/***
*filebuf.cxx - core filebuf member functions
*
*	Copyright (c) 1991-1992, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*	Contains the core member functions for filebuf class.
*
*Revision History:
*	08-08-91   KRS  Created.
*	08-20-91   KRS  Added virtual xsgetn()/xsputn() functions.
*	08-21-91   KRS	Fix circular reference between sync() and seekoff().
*			Close file in destructor only if we opened it!
*	09-06-91   KRS	Fix ios::ate case in filebuf::open().
*	09-09-91   KRS	Add support for ios::binary in filebuf::open().
*	09-10-91   KRS	Remove virtual xsputn()/xsgetn().
*	09-11-91   KRS	Fix filebuf::seekoff() for ios::cur and in_avail().
*	09-12-91   KRS	Make sure close() always closes even if sync() fails.
*			Fix seekoff call in filebuf::sync() and pbackfail().
*	09-16-91   KRS	Make virtual filebuf::setbuf() more robust.
*	09-19-91   KRS	Add calls to delbuf(1) in constructors.
*	09-20-91   KRS	C700 #4453: Improve efficiency in overflow().
*	09-29-91   KRS	Granularity split.  Move fstream into separate file.
*	10-24-91   KRS	Avoid virtual calls from virtual functions.
*	11-13-91   KRS	Use allocate() properly in overflow() and underflow().
*			Fix constructor.
*	01-03-92   KRS	Remove virtual keyword.  Add function headers and PCH.
*	01-20-92   KRS	In text mode, account for CR/LF pairs in sync().
*	02-03-92   KRS	Change for new compiler destructor behavior.
*	08-19-92   KRS	Remove sh_compat for NT.
*	08-27-92   KRS	Fix bug in close() introduced in MTHREAD work.
*
*******************************************************************************/

#include <cruntime.h>
#include <internal.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys\types.h>
#include <io.h>
#include <fstream.h>
#pragma hdrstop

#include <msdos.h>
#include <sys\stat.h>

const int filebuf::openprot	= 0644;	// CONSIDER: meaning?

const int filebuf::sh_none	= 04000;	// deny rw
const int filebuf::sh_read	= 05000;	// deny wr
const int filebuf::sh_write	= 06000;	// deny rd

const int filebuf::binary	= O_BINARY;
const int filebuf::text		= O_TEXT;

/***
*filebuf::filebuf() - filebuf default constructor
*
*Purpose:
*	Default constructor.
*
*Entry:
*
*******************************************************************************/
	filebuf::filebuf()
: streambuf()
{
    x_fOpened = 0;
    x_fd = -1;
}


/***
*filebuf::filebuf(filedesc fd) - filebuf constructor
*
*Purpose:
*	Constructor.  Initialize filebuf and attach to file descriptor.
*
*Entry:
*	fd = file descriptor to attach to filebuf
*
*******************************************************************************/
	filebuf::filebuf(filedesc fd)
: streambuf()
{
    x_fOpened = 0;
    x_fd=fd;
}


/***
*filebuf::filebuf(filedesc fd, char* p, int len) - filebuf constructor
*
*Purpose:
*	Constructor.  Initialize filebuf and attach to file descriptor.
*
*Entry:
*	fd  = file descriptor to attach to filebuf
*	p   = user-supplied buffer
*	len = length of buffer
*
*******************************************************************************/
	filebuf::filebuf(filedesc fd, char* p, int len)
:    streambuf()
{
    filebuf::setbuf(p,len);
    x_fOpened = 0;
    x_fd=fd;
}


/***
*filebuf::~filebuf() - filebuf destructor
*
*Purpose:
*	Destructor.  Close attached file only if we opened it.
*
*Entry:
*	None.
*
*******************************************************************************/
	filebuf::~filebuf()
{
	lock(); 	// no need to unlock...
	if (x_fOpened)
	    close();	// calls filebuf::sync()
	else
	    filebuf::sync();
}


/***
*filebuf* filebuf::close() - close an attached file
*
*Purpose:
*	Close attached file.
*
*Entry:
*	None.
*Exit:
*	Returns NULL if error, otherwise returns "this" pointer.
*
*******************************************************************************/
filebuf* filebuf::close()
{
    int retval;
    if (x_fd==-1)
	return NULL;

    lock();
    retval = sync();

    if ((_close(x_fd)==-1) || (retval==EOF))
	{
	unlock();
	return NULL;
	}
    x_fd = -1;
    unlock();
    return this;
}

/***
*virtual int filebuf::overflow(int c) - overflow virtual function
*
*Purpose:
*	flush any characters in the reserve area and handle 'c'.
*
*Entry:
*	c = character to output (if not EOF)
*
*Exit:
*	Returns EOF if error, otherwise returns something else.
*
*Exceptions:
*	Returns EOF if error.
*
*******************************************************************************/
int filebuf::overflow(int c)
{
    if (allocate()==EOF)	// make sure there is a reserve area
	return EOF;
    if (filebuf::sync()==EOF) // sync before new buffer created below
	return EOF;

    if (!unbuffered())
	setp(base(),ebuf());

    if (c!=EOF)
	{
	if ((!unbuffered()) && (pptr() < epptr())) // guard against recursion
	    sputc(c);
	else
	    {
	    if (_write(x_fd,&c,1)!=1)
		return(EOF);
	    }
	}
    return(1);	// return something other than EOF if successful
}

/***
*virtual int filebuf::underflow() - underflow virtual function
*
*Purpose:
*	return next character in get area, or get more characters from source.
*
*Entry:
*	None.
*
*Exit:
*	Returns current character in file.  Does not advance get pointer.
*
*Exceptions:
*	Returns EOF if error.
*
*******************************************************************************/
int filebuf::underflow()
{
    int count;
    unsigned char tbuf;

    if (in_avail())
	return (int)(unsigned char) *gptr();

    if (allocate()==EOF)	// make sure there is a reserve area
	return EOF;
    if (filebuf::sync()==EOF)
	return EOF;

    if (unbuffered())
	{
	if (_read(x_fd,(void *)&tbuf,1)<=0)
	    return EOF;
	return (int)tbuf;
	}

    if ((count=_read(x_fd,(void *)base(),blen())) <= 0)
	return EOF;	// reached EOF
    setg(base(),base(),base()+count);
    return (int)(unsigned char) *gptr(); // CONSIDER: possible recursion
}


/***
*virtual streampos filebuf::seekoff() - seekoff virtual function
*
*Purpose:
*	Seeks to given absolute or relative file offset.
*
*Entry:
*	off = offset to seek to relative to beginning, end or current
*		position in the file.
*	dir = one of ios::beg, ios::cur, or ios::end
*
*Exit:
*	Returns current file position after seek.
*
*Exceptions:
*	Returns EOF if error.
*
*******************************************************************************/
streampos filebuf::seekoff(streamoff off, ios::seek_dir dir, int)
{

    int fdir;
    long retpos;
    switch (dir) {
	case ios::beg :
	    fdir = SEEK_SET;
	    break;
	case ios::cur :
	    fdir = SEEK_CUR;
	    break;
	case ios::end :
	    fdir = SEEK_END;
	    break;
	default:
	// error
	    return(EOF);
	}
		
    if (filebuf::sync()==EOF)
	return EOF;
    if ((retpos=_lseek(x_fd, off, fdir))==-1L)
	return (EOF);
    return((streampos)retpos);
}

/*  NOT IN SPEC.
int filebuf::pbackfail(int c)
{
    if (eback()<gptr()) return sputbackc(c); // CONSIDER: should never happen

    if (filebuf::seekoff( -1, ios::cur, ios::in)==EOF)
	return EOF;
    if (!unbuffered())
	filebuf::underflow();
	// assert c = underflow()
	}
    return(c);
}
*/

#if 0
// NOT IN SPEC.
// UNDONE: consider removing this?
int filebuf::xsgetn(char * ptr, int n)
{
    int retval;
    int oldmode;

    if (x_fd==-1)
	return 0;
    if (filebuf::sync()!=EOF)
	{
	// set to BINARY and save old mode.
	oldmode = _setmode(x_fd,O_BINARY);
	}
    retval = sgetn(ptr,n);
    filebuf::sync();	// put back any excess (ignore errors)

    if (oldmode==O_TEXT)	// check != -1
	{
	_setmode(x_fd,oldmode);
	}
    return retval;
}

// NOT IN SPEC.
// UNDONE: consider removing this?
int filebuf::xsputn(const char * ptr, int n)
{
    int retval;
    int oldmode;

    if (x_fd==-1)
	return 0;
    if (filebuf::sync()!=EOF)
	{
	// set to BINARY and save old mode.
	oldmode = _setmode(x_fd,O_BINARY);
	}

    retval = sputn(ptr,n);
    filebuf::sync();	// flush output;

    if (oldmode==O_TEXT)	// check != -1
	{
	_setmode(x_fd,oldmode);
	}
    return retval;
}
#endif


/***
*virtual int filebuf::sync() - synchronize buffers with external file postion.
*
*Purpose:
*	Synchronizes buffer with external file, by flushing any output and/or
*	discarding any unread input data.  Discards any get or put area(s).
*
*Entry:
*	None.
*
*Exit:
*	Returns EOF if error, else 0.
*
*Exceptions:
*	Returns EOF if error.
*
*******************************************************************************/
int filebuf::sync()
{
    long count, nout;
    char * p;
    if (x_fd==-1)
	return(EOF);
//  lock();		// CONSIDER: do we need/want locking here?
    if (!unbuffered())
	{
	if ((count=out_waiting())!=0)
	    {
	    if ((nout =_write(x_fd,(void *) pbase(),(unsigned int)count)) != count)
		{
		// should set _pptr -= nout
		pbump(-(int)nout);
		memmove(pbase(), pbase()+nout, (int)(count-nout));
//		unlock();
		return(EOF);
		}
	    }
	setp(0,0); // empty put area

	if ((count=in_avail()) > 0)
	    {
	    // can't use seekoff here!!
	    if (_osfile[x_fd] & FTEXT)
		{
	        // If text mode, need to account for CR/LF etc.
		for (p = gptr(); p < egptr(); p++)
		    if (*p == '\n')
			count++;

		// account for EOF if read, not counted by _read
		// UNDONE: is this necessary / useful?
		if ((_osfile[x_fd] & FEOFLAG))
		    count++;
#if 0
		// UNDONE: is this correct?
		if ((gptr()==eback()) && (_osfile[x_fd] & FCRLF))
		    count--;
#endif
		}
    	    if (_lseek(x_fd, -count, SEEK_CUR)==-1L)
		{
//		unlock();
		return (EOF);
		}
	    }
	setg(0,0,0); // empty get area
	}
//  unlock();
    return(0);
}

/***
*virtual streambuf* filebuf::setbuf(char* ptr, int len) - set reserve area.
*
*Purpose:
*	Synchronizes buffer with external file, by flushing any output and/or
*	discarding any unread input data.  Discards any get or put area(s).
*
*Entry:
*	ptr = requested reserve area.  If NULL, request is for unbuffered.
*	len = size of reserve area.  If <= 0, request is for unbuffered.
*
*Exit:
*	Returns this pointer if request is honored, else NULL.
*
*Exceptions:
*	Returns NULL if request is not honored.
*
*******************************************************************************/
streambuf * filebuf::setbuf(char * ptr, int len)
{
    if (is_open() && (ebuf()))
	return NULL;
    if ((!ptr) || (len <= 0))
	unbuffered(1);
    else
	{
	lock();	// consider: necessary?
	setb(ptr, ptr+len, 0);
	unlock();
	}
    return this;
}