streamb.cpp

C标准库源代码

/***
*streamb.cpp - fuctions for streambuf class.
*
*       Copyright (c) 1990-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Functions for streambuf class.
*
*******************************************************************************/

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


#ifndef BUFSIZ
#define BUFSIZ 512
#endif  /* BUFSIZ */

/***
*streambuf::streambuf() -
*
*Purpose:
*       Default constructor.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

streambuf::streambuf()
{
    _fAlloc = 0;
    _fUnbuf = 0;
    x_lastc = EOF;
    _base = NULL;
    _ebuf = NULL;
    _pbase = NULL;
    _pptr = NULL;
    _epptr = NULL;
    _eback = NULL;
    _gptr = NULL;
    _egptr = NULL;

#ifdef _MT
    LockFlg = -1;               // default is now : locking
    _mtlockinit(lockptr());
#endif  /* _MT */

}

/***
*streambuf::streambuf(char* pBuf, int cbBuf) -
*
*Purpose:
*       Constructor which specifies a buffer area.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

streambuf::streambuf( char* pBuf, int cbBuf )
{
    _fAlloc = 0;
    _fUnbuf = 0;
    x_lastc = EOF;
    _base = pBuf;
    _ebuf = pBuf + (unsigned)cbBuf;
    _pbase = NULL;
    _pptr = NULL;
    _epptr = NULL;
    _eback = NULL;
    _gptr = NULL;
    _egptr = NULL;

    if( pBuf == NULL || cbBuf == 0 ){
        _fUnbuf = 1;
        _base = NULL;
        _ebuf = NULL;
    }

#ifdef _MT
    LockFlg = -1;               // default is now : locking
    _mtlockinit(lockptr());
#endif  /* _MT */

}


/***
*virtual streambuf::~streambuf() -
*
*Purpose:
*       Destructor.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

streambuf::~streambuf()
{
#ifdef _MT
    _mtlockterm(lockptr());
#endif  /* _MT */

    sync();     // make sure buffer empty before possibly destroying it
    if( (_fAlloc) && (_base) )
        delete _base;
}


/***
* virtual streambuf * streambuf::setbuf(char * p, int len) -
*
*Purpose:
*       Offers the array at p with len bytes to be used as a reserve area.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

streambuf * streambuf::setbuf(char * p, int len)
{
    if (!_base)
        {
        if ((!p) || (!len))
            _fUnbuf = 1;        // mark as unbuffered
        else
            {
            _base = p;
            _ebuf = p + (unsigned)len;
            _fUnbuf = 0;
            }
        return (this);
        }
    return((streambuf *)NULL);
}


/***
*virtual int streambuf::xsputn( char* pBuf, int cbBuf ) -
*
*Purpose:
*       Tries to output cbBuf characters.  Returns number of characters
*       that were outputted.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

int streambuf::xsputn( const char* pBuf, int cbBuf )
{
    int cbOut;

    for (cbOut = 0; cbBuf--; cbOut++)
        {
        if ((_fUnbuf) || (_pptr >= _epptr))
            {
            if (overflow((unsigned char)*pBuf)==EOF)    // 0-extend 0xFF !=EOF
                break;
            }
        else
            {
            *(_pptr++) = *pBuf;
            }
        pBuf++;
        }
    return cbOut;
}

/***
*virtual int streambuf::xsgetn( char* pBuf, int cbBuf ) -
*
*Purpose:
*       Tries to input cbBuf characters.  Returns number of characters
*       that were read from streambuf.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

// #pragma intrinsic(memcpy,__min)

int streambuf::xsgetn( char * pBuf, int cbBuf)
{
    int count;
    int cbIn = 0;
    if (_fUnbuf)
        {
        if (x_lastc==EOF)
            x_lastc=underflow();

        while (cbBuf--)
            {
            if (x_lastc==EOF)
                break;
            *(pBuf++) = (char)x_lastc;
            cbIn++;
            x_lastc=underflow();
            }
        }
    else
        {
        while (cbBuf)
            {
            if (underflow()==EOF)       // make sure something to read
                break;
            count = __min(egptr() - gptr(),cbBuf);
            if (count>0)
                {
                memcpy(pBuf,gptr(),count);
                pBuf  += count;
                _gptr += count;
                cbIn  += count;
                cbBuf -= count;
                }
            }
        }
    return cbIn;
}

/***
*virtual int streambuf::sync() -
*
*Purpose:
*       Tries to flush all data in put area and give back any data in the
*       get area (if possible), leaving both areas empty on exit.
*       Default behavior is to fail unless buffers empty.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

int streambuf::sync()
{
    if ((gptr() <_egptr) || (_pptr > _pbase))
        {
        return EOF;
        }
    return 0;
}

/***
*int streambuf::allocate() -
*
*Purpose:
*       Tries to set up a Reserve Area.  If one already exists, or if
*       unbuffered, just returns 0.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

int streambuf::allocate()
{
    if ((_fUnbuf) || (_base))
        return 0;
    if (doallocate()==EOF) return EOF;

    return(1);
}

/***
*virtual int streambuf::doallocate() -
*
*Purpose:
*       Tries to set up a Reserve Area.  Returns EOF if unsuccessful.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

int streambuf::doallocate()
{
    char * tptr;
    if (!( tptr = _new_crt char[BUFSIZ]))
        return(EOF);
    setb(tptr, tptr + BUFSIZ, 1);
    return(1);
}

/***
*void streambuf::setb(char * b, char * eb, int a = 0) -
*
*Purpose:
*       Sets up reserve area.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

void streambuf::setb(char * b, char * eb, int a )
{
    if ((_fAlloc) && (_base))
        delete _base;
    _base = b;
    _fAlloc = a;
    _ebuf = eb;
}

/***
*virtual streampos streambuf::seekoff(streamoff off, ios::seekdir dir, int mode)
*
*Purpose:
*       seekoff member function.  seek forward or backward in the stream.
*       Default behavior: returns EOF.
*
*Entry:
*       off  = offset (+ or -) to seek by
*       dir  = one of ios::beg, ios::end, or ios::cur.
*       mode = ios::in or ios::out.
*
*Exit:
*       Returns new file position or EOF if error or seeking not supported.
*
*Exceptions:
*       Returns EOF if error.
*
*******************************************************************************/
streampos streambuf::seekoff(streamoff,ios::seek_dir,int)
{
return EOF;
}

/***
*virtual streampos streambuf::seekpos(streampos pos, int mode) -
*
*Purpose:
*       seekoff member function.  seek to absolute file position.
*       Default behavior: returns seekoff(streamoff(pos), ios::beg, mode).
*
*Entry:
*       pos  = absolute offset to seek to
*       mode = ios::in or ios::out.
*
*Exit:
*       Returns new file position or EOF if error or seeking not supported.
*
*Exceptions:
*       Returns EOF if error.
*
*******************************************************************************/
streampos streambuf::seekpos(streampos pos,int mode)
{
return seekoff(streamoff(pos), ios::beg, mode);
}

/***
*virtual int streambuf::pbackfail(int c) - handle failure of putback
*
*Purpose:
*       pbackfail member function.  Handle exception of pback function.
*       Default behavior: returns EOF.  See spec. for details.
*
*       Note: the following implementation gives default behavior, thanks
*       to the default seekoff, but also supports derived classes properly:
*
*Entry:
*       c = character to put back
*
*Exit:
*       Returns c if successful or EOF on error.
*
*Exceptions:
*       Returns EOF if error.  Behavior is undefined if c was not the
*       previous character in the stream.
*
*******************************************************************************/
int streambuf::pbackfail(int c)
{
    if (eback()<gptr()) return sputbackc((char)c);

    if (seekoff( -1, ios::cur, ios::in)==EOF)  // always EOF for streambufs
        return EOF;
    if (!unbuffered() && egptr())
        {
        memmove((gptr()+1),gptr(),(egptr()-(gptr()+1)));
        *gptr()=(char)c;
        }
    return(c);
}