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Difference between revisions of "cpp/io/basic ostringstream"

From cppreference.com
< cpp‎ | io
(no, this certainly does not belong in the lead (and the construction isn't what's expensive anyway).)
(make the description more understandable)
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The class template {{tt|std::basic_ostringstream}} implements output operations on memory ({{lc|std::basic_string}}) based streams. It essentially wraps a raw string device implementation ({{lc|std::basic_stringbuf}}) into a higher-level interface ({{lc|std::basic_ostream}}). The complete interface to unique {{tt|std::basic_stringbuf}} members is provided.
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The class template {{tt|std::basic_ostringstream}} implements output operations on string based streams. It effectively stores an instance of {{lc|std::basic_string}} and performs output operations to it.
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At the low level, the class essentially wraps a raw string device implementation of {{lc|std::basic_stringbuf}} into a higher-level interface of {{lc|std::basic_ostream}}. The complete interface to unique {{tt|std::basic_stringbuf}} members is provided.
  
 
{{inheritance diagram/std-basic_ostringstream}}
 
{{inheritance diagram/std-basic_ostringstream}}

Revision as of 10:19, 10 August 2019

 
C++
 
Input/output library
 
std::basic_ostringstream
 
Defined in header <sstream>
template<

    class CharT,
    class Traits = std::char_traits<CharT>

> class basic_ostringstream;
 (until C++11)
template<

    class CharT,
    class Traits = std::char_traits<CharT>,
    class Allocator = std::allocator<CharT>

> class basic_ostringstream;
 (since C++11)

The class template std::basic_ostringstream implements output operations on string based streams. It effectively stores an instance of std::basic_string and performs output operations to it.

At the low level, the class essentially wraps a raw string device implementation of std::basic_stringbuf into a higher-level interface of std::basic_ostream. The complete interface to unique std::basic_stringbuf members is provided.

cpp/io/ios basecpp/io/basic ioscpp/io/basic ostreamstd-basic ostringstream-inheritance.svg

Inheritance diagram

Two specializations for common character types are also defined:

Defined in header <sstream>
Type Definition
ostringstream basic_ostringstream<char>
wostringstream basic_ostringstream<wchar_t>

Contents

Member types

Member type Definition
char_type CharT[edit]
traits_type Traits; the program is ill-formed if Traits::char_type is not CharT.[edit]
int_type Traits::int_type[edit]
pos_type Traits::pos_type[edit]
off_type Traits::off_type[edit]
allocator_type Allocator[edit]

Member functions

 constructs the string stream
(public member function) [edit]
(C++11)
 moves the string stream
(public member function) [edit]
(C++11)
 swaps two string streams
(public member function) [edit]
returns the underlying raw string device object
(public member function) [edit]
String operations
gets or sets the contents of underlying string device object
(public member function) [edit]

Non-member functions

(C++11)
 specializes the std::swap algorithm
(function template) [edit]

Inherited from std::basic_ostream

Member functions

Formatted output
inserts formatted data
(public member function of std::basic_ostream<CharT,Traits>) [edit]
Unformatted output
inserts a character
(public member function of std::basic_ostream<CharT,Traits>) [edit]
inserts blocks of characters
(public member function of std::basic_ostream<CharT,Traits>) [edit]
Positioning
returns the output position indicator
(public member function of std::basic_ostream<CharT,Traits>) [edit]
sets the output position indicator
(public member function of std::basic_ostream<CharT,Traits>) [edit]
Miscellaneous
synchronizes with the underlying storage device
(public member function of std::basic_ostream<CharT,Traits>) [edit]

Member classes

 implements basic logic for preparation of the stream for output operations
(public member class of std::basic_ostream<CharT,Traits>) [edit]

Inherited from std::basic_ios

Member types

Member type Definition
char_type CharT
traits_type Traits
int_type Traits::int_type
pos_type Traits::pos_type
off_type Traits::off_type

Member functions

State functions
checks if no error has occurred i.e. I/O operations are available
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if end-of-file has been reached
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if an error has occurred
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if a non-recoverable error has occurred
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if an error has occurred (synonym of fail())
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if no error has occurred (synonym of !fail())
(public member function of std::basic_ios<CharT,Traits>) [edit]
returns state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
sets state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
modifies state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
Formatting
copies formatting information
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages the fill character
(public member function of std::basic_ios<CharT,Traits>) [edit]
Miscellaneous
manages exception mask
(public member function of std::basic_ios<CharT,Traits>) [edit]
sets the locale
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages associated stream buffer
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages tied stream
(public member function of std::basic_ios<CharT,Traits>) [edit]
narrows characters
(public member function of std::basic_ios<CharT,Traits>) [edit]
widens characters
(public member function of std::basic_ios<CharT,Traits>) [edit]

Inherited from std::ios_base

Member functions

Formatting
manages format flags
(public member function of std::ios_base) [edit]
sets specific format flag
(public member function of std::ios_base) [edit]
clears specific format flag
(public member function of std::ios_base) [edit]
manages decimal precision of floating point operations
(public member function of std::ios_base) [edit]
manages field width
(public member function of std::ios_base) [edit]
Locales
sets locale
(public member function of std::ios_base) [edit]
returns current locale
(public member function of std::ios_base) [edit]
Internal extensible array
[static]
 returns a program-wide unique integer that is safe to use as index to pword() and iword()
(public static member function of std::ios_base) [edit]
resizes the private storage if necessary and access to the long element at the given index
(public member function of std::ios_base) [edit]
resizes the private storage if necessary and access to the void* element at the given index
(public member function of std::ios_base) [edit]
Miscellaneous
registers event callback function
(public member function of std::ios_base) [edit]
[static]
 sets whether C++ and C I/O libraries are interoperable
(public static member function of std::ios_base) [edit]
Member classes
stream exception
(public member class of std::ios_base) [edit]
initializes standard stream objects
(public member class of std::ios_base) [edit]

Member types and constants

Type Explanation
stream open mode type

The following constants are also defined:

Constant Explanation[edit]
app seek to the end of stream before each write[edit]
binary open in binary mode[edit]
in open for reading[edit]
out open for writing[edit]
trunc discard the contents of the stream when opening[edit]
ate seek to the end of stream immediately after open[edit]
noreplace (C++23) open in exclusive mode[edit]

(typedef) [edit]
formatting flags type

The following constants are also defined:

Constant Explanation[edit]
dec use decimal base for integer I/O: see std::dec[edit]
oct use octal base for integer I/O: see std::oct[edit]
hex use hexadecimal base for integer I/O: see std::hex[edit]
basefield dec | oct | hex. Useful for masking operations[edit]
left left adjustment (adds fill characters to the right): see std::left[edit]
right right adjustment (adds fill characters to the left): see std::right[edit]
internal internal adjustment (adds fill characters to the internal designated point): see std::internal[edit]
adjustfield left | right | internal. Useful for masking operations[edit]
scientific generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific[edit]
fixed generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed[edit]
floatfield scientific | fixed. Useful for masking operations[edit]
boolalpha insert and extract bool type in alphanumeric format: see std::boolalpha[edit]
showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase[edit]
showpoint generate a decimal-point character unconditionally for floating-point number output: see std::showpoint[edit]
showpos generate a + character for non-negative numeric output: see std::showpos[edit]
skipws skip leading whitespace before certain input operations: see std::skipws[edit]
unitbuf flush the output after each output operation: see std::unitbuf[edit]
uppercase replace certain lowercase letters with their uppercase
equivalents in certain output operations: see std::uppercase[edit]

(typedef) [edit]
state of the stream type

The following constants are also defined:

Constant Explanation[edit]
goodbit no error[edit]
badbit irrecoverable stream error[edit]
failbit input/output operation failed (formatting or extraction error)[edit]
eofbit associated input sequence has reached end-of-file[edit]

(typedef) [edit]
seeking direction type

The following constants are also defined:

Constant Explanation[edit]
beg the beginning of a stream[edit]
end the ending of a stream[edit]
cur the current position of stream position indicator[edit]

(typedef) [edit]
specifies event type
(enum) [edit]
callback function type
(typedef) [edit]
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