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Difference between revisions of "cpp/io"

From cppreference.com
< cpp
m
(templatize)
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{{dsc h2 | Abstraction}}
 
{{dsc h2 | Abstraction}}
 
{{dsc header | ios }}
 
{{dsc header | ios }}
−
{{dsc class | cpp/io/ios_base | manages formatting flags and input/output exceptions}}
+
{{dsc inc | cpp/io/dsc ios_base}}
−
{{dsc tclass | cpp/io/basic_ios | manages an arbitrary stream buffer}}
+
{{dsc inc | cpp/io/dsc basic_ios}}
 
{{dsc header | streambuf }}
 
{{dsc header | streambuf }}
−
{{dsc tclass | cpp/io/basic_streambuf | abstracts a raw device}}
+
{{dsc inc | cpp/io/dsc basic_streambuf}}
 
{{dsc header | ostream }}
 
{{dsc header | ostream }}
−
{{dsc tclass | cpp/io/basic_ostream | wraps a given abstract device ({{lc|std::basic_streambuf}})<br/> and provides high-level output interface}}
+
{{dsc inc | cpp/io/dsc basic_ostream}}
 
{{dsc header | istream }}
 
{{dsc header | istream }}
−
{{dsc tclass | cpp/io/basic_istream | wraps a given abstract device ({{lc|std::basic_streambuf}})<br/> and provides high-level input interface}}
+
{{dsc inc | cpp/io/dsc basic_istream}}
−
{{dsc tclass | cpp/io/basic_iostream | wraps a given abstract device ({{lc|std::basic_streambuf}})<br/> and provides high-level input/output interface}}
+
{{dsc inc | cpp/io/dsc basic_iostream}}
 
{{dsc h2 | File I/O implementation}}
 
{{dsc h2 | File I/O implementation}}
 
{{dsc header | fstream }}
 
{{dsc header | fstream }}
−
{{dsc tclass | cpp/io/basic_filebuf | implements raw file device}}
+
{{dsc inc | cpp/io/dsc basic_filebuf}}
−
{{dsc tclass | cpp/io/basic_ifstream | implements high-level file stream input operations}}
+
{{dsc inc | cpp/io/dsc basic_ifstream}}
−
{{dsc tclass | cpp/io/basic_ofstream | implements high-level file stream output operations}}
+
{{dsc inc | cpp/io/dsc basic_ofstream}}
−
{{dsc tclass | cpp/io/basic_fstream | implements high-level file stream input/output operations}}
+
{{dsc inc | cpp/io/dsc basic_fstream}}
 
{{dsc h2 | String I/O implementation}}
 
{{dsc h2 | String I/O implementation}}
 
{{dsc header | sstream }}
 
{{dsc header | sstream }}
−
{{dsc tclass | cpp/io/basic_stringbuf | implements raw string device}}
+
{{dsc inc | cpp/io/dsc basic_stringbuf}}
−
{{dsc tclass | cpp/io/basic_istringstream | implements high-level string stream input operations}}
+
{{dsc inc | cpp/io/dsc basic_istringstream}}
−
{{dsc tclass | cpp/io/basic_ostringstream | implements high-level string stream output operations}}
+
{{dsc inc | cpp/io/dsc basic_ostringstream}}
−
{{dsc tclass | cpp/io/basic_stringstream | implements high-level string stream input/output operations}}
+
{{dsc inc | cpp/io/dsc basic_stringstream}}
 
{{dsc h2 | Array I/O implementations}}
 
{{dsc h2 | Array I/O implementations}}
 
{{dsc header | strstream }}
 
{{dsc header | strstream }}
−
{{dsc class | cpp/io/strstreambuf | notes={{mark deprecated}} | implements raw character array device}}
+
{{dsc inc | cpp/io/dsc strstreambuf}}
−
{{dsc class | cpp/io/istrstream | notes={{mark deprecated}} | implements character array input operations}}
+
{{dsc inc | cpp/io/dsc istrstream}}
−
{{dsc class | cpp/io/ostrstream | notes={{mark deprecated}} | implements character array output operations}}
+
{{dsc inc | cpp/io/dsc ostrstream}}
−
{{dsc class | cpp/io/strstream | notes={{mark deprecated}} | implements character array input/output operations}}
+
{{dsc inc | cpp/io/dsc strstream}}
 
{{dsc h2 | Synchronized output }}
 
{{dsc h2 | Synchronized output }}
 
{{dsc header | syncstream }}
 
{{dsc header | syncstream }}
−
{{dsc tclass | cpp/io/basic_syncbuf | synchronized output device wrapper|notes={{mark c++20}}}}
+
{{dsc inc | cpp/io/dsc basic_syncbuf}}
−
{{dsc tclass | cpp/io/basic_osyncstream | synchronized output stream wrapper|notes={{mark c++20}}}}
+
{{dsc inc | cpp/io/dsc basic_osyncstream}}
 
{{dsc end}}
 
{{dsc end}}
  
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The following typedefs for common character types are provided:
 
The following typedefs for common character types are provided:
  
−
<source lang="cpp">
+
{{source|
 
typedef basic_ios<char>                ios;
 
typedef basic_ios<char>                ios;
 
typedef basic_ios<wchar_t>            wios;
 
typedef basic_ios<wchar_t>            wios;
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typedef basic_stringstream<wchar_t>  wstringstream;
 
typedef basic_stringstream<wchar_t>  wstringstream;
  
−
typedef basic_osyncstream<char>   osyncstream;
+
typedef basic_osyncstream<char>     osyncstream;
 
typedef basic_osyncstream<wchar_t> wosyncstream;
 
typedef basic_osyncstream<wchar_t> wosyncstream;
−
</source>
+
}}
  
 
====Predefined standard stream objects====
 
====Predefined standard stream objects====
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{{dsc begin}}
 
{{dsc begin}}
 
{{dsc header | ios }}
 
{{dsc header | ios }}
−
{{dsc typedef | cpp/io/streamoff | represents relative file/stream position (offset from fpos), sufficient to represent any file size }}
+
{{dsc inc | cpp/io/dsc streamoff}}
−
{{dsc typedef | cpp/io/streamsize | represents the number of characters transferred in an I/O operation or the size of an I/O buffer}}
+
{{dsc inc | cpp/io/dsc streamsize}}
−
{{dsc tclass  | cpp/io/fpos | represents absolute position in a stream or a file}}
+
{{dsc inc | cpp/io/dsc fpos}}
 
{{dsc end}}
 
{{dsc end}}
  

Revision as of 17:52, 25 November 2018

 
C++
 
Input/output library
 

C++ includes two input/output libraries: a modern, stream-based I/O library and the standard set of C-style I/O functions.

Contents

Stream-based I/O

The stream-based input/output library is organized around abstract input/output devices. These abstract devices allow the same code to handle input/output to files, memory streams, or custom adaptor devices that perform arbitrary operations (e.g. compression) on the fly.

Most of the classes are templated, so they can be adapted to any basic character type. Separate typedefs are provided for the most common basic character types (char and wchar_t). The classes are organized into the following hierarchy:

cpp/io/ios basecpp/io/basic ioscpp/io/basic istreamcpp/io/basic ifstreamcpp/io/basic istringstreamcpp/io/basic ostreamcpp/io/basic ofstreamcpp/io/basic ostringstreamcpp/io/basic fstreamcpp/io/basic stringstreamcpp/io/basic iostreamstd-io-complete-inheritance.svg

Inheritance diagram

Abstraction
Defined in header <ios>
manages formatting flags and input/output exceptions
(class) [edit]
manages an arbitrary stream buffer
(class template) [edit]
Defined in header <streambuf>
abstracts a raw device
(class template) [edit]
Defined in header <ostream>
wraps a given abstract device (std::basic_streambuf)
and provides high-level output interface
(class template) [edit]
Defined in header <istream>
wraps a given abstract device (std::basic_streambuf)
and provides high-level input interface
(class template) [edit]
wraps a given abstract device (std::basic_streambuf)
and provides high-level input/output interface
(class template) [edit]
File I/O implementation
Defined in header <fstream>
implements raw file device
(class template) [edit]
implements high-level file stream input operations
(class template) [edit]
implements high-level file stream output operations
(class template) [edit]
implements high-level file stream input/output operations
(class template) [edit]
String I/O implementation
Defined in header <sstream>
implements raw string device
(class template) [edit]
implements high-level string stream input operations
(class template) [edit]
implements high-level string stream output operations
(class template) [edit]
implements high-level string stream input/output operations
(class template) [edit]
Array I/O implementations
Defined in header <strstream>
(deprecated in C++98)(removed in C++26)
 implements raw character array device
(class) [edit]
(deprecated in C++98)(removed in C++26)
 implements character array input operations
(class) [edit]
(deprecated in C++98)(removed in C++26)
 implements character array output operations
(class) [edit]
(deprecated in C++98)(removed in C++26)
 implements character array input/output operations
(class) [edit]
Synchronized output
Defined in header <syncstream>
(C++20)
 synchronized output device wrapper
(class template) [edit]
(C++20)
 synchronized output stream wrapper
(class template) [edit]

Typedefs

The following typedefs for common character types are provided: 

typedef basic_ios<char>                ios;
typedef basic_ios<wchar_t>            wios;
 
typedef basic_streambuf<char>     streambuf;
typedef basic_streambuf<wchar_t> wstreambuf;
typedef basic_filebuf<char>         filebuf;
typedef basic_filebuf<wchar_t>     wfilebuf;
typedef basic_stringbuf<char>     stringbuf;
typedef basic_stringbuf<wchar_t> wstringbuf;
typedef basic_syncbuf<char>         syncbuf;
typedef basic_syncbuf<wchar_t>     wsyncbuf;
 
typedef basic_istream<char>         istream;
typedef basic_istream<wchar_t>     wistream;
typedef basic_ostream<char>         ostream;
typedef basic_ostream<wchar_t>     wostream;
typedef basic_iostream<char>       iostream;
typedef basic_iostream<wchar_t>   wiostream;
 
typedef basic_ifstream<char>       ifstream;
typedef basic_ifstream<wchar_t>   wifstream;
typedef basic_ofstream<char>       ofstream;
typedef basic_ofstream<wchar_t>   wofstream;
typedef basic_fstream<char>         fstream;
typedef basic_fstream<wchar_t>     wfstream;
 
typedef basic_istringstream<char>     istringstream;
typedef basic_istringstream<wchar_t> wistringstream;
typedef basic_ostringstream<char>     ostringstream;
typedef basic_ostringstream<wchar_t> wostringstream;
typedef basic_stringstream<char>       stringstream;
typedef basic_stringstream<wchar_t>   wstringstream;
 
typedef basic_osyncstream<char>     osyncstream;
typedef basic_osyncstream<wchar_t> wosyncstream;

Predefined standard stream objects

Defined in header <iostream>
reads from the standard C input stream stdin
(global object)[edit]
writes to the standard C output stream stdout
(global object)[edit]
writes to the standard C error stream stderr, unbuffered
(global object)[edit]
writes to the standard C error stream stderr
(global object)[edit]

I/O Manipulators

The stream-based I/O library uses I/O manipulators (e.g. std::boolalpha, std::hex, etc.) to control how streams behave.

Types

The following auxiliary types are defined:

Defined in header <ios>
represents relative file/stream position (offset from fpos), sufficient to represent any file size
(typedef) [edit]
represents the number of characters transferred in an I/O operation or the size of an I/O buffer
(typedef) [edit]
represents absolute position in a stream or a file
(class template) [edit]

The following specializations of std::fpos are provided:

Defined in header <ios>
Type Definition
streampos std::fpos<std::char_traits<char>::state_type>
wstreampos std::fpos<std::char_traits<wchar_t>::state_type>

Error category interface

Defined in header <ios>
(C++11)
 the IO stream error codes
(enum) [edit]
(C++11)
 identifies the iostream error category
(function) [edit]

C-style IO

C++ also includes the input/output functions defined by C, such as std::fopen, std::getc, etc.

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