IO_CACHE_istream Class Reference

A file input stream based on IO_CACHE class. More...

#include <basic_istream.h>

Inheritance diagram for IO_CACHE_istream:

Public Member Functions
	IO_CACHE_istream ()
	IO_CACHE_istream (const IO_CACHE_istream &)=delete
IO_CACHE_istream &	operator= (const IO_CACHE_istream &)=delete
	~IO_CACHE_istream () override
bool	open (PSI_file_key log_file_key, PSI_file_key log_cache_key, const char *file_name, myf flags, size_t cache_size=IO_SIZE *2)
	Open the stream. More...
void	close ()
	Closes the stream. More...
ssize_t	read (unsigned char *buffer, size_t length) override
	Read some bytes from the input stream. More...
bool	seek (my_off_t bytes) override
	Puts the read position to a given offset. More...
my_off_t	length () override
	Get the length of the file. More...
Public Member Functions inherited from Basic_seekable_istream
	~Basic_seekable_istream () override=default
Public Member Functions inherited from Basic_istream
virtual	~Basic_istream ()=default

Private Attributes
IO_CACHE	m_io_cache

Detailed Description

A file input stream based on IO_CACHE class.

It can be used to open a file and provide a Basic_seekable_istream based on the file.

Constructor & Destructor Documentation

IO_CACHE_istream() [1/2]

IO_CACHE_istream::IO_CACHE_istream ( )

default

IO_CACHE_istream() [2/2]

IO_CACHE_istream::IO_CACHE_istream ( const IO_CACHE_istream &  )

delete

~IO_CACHE_istream()

IO_CACHE_istream::~IO_CACHE_istream ( )

override

Member Function Documentation

close()

void IO_CACHE_istream::close

(

)

Closes the stream.

It deinitializes IO_CACHE and closes the file it opened.

length()

my_off_t IO_CACHE_istream::length ( )

overridevirtual

Get the length of the file.

Implements Basic_seekable_istream.

open()

bool IO_CACHE_istream::open	(	PSI_file_key	log_file_key,
		PSI_file_key	log_cache_key,
		const char *	file_name,
		myf	flags,
		size_t	cache_size = IO_SIZE * 2
	)

Open the stream.

It opens related file and initializes IO_CACHE.

Parameters

[in]	log_file_key	The PSI_file_key for this stream
[in]	log_cache_key	The PSI_file_key for the IO_CACHE
[in]	file_name	The file to be opened
[in]	flags	The flags used by IO_CACHE.
[in]	cache_size	Cache size of the IO_CACHE.

Return values

false	Success
true	Error

operator=()

IO_CACHE_istream & IO_CACHE_istream::operator= ( const IO_CACHE_istream &  )

delete

read()

ssize_t IO_CACHE_istream::read ( unsigned char *  buffer, size_t  length  )

overridevirtual

Read some bytes from the input stream.

It should read exact 'length' bytes unless error happens or it reaches the end of the stream. It should block when reaching the end of a pipe that is not closed.

Parameters

[out]	buffer	Where data will be put in.
[in]	length	The number of bytes that you want to read. length should not be larger than max long.

Returns

Return values fall into three cases:

Return values

'length'	Read 'length' bytes successfully
>=0	Reach EOF, return the number of bytes actually read. It is between 0 and length-1.
-1	Error.

Implements Basic_istream.

seek()

bool IO_CACHE_istream::seek ( my_off_t  offset )

overridevirtual

Puts the read position to a given offset.

The offset counts from the beginning of the stream. In case an implementing class transforms the data in a way that does not preserve positions, the offset here will be relative to the bytes that are read out from the stream, not relative to the bytes in lower layer storage.

it is allowed for a subclass to return success even if the position is greater than the size of the file. Error may be returned by the next read for this case. Users should call length() if they need to check that the position is within bounds.

Parameters

[in]

offset

Where the read position will be.

Return values

false	Success
true	Error

Implements Basic_seekable_istream.

Member Data Documentation

m_io_cache

IO_CACHE IO_CACHE_istream::m_io_cache

private

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

• sql/basic_istream.h
• sql/basic_istream.cc