what to do with unused array elements

droseman · 11-05-2009, 05:17 AM

Hello,

I have some arrays in my code which will contain different messages of varying lengths, so I have sized my arrays to take the longest ones (plus 1 or two elements on the end), but how do I ensure that if the message is shorter than maximum, there is not junk in the unused elements which would be sent out my serial port?

Thanks
Dave

RockyMarrone · 11-05-2009, 05:32 AM

before filling the value in your array just

Code:

memset(array, 0,  sizeof(size) * MAX_NUMBER)

and initailize your array like

Code:

array[MAX_NUMBER] = {0}

whiteflags · 11-05-2009, 05:44 AM

The third argument to memset is computed like (sizeof(array[0]) * MAX_NUMBER), because the function expects a number of bytes.

droseman · 11-05-2009, 06:12 AM

Thanks for that info Rocky, that sounds like just what I need. Just to clarify, I invoke this function when I am declaring my arrays? Also, can I insert this code into a struct member declaration, or would I have to declare my arrays separately first?

--dave

RockyMarrone · 11-05-2009, 06:30 AM

You are most welcome Enjoy C/C++ programming

11-05-2009, 05:17 AM	#1
droseman Embedded in C... Join Date: Sep 2008 Location: Basingstoke, Hampshire Posts: 65	what to do with unused array elements Hello, I have some arrays in my code which will contain different messages of varying lengths, so I have sized my arrays to take the longest ones (plus 1 or two elements on the end), but how do I ensure that if the message is shorter than maximum, there is not junk in the unused elements which would be sent out my serial port? Thanks Dave
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11-05-2009, 05:32 AM	#2
RockyMarrone Registered User Join Date: Oct 2009 Location: While(1) Posts: 316	before filling the value in your array just Code: memset(array, 0, sizeof(size) * MAX_NUMBER) and initailize your array like Code: array[MAX_NUMBER] = {0}
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11-05-2009, 05:44 AM	#3
whiteflags Registered User Join Date: Apr 2006 Location: United States Posts: 3,202	The third argument to memset is computed like (sizeof(array[0]) * MAX_NUMBER), because the function expects a number of bytes. __________________ Os iusti meditabitur sapientiam Et lingua eius loquetur indicium "There is nothing either good or bad, but thinking makes it so." (Shakespeare, Hamlet, Act II scene ii) http://www.myspace.com/whiteflags99
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11-05-2009, 06:12 AM	#4
droseman Embedded in C... Join Date: Sep 2008 Location: Basingstoke, Hampshire Posts: 65	Thanks for that info Rocky, that sounds like just what I need. Just to clarify, I invoke this function when I am declaring my arrays? Also, can I insert this code into a struct member declaration, or would I have to declare my arrays separately first? --dave Last edited by droseman; 11-05-2009 at 06:14 AM. Reason: extra info
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11-05-2009, 06:30 AM	#5
RockyMarrone Registered User Join Date: Oct 2009 Location: While(1) Posts: 316	You are most welcome Enjoy C/C++ programming
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