std::basic_streambuf::in_avail

• If the get pointer (gptr) has a value and this is less than the end pointer (egptr): The function returns the number of characters directly available at the get pointer before the end pointer (i.e., it returns (egptr()-gptr()) without calling any virtual member function).
• If the get pointer (gptr) is either null or has reached the end pointer (egptr): The function calls the protected virtual member function showmanyc to obtain the number of characters expected to be available after an underflow.

Parameters

Return Value

Example

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// get file size using pubseekoff
#include <iostream>     // std::cout, std::streambuf, std::streamsize
#include <fstream>      // std::ifstream
int main () {
  std::ifstream ifs ("test.txt");
  if (ifs.good()) {
    std::streambuf* pbuf = ifs.rdbuf();
    char c; ifs >> c;
    std::streamsize size = pbuf->in_avail();
    std::cout << "first character in file: " << c << '\n';
    std::cout << size << " characters in buffer after it\n";
  }
  ifs.close();
  return 0;
}

Data races

Exception safety

See also

basic_streambuf::gptr

Pointer to current position of input sequence (protected member function)

basic_streambuf::egptr

Pointer to end of input sequence (protected member function)

basic_streambuf::showmanyc

Get number of characters available (protected virtual member function)

basic_filebuf::showmanyc

Get number of characters available (public member function)