pp::FileIO Class Reference

The FileIO class represents a regular file. More...

#include <file_io.h>

Inheritance diagram for pp::FileIO:

Collaboration diagram for pp::FileIO:

Public Member Functions
	FileIO ()
	FileIO (const InstanceHandle &instance)
	FileIO (const FileIO &other)
int32_t	Open (const FileRef &file_ref, int32_t open_flags, const CompletionCallback &cc)
int32_t	Query (PP_FileInfo *result_buf, const CompletionCallback &cc)
int32_t	Touch (PP_Time last_access_time, PP_Time last_modified_time, const CompletionCallback &cc)
int32_t	Read (int64_t offset, char *buffer, int32_t bytes_to_read, const CompletionCallback &cc)
int32_t	Read (int32_t offset, int32_t max_read_length, const CompletionCallbackWithOutput< std::vector< char > > &cc)
int32_t	Write (int64_t offset, const char *buffer, int32_t bytes_to_write, const CompletionCallback &cc)
int32_t	SetLength (int64_t length, const CompletionCallback &cc)
int32_t	Flush (const CompletionCallback &cc)
void	Close ()
Public Member Functions inherited from pp::Resource
	Resource ()
	The default constructor. More...
	Resource (const Resource &other)
virtual	~Resource ()
	Destructor. More...
Resource &	operator= (const Resource &other)
bool	is_null () const
PP_Resource	pp_resource () const
PP_Resource	detach ()

Additional Inherited Members
Protected Member Functions inherited from pp::Resource
	Resource (PP_Resource resource)
	Resource (PassRef, PP_Resource resource)
void	PassRefFromConstructor (PP_Resource resource)
void	Clear ()
	Sets this resource to null. This releases ownership of the resource. More...

Detailed Description

The FileIO class represents a regular file.

Definition at line 23 of file file_io.h.

Constructor & Destructor Documentation

pp::FileIO::FileIO

(

)

Default constructor for creating an is_null() FileIO object.

pp::FileIO::FileIO ( const InstanceHandle &  instance )

explicit

A constructor used to create a FileIO and associate it with the provided Instance.

Parameters

[in]

instance

The instance with which this resource will be associated.

pp::FileIO::FileIO

(

const FileIO &

other

)

The copy constructor for FileIO.

Parameters

[in]

other

A reference to a FileIO.

Member Function Documentation

void pp::FileIO::Close

(

)

Close() cancels any IO that may be pending, and closes the FileIO object. Any pending callbacks will still run, reporting PP_ERROR_ABORTED if pending IO was interrupted. It is not valid to call Open() again after a call to this method.

Note: If the FileIO object is destroyed, and it is still open, then it will be implicitly closed, so you are not required to call Close().

int32_t pp::FileIO::Flush

(

const CompletionCallback &

cc

)

Flush() flushes changes to disk. This call can be very expensive!

Parameters

[in]

cc

A CompletionCallback to be called upon completion of Flush().

Returns

An int32_t containing an error code from pp_errors.h.

int32_t pp::FileIO::Open	(	const FileRef &	file_ref,
		int32_t	open_flags,
		const CompletionCallback &	cc
	)

Open() opens the specified regular file for I/O according to the given open flags, which is a bit-mask of the PP_FileOpenFlags values. Upon success, the corresponding file is classified as "in use" by this FileIO object until such time as the FileIO object is closed or destroyed.

Parameters

[in]	file_ref	A PP_Resource corresponding to a file reference.
[in]	open_flags	A bit-mask of the PP_FileOpenFlags values. Valid values are: PP_FILEOPENFLAG_READ PP_FILEOPENFLAG_WRITE PP_FILEOPENFLAG_CREATE PP_FILEOPENFLAG_TRUNCATE PP_FILEOPENFLAG_EXCLUSIVE See PP_FileOpenFlags in ppb_file_io.h for more details on these flags.
[in]	cc	A CompletionCallback to be called upon completion of Open().

Returns

An int32_t containing an error code from pp_errors.h.

int32_t pp::FileIO::Query	(	PP_FileInfo *	result_buf,
		const CompletionCallback &	cc
	)

Query() queries info about the file opened by this FileIO object. This function will fail if the FileIO object has not been opened.

Parameters

[in]	result_buf	The PP_FileInfo structure representing all information about the file.
[in]	cc	A CompletionCallback to be called upon completion of Query(). result_buf must remain valid until after the callback runs. If you pass a blocking callback, result_buf must remain valid until after Query() returns.

Returns

An int32_t containing an error code from pp_errors.h.

int32_t pp::FileIO::Read	(	int64_t	offset,
		char *	buffer,
		int32_t	bytes_to_read,
		const CompletionCallback &	cc
	)

Reads from an offset in the file.

The size of the buffer must be large enough to hold the specified number of bytes to read. This function might perform a partial read, meaning that all the requested bytes might not be returned, even if the end of the file has not been reached.

This function reads into a buffer that the caller supplies. This buffer must remain valid as long as the FileIO resource is alive. If you use a completion callback factory and it goes out of scope, it will not issue the callback on your class, BUT the callback factory can NOT cancel the request from the browser's perspective. This means that the browser will still try to write to your buffer even if the callback factory is destroyed!

So you must ensure that your buffer outlives the FileIO resource. If you have one class and use the FileIO resource exclusively from that class and never make any copies, this will be fine: the resource will be destroyed when your class is. But keep in mind that copying a pp::FileIO object just creates a second reference to the original resource. For example, if you have a function like this: pp::FileIO MyClass::GetFileIO(); where a copy of your FileIO resource could outlive your class, the callback will still be pending when your class goes out of scope, creating the possibility of writing into invalid memory. So it's recommended to keep your FileIO resource and any output buffers tightly controlled in the same scope.

Caveat: This Read() is potentially unsafe if you're using a CompletionCallbackFactory to scope callbacks to the lifetime of your class. When your class goes out of scope, the callback factory will not actually cancel the callback, but will rather just skip issuing the callback on your class. This means that if the FileIO object outlives your class (if you made a copy saved somewhere else, for example), then the browser will still try to write into your buffer when the asynchronous read completes, potentially causing a crash.

See the other version of Read() which avoids this problem by writing into CompletionCallbackWithOutput, where the output buffer is automatically managed by the callback.

Parameters

[in]	offset	The offset into the file.
[in]	buffer	The buffer to hold the specified number of bytes read.
[in]	bytes_to_read	The number of bytes to read from offset.
[in]	cc	A CompletionCallback to be called upon completion of Read(). buffer must remain valid until after the callback runs. If you pass a blocking callback, buffer must remain valid until after Read() returns.

Returns

An The number of bytes read an error code from pp_errors.h. If the return value is 0, then end-of-file was reached. It is valid to call Read() multiple times with a completion callback to queue up parallel reads from the file at different offsets.

int32_t pp::FileIO::Read	(	int32_t	offset,
		int32_t	max_read_length,
		const CompletionCallbackWithOutput< std::vector< char > > &	cc
	)

Read() reads from an offset in the file. A PP_ArrayOutput must be provided so that output will be stored in its allocated buffer. This function might perform a partial read.

Parameters

[in]	file_io	A PP_Resource corresponding to a file FileIO.
[in]	offset	The offset into the file.
[in]	max_read_length	The maximum number of bytes to read from offset.
[in]	output	A PP_ArrayOutput to hold the output data.
[in]	callback	A PP_CompletionCallback to be called upon completion of Read().

Returns

The number of bytes read or an error code from pp_errors.h. If the return value is 0, then end-of-file was reached. It is valid to call Read() multiple times with a completion callback to queue up parallel reads from the file, but pending reads cannot be interleaved with other operations.

int32_t pp::FileIO::SetLength	(	int64_t	length,
		const CompletionCallback &	cc
	)

SetLength() sets the length of the file. If the file size is extended, then the extended area of the file is zero-filled. The FileIO object must have been opened with write access.

Parameters

[in]	length	The length of the file to be set.
[in]	cc	A CompletionCallback to be called upon completion of SetLength().

Returns

An int32_t containing an error code from pp_errors.h.

int32_t pp::FileIO::Touch	(	PP_Time	last_access_time,
		PP_Time	last_modified_time,
		const CompletionCallback &	cc
	)

Touch() Updates time stamps for the file opened by this FileIO object. This function will fail if the FileIO object has not been opened.

Parameters

[in]	last_access_time	The last time the FileIO was accessed.
[in]	last_modified_time	The last time the FileIO was modified.
[in]	cc	A CompletionCallback to be called upon completion of Touch().

Returns

An int32_t containing an error code from pp_errors.h.

int32_t pp::FileIO::Write	(	int64_t	offset,
		const char *	buffer,
		int32_t	bytes_to_write,
		const CompletionCallback &	cc
	)

Write() writes to an offset in the file. This function might perform a partial write. The FileIO object must have been opened with write access.

Parameters

[in]	offset	The offset into the file.
[in]	buffer	The buffer to hold the specified number of bytes read.
[in]	bytes_to_write	The number of bytes to write to offset.
[in]	cc	A CompletionCallback to be called upon completion of Write().

Returns

An The number of bytes written or an error code from pp_errors.h. If the return value is 0, then end-of-file was reached. It is valid to call Write() multiple times with a completion callback to queue up parallel writes to the file at different offsets.

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

• file_io.h