ftelli64.c

不错的东西 请查看 WINCE OS

//
// Copyright (c) Microsoft Corporation.  All rights reserved.
//
//
// This source code is licensed under Microsoft Shared Source License
// Version 1.0 for Windows CE.
// For a copy of the license visit http://go.microsoft.com/fwlink/?LinkId=3223.
//
/***
*ftelli64.c - get current file position
*
*
*Purpose:
*       defines _ftelli64() - find current current position of file pointer
*
*******************************************************************************/

#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <dbgint.h>
#include <msdos.h>
#include <internal.h>
#include <mtdll.h>

/***
*__int64 _ftelli64(stream) - query stream file pointer
*
*Purpose:
*       Find out what stream's position is. coordinate with buffering; adjust
*       backward for read-ahead and forward for write-behind. This is NOT
*       equivalent to fseek(stream,0L,1), because fseek will remove an ungetc,
*       may flush buffers, etc.
*
*Entry:
*       FILEX *stream - stream to query for position
*
*Exit:
*       return present file position if succeeds
*       returns -1i64 and sets errno if fails
*
*Exceptions:
*
*******************************************************************************/

__int64 __cdecl _ftelli64 (
        FILEX *stream
        )
{
        __int64 retval;

    if(!CheckStdioInit())
        return -1L;

    _ASSERTE(stream != NULL);

        if (! _lock_validate_str(stream))
            return -1;

    if (inuse(stream))
            retval = _ftelli64_lk (stream);
    else
        retval = -1L;

        _unlock_str(stream);

        return(retval);
}


/***
*_ftelli64_lk() - _ftelli64() core routine (assumes stream is locked).
*
*Purpose:
*       Core _ftelli64() routine (assumes caller has aquired stream lock).
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/

__int64 __cdecl _ftelli64_lk (FILEX *str)
{
        REG1 FILEX *stream;
        unsigned int offset;
        __int64 filepos;
        REG2 char *p;
        char *max;
        unsigned int rdcnt;

        _ASSERTE(str != NULL);

        /* Init stream pointer and file descriptor */
        stream = str;

        if (stream->_cnt < 0)
                stream->_cnt = 0;

        if ((filepos = _lseeki64(stream, 0i64, SEEK_CUR)) < 0L)
                return(-1i64);

        if (!bigbuf(stream))            /* _IONBF or no buffering designated */
                return(filepos - stream->_cnt);

        offset = stream->_ptr - stream->_base;

        if (stream->_flag & (_IOWRT|_IOREAD)) {
        if (_osfilestr(stream) & FTEXT)
                        for (p = stream->_base; p < stream->_ptr; p++)
                                if (*p == '\n')  /* adjust for '\r' */
                                        offset++;
        }
        else if (!(stream->_flag & _IORW)) 
        {
            SetLastError(ERROR_INVALID_PARAMETER);
            return(-1i64);
        }

        if (filepos == 0i64)
                return((__int64)offset);

        if (stream->_flag & _IOREAD)    /* go to preceding sector */

                if (stream->_cnt == 0)  /* filepos holds correct location */
                        offset = 0;

                else {

                        /* Subtract out the number of unread bytes left in the
                           buffer. [We can't simply use _iob[]._bufsiz because
                           the last read may have hit EOF and, thus, the buffer
                           was not completely filled.] */

                        rdcnt = stream->_cnt + (stream->_ptr - stream->_base);

                        /* If text mode, adjust for the cr/lf substitution. If
                           binary mode, we're outta here. */
            if (_osfilestr(stream) & FTEXT) {
                                /* (1) If we're not at eof, simply copy _bufsiz
                                   onto rdcnt to get the # of untranslated
                                   chars read. (2) If we're at eof, we must
                                   look through the buffer expanding the '\n'
                                   chars one at a time. */

                                /* [NOTE: Performance issue -- it is faster to
                                   do the two _lseek() calls than to blindly go
                                   through and expand the '\n' chars regardless
                                   of whether we're at eof or not.] */

                                if (_lseeki64(stream, 0i64, SEEK_END) == filepos) {

                                        max = stream->_base + rdcnt;
                                        for (p = stream->_base; p < max; p++)
                                                if (*p == '\n')
                                                        /* adjust for '\r' */
                                                        rdcnt++;

                                        /* If last byte was ^Z, the lowio read
                                           didn't tell us about it.  Check flag
                                           and bump count, if necessary. */

                                        if (stream->_flag & _IOCTRLZ)
                                                ++rdcnt;
                                }

                                else {

                                        _lseeki64(stream, filepos, SEEK_SET);

                                        /* We want to set rdcnt to the number
                                           of bytes originally read into the
                                           stream buffer (before crlf->lf
                                           translation). In most cases, this
                                           will just be _bufsiz. However, the
                                           buffer size may have been changed,
                                           due to fseek optimization, at the
                                           END of the last _filbuf call. */

                                        if ( (rdcnt <= _SMALL_BUFSIZ) &&
                                             (stream->_flag & _IOMYBUF) &&
                                             !(stream->_flag & _IOSETVBUF) )
                                        {
                                                /* The translated contents of
                                                   the buffer is small and we
                                                   are not at eof. The buffer
                                                   size must have been set to
                                                   _SMALL_BUFSIZ during the
                                                   last _filbuf call. */

                                                rdcnt = _SMALL_BUFSIZ;
                                        }
                                        else
                                                rdcnt = stream->_bufsiz;


                                        /* If first byte in untranslated buffer
                                           was a '\n', assume it was preceeded
                                           by a '\r' which was discarded by the
                                           previous read operation and count
                                           the '\n'. */
                    if  (_osfilestr(stream) & FCRLF)
                                                ++rdcnt;
                                }

                        } /* end if FTEXT */

                        filepos -= (__int64)rdcnt;

                } /* end else stream->_cnt != 0 */

        return(filepos + (__int64)offset);
}