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overmindx
Joined: 06 Oct 2008
Posts: 43
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| length of float array |
 Posted: Tue Mar 27, 2012 4:20 am |
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hi,
if i have a float array
| Code: |
float arr[20] = {};
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and during the course of my process, this array is being filled up with values. how can i find out the length of my array that is being used. i mean, is there like a function like strlen but will work with float arrays?
please help |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19510
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| Posted: Tue Mar 27, 2012 4:32 am |
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No.
Strlen only 'works', because a 'string' in C is 'null terminated'. So the routine can look through the characters till it finds this 'null', and know how long the string is.
Assuming that you value can never have some specific unused byte value (for example all four bytes=0xff - which is an unused pattern in both IEEE float, and CCS float), then you could generate a 'strlen' equivalent, by filling the array with this value, and testing where it is in the array to find the number of locations used - remember though that just as with a 'string', this would then require the array to be one number _larger_, so there is always room for the extra terminator.
However I have to point out, that if you are filling the array, then you must have a counter saying where you are writing the data, and this in itself tells you how many values are 'in use'.....
Best Wishes |
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RF_Developer
Joined: 07 Feb 2011
Posts: 839
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| Posted: Tue Mar 27, 2012 6:17 am |
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In C strings are a special case of character arrays as Ttelmah points out. In C all arrays are fixed length. They don't change size. How much data you put into them is entirely your business, and for you to keep track of.
Maybe you're used to C# which has flexible collections. This built on C++'s standard library which includes collection-like objects. These simply don't exist in C. That's a good thing, as otherwise the memory overhead would be so overwhelming that almost none of our code would fit in a PIC.
RF Developer |
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Tue Mar 27, 2012 6:45 am |
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for one of my projects i had a buffer that got filled with a string comming in through serial.
the buffer contained commands to be executed, and they varied in length.
so what i did was prior to listening for an incomming command i would initialize my buffer to all NULL:
| Code: | | Buffer = {'\0','\0','\0','\0','\0','\0','\0','\0','\0'} //not actual code. |
my serial ISR would strart filling up the buffer from Buffer[0];.
so i ended up with somthing like:
| Code: | | Buffer = {'f','o','o','b','a','r','\0','\0','\0'} //not actual code |
from then on, i could do what ever string manipulations i needed.
in my case, STRSTR().
you can also have a string as such:
| Code: | | Buffer = {'f','o','o','b','a','r','1','\0','f','o','o','b','a','r','2','\0','f','o','o','b','a','r','3','\0'} //not actual code |
do comparisons and searches starting from other possitions not '0'.
maybe that helps you.
G.
_________________
CCS PCM 5.078 & CCS PCH 5.093 |
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