QL Software
1 rem --------------------- cut here ---------------------| rem 1 CLS:DELETE_DIRECTORY 'ram1_','temp_', 1 2 : rem NB! WARNING! ACHTUNG! VARSKU I SKAUEN! VARNING! LET OP! VIVA!;> rem rem Careless use of this program rem rem may have A D E V A S T A T I N G E F F E C T rem rem on your life rem for all I know. I could list reams of possible ways things could rem go wrong, and the consequences subsequent thereunto, as a result rem of using this potentially HAZARDOUS software; whether used as rem intended, or in error. Please take this WARNING seriously, rem because you see, whatever happens, that'll be ENTIRELY rem YOUR OWN FAULT. I accept NO responsibility WHATSOEVERNONOTI! rem for YOUR ACTIONS - or your rotten luck, for that matter. rem However, if you like it, if it improves your understanding or rem inspires you if, in a funny sort of way, it leads to your rem promotion, or saves your marriage, teaches your kids to break rem the bank, or.. Then REMEMEBER ME. That's MY doing. That shows I rem got it right, and that YOU took good note of this warning! 10 REMark DELETE_DIRECTORY 11 REMark S*BASIC PROCedure to delete an 12 REMark entire directory tree 13 REMark Requires tk2 or equivalent 14 REMark ©PWitte 1998 15 REMark Use at own risk! No warranties! 16 REMark Parameters: 17 REMark dev$ = device; eg win1_, ram2_ 18 REMark dir$ = directory; eg temp_ 19 REMark tree: 0 => files only 20 REMark <>0 => dirs and files 21 : rem For the benefit of qlers (of all ages) who, like myself, rem enjoy reading (short snippets!) of other people's commented rem code. I enjoy a small, well-defined problem - like rem traversing the directory tree - much as others might like a rem crossword puzzle. Except this is fun! rem rem If you just want to get on and try it: rem cut out the bit between the two --- cut here --- lines. rem Save it as a file named say, flp1_DelDir.txt. rem LOAD 'flp1_deldir.txt' into BASIC. rem SAVE 'win1_temp_DelDir_bas', for example. rem Re-LOAD it and check if any lines start with MIStake. rem rem Genuine bug or incompatibility reports (and comments) rem welcomed - and where appropriate, may be dealt with. rem NB No other support provided! rem NB These rem lines may miraclulously disappear! 1000 DEFine PROCedure DELETE_DIRECTORY(dev$, dir$, tree) rem To remind the user what s/he's about to do, an awkward name rem has been chosen. rem rem The selection of parameters has been made to avoid parsing. rem ---------- rem The dir$ parameter seeds the name variable n$. The reason for rem for not re-using the dir$ parameter and dispensing with n$ rem altogether is that n$ changes, and if dir$ were used as a rem variable an unintended change would be passed all the way rem back to the calling code's variables! In S*BASIC all rem parameters are passed by Reference ie, the parameter passes rem an actual copy of the calling variable - a very nice feature. rem But in this instance it would be safer to pass the variable rem by Value ie, only the value is passed, completely disociated rem from the variable. (I'll have a bit more to say on that rem subject in an upcomming QHJ article (if my contribution is rem deemed acceptable)). rem rem tree is simply a switch to enable the whole sub-directory rem tree to be scanned. In SBASIC it defaults to off, as all rem variables are pre-initialled to zero/nul. In SuperBASIC rem a value must always be supplied. rem rem I've chosen a none-recursive tree traversal algorithm here rem As traversing a tree structure is by nature a recursive rem operation this entails the use of a stack. This stack only rem explicitly needs to store the S*BASIC channel numbers; the rem remaining information required - namely our current file rem position in each open directory - is "remembered" by the rem the file system itself. 1010 LOCal c%, t%, pos, ch%(17), n$(36) 1020 n$ = dir$: c% = 0 rem The maximum level of recursion can only be 19 deep (0..18) rem DIM ch%(18), or rather LOCal ch%(18), sets it up. rem (Remember we only need to store the S*BASIC channel rem numbers, and they're integer.) rem rem c% is our stack pointer, and for SuperBASIC's sake, we rem initialise it to 0. rem rem t% is just a help variable to store the type of the file rem we're looking at. rem rem pos maintains our current-directory record position, rem rem n$(36) contains the current directory or file name. 1030 REPeat dir_loop rem The outer loop is invoked each time a new directory rem is to be opened ie, the first time, and then for every rem recursive step down the sub-tree. 1040 ch%(c%) = FOP_DIR(dev$ & n$) rem Here the current directory is opened and it's channel rem number is stacked. rem (The very first time through the loop c% = 0, and rem n$ contains the value passed in dir$) 1050 IF ch%(c%) < 0: Action '', ch%(c%) rem If an error occurs the channel number will be a negative rem error code, thanks to FOP_DIR. rem rem The Action sub-routine is defined below. Taking the action rem routine out of the main body of the code perhaps makes it rem easyer to modify for other tasks. The action routine does rem not return on an error parameter! 1060 pos = -64 rem Initialise pos (somewhere where we can see it!) 1070 REPeat file_loop rem The inner loop goes through every entry in a directory file rem once: If the current entry is a new directory file, it rem temporarily postpones what it's doing and then does the whole rem sub-tree (and any sub-trees of that again) before returning rem to continue processing the next entry. 1080 pos = pos + 64 rem Each directory entry, or record, is 64 bytes long, starting rem at position 0. The structure of the directory header table rem looks like this (there doesn't appear to be an "official" rem version, so here's mine (appended)): rem 1090 IF pos >= FLEN(#ch%(c%)) THEN rem here we're checking for End Of File 1100 n$ = FNAME$(#ch%(c%)): CLOSE#ch%(c%) rem All subdirectories and files in Current Directory (CD) have rem been deleted at this point. We lost the CD's name when we rem start processing it, but it can be regained from its rem Channel Definition Block with FNAME$. We're done with rem this directory, all that's left to do now is to close it and 1110 IF tree: Action 'Deleting', 1 rem delete it (if appropriate). rem rem Here the tree switch is checked to see if all subdirectories rem have been deleted (you can only DELETE an empty directory). 1120 c% = c% - 1: IF c% < 0: EXIT dir_loop rem Pop the stack ie, proceed to a higher level. If the stack rem "underflows" (c% < 0) then it's the end - we're done! 1130 pos = INT(FPOS(#ch%(c%)) / 64) * 64 rem At line 1130 we don't know exactly where the file pointer is! rem Getting it is no problem: pos = FPOS(ch%(c%)). But it has to rem be aligned to the record boundry, so amputate any bits rem sticking out. (INT is word sized in SuperBASIC, so this could rem error on a hard disk! (if youre lucky enough to have one..)) 1140 ELSE rem This is the second main program block. The first block dealt rem with rear-guard action; closing doors, turning off lights, rem picking up new trails.. This part does most of the work. It rem gets information from the file header, sorts directories from rem files, and makes other decisions based on parameters and rem data. 1150 GET#ch%(c%)\ pos + 14; n$ rem GET (and BGET, both inluded in tk2 and similar toolkits) has rem the following syntax: rem GET #channel [\ position], items rem The name of the file (or directory) is located at record rem base (ie, pos) + 14 (see end of listing). It's a string in rem the internal format, len.w + chars.bb 1160 IF LEN(n$) > 0 THEN rem If the filename length is 0, the file has been deleted, rem although its slot in the directory still remains. This rem may be re-used when a new file is added to the directory. 1170 BGET#ch%(c%)\ pos + 5; t% 1180 IF t% = 255 THEN rem File type 255 indicates a directory. A minority of drivers rem may use a different type number for this! (eg Thor?) 1190 IF tree THEN 1200 Action 'Checking', 2 rem Only go down this rabbit hole if the tree flag is set. 1210 c% = c% + 1: EXIT file_loop 1220 END IF 1230 ELSE 1240 Action 'Deleting', 0 rem Here we have a file or a (now) empty directory, so do the rem business! 1250 END IF 1260 END IF 1270 END IF 1280 END REPeat file_loop 1290 END REPeat dir_loop 1300 END DEFine 1310 : rem The following routine is the sharp end of the enterprise. rem It could be doing other stuff than deleting files; for rem example just displaying information about them. 2000 DEFine PROCedure Action(tx$, type) 2010 IF CODE(INKEY$(#0; 0)) = 27: CLOSE: ERT -1 2020 IF type THEN 2030 IF type < 0: CLOSE: ERT type rem We've made this routine respond to different codes. Here rem is the response to any negative code: an error. TK2's rem CLOSE routine, without a channel number, closes ALL open rem channels > #2. ERT throws the error code given and halts rem the program. 2040 PRINT \ tx$! dev$; n$! '->' 2050 IF type = 1: DELETE dev$ & n$ rem Code (ie type) 1 does the business for directories.. 2060 ELSE 2070 PRINT tx$! n$ 2080 DELETE dev$ & n$ rem ..while code 0 does the same for simple files. 2090 END IF 2100 END DEFine 2110 : rem rem File Header Definition rem mnemonic pos size description rem rem fht_len 0 long file length rem fht_acces 4 byte file access key rem fht_type 5 byte file type: rem rem fht.bod 0 basic program or ordinary data files rem fht.exe 1 executable program rem fht.rel 2 relocatable object files rem fht.thd 3 Thor directory files (ArgOS) rem Others ? rem fht.dir 255 directory files (standard) rem rem fht_finf 6 8 bytes of file type-dependent information rem fht_data 6 long default data space for executable files rem rem fht_name 14 qstr name string rem fht.nmln 36 max file name length rem fht_updt 52 long date of last update rem fht_vers 56 word version number rem fht_filn 58 word file number rem fht_bkdt 60 long date of last backup rem -------------------------- cut here ---------------------------|
QL Software