Namespaces
Variants
Views
Actions

std::basic_istream::read

From cppreference.com
< cpp‎ | io‎ | basic istream
Revision as of 06:49, 14 June 2013 by P12 (Talk | contribs)

basic_istream& read( char_type* s, std::streamsize count );

Extracts characters from stream.

Behaves as UnformattedInputFunction. After constructing and checking the sentry object, extracts characters and stores them into successive locations of the character array whose first element is pointed to by s. Characters are extracted and stored until any of the following conditions occurs:

  • count characters were extracted and stored
  • end of file condition occurs on the input sequence (in which case, setstate(failbit|eofbit) is called. The number of successfully extracted characters can be queried using gcount().

Contents

Parameters

s - pointer to the character array to store the characters to
count - number of characters to read

Return value

*this

Exceptions

failure if an error occurred (the error state flag is not goodbit) and exceptions() is set to throw for that state.

If an internal operation throws an exception, it is caught and badbit is set. If exceptions() is set for badbit, the exception is rethrown.

Example

read() is often used for binary I/O

#include <iostream>
#include <string>
#include <sstream>
#include <cstdint>
 
int main()
{
    std::string bin = {'\x12', '\x12', '\x12', '\x12'};
    std::istringstream raw(bin);
    std::uint32_t n;
    raw.read(reinterpret_cast<char*>(&n), sizeof n);
    std::cout << std::hex << std::showbase << n << '\n';
}

Output:

0x12121212

See also

inserts blocks of characters
(public member function of std::basic_ostream) [edit]
extracts formatted data
(public member function) [edit]
extracts already available blocks of characters
(public member function) [edit]
extracts characters
(public member function) [edit]
extracts characters until the given character is found
(public member function) [edit]
reads from a file
(function) [edit]