/*** *popen.c - initiate a pipe and a child command * * Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved. * *Purpose: * Defines _popen() and _pclose(). * *******************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* size for pipe buffer */ #define PSIZE 1024 #define STDIN 0 #define STDOUT 1 /* definitions for table of stream pointer - process handle pairs. the table * is created, maintained and accessed by the idtab function. _popen and * _pclose gain access to table entries only by calling idtab. Note that the * table is expanded as necessary (by idtab) and free table entries are reused * (an entry is free if its stream field is NULL), but the table is never * contracted. */ typedef struct { FILE *stream; int prochnd; } IDpair; /* number of entries in idpairs table */ #ifndef _UNICODE unsigned __idtabsiz = 0; #else /* _UNICODE */ extern unsigned __idtabsiz; #endif /* _UNICODE */ /* pointer to first table entry */ #ifndef _UNICODE IDpair *__idpairs = NULL; #else /* _UNICODE */ extern IDpair *__idpairs; #endif /* _UNICODE */ /* function to find specified table entries. also, creates and maintains * the table. */ static IDpair * __cdecl idtab(FILE *); /*** *FILE *_popen(cmdstring,type) - initiate a pipe and a child command * *Purpose: * Creates a pipe and asynchronously executes a child copy of the command * processor with cmdstring (see system()). If the type string contains * an 'r', the calling process can read child command's standard output * via the returned stream. If the type string contains a 'w', the calling * process can write to the child command's standard input via the * returned stream. * *Entry: * _TSCHAR *cmdstring - command to be executed * _TSCHAR *type - string of the form "r|w[b|t]", determines the mode * of the returned stream (i.e., read-only vs write-only, * binary vs text mode) * *Exit: * If successful, returns a stream associated with one end of the created * pipe (the other end of the pipe is associated with either the child * command's standard input or standard output). * * If an error occurs, NULL is returned. * *Exceptions: * *******************************************************************************/ FILE * __cdecl _tpopen ( const _TSCHAR *cmdstring, const _TSCHAR *type ) { int phdls[2]; /* I/O handles for pipe */ int ph_open[2]; /* flags, set if correspond phdls is open */ int i1; /* index into phdls[] */ int i2; /* index into phdls[] */ int tm = 0; /* flag indicating text or binary mode */ int stdhdl; /* either STDIN or STDOUT */ HANDLE osfhndsv1; /* used to save _osfhnd(stdhdl) */ long osfhndsv2; /* used to save _osfhnd(phdls[i2]) */ char osfilesv1; /* used to save _osfile(stdhdl) */ char osfilesv2; /* used to save _osfile(phdls[i2]) */ HANDLE oldhnd; /* used to hold OS file handle values... */ HANDLE newhnd; /* ...in calls to DuplicateHandle API */ FILE *pstream; /* stream to be associated with pipe */ HANDLE prochnd; /* handle for current process */ _TSCHAR *cmdexe; /* pathname for the command processor */ int childhnd; /* handle for child process (cmd.exe) */ IDpair *locidpair; /* pointer to IDpair table entry */ /* first check for errors in the arguments */ if ( (cmdstring == NULL) || (type == NULL) || ((*type != 'w') && (*type != _T('r'))) ) goto error1; /* do the _pipe(). note that neither of the resulting handles will * be inheritable. */ if ( *(type + 1) == _T('t') ) tm = _O_TEXT; else if ( *(type + 1) == _T('b') ) tm = _O_BINARY; tm |= _O_NOINHERIT; if ( _pipe( phdls, PSIZE, tm ) == -1 ) goto error1; /* test *type and set stdhdl, i1 and i2 accordingly. */ if ( *type == _T('w') ) { stdhdl = STDIN; i1 = 0; i2 = 1; } else { stdhdl = STDOUT; i1 = 1; i2 = 0; } /* the pipe now exists. the following steps must be carried out before * the child process (cmd.exe) may be spawned: * * 1. save a non-inheritable dup of stdhdl * * 2. force stdhdl to be a dup of ph[i1]. close both ph[i1] and * the original OS handle underlying stdhdl * * 3. associate a stdio-level stream with ph[i2]. */ /* set flags to indicate pipe handles are open. note, these are only * used for error recovery. */ ph_open[ 0 ] = ph_open[ 1 ] = 1; /* get the process handle, it will be needed in some API calls */ prochnd = GetCurrentProcess(); /* MULTI-THREAD: ASSERT LOCK ON STDHDL HERE!!!! */ _lock_fh( stdhdl ); /* save a non-inheritable copy of stdhdl for later restoration. */ oldhnd = (HANDLE)_osfhnd( stdhdl ); if ( (oldhnd == INVALID_HANDLE_VALUE) || !DuplicateHandle( prochnd, oldhnd, prochnd, &osfhndsv1, 0L, FALSE, /* non-inheritable */ DUPLICATE_SAME_ACCESS ) ) { goto error2; } osfilesv1 = _osfile( stdhdl ); /* force stdhdl to an inheritable dup of phdls[i1] (i.e., force * STDIN to the pipe read handle or STDOUT to the pipe write handle) * and close phdls[i1] (so there won't be a stray open handle on the * pipe after a _pclose). also, clear ph_open[i1] flag so that error * recovery won't try to close it again. */ if ( !DuplicateHandle( prochnd, (HANDLE)_osfhnd( phdls[i1] ), prochnd, &newhnd, 0L, TRUE, /* inheritable */ DUPLICATE_SAME_ACCESS ) ) { goto error3; } (void)CloseHandle( (HANDLE)_osfhnd(stdhdl) ); _free_osfhnd( stdhdl ); _set_osfhnd( stdhdl, (long)newhnd ); _osfile( stdhdl ) = _osfile( phdls[i1] ); (void)_close( phdls[i1] ); ph_open[ i1 ] = 0; /* associate a stream with phdls[i2]. note that if there are no * errors, pstream is the return value to the caller. */ if ( (pstream = _tfdopen( phdls[i2], type )) == NULL ) goto error4; /* MULTI-THREAD: ASSERT LOCK ON IDPAIRS HERE!!!! */ _mlock( _POPEN_LOCK ); /* next, set locidpair to a free entry in the idpairs table. */ if ( (locidpair = idtab( NULL )) == NULL ) goto error5; /* temporarily change the osfhnd and osfile entries so that * the child doesn't get any entries for phdls[i2]. */ osfhndsv2 = _osfhnd( phdls[i2] ); _osfhnd( phdls[i2] ) = (long)INVALID_HANDLE_VALUE; osfilesv2 = _osfile( phdls[i2] ); _osfile( phdls[i2] ) = 0; /* spawn the child copy of cmd.exe. the algorithm is adapted from * SYSTEM.C, and behaves the same way. */ if ( ((cmdexe = _tgetenv(_T("COMSPEC"))) == NULL) || (((childhnd = _tspawnl( _P_NOWAIT, cmdexe, cmdexe, _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 ); }