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std::basic_...m::readsome(3) C++ Standard Libary std::basic_...m::readsome(3) NAME std::basic_istream::readsome - std::basic_istream::readsome Synopsis std::streamsize readsome( char_type* s, std::streamsize count ); Extracts up to count immediately available characters from the input stream. The extracted characters are stored into the character array pointed to by s. Behaves as UnformattedInputFunction. After constructing and checking the sentry object, * If rdbuf()->in_avail() == -1, calls setstate(eofbit) and ex- tracts no characters. * If rdbuf()->in_avail() == 0, extracts no characters. * If rdbuf()->in_avail() > 0, extracts std::min(rd- buf()->in_avail(), count) characters and stores them into successive locations of the character array whose first element is pointed to by s. Parameters s - pointer to the character array to store the characters to count - maximum number of characters to read Return value The number of characters actually extracted. 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 bad- bit is set. If exceptions() is set for badbit, the exception is rethrown. Notes The behavior of this function is highly implementation-specific. For example, when used with std::ifstream, some library implementations fill the un- derlying filebuf with data as soon as the file is opened (and readsome() on such im- plementations reads data, potentially, but not necessarily, the entire file), while other implementations only read from file when an actual input operation is requested (and readsome() issued after file opening never extracts any characters). Likewise, a call to std::cin.readsome() may return all pending unprocessed con- sole input, or may always return zero and extract no characters. Example // Run this code #include <iostream> #include <sstream> int main() { char c[10] = {}; std::istringstream input("This is sample text."); // std::string- buf makes its entire // buffer avail- able for unblocking read input.readsome(c, 5); // reads 'This ' and stores in c[0] .. c[4] input.readsome(c, 9); // reads 'is sample' and stores in c[0] .. c[8] std::cout << c; } Output: is sample See also read extracts blocks of characters (public member function) in_avail obtains the number of characters immediately available in the get area (public member function of std::basic_stream- buf<CharT,Traits>) http://cppreference.com 2022.07.31 std::basic_...m::readsome(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | See also
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