istream.cpp

C标准库源代码,能提高对C的理解,不错的哦

/***
* istream.cpp - definitions for istream and istream_withassign classes
*
*       Copyright (c) 1991-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Definitions of member functions for istream and istream_withassign
*       classes.
*       [AT&T C++]
*
*******************************************************************************/

#include <cruntime.h>
#include <internal.h>
#include <stdlib.h>
#include <ctype.h>
#include <iostream.h>
#include <dbgint.h>
#pragma hdrstop

        istream::istream()
// : ios()
{
        x_flags |= ios::skipws;
        x_gcount = 0;
        _fGline = 0;
}

        istream::istream(streambuf* _inistbf)
// : ios()
{
        init(_inistbf);

        x_flags |= ios::skipws;
        x_gcount = 0;
        _fGline = 0;
}

        istream::istream(const istream& _istrm)
// : ios()
{
        init(_istrm.rdbuf());

        x_flags |= ios::skipws;
        x_gcount = 0;
        _fGline = 0;
}

        istream::~istream()
// : ~ios()
{
}

// used by ios::sync_with_stdio()
istream& istream::operator=(streambuf * _sbuf)
{
        if (delbuf() && rdbuf())
            delete rdbuf();

        bp = 0;

        this->ios::operator=(ios());    // initialize ios members
        delbuf(0);                      // important!
        init(_sbuf);    // set up bp

        x_flags |= ios::skipws;         // init istream members too
        x_gcount = 0;

        return *this;
}
int istream::ipfx(int need)
{
    lock();
    if (need)           // reset gcount if unformatted input
        x_gcount = 0;
    if (state)          // return 0 iff error condition
        {
        state |= ios::failbit;  // solves cin>>buf problem
        unlock();
        return 0;
        }
    if (x_tie && ((need==0) || (need > bp->in_avail())))
        {
        x_tie->flush();
        }
    lockbuf();
    if ((need==0) && (x_flags & ios::skipws))
        {
        eatwhite();
        if (state)      // eof or error
            {
            state |= ios::failbit;
            unlockbuf();
            unlock();
            return 0;
            }
        }
    // leave locked ; isfx() will unlock
    return 1;           // return nz if okay
}

// formatted input functions

istream& istream::operator>>(char * s)
{
    int c;
    unsigned int i, lim;
    if (ipfx(0))
        {
        lim = (unsigned)(x_width-1);
        x_width = 0;
        if (!s)
            {
            state |= ios::failbit;
            }
        else
            {
            for (i=0; i< lim; i++)
                {
                c=bp->sgetc();
                if (c==EOF)
                    {
                    state |= ios::eofbit;
                    if (!i)
                        state |= ios::failbit|ios::badbit;
                    break;
                    }
                else if (isspace(c))
                    {
                    break;
                    }
                else
                    {
                    s[i] = (char)c;
                    bp->stossc(); // advance pointer
                    }
                }
            if (!i)
                state |= ios::failbit;
            else
                s[i] = '\0';
            }
        isfx();
        }
    return *this;
}

int istream::peek()
{
int retval;
    if (ipfx(1))
        {
        retval = (bp->sgetc());
        isfx();
        }
    else
        retval = EOF;
    return retval;
}

istream& istream::putback(char c)
{
      if (good())
        {
        lockbuf();

        if (bp->sputbackc(c)==EOF)
            {
            clear(state | ios::failbit);
            }

        unlockbuf();
        }
    return *this;
}

int istream::sync()
{
    int retval;
    lockbuf();

    if ((retval=bp->sync())==EOF)
        {
        clear(state | (ios::failbit|ios::badbit));
        }

    unlockbuf();
    return retval;
}

void istream::eatwhite()
{
    int c;
    lockbuf();
    c = bp->sgetc();
    for ( ; ; )
        {
        if (c==EOF)
            {
            clear(state | ios::eofbit);
            break;
            }
        if (isspace(c))
            {
            c = bp->snextc();
            }
        else
            {
            break;
            }
        }
    unlockbuf();
}

        istream_withassign::istream_withassign()
: istream()
{
}

        istream_withassign::istream_withassign(streambuf* _is)
: istream(_is)
{
}

        istream_withassign::~istream_withassign()
// : ~istream()
{
}