CODEWITHSUNDEEP
cstringinthex
Glove
Glove

Reputation: 960

hexadecimal string to int conversion in C

I have a text file with hexadecimal values, after I fscanf a value I need to know how I can convert it from hexadecimal string to an int. And then convert it back to hexadecimal string for a later print. Anyone knows an algorithm for this? thank you.

Upvotes: 0

Views: 2609

Answers (3)

Daniel
Daniel

Reputation: 6775

As Marlon said above:

int a, b, c;
fscanf(fp, "%x %x %x", &a, &b, &c);

To print back as hex strings

fprintf(fp, "%x %x %x", a, b, c);

I think that you might be confused about the way the computer stores variables of type int. They are not stored in base 10. They are stored in binary, as I'm sure you know. That means that there is nothing special about assigning a hex value to an int. It won't be stored any differently. Using the %x just shows that you want the program to understand that the number you are giving it is a hex number (for example so it knows to store the string "10" as 10000(2) rather than as 1010(2). Same thing with output. If your variable a has the binary 10000(2) and you print it using %x, the program knows that the output should be 10. If you use %d, it knows that the output should be 16.

Upvotes: 2

Marlon
Marlon

Reputation: 20332

You should use the %x format specifier instead of %s to read your values. This will read the data as hexadecimal integers.

For example, if your file looks like this:

ff3c 5a cb2d

Then you can read those 3 values like this:

int a, b, c;
fscanf(fp, "%x %x %x", &a, &b, &c); // a = 0xff3c, b = 0x5a, c = 0xcb2d

Upvotes: 4

Oliver Charlesworth
Oliver Charlesworth

Reputation: 272812

Use the %x format specifier in your fscanf and fprintf strings.

Upvotes: 3

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