cv::FileStorage Class Reference

#include <core.hpp>

Public Types
enum	{   READ =0, WRITE =1, APPEND =2, MEMORY =4,   FORMAT_MASK =(7<<3), FORMAT_AUTO =0, FORMAT_XML =(1<<3), FORMAT_YAML =(2<<3) }
	file storage mode More...
enum	{ UNDEFINED =0, VALUE_EXPECTED =1, NAME_EXPECTED =2, INSIDE_MAP =4 }

Public Member Functions
	FileStorage ()
	the default constructor More...
	FileStorage (const string &source, int flags, const string &encoding=string())
	the full constructor that opens file storage for reading or writing More...
	FileStorage (CvFileStorage *fs)
	the constructor that takes pointer to the C FileStorage structure More...
virtual	~FileStorage ()
	the destructor. calls release() More...
virtual bool	open (const string &filename, int flags, const string &encoding=string())
	opens file storage for reading or writing. The previous storage is closed with release() More...
virtual bool	isOpened () const
	returns true if the object is associated with currently opened file. More...
virtual void	release ()
	closes the file and releases all the memory buffers More...
string	releaseAndGetString ()
	closes the file, releases all the memory buffers and returns the text string More...
FileNode	getFirstTopLevelNode () const
	returns the first element of the top-level mapping More...
FileNode	root (int streamidx=0) const
	returns the top-level mapping. YAML supports multiple streams More...
FileNode	operator[] (const string &nodename) const
	returns the specified element of the top-level mapping More...
FileNode	operator[] (const char *nodename) const
	returns the specified element of the top-level mapping More...
CvFileStorage *	operator* ()
	returns pointer to the underlying C FileStorage structure More...
const CvFileStorage *	operator* () const
	returns pointer to the underlying C FileStorage structure More...
void	writeRaw (const string &fmt, const uchar *vec, size_t len)
	writes one or more numbers of the specified format to the currently written structure More...
void	writeObj (const string &name, const void *obj)
	writes the registered C structure (CvMat, CvMatND, CvSeq). See cvWrite() More...

Static Public Member Functions
static string	getDefaultObjectName (const string &filename)
	returns the normalized object name for the specified file name More...

Public Attributes
Ptr< CvFileStorage >	fs
	the underlying C FileStorage structure More...
string	elname
	the currently written element More...
vector< char >	structs
	the stack of written structures More...
int	state
	the writer state More...

Detailed Description

XML/YAML File Storage Class.

The class describes an object associated with XML or YAML file. It can be used to store data to such a file or read and decode the data.

The storage is organized as a tree of nested sequences (or lists) and mappings. Sequence is a heterogenious array, which elements are accessed by indices or sequentially using an iterator. Mapping is analogue of std::map or C structure, which elements are accessed by names. The most top level structure is a mapping. Leaves of the file storage tree are integers, floating-point numbers and text strings.

For example, the following code:

// open file storage for writing. Type of the file is determined from the extension
FileStorage fs("test.yml", FileStorage::WRITE);
fs << "test_int" << 5 << "test_real" << 3.1 << "test_string" << "ABCDEFGH";
fs << "test_mat" << Mat::eye(3,3,CV_32F);

fs << "test_list" << "[" << 0.0000000000001 << 2 << CV_PI << -3435345 << "2-502 2-029 3egegeg" <<
"{:" << "month" << 12 << "day" << 31 << "year" << 1969 << "}" << "]";
fs << "test_map" << "{" << "x" << 1 << "y" << 2 << "width" << 100 << "height" << 200 << "lbp" << "[:";

const uchar arr[] = {0, 1, 1, 0, 1, 1, 0, 1};
fs.writeRaw("u", arr, (int)(sizeof(arr)/sizeof(arr[0])));

fs << "]" << "}";

will produce the following file:

%YAML:1.0
test_int: 5
test_real: 3.1000000000000001e+00
test_string: ABCDEFGH
test_mat: !!opencv-matrix
    rows: 3
    cols: 3
    dt: f
    data: [ 1., 0., 0., 0., 1., 0., 0., 0., 1. ]
test_list:
    - 1.0000000000000000e-13
    - 2
    - 3.1415926535897931e+00
    - -3435345
    - "2-502 2-029 3egegeg"
    - { month:12, day:31, year:1969 }
test_map:
    x: 1
    y: 2
    width: 100
    height: 200
    lbp: [ 0, 1, 1, 0, 1, 1, 0, 1 ]

and to read the file above, the following code can be used:

// open file storage for reading.
// Type of the file is determined from the content, not the extension
FileStorage fs("test.yml", FileStorage::READ);
int test_int = (int)fs["test_int"];
double test_real = (double)fs["test_real"];
string test_string = (string)fs["test_string"];

Mat M;
fs["test_mat"] >> M;

FileNode tl = fs["test_list"];
CV_Assert(tl.type() == FileNode::SEQ && tl.size() == 6);
double tl0 = (double)tl[0];
int tl1 = (int)tl[1];
double tl2 = (double)tl[2];
int tl3 = (int)tl[3];
string tl4 = (string)tl[4];
CV_Assert(tl[5].type() == FileNode::MAP && tl[5].size() == 3);

int month = (int)tl[5]["month"];
int day = (int)tl[5]["day"];
int year = (int)tl[5]["year"];

FileNode tm = fs["test_map"];

int x = (int)tm["x"];
int y = (int)tm["y"];
int width = (int)tm["width"];
int height = (int)tm["height"];

int lbp_val = 0;
FileNodeIterator it = tm["lbp"].begin();

for(int k = 0; k < 8; k++, ++it)
   lbp_val |= ((int)*it) << k;

Member Enumeration Documentation

anonymous enum

file storage mode

Enumerator
READ
WRITE	read mode
APPEND	write mode
MEMORY	append mode
FORMAT_MASK
FORMAT_AUTO
FORMAT_XML
FORMAT_YAML

anonymous enum

Enumerator
UNDEFINED
VALUE_EXPECTED
NAME_EXPECTED
INSIDE_MAP

Constructor & Destructor Documentation

cv::FileStorage::FileStorage

(

)

the default constructor

cv::FileStorage::FileStorage	(	const string &	source,
		int	flags,
		const string &	encoding = string()
	)

the full constructor that opens file storage for reading or writing

cv::FileStorage::FileStorage

(

CvFileStorage *

fs

)

the constructor that takes pointer to the C FileStorage structure

virtual cv::FileStorage::~FileStorage ( )

virtual

the destructor. calls release()

Member Function Documentation

static string cv::FileStorage::getDefaultObjectName ( const string &  filename )

static

returns the normalized object name for the specified file name

FileNode cv::FileStorage::getFirstTopLevelNode ( ) const

inline

returns the first element of the top-level mapping

virtual bool cv::FileStorage::isOpened ( ) const

virtual

returns true if the object is associated with currently opened file.

virtual bool cv::FileStorage::open ( const string &  filename, int  flags, const string &  encoding = string()  )

virtual

opens file storage for reading or writing. The previous storage is closed with release()

CvFileStorage* cv::FileStorage::operator* ( )

inline

returns pointer to the underlying C FileStorage structure

const CvFileStorage* cv::FileStorage::operator* ( ) const

inline

returns pointer to the underlying C FileStorage structure

FileNode cv::FileStorage::operator[]

(

const string &

nodename

)

const

returns the specified element of the top-level mapping

FileNode cv::FileStorage::operator[]

(

const char *

nodename

)

const

returns the specified element of the top-level mapping

virtual void cv::FileStorage::release ( )

virtual

closes the file and releases all the memory buffers

string cv::FileStorage::releaseAndGetString

(

)

closes the file, releases all the memory buffers and returns the text string

FileNode cv::FileStorage::root

(

int

streamidx = 0

)

const

returns the top-level mapping. YAML supports multiple streams

void cv::FileStorage::writeObj	(	const string &	name,
		const void *	obj
	)

writes the registered C structure (CvMat, CvMatND, CvSeq). See cvWrite()

void cv::FileStorage::writeRaw	(	const string &	fmt,
		const uchar *	vec,
		size_t	len
	)

writes one or more numbers of the specified format to the currently written structure

Member Data Documentation

string cv::FileStorage::elname

the currently written element

Ptr<CvFileStorage> cv::FileStorage::fs

the underlying C FileStorage structure

int cv::FileStorage::state

the writer state

vector<char> cv::FileStorage::structs

the stack of written structures

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

• core/core.hpp
• operations.hpp