Getting unique list of paths in C?
in [TCL]
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From: Fredrik Karlsson on 28 Nov 2009 09:23 Hi, I am trying to get a unique list of paths for later glob:ing, but I cannot get stuff to be removed from the list I am using. What am I doing wrong? directories = Tcl_NewObj(); Tcl_IncrRefCount(directories); // Get some sample dirs in Tcl_ListObjAppendElement(interp, directories, Tcl_NewStringObj("/ Users/zak/Desktop/emutestdb/aetobi",-1)); Tcl_ListObjAppendElement(interp, directories, Tcl_NewStringObj("/ Users/zak/Desktop/emutestdb/epgdorsal",-1)); Tcl_ListObjAppendElement(interp, directories, Tcl_NewStringObj("/ Users/zak/Desktop/emutestdb/epgdorsal",-1)); Tcl_ListObjAppendElement(interp, directories, Tcl_NewStringObj("/ Users/zak/Desktop/emutestdb/epgdorsal",-1)); for(i=0; Tcl_ListObjLength(interp, directories, &imax) && i < imax ; i++ ){ Tcl_ListObjIndex(interp, directories, i, &currDirectory); Tcl_IncrRefCount(currDirectory); /*Now loop through the upcomming list backwards and delete identical entries */ for(j=imax-1; j > i ;j--){ Tcl_ListObjIndex(interp, directories, j, &compDirectory); Tcl_IncrRefCount(compDirectory); if(Tcl_FSEqualPaths(currDirectory,compDirectory) == 1){ //Delete from list //This should work since j then should be the index of the previous entry Tcl_ListObjReplace(interp, directories, j, 1, 0, NULL); } } Tcl_DecrRefCount(currDirectory); Tcl_DecrRefCount(compDirectory); } I would appreciate all the help I can get on this. /Fredrik
From: Alexandre Ferrieux on 28 Nov 2009 10:09 On 28 nov, 15:23, Fredrik Karlsson <dargo...(a)gmail.com> wrote: > > for(i=0; Tcl_ListObjLength(interp, directories, &imax) && i < imax ; In addition to being of questionable readability, the && above will fail systematically because Tcl_ListObjLength returns TCL_OK, which is zero, yielding false. You want: for(i=0; (TCL_OK==Tcl_ListObjLength(interp, directories, &imax)) && i < imax ; Note that while I had to RTFM to detect this, you could have easily single-stepped or printf'ed the bug away. Try this before asking next time. As a side note, I wonder what you're trying to achieve at C level; indeed all these operations are trivially handled in a few lines of Tcl... -Alex
From: Gerald W. Lester on 28 Nov 2009 11:36 Fredrik Karlsson wrote: > Hi, > > I am trying to get a unique list of paths for later glob:ing, but I > cannot get stuff to be removed from the list I am using. What am I > doing wrong? Doing it in C. This is a simple task in Tcl. Just call Tcl_*Eval* with a Tcl command. >... > I would appreciate all the help I can get on this. The Tcl to eval would be: set directories [lsort -unique $directories] -- +------------------------------------------------------------------------+ | Gerald W. Lester | |"The man who fights for his ideals is the man who is alive." - Cervantes| +------------------------------------------------------------------------+
From: Fredrik Karlsson on 30 Nov 2009 10:22 On 28 Nov, 17:36, "Gerald W. Lester" <Gerald.Les...(a)cox.net> wrote: > The Tcl to eval would be: > set directories [lsort -unique $directories] Hi, Yes, to be honest, I had forgot about Tcl_Eval().. though, I do admit that I maybe would have not wanted to use it anyway. What happens if the user input is "Some file {which I will explain "later' `with" (qoutes removed) or something really nasty. I am really insecure when it comes to protecting strings in a fool-proof way. I am sure that {} protecting it solves lots of issues, but maybe strings that are not meant to be evaluated as part of a Tcl script should be kept from being possibly evaluated as part of a script as much as possible? Just my paranoia, maybe, but keeping user input away from parsing as much as possible seems safer to me. If I am wrong, please tell me. /Fredrik
From: Donal K. Fellows on 30 Nov 2009 11:14
On 30 Nov, 15:22, Fredrik Karlsson <dargo...(a)gmail.com> wrote: > Yes, to be honest, I had forgot about Tcl_Eval().. though, I do admit > that I maybe would have not wanted to use it anyway. What happens if > the user input is > "Some file {which I will explain "later' `with" (qoutes removed) or > something really nasty. That's when you either use an appropriate construction function to build the string (Tcl_NewListObj and Tcl_DStringAppendElement are useful here), or switch to using Tcl_EvalObjv. The latter has no quoting hazards, guaranteed (and in fact bypasses the parsing stage entirely). > Just my paranoia, maybe, but keeping user input away from parsing as > much as possible seems safer to me. If I am wrong, please tell me. Sounds very sensible to me. Good thing we've got the tools to do it already. Donal. |