C++

參考

<fstream>

basic_filebuf

protected virtual member function
<fstream>

std::basic_filebuf::uflow

int_type uflow();
Get character on overflow and advance position
Returns the character at the current input position, and advances the input position pointer.

Before that, this function attempts to read characters from the associated file and -if the object keeps an intermediate buffer- makes them available by altering the internal input buffer pointers (gptr, egptr and eback) as needed.

If there are no more characters available and the function did not succeed in reading more characters from the associated file, it returns the end-of-file value (traits_type::eof()), indicating failure.

This virtual member function overrides the inherited member basic_streambuf::uflow, called by members such as sbumpc to request a new character when there are no read positions available at the get pointer (gptr).

The behavior of this member function is similar to that of underflow, except that this function advances the input position.

引數

無

返回值

受控輸入序列當前位置的字元，使用成員 traits_type::to_int_type 轉換為 int_type 型別的值。
If there are no more characters to read from the controlled input sequence, it returns the end-of-file value (traits_type::eof()).
成員型別int_type是能夠表示任何字元值或特殊*檔案結束*符的整型。

資料競爭

修改 basic_filebuf 物件。
同時訪問同一個檔案流緩衝區物件可能導致資料爭用。

異常安全

基本保證：如果丟擲異常，*檔案流緩衝區*處於有效狀態。

另見

basic_filebuf::underflow
在下溢時獲取字元 (保護虛成員函式)
basic_streambuf::uflow
在下溢時獲取字元並前進位置 (保護虛成員函式)
basic_streambuf::sbumpc
獲取當前字元並前進到下一個位置 (公有成員函式)