Bitset< B > Class Template Reference

A simple bitset wrapper class, which lets you access an existing range of bytes (not owned by it!) as if it was a std::bitset or std::vector<bool>. More...

#include <ut0bitset.h>

Public Member Functions
	Bitset ()
	Constructor. More...
	Bitset (B *data, size_t size_bytes)
Bitset	bytes_subspan (size_t byte_offset, size_t bytes_count) const
	Returns a wrapper around [pos,pos+len) fragment of the buffer, where pos and len are measured in bytes. More...
Bitset	bytes_subspan (size_t byte_offset) const
	Returns a wrapper around fragment of the buffer starting at pos, where pos is measured in bytes. More...
void	copy_from (const byte *bitset) const
	Copy a bits from other buffer into this one. More...
void	set (size_t pos, bool v=true) const
	Set the specified bit to the value 'bit'. More...
void	set () const
	Set all bits to true. More...
void	reset () const
	Set all bits to false. More...
void	reset (size_t pos) const
	Sets the specified bit to false. More...
uint64_t	to_uint64 () const
	Converts the content of the bitset to an uint64_t value, such that (value>>i&1) if and only if test(i). More...
size_t	find_set (size_t start_pos) const
	Finds the smallest position which is set and is not smaller than start_pos. More...
bool	test (size_t pos) const
	Test if the specified bit is set or not. More...
size_t	size_bytes () const
	Get the size of current bitset in bytes. More...
B *	data () const
	Get the bitset's bytes buffer. More...

Static Public Attributes
constexpr static size_t	NOT_FOUND = std::numeric_limits<size_t>::max()
	Value used by find_set to indicate it could not find a bit set to 1. More...

Static Private Member Functions
static constexpr uint64_t	to_uint64 (const byte *bytes)
	Converts 8 bytes to uint64_t value, such that (value>>i&1) equals the i-th bit, i.e. More...

Private Attributes
B *	m_data
	The buffer containing the bitmap. More...
size_t	m_size_bytes
	The length of the buffer containing the bitmap in bytes. More...

Detailed Description

template<typename B = byte>
class Bitset< B >

A simple bitset wrapper class, which lets you access an existing range of bytes (not owned by it!) as if it was a std::bitset or std::vector<bool>.

NOTE: Because it is a wrapper, its semantics are similar to std::span. For example const Bitset<> can still let someone modify the bits via set() or reset(). If you want to prevent someone from editing the buffer, you'd need Bitset<const byte>. For same reason, bitset1=bitset2 will just repoint bitset1 to the same range of bytes as bitset2 without copying any bits. If you want to copy the bits use bitset1.copy_from(bitset2.bitset()) instead.

Constructor & Destructor Documentation

Bitset() [1/2]

template<typename B = byte>

Bitset< B >::Bitset ( )

inline

Constructor.

Bitset() [2/2]

template<typename B = byte>

Bitset< B >::Bitset ( B *  data, size_t  size_bytes  )

inline

Member Function Documentation

bytes_subspan() [1/2]

template<typename B = byte>

Bitset Bitset< B >::bytes_subspan ( size_t  byte_offset ) const

inline

Returns a wrapper around fragment of the buffer starting at pos, where pos is measured in bytes.

Parameters

[in]

byte_offset

position of first byte of selected slice

Returns

Bitset wrapping the sub-array

bytes_subspan() [2/2]

template<typename B = byte>

Bitset Bitset< B >::bytes_subspan ( size_t  byte_offset, size_t  bytes_count  ) const

inline

Returns a wrapper around [pos,pos+len) fragment of the buffer, where pos and len are measured in bytes.

Parameters

[in]	byte_offset	position of first byte of selected slice
[in]	bytes_count	length of the slice in bytes

Returns

Bitset wrapping the sub-array

copy_from()

template<typename B = byte>

void Bitset< B >::copy_from ( const byte *  bitset ) const

inline

Copy a bits from other buffer into this one.

Parameters

[in]

bitset

byte array to bits copy from

data()

template<typename B = byte>

B * Bitset< B >::data ( ) const

inline

Get the bitset's bytes buffer.

Returns

current bitset

find_set()

template<typename B = byte>

size_t Bitset< B >::find_set ( size_t  start_pos ) const

inline

Finds the smallest position which is set and is not smaller than start_pos.

Parameters

[in]

start_pos

The position from which to start the search.

Returns

Smallest pos for which test(pos)==true and start_pos<=pos. In case there's no such pos, returns NOT_FOUND

reset() [1/2]

template<typename B = byte>

void Bitset< B >::reset ( void  ) const

inline

Set all bits to false.

reset() [2/2]

template<typename B = byte>

void Bitset< B >::reset ( size_t  pos ) const

inline

Sets the specified bit to false.

Parameters

[in]

pos

specified bit

set() [1/2]

template<typename B = byte>

void Bitset< B >::set ( ) const

inline

Set all bits to true.

set() [2/2]

template<typename B = byte>

void Bitset< B >::set ( size_t  pos, bool  v = true  ) const

inline

Set the specified bit to the value 'bit'.

Parameters

[in]	pos	specified bit
[in]	v	true or false

size_bytes()

template<typename B = byte>

size_t Bitset< B >::size_bytes ( ) const

inline

Get the size of current bitset in bytes.

Returns

the size of the bitset

test()

template<typename B = byte>

bool Bitset< B >::test ( size_t  pos ) const

inline

Test if the specified bit is set or not.

Parameters

[in]

pos

the specified bit

Returns

True if this bit is set, otherwise false

to_uint64() [1/2]

template<typename B = byte>

uint64_t Bitset< B >::to_uint64 ( ) const

inline

Converts the content of the bitset to an uint64_t value, such that (value>>i&1) if and only if test(i).

The m_size must be at most 8 bytes.

Returns

content of the bitset as uint64_t mapping i-th bit to 2^i

to_uint64() [2/2]

template<typename B = byte>

static constexpr uint64_t Bitset< B >::to_uint64 ( const byte *  bytes )

inlinestaticconstexprprivate

Converts 8 bytes to uint64_t value, such that (value>>i&1) equals the i-th bit, i.e.

(bytes[i/8]>>i%8 & 1). For example, the returned value equals bytes[0] modulo 256.

Parameters

[in]

bytes

the bytes to convert

Returns

uint64_t created by concatenating the bytes in the right order: on Little-Endian it's an identity, on Big-Endian it's std::byteswap.

Member Data Documentation

m_data

template<typename B = byte>

B* Bitset< B >::m_data

private

The buffer containing the bitmap.

First bit is the lowest bit of the first byte of this buffer.

m_size_bytes

template<typename B = byte>

size_t Bitset< B >::m_size_bytes

private

The length of the buffer containing the bitmap in bytes.

Number of bits is 8 times larger than this

NOT_FOUND

template<typename B = byte>

constexpr static size_t Bitset< B >::NOT_FOUND = std::numeric_limits<size_t>::max()

staticconstexpr

Value used by find_set to indicate it could not find a bit set to 1.

It is guaranteed to be larger than the size of the vector.

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

• storage/innobase/include/ut0bitset.h