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John Morley
Joined: 09 Aug 2004
Posts: 97
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| Parsing a variable length string..... |
 Posted: Thu Mar 10, 2011 1:36 pm |
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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;
}
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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 |
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temtronic
Joined: 01 Jul 2010
Posts: 9224
Location: Greensville,Ontario
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| Posted: Thu Mar 10, 2011 2:43 pm |
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| Somehow I feel that the 'isdigit' function would be useful for parsing if x,xx,y,yyy are numbers... |
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newguy
Joined: 24 Jun 2004
Posts: 1907
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| Posted: Thu Mar 10, 2011 3:52 pm |
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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. |
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