Category : C++ Source Code
Archive : VCCRT1.ZIP
Filename : STREAMB.CXX
Output of file : STREAMB.CXX contained in archive : VCCRT1.ZIP
*streamb.cxx - fuctions for streambuf class.
*
* Copyright (c) 1990-1992, Microsoft Corporation. All rights reserved.
*
*Purpose:
* Functions for streambuf class.
*
*******************************************************************************/
#include
#include
#include
#pragma hdrstop
#ifndef BUFSIZ
#define BUFSIZ 512
#endif
/***
*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;
}
/***
*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;
}
}
/***
*virtual streambuf::~streambuf() -
*
*Purpose:
* Destructor.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
streambuf::~streambuf()
{
// x_lastc = EOF;
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;
#if 0
if (!this)
printf("xsputn: this = NULL\n");
#endif
for (cbOut = 0; cbBuf--; cbOut++)
{
if ((_fUnbuf) || (_pptr >= _epptr))
{
// UNDONE: can be optimized like sgetn !!
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;
}
// #pragma function(memcpy, __min)
/***
*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;
}
#if 0
/***
*int streambuf::sputn( char* pBuf, int cbBuf ) -
*
*Purpose:
* Tries to output cbBuf characters. Returns number of characters
* that were output.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
int streambuf::sputn( const char* pBuf, int cbBuf )
{
// UNDONE:
return xsputn(pBuf, cbBuf);
}
/***
*int streambuf::sgetn( char* pBuf, int cbBuf ) -
*
*Purpose:
* Tries to input cbBuf characters. Returns number of characters
* that were read from streambuf.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
int streambuf::sgetn( char * pBuf, int cbBuf)
{
// UNDONE:
return xsgetn(pBuf, cbBuf);
}
#endif
/***
*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 char[BUFSIZ]))
return(EOF);
setb(tptr, tptr + BUFSIZ, 1);
return(1);
}
/***
*void streambuf::unbuffered(int fUnbuf) -
*
*Purpose:
* Sets unbuffered status.
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
// void streambuf::unbuffered(int fUnbuf)
// {
// _fUnbuf = fUnbuf;
// if ((_fUnbuf) && (_base)) delete _base; // UNDONE: not doc'd as such ??
// }
/***
*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;
}
#if 0
int streambuf::overflow(int d)
{
printf("Error: *%p streambuf::overflow(%d) called!\n",this,d);
return EOF;
}
int streambuf::underflow()
{
printf("Error: *%p streambuf::underflow() called!\n",this);
return EOF;
}
#endif
/***
*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()
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);
}
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