popen.c

C标准库源代码

                                    _T("/c"),
                                    cmdstring,
                                    NULL ))
             == -1) && ((errno == ENOENT) || (errno == EACCES))) ) {
                /*
                 * either COMSPEC wasn't defined, or the spawn failed because
                 * cmdexe wasn't found or was inaccessible. in either case, try to
                 * spawn "cmd.exe" (Windows NT) or "command.com" (Windows 95) instead
                 * Note that spawnlp is used here so that the path is searched.
                 */
                cmdexe = ( _osver & 0x8000 ) ? _T("command.com") : _T("cmd.exe");
                childhnd = _tspawnlp( _P_NOWAIT,
                                     cmdexe,
                                     cmdexe,
                                     _T("/c"),
                                     cmdstring,
                                     NULL);
        }

        _osfhnd( phdls[i2] ) = osfhndsv2;
        _osfile( phdls[i2] ) = osfilesv2;

        /* check if the last (perhaps only) spawn attempt was successful
         */
        if ( childhnd == -1 )
                goto error6;

        /* restore stdhdl for the current process, set value of *locidpair,
         * close osfhndsv1 (note that CloseHandle must be used instead of close)
         * and return pstream to the caller
         */

        (void)DuplicateHandle( prochnd,
                               osfhndsv1,
                               prochnd,
                               &newhnd,
                               0L,
                               TRUE,                    /* inheritable */
                               DUPLICATE_CLOSE_SOURCE | /* close osfhndsv1 */
                               DUPLICATE_SAME_ACCESS );

        (void)CloseHandle( (HANDLE)_osfhnd(stdhdl) );
        _free_osfhnd( stdhdl );

        _set_osfhnd( stdhdl, (long)newhnd );
        _osfile(stdhdl) = osfilesv1;

        /* MULTI-THREAD: RELEASE LOCK ON STDHDL HERE!!!!
         */
        _unlock_fh( stdhdl );

        locidpair->prochnd = childhnd;
        locidpair->stream = pstream;

        /* MULTI-THREAD: RELEASE LOCK ON IDPAIRS HERE!!!!
         */
        _munlock( _POPEN_LOCK );

        /* all successful calls to _popen return to the caller via this return
         * statement!
         */
        return( pstream );

        /**
         * error handling code. all detected errors end up here, entering
         * via a goto one of the labels. note that the logic is currently
         * a straight fall-thru scheme (e.g., if entered at error5, the
         * code for error5, error4,...,error1 is all executed).
         **********************************************************************/

        error6: /* make sure locidpair is reusable
                 */
                locidpair->stream = NULL;

        error5: /* close pstream (also, clear ph_open[i2] since the stream
                 * close will also close the pipe handle)
                 */
                (void)fclose( pstream );
                ph_open[ i2 ] = 0;

                /* MULTI-THREAD: RELEASE LOCK ON IDPAIRS HERE!!!!
                 */
                _munlock(_POPEN_LOCK);

        error4: /* restore stdhdl
                 */

                (void)DuplicateHandle( prochnd,
                                       osfhndsv1,
                                       prochnd,
                                       &newhnd,
                                       0L,
                                       TRUE,
                                       DUPLICATE_SAME_ACCESS );

                (void)CloseHandle( (HANDLE)_osfhnd(stdhdl) );
                _free_osfhnd( stdhdl );

                _set_osfhnd( stdhdl, (long)newhnd );
                _osfile( stdhdl ) = osfilesv1;

                /* MULTI-THREAD: RELEASE LOCK ON STDHDL HERE!!!!
                 */
                _unlock_fh( stdhdl );

        error3: /* close osfhndsv1
                 */

                CloseHandle( osfhndsv1 );

        error2: /* close handles on pipe (if they are still open)
                 */
                if ( ph_open[i1] )
                        _close( phdls[i1] );
                if ( ph_open[i2] )
                        _close( phdls[i2] );

        error1: /* return NULL to the caller indicating failure
                 */
                return( NULL );
}

#ifndef _UNICODE

/***
*int _pclose(pstream) - wait on a child command and close the stream on the
*   associated pipe
*
*Purpose:
*       Closes pstream then waits on the associated child command. The
*       argument, pstream, must be the return value from a previous call to
*       _popen. _pclose first looks up the process handle of child command
*       started by that _popen and does a cwait on it. Then, it closes pstream
*       and returns the exit status of the child command to the caller.
*
*Entry:
*       FILE *pstream - file stream returned by a previous call to _popen
*
*Exit:
*       If successful, _pclose returns the exit status of the child command.
*       The format of the return value is that same as for cwait, except that
*       the low order and high order bytes are swapped.
*
*       If an error occurs, -1 is returned.
*
*Exceptions:
*
*******************************************************************************/

int __cdecl _pclose (
        FILE *pstream
        )
{
        IDpair *locidpair;        /* pointer to entry in idpairs table */
        int termstat;             /* termination status word */
        int retval = -1;          /* return value (to caller) */

        /* MULTI-THREAD: LOCK IDPAIRS HERE!!!!
         */
        _mlock(_POPEN_LOCK);

        if ( (pstream == NULL) || ((locidpair = idtab(pstream)) == NULL) )
                /* invalid pstream, exit with retval == -1
                 */
                goto done;

        /* close pstream
         */
        (void)fclose(pstream);

        /* wait on the child (copy of the command processor) and all of its
         * children.
         */
        if ( (_cwait(&termstat, locidpair->prochnd, _WAIT_GRANDCHILD) != -1) ||
             (errno == EINTR) )
                retval = termstat;

        /* Mark the IDpairtable entry as free (note: prochnd was closed by the
         * preceding call to _cwait).
         */
        locidpair->stream = NULL;
        locidpair->prochnd = 0;

        /* only return path!
         */
        done:
                /* MULTI-THREAD: RELEASE LOCK ON IDPAIRS HERE!!!!
                 */
                _munlock(_POPEN_LOCK);
                return(retval);
}

#endif  /* _UNICODE */

/***
* static IDpair * idtab(FILE *pstream) - find an idpairs table entry
*
*Purpose:
*   Find an entry in the idpairs table.  This function finds the entry the
*   idpairs table entry corresponding to pstream. In the case where pstream
*   is NULL, the entry being searched for is any free entry. In this case,
*   idtab will create the idpairs table if it doesn't exist, or expand it (by
*   exactly one entry) if there are no free entries.
*
*   [MTHREAD NOTE:  This routine assumes that the caller has acquired the
*   idpairs table lock.]
*
*Entry:
*   FILE *pstream - stream corresponding to table entry to be found (if NULL
*                   then find any free table entry)
*
*Exit:
*   if successful, returns a pointer to the idpairs table entry. otherwise,
*   returns NULL.
*
*Exceptions:
*
*******************************************************************************/

static IDpair * __cdecl idtab (
        FILE *pstream
        )
{

        IDpair * pairptr;       /* ptr to entry */
        IDpair * newptr;        /* ptr to newly malloc'd memory */


        /* search the table. if table is empty, appropriate action should
         * fall out automatically.
         */
        for ( pairptr = __idpairs ; pairptr < (__idpairs+__idtabsiz) ; pairptr++ )
                if ( pairptr->stream == pstream )
                        break;

        /* if we found an entry, return it.
         */
        if ( pairptr < (__idpairs + __idtabsiz) )
                return(pairptr);

        /* did not find an entry in the table.  if pstream was NULL, then try
         * creating/expanding the table. otherwise, return NULL. note that
         * when the table is created or expanded, exactly one new entry is
         * produced. this must not be changed unless code is added to mark
         * the extra entries as being free (i.e., set their stream fields to
         * to NULL).
         */
        if ( (pstream != NULL) || ((newptr = (IDpair *)_realloc_crt((void *)__idpairs,
             (__idtabsiz + 1)*sizeof(IDpair))) == NULL) )
                /* either pstream was non-NULL or the attempt to create/expand
                 * the table failed. in either case, return a NULL to indicate
                 * failure.
                 */
                return( NULL );

        __idpairs = newptr;             /* new table ptr */
        pairptr = newptr + __idtabsiz;  /* first new entry */
        __idtabsiz++;                   /* new table size */

        return( pairptr );

}