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Forum Index : Microcontroller and PC projects : Longstring Split
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Malibu Senior Member Joined: 07/07/2018 Location: AustraliaPosts: 228 |
With lots of coding using the WebMite, I find there's a lot of string manipulation - sometimes with longstrings and sometimes normal strings with conversions back and forth, finding character positions, extracting strings and so on... So I wondered if there was maybe another way to tackle it. I miss the old VB6 'Split' function, so based on that, I tried a similar idea for longstrings. This function takes a longstring, splits it at a delimiter character and stores the results in an array of 'normal' strings to be worked on later. Usage: Call the function and pass the longstring + the delimiter character, and the number of array elements created are passed back. ie: timer = 0 ArrElements = LSplit(ConnData(), "&") ? "Elapsed time stamp " + str$(timer) for i = 1 to ArrElements ? "Next element : "; ? SplitArr(i) next i function LSplit(LSplitStr() as integer, Delimiter as string) as integer local integer i = 0, j = 0, NextPos = 0, LastPos = 0 if LCheck(LSplitStr(), Delimiter) = 0 then 'check if we have valid parameters exit function endif do NextPos = linstr(LSplitStr(), Delimiter, NextPos + 1) 'find the next delimiter if NextPos = 0 then 'if it's not found exit do 'there's nothing more to look for, get out else 'otherwise j = j + 1 'add to the variable endif loop 'go and look again on error skip 'in case the array doesn't exist erase SplitArr() 'get rid of any existing array dim string SplitArr(j + 1) 'create a new array for the split results... +1 for the last result for j = 1 to bound(SplitArr()) '1 to the number of elements in the array NextPos = linstr(LSplitStr(), Delimiter, LastPos + 1) 'get the next delimiter position if NextPos = 0 then 'if there's none left NextPos = llen(LSplitStr()) + 1 'set the nextpos to the end of the string (+1 to be subtracted later) endif SplitArr(j) = lgetstr$(LSplitStr(), LastPos + 1, NextPos - LastPos) 'add the string to the array on error skip if right$(splitarr(j), 1) = delimiter then SplitArr(j) = left$(SplitArr(j), len(SplitArr(j)) - 1) 'remove the delimter char from the stored string endif LastPos = NextPos 'reset the variables for the next loop around LSplit = j 'keep track of how many elements there are next j end function function LCheck(LSplitStr() as integer, Delimiter as string) as integer if llen(LSplitStr()) = 0 then 'zero length string ? "Longstring is required" 'as it says LCheck = 0 exit function 'get out endif if Delimiter = "" then 'no delimiter ? "Delimiter is required" 'as it says LCheck = 0 exit function 'get out endif if len(Delimiter) > 1 then ? "Too many characters in the delimiter" LCheck = 0 exit function endif if linstr(LSplitStr(), Delimiter, 1) = 0 then ? "Delimiter char not found" 'as it says LCheck = 0 exit function 'get out endif LCheck = 1 end function So far seems to work OK, hopefully others might find it useful Edit: Fixed a line of code that could result in losing a character on the fina; element of the array Edited 2024-10-05 10:43 by Malibu John |
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EDNEDN Senior Member Joined: 18/02/2023 Location: United StatesPosts: 117 |
I think a better solution would be a string type that can expand or shrink to whatever size is needed to hold the data. There were limitations on the max string length in the Microsoft Basic. But those limitations can be ignored now days. Wouldn't it make sense to have strings of arbitrary length and self-adjusting in memory usage in MMBasic? In the Microsoft system the first byte said how long the string was. If the first 3 (or 4) bytes specified the string length in MMBasic, your needs would be met? The biggest problem I see is the garbage collection. It would chew up and fragment the heap. But even that isn't too big of a deal. Doing the garbage collection to de-fragment the free memory area of the heap would be almost trivial. (With the understanding that defragmentation is expensive computationally and if you are operating at the edge of free memory your program is going to slow down.) |
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Malibu Senior Member Joined: 07/07/2018 Location: AustraliaPosts: 228 |
Sorry EDN, I might have been a little confusing in my post. It took me a few reads of your post for me to understand what your suggestion was pointing to... I don't mean a string of a long length, I mean a LongString of the data type From the manual In my case, a longstring is the data that comes in as a HTTP request, sometimes containing POST data that needs to be tended to. I find it's easier to break a 'longstring' into a 'normal' string (or array) and deal with smaller chunks. A HTTP request from this to this ...is easier for my barely functioning brain-cells to follow John |
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JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3797 |
It's also going to mess with the (mostly?) predictable real-time nature of MMBasic. (Not to mention adding quite complex code liable to have bugs.) I suspect it wouldn't fit on several/most PIC32 CPUs as space is at a real premium on them. John |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6766 |
One of the beautiful things about MMBasic is that it has no garbage collection and doesn't need it. It's an elegant system designed for machines with little RAM. If you even hint that it might be a good idea to introduce it Geoff and Peter will likely "send the boys round" to persuade you differently. ;) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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