basic_stringstream

Overview

basic_stringstream class is designed to read from and write to memory stream.

Details

The class template basic_stringstream provides support for high level input and output operations on memory streams. The supported operations include formatted input and output (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input and output(e.g. raw characters and character arrays). 

basic_stringstream class is basically derived class of  basic_istringstream and basic_ostringstream. It has no additional functionality other than constructor. 

Syntax

template<class CharT, class Traits = char_traits<CharT>> 
class basic_stringstream: public basic_iostream<CharT,Traits>

where CharT can be char or wchar_t. It's derived from basic_ios class.

member types

Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.

Constructor

Name	Description
basic_stringstream (ios_base::openmode mode = ios_base::in) basic_stringstream (const basic_string& s, ios_base::openmode mode = ios_base::in) basic_stringstream (basic_stringstream&& buf)	Constructs an empty basic_istringstream object. Constructs basic_istringstream object with the content from s. move constructor The mode constants are defined in ios_base class. Example istringstream s, s2 {"hello, world!"};

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
istringstream s {"hello, world!"};
auto sb = s.rdbuf();
void str
(const basic_string& s) 
basic_string str()
Sets the current contents of the stream to s
Returns the current contents of the stream as string.
Example
istringstream ss,ss2;
ss.str("hello, world!");
ss2.str(ss.str());

basic_fstream

Overview

basic_fstream class is designed to read from and write to streams such as  files.

Details

The class template basic_fstream provides support for high level input and output operations on file streams. The supported operations include formatted input and output (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input and output(e.g. raw characters and character arrays). 

basic_fstream class is basically derived class of  basic_ifstream and basic_ofstream. It has no additional functionality other than constructor. 

Syntax

template<class CharT, class Traits = char_traits<CharT>> 
class basic_fstream: public basic_iostream<CharT,Traits>

where CharT can be char or wchar_t. It's derived from basic_ios class.

member types
Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.

Constructor

Name

Description

basic_fstream (const char* filename, ios_base::openmode mode = ios_base::in|ios_base::out) basic_ifstream (const string& filename, ios_base::openmode mode = ios_base::in|ios_base::out) basic_fstream( basic_fstream&& other)

Constructs a basic_fstream object, initially associated with the file identified by its first argument (filename), open with the mode specified by mode. Internally, its basic_istream base constructor is passed a pointer to a newly constructed basic_filebuf object.  Then, basic_filebuf::open(filename,mode)  is called. If the call fails, the stream's failbit flag is set. Calls the first version with basic_fstream(filename.c_str(),mode) move constructor The mode constants are defined in ios_base class.

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
ifstream file("/usr/share/dict/words");
auto sb = file.rdbuf();
bool is_open()
Checks if the file stream has an associated file.
Effectively calls rdbuf()->is_open().

Example
ifstream file("/usr/share/dict/words");
bool bsuccess = file.is_open();
void open
(const char* filename, 
ios_base::openmode mode = ios_base::in)
void  open
(const string& filename, 
ios_base::openmode mode = ios_base::in)
Opens and associates the file with name filename with the file stream.
Internally, calls rdbuf()->open(filename,mode).
If the call fails, the stream's failbit flag is set. If the stream is already associated with a file (i.e., it is already open), calling this function fails.
Calls the first version with open(filename.c_str(),mode)
The mode constants are defined in ios_base class.

Example
ifstream file;
file.open("/usr/share/dict/words");
void close()
Closes the file currently associated with the object, disassociating it from the stream.
Any pending output sequence is written to the file.
Effectively calls rdbuf()->close(). If an error occurs during operation, setstate(failbit) is called.

Example
ifstream file;
file.open("/usr/share/dict/words");
file.close();

Class Organization

Overview

The classes can be grouped into following categories - Primitive base, Intermediate base , disk based  streams and String based streams.

Details

Each of these group  of the classes can be further grouped into two more groups - Input/Output preparation and serialization.

Primitive base classes 

Preparation

These classes serve as base classes for intermediate base classes.

Name	Alias	Parent	Description
ios_base			Base class for the IO stream classes
basic_ios<char,char_traits<char>>	ios	ios_base	Base classes for input and output  stream classes for character type char.
basic_ios<wchar_t,char_traits<wchar_t>>	wios	ios_base	Base classes for input and output  stream classes for character type wchar_t.

Serialization

These base classes support read / write stream operations.

Name	Alias	Parent	Description
basic_streambuf<char,char_traits<char>>	streambuf		Base classes for Serialization/Deserialization of streams for character type char.
basic_streambuf<wchar_t,char_traits<wchar_t>>	wstreambuf		Base classes for Serialization/Deserialization of streams for character type wchar_t.

Intermediate base classes

Preparation

These classes serve as base classes for file and string based streams. 

Name	Alias	Parent	Description
basic_istream<char,char_traits<char>>	istream	ios	Base classes for input stream classes for character type char.
basic_istream<wchar_t,char_traits<wchar_t>>	wistream	wios	Base classes for input stream classes for character type wchar_t.
basic_ostream<char,char_traits<char>>	ostream	ios	Base classes for output stream classes for character type char.
basic_ostream<wchar_t,char_traits<wchar_t>>	wostream	wios	Base classes for output stream classes for character type wchar_t.
basic_iostream<char,char_traits<char>>	iostream	istream, ostream	Base classes for input and output stream classes for character type char.
basic_iostream<wchar_t,char_traits<wchar_t>>	wiostream	wistream, wostream	Base classes for input and output stream classes for character type wchar_t.

Disk based streams

Preparation

These classes support file based stream operation.

Name	Alias	Parent	Description
basic_ifstream<char,char_traits<char>>	ifstream	istream	File based input stream class for character type char.
basic_ifstream<wchar_t,char_traits<wchar_t>>	wifstream	wistream	File based input stream class for character type wchar_t.
basic_ofstream<char,char_traits<char>>	ofstream	ostream	File based output stream class for character type char.
basic_ofstream<wchar_t,char_traits<wchar_t>>	wofstream	wostream	File based output stream class for character type wchar_t.
basic_fstream<char,char_traits<char>>	fstream	iostream	File based input and output stream class for character type char.
basic_fstream<wchar_t,char_traits<wchar_t>>	wfstream	wiostream	File based input and output stream class for character type char. wchar_t.

Serialization

These classes support file based stream operations.

Name	Alias	Parent	Description
basic_filebuf<char,char_traits<char>>	filebuf	streambuf	Implements Serialization/Deserialization of file streams for character type char.
basic_filebuf<wchar_t,char_traits<wchar_t>>	wfilebuf	wstreambuf	Implements Serialization/Deserialization of file streams for character type wchar_t.

String based streams 

Preparation

These classes support string based stream operation.

Name	Alias	Parent	Description
basic_ostringstream<char,char_traits<char>>	istringstream	istream	String based input stream class for character type char.
basic_ostringstream<wchar_t,char_traits<wchar_t>>	wistringstream	wistream	String based input stream class for character type wchar_t.
basic_ostringstream<char,char_traits<char>>	ostringstream	ostream	String based output stream class for character type char.
basic_ostringstream<wchar_t,char_traits<wchar_t>>	wostringstream	wostream	String based output stream class for character type wchar_t.
basic_stringstream<char,char_traits<char>>	stringstream	iostream	String based input and output stream class for character type char.
basic_stringstream<wchar_t,char_traits<wchar_t>>	wstringstream	wiostream	String  based input and output stream class for character type char. wchar_t.

Serialization

These classes support string based stream operation.

Name	Alias	Parent	Description
basic_stringbuf<char,char_traits<char>>	stringbuf	streambuf	Implements Serialization/Deserialization of string streams for character type char.
basic_stringbuf<wchar_t,char_traits<wchar_t>>	wstringbuf	wstreambuf	Implements Serialization/Deserialization of string streams for character type wchar_t.

basic_stringbuf

Overview

basic_stringbuf is a template based class used for read from or/and write to strings in the memory.

Details

istringstream, ostringstream and stringstream  classes uses a basic_stringbuf to  read from or/and write to strings. It's derived from basic_streambuf class.

Syntax

template<class CharT, class Traits = char_traits<CharT>, class Alloc = allocator<CharT>> 
class basic_stringbuf:public basic_streambuf<CharT,Traits> 

where CharT can be char or wchar_t. 

Properties
Following properties are defined. 
Name
Definition
char_type
char,wchar_t
traits_type
char_traits<char_type>
allocator_type
allocate<char_type>
int_type
char_traits<char_type>::int_type
pos_type
char_traits<char_type>::pos_type
off_type
char_traits<char_type>::off_type

openmode
The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.  These are used in calls such as fopen(). These are bitmask type flags that can be ORed. The following describes different values.
Name
Description
in
Open file for reading.
out
Open file for writing.
ate
Set the stream's position indicator to the end of the stream on opening.
app
Set the stream's position indicator to the end of the stream before each output operation.
trunc
Any current content is discarded, assuming a length of zero on opening.
binary
Consider stream as binary rather than text.
Note it's possible to have multiple flags set. i.e., in | out set at the same time.

Note that in case of ate, writes can be on done anywhere in the stream. For example, begin or middle. In case of app, writes can be done only in the end.
Note that difference between text and binary files is that in a text file individual lines are demarcated by a newline character \n or \r\n. In case of binary files there are no such demarcation.


Constructor
Name
Description
basic_istringbuf
(ios_base::openmode mode = ios_base::in | ios_base::out)
basic_istringbuf
(const basic_string& s,
ios_base::openmode mode = ios_base::in | ios_base::out)
Constructs an empty basic_stringbuf object.
Constructs basic_stringbuf object with the content from s.
The mode constants are defined in ios_base class.

Example
stringbuf s, s2 {"hello, world!"};

Methods
These are the public functions available for the clients like istringstream, ostringstream and stringstream classes.

Name
Description
void str
(const basic_string& s) 

basic_string str()
Sets the current contents of the stream to s
Returns the current contents of the stream as string.
Example
stringbuf ss,ss2;
ss.str("hello, world!");
ss2.str(ss.str());

basic_ostringstream

Overview

basic_ostringstream are designed to send outputs to sources such as strings.

Details

The class template basic_ostringstream provides support for high level output operations on character streams based on strings. The supported operations include formatted output (e.g. integer values or whitespace-separated characters and characters strings) and unformatted output (e.g. raw characters and character arrays). 

Syntax

template<class CharT, class Traits = char_traits<CharT>, class Alloc = allocator<charT>> 
class basic_ostringstream: public basic_istream<CharT,Traits> 

where CharT can be char or wchar_t. It's derived from basic_ostream class.

member types

Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
allocator_type	Allocator<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.

Constructor

Name	Description
basic_ostringstream (ios_base::openmode mode = ios_base::out) basic_ostringstream (const basic_string& s, ios_base::openmode mode = ios_base::out)	Constructs an empty basic_istreamstream object. Constructs basic_istreamstream object with the content from s. The mode constants are defined in ios_base class. Example ostringstream s, s2 {"hello, world!"};

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
ostringstream s {"hello, world!"};
auto sb = s.rdbuf();
void str
(const basic_string& s) 
basic_string str()
Sets the current contents of the stream to s
Returns the current contents of the stream as string.
Example
ostringstream ss, ss2;
ss.str("hello, world!");
ss2.str(ss.str());

basic_istringstream

Overview

basic_istringstream are designed to receive inputs from sources such as strings.

Details

The class template basic_istringstream provides support for high level input operations on character streams based on strings. The supported operations include formatted input (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input (e.g. raw characters and character arrays). 

Syntax

template<class CharT, class Traits = char_traits<CharT>, class Alloc = allocator<charT>> 
class basic_istringstream: public basic_istream<CharT,Traits> 

where CharT can be char or wchar_t. It's derived from basic_istream class.

member types

Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
allocator_type	Allocator<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.

Constructor

Name	Description
basic_istringstream (ios_base::openmode mode = ios_base::in) basic_istringstream (const basic_string& s, ios_base::openmode mode = ios_base::in)	Constructs an empty basic_istringstream object. Constructs basic_istringstream object with the content from s. The mode constants are defined in ios_base class. Example istringstream s, s2 {"hello, world!"};

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
istringstream s {"hello, world!"};
auto sb = s.rdbuf();
void str
(const basic_string& s) 
basic_string str()
Sets the current contents of the stream to s
Returns the current contents of the stream as string.
Example
istringstream ss,ss2;
ss.str("hello, world!");
ss2.str(ss.str());

basic_filebuf

Overview

basic_filebuf is a template based class used for read from or/and write to files in the file system.

Details

ifstream, ofstream and fstream classes uses a basic_filebuf to read from or/and write to files. It's derived from basic_streambuf class.

Syntax

template<class CharT, class Traits = char_traits<CharT>> 
class basic_filebuf:public basic_streambuf<CharT,Traits> 

where CharT can be char or wchar_t.

member types

Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append. These are used in calls such as fopen(). These are bitmask type flags that can be ORed. The following describes different values.

Name	Description
in	Open file for reading.
out	Open file for writing.
ate	Set the stream's position indicator to the end of the stream on opening.
app	Set the stream's position indicator to the end of the stream before each output operation.
trunc	Any current content is discarded, assuming a length of zero on opening.
binary	Consider stream as binary rather than text.

Note it's possible to have multiple flags set. i.e., in | out set at the same time.
Note that in case of ate, writes can be on done anywhere in the stream. For example, begin or middle. In case of app, writes can be done only in the end.
Note that difference between text and binary files is that in a text file individual lines are demarcated by a newline character \n or \r\n. In case of binary files there are no such demarcation.

Methods

These are the public functions available for the clients like ifstream, ofstream and fstream classes.

Name
Description
bool is_open()
Checks if the file stream has an associated file.
Returns true if it's open. Otherwise, false.
basic_filebuf* open
(const char* filename, 
ios_base::openmode mode)
basic_filebuf* open
(const string& filename, 
ios_base::openmode mode)
Opens and associates the file with name filename with the file stream.
If the call fails, returns nullptr, otherwise returns this.
Calls the first version with open(filename.c_str(),mode)
The mode constants are defined in ios_base class. 
If the mode has both ios_base::trunc and ios_base::app set, the opening operation fails. It also fails if ios_base::trunc is set but ios_base::out is not.
void close()
Closes the file currently associated with the object, disassociating it from the stream.
Any pending output sequence is written to the file.
Example
filebuf file;
    
file.open("/usr/share/dict/words",ios_base::in);
bool bsuccess = file.is_open();
file.close();

file.open("test.txt",ios_base::out);
bsuccess = file.is_open();
file.close();

basic_ofstream

Overview

basic_ofstream are designed to send  outputs from destinations such as file system.

Details

The class template basic_ofstream provides support for high level output operations on character streams based on file systems. The supported operations include formatted output (e.g. integer values or whitespace-separated characters and characters strings) and unformatted output (e.g. raw characters and character arrays). 

Syntax

template<class CharT, class Traits = char_traits<CharT>> 
class basic_ofstream: public basic_ostream<CharT,Traits> 

where CharT can be char or wchar_t. It's derived from basic_istream class.

member types

Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append.

Constructor

Name

Description

basic_ofstream (const char* filename, ios_base::openmode mode = ios_base::out) basic_ofstream (const string& filename, ios_base::openmode mode = ios_base::out)

Constructs a basic_ofstream object, initially associated with the file identified by its first argument (filename), open with the mode specified by mode. Internally, its basic_ostream base constructor is passed a pointer to a newly constructed basic_filebuf object.  Then, basic_filebuf::open(filename,mode)  is called. If the call fails, the stream's failbit flag is set. Calls the first version with basic_ifstream(filename.c_str(),mode) The mode constants are defined in ios_base class. Example ofstream file("test.txt"); bool bsuccess = (!file);

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
ofstream file("test.txt");
auto sb = file.rdbuf();
bool is_open()
Checks if the file stream has an associated file.
Effectively calls rdbuf()->is_open().

Example
ofstream file("test.txt");
bool bsuccess = file.is_open();
void open
(const char* filename, 
ios_base::openmode mode = ios_base::out)
void  open
(const string& filename, 
ios_base::openmode mode = ios_base::out)
Opens and associates the file with name filename with the file stream.
Internally, calls rdbuf()->open(filename,mode).
If the call fails, the stream's failbit flag is set. If the stream is already associated with a file (i.e., it is already open), calling this function fails.
Calls the first version with open(filename.c_str(),mode)
The mode constants are defined in ios_base class.

Example
ifstream file;
file.open("test.txt");
void close()
Closes the file currently associated with the object, disassociating it from the stream.
Any pending output sequence is written to the file.
Effectively calls rdbuf()->close(). If an error occurs during operation, setstate(failbit) is called.

Example
ofstream file("test.txt");
file.close();

basic_ifstream

Overview

basic_ifstream are designed to receive inputs from sources such as file system.

Details

The class template basic_ifstream provides support for high level input operations on character streams based on file systems. The supported operations include formatted input (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input (e.g. raw characters and character arrays).

Syntax

template<class CharT, class Traits = char_traits<CharT>> 
class basic_ifstream: public basic_istream<CharT,Traits> 

where CharT can be char or wchar_t. It's derived from basic_istream class.

member types
Following properties are defined.

Name	Definition
char_type	char,wchar_t
traits_type	char_traits<char_type>
int_type	char_traits<char_type>::int_type
pos_type	char_traits<char_type>::pos_type
off_type	char_traits<char_type>::off_type

openmode➹

The openmode flags indicate how the streams such as disk files or memory streams can be opened for IO operations such as read, write or append. 

Constructor

Name

Description

basic_ifstream (const char* filename, ios_base::openmode mode = ios_base::in) basic_ifstream (const string& filename, ios_base::openmode mode = ios_base::in)

Constructs a basic_ifstream object, initially associated with the file identified by its first argument (filename), open with the mode specified by mode. Internally, its basic_istream base constructor is passed a pointer to a newly constructed basic_filebuf object.  Then, basic_filebuf::open(filename,mode)  is called. If the call fails, the stream's failbit flag is set. Calls the first version with basic_ifstream(filename.c_str(),mode) The mode constants are defined in ios_base class. Example ifstream file("/usr/share/dict/words"); bool bsuccess = (!file);

Methods

Name
Description
basic_streambuf* rdbuf()
Returns pointer to the underlying raw file device object.

Example
ifstream file("/usr/share/dict/words");
auto sb = file.rdbuf();
bool is_open()
Checks if the file stream has an associated file.
Effectively calls rdbuf()->is_open().

Example
ifstream file("/usr/share/dict/words");
bool bsuccess = file.is_open();
void open
(const char* filename, 
ios_base::openmode mode = ios_base::in)
void  open
(const string& filename, 
ios_base::openmode mode = ios_base::in)
Opens and associates the file with name filename with the file stream.
Internally, calls rdbuf()->open(filename,mode).
If the call fails, the stream's failbit flag is set. If the stream is already associated with a file (i.e., it is already open), calling this function fails.
Calls the first version with open(filename.c_str(),mode)
The mode constants are defined in ios_base class.

Example
ifstream file;
file.open("/usr/share/dict/words");
void close()
Closes the file currently associated with the object, disassociating it from the stream.
Any pending output sequence is written to the file.
Effectively calls rdbuf()->close(). If an error occurs during operation, setstate(failbit) is called.

Example
ifstream file;
file.open("/usr/share/dict/words");
file.close();