_istream.c

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  return __tmp;
}

template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>&
basic_istream<_CharT, _Traits>::get(_CharT& __c) {
  sentry __sentry(*this, _No_Skip_WS());
  this->_M_gcount = 0;

  if (__sentry) {
    typename _Traits::int_type __tmp = _Traits::eof();
    _STLP_TRY {
      __tmp = this->rdbuf()->sbumpc();
    }
    _STLP_CATCH_ALL {
      this->_M_handle_exception(ios_base::badbit);
    }

    if (!this->_S_eof(__tmp)) {
      this->_M_gcount = 1;
      __c = _Traits::to_char_type(__tmp);
    }
  }

  if (this->_M_gcount == 0)
    this->setstate(ios_base::eofbit | ios_base::failbit);

  return *this;
}


// Read characters and discard them.  The standard specifies a single
// function with two arguments, each with a default.  We instead use
// three overloded functions, because it's possible to implement the
// first two more efficiently than the fully general third version.
template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>& basic_istream<_CharT, _Traits>::ignore() {
  sentry __sentry(*this, _No_Skip_WS());
  this->_M_gcount = 0;

  if (__sentry) {
    int_type __c;
    _STLP_TRY {
      __c = this->rdbuf()->sbumpc();
    }
    _STLP_CATCH_ALL {
      this->_M_handle_exception(ios_base::badbit);
      return *this;
    }

    if (!this->_S_eof(__c))
      this->_M_gcount = 1;
    else
      this->setstate(ios_base::eofbit);
  }

  return *this;
}

// Putback

template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>&
basic_istream<_CharT, _Traits>::putback(_CharT __c) {
  this->_M_gcount = 0;
  sentry __sentry(*this, _No_Skip_WS());

  if (__sentry) {
    typename _Traits::int_type __tmp = _Traits::eof();
    basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
//    if (!__buf || this->_S_eof(__buf->sputbackc(__c)))
    if (__buf) {
      _STLP_TRY {
        __tmp = __buf->sputbackc(__c);
      }
      _STLP_CATCH_ALL {
        this->_M_handle_exception(ios_base::badbit);
      }
    }
    if (this->_S_eof(__tmp))
      this->setstate(ios_base::badbit);
  }
  else
    this->setstate(ios_base::failbit);

  return *this;
}

template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>& basic_istream<_CharT, _Traits>::unget() {
  this->_M_gcount = 0;

  sentry __sentry(*this, _No_Skip_WS());

  if (__sentry) {
    basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
    //     if (!__buf || _Traits::eq_int_type(__buf->sungetc(), _Traits::eof()))
    if (__buf) {
      _STLP_TRY {
        if (this->_S_eof(__buf->sungetc()))
          this->setstate(ios_base::badbit);
      }
      _STLP_CATCH_ALL {
        this->_M_handle_exception(ios_base::badbit);
      }
    } else
      this->setstate(ios_base::badbit);
  }
  else
    this->setstate(ios_base::failbit);

  return *this;
}

// Positioning and buffer control.

template <class _CharT, class _Traits>
int basic_istream<_CharT, _Traits>::sync() {
  sentry __sentry(*this, _No_Skip_WS());

  basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
  if (__buf) {
    if (__buf->pubsync() == -1) {
      this->setstate(ios_base::badbit);
      return -1;
    }
    else
      return 0;
  }
  else
    return -1;
}

template <class _CharT, class _Traits>
__BIS_pos_type__
basic_istream<_CharT, _Traits>::tellg() {
  sentry __sentry(*this, _No_Skip_WS());

  basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
  return (__buf && !this->fail()) ? __buf->pubseekoff(0, ios_base::cur, ios_base::in)
    : pos_type(-1);
}

template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>&
basic_istream<_CharT, _Traits>::seekg(pos_type __pos) {
  sentry __sentry(*this, _No_Skip_WS());

  basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
  if (!this->fail() && __buf) {
    if (__buf->pubseekpos(__pos, ios_base::in) == pos_type(-1)) {
      this->setstate(ios_base::failbit);
    }
  }
  return *this;
}

template <class _CharT, class _Traits>
basic_istream<_CharT, _Traits>&
basic_istream<_CharT, _Traits>::seekg(off_type __off, ios_base::seekdir __dir) {
  sentry __sentry(*this, _No_Skip_WS());

  basic_streambuf<_CharT, _Traits>* __buf = this->rdbuf();
  if (!this->fail() && __buf)
    __buf->pubseekoff(__off, __dir, ios_base::in);
  return *this;
}

// Formatted input of characters and character arrays.

template <class _CharT, class _Traits>
void basic_istream<_CharT, _Traits>::_M_formatted_get(_CharT& __c) {
//  typename _Traits::int_type __tmp = _Traits::eof();

  sentry __sentry(*this); // Skip whitespace.

  if (__sentry) {
    typename _Traits::int_type __tmp;// = _Traits::eof();

    _STLP_TRY {
      __tmp = this->rdbuf()->sbumpc();
    }
    _STLP_CATCH_ALL {
      this->_M_handle_exception(ios_base::badbit);
      return;
    }

    if (!this->_S_eof(__tmp))
      __c = _Traits::to_char_type(__tmp);
    else
      this->setstate(ios_base::eofbit | ios_base::failbit);
  }
}


//---------------------------------------------------------------------------
// istream's helper functions.

// A generic function for unbuffered input.  We stop when we reach EOF,
// or when we have extracted _Num characters, or when the function object
// __is_delim return true.  In the last case, it extracts the character
// for which __is_delim is true, if and only if __extract_delim is true.
// It appends a null character to the end of the string; this means that
// it may store up to _Num + 1 characters.
//
// __is_getline governs two corner cases: reading _Num characters without
// encountering delim or eof (in which case failbit is set if __is_getline
// is true); and reading _Num characters where the _Num+1'st character is
// eof (in which case eofbit is set if __is_getline is true).
//
// It is assumed that __is_delim never throws.
//
// Return value is the number of characters extracted, including the
// delimiter if it is extracted.  Note that the number of characaters
// extracted isn't necessarily the same as the number stored.

_STLP_MOVE_TO_PRIV_NAMESPACE

template < class _CharT, class _Traits, class _Is_Delim>
streamsize _STLP_CALL
__read_unbuffered(basic_istream<_CharT, _Traits>* __that, basic_streambuf<_CharT, _Traits>* __buf,
                  streamsize _Num, _CharT* __s,
                  _Is_Delim __is_delim,
                  bool __extract_delim, bool __append_null,
                  bool __is_getline)
{
  streamsize __n = 0;
  ios_base::iostate __status = 0;

  typedef typename basic_istream<_CharT, _Traits>::int_type int_type;
  // The operations that can potentially throw are sbumpc, snextc, and sgetc.
  _STLP_TRY {
    for (;;) {
      if (__n == _Num) {
        if (__is_getline) // didn't find delimiter as one of the _Num chars
          __status |= ios_base::failbit;
        break;
      }
      int_type __c = __buf->sbumpc(); // sschwarz

      if (__that->_S_eof(__c)) {
        if (__n < _Num || __is_getline)
          __status |= ios_base::eofbit;
        break;
      } else if (__is_delim(_Traits::to_char_type(__c))) {
        if (__extract_delim) { // Extract and discard current character.
          ++__n;
        } else if ( !__pushback(__buf, _Traits::to_char_type(__c)) ) { // leave delimiter
          __status |= ios_base::failbit;
        }
        break;
      }
      // regular character
      *__s++ = _Traits::to_char_type(__c);
      ++__n;
    }
  }
  _STLP_CATCH_ALL {
    __that->_M_handle_exception(ios_base::badbit);
    *__s = _STLP_DEFAULT_CONSTRUCTED(_CharT);
    return __n;
  }

  if (__append_null)
    *__s =  _STLP_DEFAULT_CONSTRUCTED(_CharT);
  if (__status)
    __that->setstate(__status);    // This might throw.
  return __n;
}

// Much like __read_unbuffered, but with one additional function object:
// __scan_delim(first, last) returns the first pointer p in [first, last)
// such that __is_delim(p) is true.

template < class _CharT, class _Traits, class _Is_Delim, class _Scan_Delim>
streamsize _STLP_CALL
__read_buffered(basic_istream<_CharT, _Traits>* __that, basic_streambuf<_CharT, _Traits>* __buf,
                 streamsize _Num, _CharT* __s,
                 _Is_Delim __is_delim, _Scan_Delim __scan_delim,
                 bool __extract_delim, bool __append_null,
                 bool __is_getline) {
  streamsize __n = 0;
  ios_base::iostate __status = 0;
  bool __done    = false;

  _STLP_TRY {
    while (__buf->_M_egptr() != __buf->_M_gptr() && !__done) {
      const _CharT* __first = __buf->_M_gptr();
      const _CharT* __last  = __buf->_M_egptr();
      //casting numeric_limits<ptrdiff_t>::max to streamsize only works is ptrdiff_t is signed or streamsize representation
      //is larger than ptrdiff_t one.
      _STLP_STATIC_ASSERT((sizeof(streamsize) > sizeof(ptrdiff_t)) ||
                          ((sizeof(streamsize) == sizeof(ptrdiff_t)) && numeric_limits<ptrdiff_t>::is_signed))
      ptrdiff_t __request = __STATIC_CAST(ptrdiff_t, (min) (__STATIC_CAST(streamsize, (numeric_limits<ptrdiff_t>::max)()), _Num - __n));

      const _CharT* __p  = __scan_delim(__first, __last);
      ptrdiff_t __chunk = (min) (ptrdiff_t(__p - __first), __request);
      _Traits::copy(__s, __first, __chunk);
      __s += __chunk;
      __n += __chunk;
      __buf->_M_gbump((int)__chunk);

      // We terminated by finding delim.
      if (__p != __last && __p - __first <= __request) {
        if (__extract_delim) {
          __n += 1;
          __buf->_M_gbump(1);
        }
        __done = true;
      }

      // We terminated by reading all the characters we were asked for.
      else if (__n == _Num) {

        // Find out if we have reached eof.  This matters for getline.
        if (__is_getline) {
          if (__chunk == __last - __first) {
            if (__that->_S_eof(__buf->sgetc()))
              __status |= ios_base::eofbit;
          }
          else
            __status |= ios_base::failbit;
        }
        __done   = true;
      }

      // The buffer contained fewer than _Num - __n characters.  Either we're
      // at eof, or we should refill the buffer and try again.
      else {
        if (__that->_S_eof(__buf->sgetc())) {
          __status |= ios_base::eofbit;
          __done = true;
        }
      }
    } // Close the while loop.
  }
  _STLP_CATCH_ALL {
    __that->_M_handle_exception(ios_base::badbit);
    __done = true;
  }

  if (__done) {
    if (__append_null)
        *__s =  _STLP_DEFAULT_CONSTRUCTED(_CharT);
    if (__status != 0)
      __that->setstate(__status);   // This might throw.
    return __n;
  }

  // If execution has reached this point, then we have an empty buffer but
  // we have not reached eof.  What that means is that the streambuf has
  // decided to switch from buffered to unbuffered input.  We switch to
  // to __read_unbuffered.

  return __n + __read_unbuffered(__that,  __buf, _Num - __n, __s, __is_delim,
                                 __extract_delim,__append_null,__is_getline);
}