Reading Hexadecimal value of an ASCII character..

[Duncan McLeod]

Morning everyone,

I'm still new to the programming world of C. I don't like asking for help but i think i may be asking for lots of help in the future months to come :(

Here's my problem..

I've been trying to write a command line program that will read a binary file, now say the following is an example of what i'm talking about:

00 00 FF 01 02 03 00 EF 34 67
00 01 FF 01 02 03 00 EF 34 67
00 02 FF 02 02 03 00 EF 34 67

The above Hex values all represent an individual character that have been formatted into lines of 10, in the binary file it's just one line of 30 characters.
what i'm trying to do is to count the occurances of a set of values into a counter and move on to read the next occurance.

so say i want to count how many times FF 01 appears in the file, however i only want it to count the ones that appear in the 3rd and 4th bit of every line. or:

00 00 FF 01 02 03 00 EF 34 67
00 01 FF 01 02 03 00 EF 34 67
00 02 FF 02 02 03 00 EF 34 67

how can i go about doing this? i've been racking my brain trying to come up with an answer but still no joy, Can anyone help me?

[sicarie]

Two ways come to mind, but both need to ensure that the formatting of the file is standard. You can use a regex to parse for groups, or pull it apart yourself with strtok() .

[Duncan McLeod]

ok, i've had a look at those, and creating tokens sounds like the better idea, however i've had another idea.workaround,

i could read the 4th and 5th bytes as a string using some form or character movement >> and compare that to a user input, then use an if statement to return true/false then move (??) spaces to the next occurance and repeat.

would this process work? could someone write a wuick line of code to express the movement of the pointer to the next value to check.

Regards

[sicarie]

Well, that would depend on how it is stored in memory, but the theory is correct. You'd probably have to worry about what came before as well (and 'and' it with something after you move it that will wipe out the first part and keep the second). But that would be a pain, strtok() would be a lot easier, IMHO.

[Duncan McLeod]

after having a good read about strtok() i don't beleive that i can use that to get the desired effect of the program, as i'm not working with ASCII at all. i would need the delimiter value so that strtok can follow the delimitered pattern, and there might not always be one.

If i want the values in Bold to be counted to their own counter, e.g 08 00 is one value i want to use and 08 01 is another, there may not always be a 00 infront of them, and if i used that as the starting point wouldn't it get confused with all the other 00's there?

01 00 08 00 1F FE 00 00 00 00 00 00 00 00
03 00 08 00 1F FE 00 00 00 00 00 01 00 00
02 00 08 01 1F FE 00 00 00 00 00 02 00 00
00 00 08 01 1F FE 00 00 00 00 00 03 00 00

Taking a step back and looking at it logically could i use an array structure to cut the continuous data... e.g (003265694732986859437210874169) into 3 arrays of 10 and then further divide each array into smaller arrays of 2+2+2+4 = 10 so that each of the smaller arrays A1-4 B1-4 C1-4 can be called into a true/false statement that can then be counted to a counter then printed on the screen?

The purpose of this is not to get the information to show up on the screen but to show how many times 08 00 apears in the file that is being read.

regards

[Duncan McLeod]

sorry i got a little too trigger happy with my keys, i meant to put in:

01 00 08 00 1F FE 00 00 00 00
03 00 08 00 1F FE 00 00 01 00
02 00 08 01 1F FE 00 00 02 00
00 00 08 01 1F FE 00 00 03 00

[ 01 00 ][ 08 00 ][ 1F FE 00 00 ][ 00 00 ]
[ 03 00 ][ 08 00 ][ 1F FE 00 00 ][ 01 00 ]
[ 02 00 ][ 08 01 ][ 1F FE 00 00 ][ 02 00 ]
[ 00 00 ][ 08 01 ][ 1F FE 00 00 ][ 03 00 ]