uint16_t	get_flags ()
	Gets the flags field. More...

void	write_header_checksum (uint8_t *base)
	Computes and writes checksum field. More...

virtual size_t	encoded_length ()
	Returns length of serizlized block header. More...

virtual void	encode (uint8_t **bufp)
	Encodes serialized representation of block header. More...

virtual void	decode (const uint8_t *bufp, size_t remainp)
	Decodes serialized block header. More...

bool	equals (const BlockHeader &other) const
	Equality test. More...

Static Public Attributes
static const uint16_t	LatestVersion = 1

Protected Attributes
char	m_magic [10]
	"Magic" string used to identify start of block header More...

uint16_t	m_flags
	Flags. More...

uint32_t	m_data_length
	Uncompressed length of the data stored within the block. More...

uint32_t	m_data_zlength
	Compressed length of the data stored within the block. More...

uint32_t	m_data_checksum
	Checksum of (possibly compressed) data stored within the block. More...

uint16_t	m_compression_type
	Type of data compression used (see BlockCompressionCodec::Type) More...

Private Attributes
uint16_t	m_version
	Serialization format version number More...

Detailed Description

Base class for block headers.

The commit log files and cell store files consist of a series of (optionally compressed) blocks of data, each beginning with a header. This class is a base class that holds fields that are common to all derived header classes and provides methods for encoding and decoding these common fields to disk.

Definition at line 48 of file BlockHeader.h.

Constructor & Destructor Documentation

BlockHeader::BlockHeader	(	uint16_t	version = `LatestVersion`,
		const char *	magic = `0`
	)

Constructor.

Initializes m_version to version, m_magic with the first ten bytes of magic, and initializes all other members to their default values.

Parameters

version	Version of block header to initialize
magic	Pointer to magic character sequence

Definition at line 50 of file BlockHeader.cc.

virtual Hypertable::BlockHeader::~BlockHeader ( )

inlinevirtual

Destructor.

Definition at line 64 of file BlockHeader.h.

Member Function Documentation

bool Hypertable::BlockHeader::check_magic ( const char * magic )

inline

Compares a given character sequence with the magic field.

Parameters

magic Pointer to character sequence for which to compare

Returns: true if m_magic field matches the first ten bytes of magic, false otherwise

Definition at line 86 of file BlockHeader.h.

void BlockHeader::decode	(	const uint8_t **	bufp,
		size_t *	remainp
	)

virtual

Decodes serialized block header.

See also: encode() for layout

Parameters

bufp	Address of pointer to beginning of serialized block header (advanced by call)
remainp	Address of variable holding remaining valid data pointed to by `bufp` (decremented by call)

Reimplemented in Hypertable::BlockHeaderCommitLog, and Hypertable::BlockHeaderCellStore.

Definition at line 104 of file BlockHeader.cc.

void BlockHeader::encode ( uint8_t ** bufp )

virtual

Encodes serialized representation of block header.

The encoding has the following format:

Encoding	Description
char[10]	Magic string
int16	Header checksum
int16	Flags
int8	Header length
int8	Compression type
int32	Data checksum
int32	Uncompressed data length
int32	Compressed data length

Parameters

bufp	Address of pointer to destination (advanced by call)

Reimplemented in Hypertable::BlockHeaderCommitLog, and Hypertable::BlockHeaderCellStore.

Definition at line 82 of file BlockHeader.cc.

size_t BlockHeader::encoded_length ( )

virtual

Returns length of serizlized block header.

See also: encode() for layout

Returns: Length of serialized block header.

Reimplemented in Hypertable::BlockHeaderCommitLog, and Hypertable::BlockHeaderCellStore.

Definition at line 76 of file BlockHeader.cc.

bool BlockHeader::equals ( const BlockHeader & other ) const

Equality test.

This method compares the members of the object to the members of other, returning true if they're all equal.

Returns: true if object is logically equal to other, false otherwise.

Definition at line 143 of file BlockHeader.cc.

uint16_t Hypertable::BlockHeader::get_compression_type ( )

inline

Gets the compression type field.

Returns: Compression type (see BlockCompressionCodec::Type)

Definition at line 128 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::get_data_checksum ( )

inline

Gets the checksum field.

Returns: Checksum of compressed data

Definition at line 118 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::get_data_length ( )

inline

Gets the uncompressed data length field.

Returns: Uncompressed length of data

Definition at line 96 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::get_data_zlength ( )

inline

Gets the compressed data length field.

Returns: Compressed length of data

Definition at line 106 of file BlockHeader.h.

uint16_t Hypertable::BlockHeader::get_flags ( )

inline

Gets the flags field.

Returns: Block header flags

Definition at line 138 of file BlockHeader.h.

const char* Hypertable::BlockHeader::get_magic ( )

inline

Gets a pointer to the "magic" field.

Returns: Pointer to m_magic

Definition at line 79 of file BlockHeader.h.

void Hypertable::BlockHeader::set_compression_type ( uint16_t type )

inline

Sets the compression type field.

Parameters

type	Compression type (see BlockCompressionCodec::Type)

Definition at line 123 of file BlockHeader.h.

void Hypertable::BlockHeader::set_data_checksum ( uint32_t checksum )

inline

Sets the checksum field.

The checksum field stores the fletcher32 checksum of the compressed data

Parameters

checksum Checksum of compressed data

Definition at line 113 of file BlockHeader.h.

void Hypertable::BlockHeader::set_data_length ( uint32_t length )

inline

Sets the uncompressed data length field.

Parameters

length Uncompressed length of data

Definition at line 91 of file BlockHeader.h.

void Hypertable::BlockHeader::set_data_zlength ( uint32_t zlength )

inline

Sets the compressed data length field.

Parameters

zlength Compressed length of data

Definition at line 101 of file BlockHeader.h.

void Hypertable::BlockHeader::set_flags ( uint16_t flags )

inline

Sets the flags field.

Parameters

flags Block header flags

Definition at line 133 of file BlockHeader.h.

void Hypertable::BlockHeader::set_magic ( const char * magic )

inline

Sets the "magic" field.

The "magic" field is meant to contain an easily identifiable string of ten characters and is written as the first field of the block header. If a file containing a sequence of blocks gets corrupt, the magic field can be used to identify the beginning of any non-corrupted blocks for recovery purposes.

Parameters

magic Pointer to magic character sequence

Definition at line 74 of file BlockHeader.h.

void BlockHeader::write_header_checksum ( uint8_t * base )

Computes and writes checksum field.

The checksum field is a two-byte field that is located immediately after the ten-byte magic string in the serialized header format (see encode()). The checksum is computed over all of the fields that follow the checksum field in the serialized format (including derived portions). This method computes the checksum and then writes it into the serialized header at location base+10. It should be called at the end of the decode() method of derived block header classes in order to compute the checksum after all fields have been written.

Parameters

base	Pointer to beginning of serialized block header

Definition at line 62 of file BlockHeader.cc.

Member Data Documentation

const uint16_t BlockHeader::LatestVersion = 1

static

Definition at line 52 of file BlockHeader.h.

uint16_t Hypertable::BlockHeader::m_compression_type

protected

Type of data compression used (see BlockCompressionCodec::Type)

Definition at line 229 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::m_data_checksum

protected

Checksum of (possibly compressed) data stored within the block.

Definition at line 226 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::m_data_length

protected

Uncompressed length of the data stored within the block.

Definition at line 220 of file BlockHeader.h.

uint32_t Hypertable::BlockHeader::m_data_zlength

protected

Compressed length of the data stored within the block.

Definition at line 223 of file BlockHeader.h.

uint16_t Hypertable::BlockHeader::m_flags

protected

Flags.

Definition at line 217 of file BlockHeader.h.

char Hypertable::BlockHeader::m_magic[10]

protected

"Magic" string used to identify start of block header

Definition at line 214 of file BlockHeader.h.

uint16_t Hypertable::BlockHeader::m_version

private

Serialization format version number

Definition at line 233 of file BlockHeader.h.

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

/home/doug/src/hypertable/src/cc/Hypertable/Lib/BlockHeader.h
/home/doug/src/hypertable/src/cc/Hypertable/Lib/BlockHeader.cc

Public Member Functions

Static Public Attributes

Protected Attributes

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation