Extracts characters from stream.

Behaves asUnformattedInputFunction. 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 bys. 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 usinggcount().

[edit]Parameters

[edit]Return value

*this

[edit]Exceptions

If an internal operation throws an exception, it is caught andbadbit is set. Ifexceptions() is set forbadbit, the exception is rethrown.

[edit]Notes

When using a non-converting locale (the default locale is non-converting), the overrider of this function instd::basic_ifstream may be optimized for zero-copy bulk I/O (by means of overridingstd::streambuf::xsgetn).

[edit]Example

#include <cstdint>#include <fstream>#include <iostream>#include <sstream>#include <string> int main(){// read() is often used for binary I/Ostd::string bin={'\x12','\x12','\x12','\x12'};std::istringstream raw(bin);std::uint32_t n;if(raw.read(reinterpret_cast<char*>(&n), sizeof n))std::cout<<std::hex<<std::showbase<< n<<'\n'; // prepare file for next snippetstd::ofstream("test.txt", std::ios::binary)<<"abcd1\nabcd2\nabcd3"; // read entire file into stringif(std::ifstream is{"test.txt", std::ios::binary| std::ios::ate}){auto size= is.tellg();std::string str(size,'\0');// construct string to stream size        is.seekg(0);if(is.read(&str[0], size))std::cout<< str<<'\n';}}

0x12121212abcd1abcd2abcd3

[edit]See also

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