Tricks of the Windows Gam…ming Gurus (2nd Edition)/Disc2.iso/vc98/crt/src/filebuf1.cpp

C/C++ Source or Header | 1998-06-17 | 5.6 KB | 225 lines

/***
*filebuf1.cpp - non-core filebuf member functions.
*
*       Copyright (c) 1991-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Contains optional member functions for filebuf class.
*
*******************************************************************************/

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

#include <sys\stat.h>

/***
*filebuf* filebuf::attach(filedesc fd) - filebuf attach function
*
*Purpose:
*       filebuf attach() member function.  Attach filebuf object to the
*       given file descriptor previously obtained from _open() or _sopen().
*
*Entry:
*       fd = file descriptor.
*
*Exit:
*       Returns this pointer or NULL if error.
*
*Exceptions:
*       Returns NULL if fd = -1.
*
*******************************************************************************/
filebuf* filebuf::attach(filedesc fd)
{
    if (x_fd!=-1)
        return NULL;    // error if already attached

    lock();
    x_fd = fd;
    if ((fd!=-1) && (!unbuffered()) && (!ebuf()))
        {
        char * sbuf = _new_crt char[BUFSIZ];
        if (!sbuf)
            {
            unbuffered(1);
            }
        else
            {
            streambuf::setb(sbuf,sbuf+BUFSIZ,1);
            }
        }
    unlock();
    return this;
}

/***
*filebuf* filebuf::open(const char* name, int mode, int share) - filebuf open
*
*Purpose:
*       filebuf open() member function.  Open a file and attach to filebuf
*       object.
*
*Entry:
*       name  = file name string.
*       mode  = open mode: Combination of ios:: in, out, binary, nocreate, app,
*               ate, noreplace and trunc.  See spec. for details on behavior.
*       share = share mode (optional).  sh_compat, sh_none, sh_read, sh_write.
*
*Exit:
*       Returns this pointer or NULL if error.
*
*Exceptions:
*       Returns NULL if filebuf is already attached to an open file, or if
*       invalid mode options, or if call to _sopen or filebuf::seekoff() fails.
*
*******************************************************************************/
filebuf* filebuf::open(const char* name, int mode, int share)
{
    int dos_mode;
    int smode;
    if (x_fd!=-1)
        return NULL;    // error if already open
// translate mode argument
    dos_mode = (mode & ios::binary) ? O_BINARY : O_TEXT;
    if (!(mode & ios::nocreate))
        dos_mode |= O_CREAT;
    if (mode & ios::noreplace)
        dos_mode |= O_EXCL;
    if (mode & ios::app)
        {
        mode |= ios::out;
        dos_mode |= O_APPEND;
        }
    if (mode & ios::trunc)
        {
        mode |= ios::out;  // IMPLIED
        dos_mode |= O_TRUNC;
        }
    if (mode & ios::out)
        {
        if (mode & ios::in)
            {
            dos_mode |= O_RDWR;
            }
        else
            {
            dos_mode |= O_WRONLY;
            }
        if (!(mode & (ios::in|ios::app|ios::ate|ios::noreplace)))
            {
            mode |= ios::trunc; // IMPLIED
            dos_mode |= O_TRUNC;
            }
        }
    else if (mode & ios::in)
        dos_mode |= O_RDONLY;
    else
        return NULL;    // error if not ios:in or ios::out

    smode = _SH_DENYNO; // default for NT
    share &= (sh_read|sh_write|sh_none); // ignore other bits
    if (share)  // optimization  openprot serves as default
        {
        switch (share)
            {
/*          case 03000 : Reserved for sh_compat  */

//          case sh_none :
            case 04000 :
                smode = _SH_DENYRW;
                break;
//          case sh_read :
            case 05000 :
                smode = _SH_DENYWR;
                break;
//          case sh_write :
            case 06000 :
                smode = _SH_DENYRD;
                break;
//          case (sh_read|sh_write) :
            case 07000 :
                smode = _SH_DENYNO;
                break;
            default :   // unrecognized value same as default
                break;
            };
        }

    x_fd = _sopen(name, dos_mode, smode, S_IREAD|S_IWRITE);
    if (x_fd==-1)
        return NULL;
    lock();
    x_fOpened = 1;
    if ((!unbuffered()) && (!ebuf()))
        {
        char * sbuf = _new_crt char[BUFSIZ];
        if (!sbuf)
            {
            unbuffered(1);
            }
        else
            {
            streambuf::setb(sbuf,sbuf+BUFSIZ,1);
            }
        }
    if (mode & ios::ate)
        if (seekoff(0,ios::end,mode)==EOF)
            {
            close();
            unlock();
            return NULL;
            }
    unlock();
    return this;
}

/***
*int filebuf::setmode(int mode) - filebuf setmode function
*
*Purpose:
*       filebuf setmode() member function.  Set binary or text access mode.
*       Calls _setmode().
*
*       MS-specific extension.
*
*Entry:
*       mode = filebuf::binary or filebuf::text.
*
*Exit:
*       Returns previous mode, or -1 error.
*
*Exceptions:
*       Return -1 (EOF) if invalid argument or _setmode fails.
*
*******************************************************************************/
int filebuf::setmode(int mode)
{
    int retval;
    if ((mode!=filebuf::binary) && (mode!=filebuf::text))
        return -1;

    lock();
    if ((x_fd==-1) || (sync()==EOF))
        {
        retval = -1;
        }
    else
        {
        retval = _setmode(x_fd,mode);
        }

    unlock();
    return retval;
}