[C]Hex from file to ASCII

sloppyjoe · **Joined:** 17 Mar 2009 21:04 **Posts:** 7

Need help again, working on a program that will take a string inputted by the user and write it to a file in hex form, I have done this but I also want it to be able to read hex from files and output it to ascii this is where I am having problems I began the function:

Code:

int readdata(void)
{
char file_name[40];
char filedata[9000];
int q=0;      /*number of characters file has*/
int count;     /*EOF flag from file*/
int i=0;
FILE *fp;
gets(file_name);
fp=fopen(file_name, "r");
if(fp==null) {
       printf("cannot find file");
       exit(8);
       }
while(1) {
ch=fgetc(fp);
count++;
if(count==EOF) break;
}
filedata=fscanf(fp, "%[^' ']%*x", struct.memberSTRING);
}

I am stumped (from this point) & am %99.9 certain that is entirely wrong can anyone help?

aluigi · **Posted:** 30 Apr 2009 23:42

depends all by the format of the input for making the tool more or less compatible (for example my hex2byte tool is written with compatibility in mind), anyway the following is a simple example able to catch any sequence of hex numbers attached or separated by spaces:

Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    FILE    *fd,
            *fdo;
    int     c;

    if(argc < 3) exit(1);

    fd  = fopen(argv[1], "rb");
    fdo = fopen(argv[2], "wb");
    if(!fd || !fdo) exit(1);

    while((fscanf(fd, "%02x", &c) == 1)) {
        fputc(c, fdo);
    }

    fclose(fd);
    fclose(fdo);
    return(0);
}

sloppyjoe · **Joined:** 17 Mar 2009 21:04 **Posts:** 7

you sir, are a genius!

aluigi · **Posted:** 01 May 2009 02:11

all merit of the *scanf functions :)

just remaining in theme of *scanf remember to never use the short and char form for specifying the output numbers, for example "char c; sscanf(buffer, "%02hhx", &c);" or "char c[1000]; for(blah) sscanf(buffer, "%02hhx", c);" because there is the risk to corrupting some parts of the adjacent memory.
so even if you are an optimization maniac and the output is a buffer use ever a temporary integer for placing the captured value of scanf.

Luigi Auriemma

[C]Hex from file to ASCII