 |
 |
| View previous topic :: View next topic |
| Author |
Message |
John Morley
Joined: 09 Aug 2004
Posts: 97
|
| Parsing a variable length string..... |
 Posted: Thu Mar 10, 2011 1:36 pm |
 |
|
Hi All,
I need to parse a string that contains fields of variable length. I've got it working, but my "solution" seems to be a bit of a kludge, so I'm hoping to get some other ideas!
I need to parse a string in these formats:
A=xxx, B=yyy<Cr> or A=xxx B=yyy<Cr>
These strings are identical except one has a comma separator, and the other has a space. Note the 'xxx' and 'yyy' portions can be 'x', 'xx', or 'xxx' and 'y', 'yy', or 'yyy'.
To illustrate my technique, I'll just show how I get the first part:
| Code: |
for(iIndex = 2 ; Msg_Buffer[iIndex] != ',' && Msg_Buffer[iIndex] != ' ' ; iIndex++)
{
DigitCount++;
}
// Let's decode the address and act on it.....
switch (DigitCount)
{
case 1: // here we have a single digit
RcvAddress = gethexbyte(Msg_Buffer[2]);
break;
case 2: // here we have 2 digits
RcvAddress = (10 *gethexbyte(Msg_Buffer[2])) + gethexbyte(Msg_Buffer[3]);
break;
case 3: // here we have 3 digits
RcvAddress = (100 * gethexbyte(Msg_Buffer[2])) + (10 * gethexbyte(Msg_Buffer[3])) + gethexbyte(Msg_Buffer[4]) ;
break;
}
|
Again, it's working, but it seems like there must be a 'cleaner' approach? I'd like to do it all in the 'For Loop', but the problem is that the digit 'weight' is not known until the total number of digits is determined.
Thanks,
John
_________________
John Morley |
|
 |
temtronic
Joined: 01 Jul 2010
Posts: 9241
Location: Greensville,Ontario
|
|
| Posted: Thu Mar 10, 2011 2:43 pm |
|
|
| Somehow I feel that the 'isdigit' function would be useful for parsing if x,xx,y,yyy are numbers... |
|
|
newguy
Joined: 24 Jun 2004
Posts: 1908
|
|
| Posted: Thu Mar 10, 2011 3:52 pm |
|
|
What I'd do is:
| Code: | #define CR 0x0d
int1 found_A = FALSE;
int1 found_B = FALSE;
int16 first_digit = 0;
int16 second_digit = 0; // set these variable sizes to whatever you like
i = 0;
do {
switch (MsgBuffer[i]) {
case 'A':
found_A = TRUE;
found_B = FALSE;
break;
case 'B':
found_B = TRUE;
found_A = FALSE;
break;
default:
if (found_A && isdigit(MsgBuffer[i]) {
first_digit = (10 * first_digit) + (MsgBuffer[i] - 0x30);
}
if (found_B && isdigit(MsgBuffer[i]) {
second_digit = (10 * second_digit) + (MsgBuffer[i] - 0x30);
}
}
i++;
} while (MsgBuffer[i] != CR); |
This will fail if the CR isn't in the string, but the nice thing about it is that A and B can be out of order (B comes before A) and the algorithm will still properly extract your data.
I also assumed that the number is in ascii format in the string, and that's the reason for the 0x30 offset being subtracted. |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
