C++ istream::isfx方法代码示例

ios::iostate __getaline( istream &istrm, char *buf, int len,
/***************************************************************/
    char delim, int is_get, int &chars_read ) {
// Read characters into buffer "buf".
// At most "len - 1" characters are read, and a 0 is added at the end.
// If "delim" is encountered, it is left in the stream and the read is
// terminated (and the NULLCHAR is added).
// Used by:
//    get( char *buf, int len, char delim )
//    getline( char *buf, int len, char delim )
//
// NOTE: Borland sets eofbit only. A full buffer just stops reading.
//       If something has been read, set eofbit anyway.
//
//       The proposed standard says to set failbit if the buffer is filled
//       without finding the delimiter (if doing a "getline"), or if a read
//       fails and no characters are extracted. It says nothing about eofbit.
//
//       Currently we set eofbit only if eof occurs on first character read.
//       failbit is set if no characters were read.
//
//       Failbit was being set (prior to Nov15,95) when len-1 characters were
//       read in the buffer.  At that time we discerned that no one else
//       was setting failbit in that case, so we stopped doing it.

    int           c;
    int           offset;
    ios::iostate  state = 0;
    streambuf    *sb;

    offset = 0;
    __lock_it( istrm.__i_lock );
    if( len > 1 && istrm.ipfx( 1 ) ) {
        sb = istrm.rdbuf();
        __lock_it( sb->__b_lock );
        len--;  // leave a space for the NULLCHAR
        while( offset < len ) {
            c = sb->speekc();
            if( c == EOF ) {
                if( offset == 0 ) {
                    state |= ios::eofbit;
                }
                break;
            }
            if( c == delim ) {
                if( !is_get ) {
                    sb->sbumpc();
                }
                break;
            }
            buf[offset++] = (char)c;
            sb->sbumpc();
        }
        istrm.isfx();
    }
    buf[offset]  = '\0';
    chars_read = offset;

    // the draft standard says that no characters is an
    // error if using get() or getline().
    // the IOStreams Handbook suggests that no characters is not
    // an error if the delim was seen, this seems to be what our
    // competitors do.
    if( (offset == 0) && (c != delim) ) {
        state |= ios::failbit;
    }
    // the draft standard says that len-1 characters is an
    // error if using getline()
    // our competitors don't agree with the draft, we won't follow the
    // draft either
    #if 0
    if( offset == len && !is_get ) {
        state |= ios::failbit;
    }
    #endif
    return( state );
}