Data Object

A data object is an abstraction for objects that can provide data. More...

Typedefs
typedef struct data_object	data_object_t
	Opaque type for data object ADT.
typedef int(	data_object_file_close_func )(int fd)
	A function used to close the file owned by a file data_object_t.
typedef void(	data_object_memory_free_func )(void *)
	A function used to free the data owned by a memory data_object_t.
Enumerations
enum	data_object_flags { DATA_OBJECT_READ = 1, DATA_OBJECT_WRITE = 2, DATA_OBJECT_RW = 3 }
	Flags for the usage of data returned by data_object_get_data(). More...
Functions
int	data_object_get_data (data_object_t obj, void buf, off_t offset, off_t length, data_object_flags flags)
	Gets a pointer to data from the data object.
int	data_object_free (data_object_t *obj)
	Frees the data object and its resources.
int	data_object_update_usage (void *obj, int change)
	Updates the usage count of this data object.
int	data_object_get_size (data_object_t obj, off_t size)
	Gets the size of the data object.
int	data_object_compare (int result, data_object_t obj1, data_object_t *obj2)
	Compares the data held by two data objects.
Constructors

int	data_object_file_new (data_object_t **obj, int fd)
	Creates a new file data object.
int	data_object_tempfile_new (data_object_t *obj, int fd, char path)
	Creates a new temporary file data object.
int	data_object_file_set_close_func (data_object_t obj, data_object_file_close_func file_close)
	Sets the function used to close the file associated with the data object.
Constructors

int	data_object_memory_new (data_object_t *obj, void data, size_t size)
	Creates a new memory data object initialized with data.
int	data_object_memory_set_free_func (data_object_t obj, data_object_memory_free_func mem_free)
	Sets the function used to free the data held by the data object.

Detailed Description

A data object is an abstraction for objects that can provide data.

It provides a common API to transparently get the data regardless of the particular source they come from.

The two main data object types are the memory data object and the file data object. To create a data object one must use the provided constructor for the particular type.

Enumeration Type Documentation

enum data_object_flags

Flags for the usage of data returned by data_object_get_data().

Enumerator:

DATA_OBJECT_READ	Data will be used just for reading.
DATA_OBJECT_WRITE	Data will be used just for writing.
DATA_OBJECT_RW	Data will be used for both reading and writing.

Definition at line 58 of file data_object.h.

Function Documentation

int data_object_compare	(	int *	result,
		data_object_t *	obj1,
		data_object_t *	obj2
	)

Compares the data held by two data objects.

Note that the compare is based on reference equality (eg for memory data objects if their data is located at the same memory area, for file objects if they are associated with the same file) not byte by byte comparison.

Parameters:

`[out]`	result	0 if they are equal, 1 otherwise
	obj1	one of the data objects to compare
	obj2	the other data object to compare

Returns:: the operation error code

Definition at line 194 of file data_object.c.

Referenced by create_overlap_graph(), and write_segcol_rest().

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int data_object_file_new	(	data_object_t **	obj,
		int	fd
	)

Creates a new file data object.

The data object by default doesn't own the file passed to it. That means that when the data object is freed the file will not be closed. To change data ownership by the data_object_t use data_object_set_data_ownership().

Parameters:

`[out]`	obj	the created data object
	fd	the file descriptor of the file to use

Returns:: the operation error code

Definition at line 90 of file data_object_file.c.

References data_object_create_impl().

Referenced by bless_buffer_save(), bless_buffer_source_file(), and data_object_tempfile_new().

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int data_object_file_set_close_func	(	data_object_t *	obj,
		data_object_file_close_func *	file_close
	)

Sets the function used to close the file associated with the data object.

If the function is NULL, the file wont be closed when the data object is freed.

Parameters:

	obj	the data object
	file_close	the function used to close the file associated with the data object

Returns:: the operation error code

Definition at line 204 of file data_object_file.c.

References data_object_get_impl().

Referenced by bless_buffer_source_file(), and segcol_store_in_file().

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int data_object_free ( data_object_t * obj )

Frees the data object and its resources.

Parameters:

obj

the data object to free

Returns:: the operation error code

Definition at line 121 of file data_object.c.

Referenced by bless_buffer_save(), bless_buffer_source_file(), bless_buffer_source_memory(), data_object_tempfile_new(), data_object_update_usage(), segcol_store_in_file(), and segcol_store_in_memory().

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int data_object_get_data	(	data_object_t *	obj,
		void **	buf,
		off_t	offset,
		off_t *	length,
		data_object_flags	flags
	)

Gets a pointer to data from the data object.

This function provides a pointer that points to a location that contains the data range requested. It is possible that a call to this function retrieves only some of the requested data. Subsequent calls may be needed to complete the whole operation.

Furthermore, the pointer returned is valid only as long as no other access is made to the data object (watch out for concurrency issues!).

Parameters:

	obj	the obj to get the data from
`[out]`	buf	the location that will contain the data
	offset	the offset in the data object to get data from
`[in,out]`	length	the length of the data to get, on return will contain the length of the data that was actually retrieved. The returned length always fits in an ssize_t variable.
	flags	whether the data will be read or written to (or both)

Returns:: the operation error code

Definition at line 108 of file data_object.c.

Referenced by read_data_object(), and write_data_object().

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int data_object_get_size	(	data_object_t *	obj,
		off_t *	size
	)

Gets the size of the data object.

Parameters:

	obj	the data object to get the size of
`[out]`	size	the size of the data object

Returns:: the operation error code

Definition at line 175 of file data_object.c.

int data_object_memory_new	(	data_object_t **	obj,
		void *	data,
		size_t	size
	)

Creates a new memory data object initialized with data.

The data object by default doesn't own the data passed to it. That means that when the data object is freed the data will not be freed. To change data ownership by the data_object_t use data_object_set_data_ownership().

Parameters:

`[out]`	obj	the created data object
	data	the data that this data object will contain
	size	the size of the data (and the data object)

Returns:: the operation error code

Definition at line 76 of file data_object_memory.c.

References data_object_create_impl().

Referenced by bless_buffer_source_memory(), and segcol_store_in_memory().

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int data_object_memory_set_free_func	(	data_object_t *	obj,
		data_object_memory_free_func *	mem_free
	)

Sets the function used to free the data held by the data object.

If the function is NULL, the data won't be freed when the data object is freed.

Parameters:

	obj	the data object
	mem_free	the function used to free the data held by the data object

Returns:: the operation error code

Definition at line 122 of file data_object_memory.c.

References data_object_get_impl().

Referenced by bless_buffer_source_memory(), and segcol_store_in_memory().

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int data_object_tempfile_new	(	data_object_t **	obj,
		int	fd,
		char *	path
	)

Creates a new temporary file data object.

When the data object is freed the temporary file will be deleted from the file system.

The data object by default doesn't own the file passed to it. That means that when the data object is freed the file will not be closed. To change data ownership by the data_object_t use data_object_set_data_ownership().

Parameters: