FILE + conversion from dec to hex = I need help

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Re: FILE + conversion from dec to hex = I need help

#11

Nov 12th, 2006

you could google for your question. Here is one way to do it. And another here.

Last edited by Ancient Dragon : Nov 12th, 2006 at 2:24 pm.

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Re: FILE + conversion from dec to hex = I need help

#12

Nov 12th, 2006

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Originally Posted by Sin-da-cat

So my questions would be:

1. is my general idea alright?

Yes. But you should pass in the hex array. C cannot return a character array. Also, format your code. Indentation is extremely important at all times. So is spacing between terms, like:

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while (fscanf(a, "%d", &broj) != EOF)

Much easier to read.

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char dek_hex(int m){    /* this is where my problems start. No matter
                           how I write the function, I keep getting all 
                           kinds of error messages */

Unless you post something you've tried, we have nothing to help with.

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Originally Posted by Sin-da-cat

2. what should my function look like?

Basic idea in my previous post.

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Originally Posted by Sin-da-cat

3. can it be done without a function?

Yes it can. Considerations:
function: Modularizes the program, easier to reuse the function in another program later. Somewhat easier to debug.
non-function: Not passing the hex array is a minor benefit.

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Originally Posted by Ancient Dragon

like I mentioned in my previous post, printf() family of functions, which includes ssprintf(), will convert int to hex using "%X" .

Wouldn't this nullify the purpose of understanding how decimal to hex works?

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Re: FILE + conversion from dec to hex = I need help

#13

Nov 13th, 2006

OK, nevermind, I figured it out. I threw out the function and just did the whole conversion from dec to hex in the body of 'fscanf' with local variables. I realized using a function was a completely pointless complication.

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#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main(){
FILE *c,*b;
int a;
c=fopen("C:\\C_fajlovi\\dec.txt","r");
b=fopen("C:\\C_fajlovi\\hex.txt","w");
if (c==NULL){
puts("Error!");
exit(1);
}
if (b==NULL){
puts("Error!");
exit(1);
}
while (fscanf(c,"%d",&a)!=EOF){
 char s[30],temp;
 int i=0;
 if (a==0)
  s[i++]='0';
    while (a>0){                                    /*turning a dec (int) to a hex (string) value*/
        if ((a%16)<=9)
         s[i++]=(a%16)+'0';
        else if ((a%16)==10)
         s[i++]='A';
        else if ((a%16)==11)
         s[i++]='B';
        else if ((a%16)==12)
         s[i++]='C';
        else if ((a%16)==13)
         s[i++]='D';
        else if ((a%16)==14)
         s[i++]='E';
        else
         s[i++]='F';
        a/=16;
        }
    s[i]='\0';                 /*I was missing this part the last time, which is one of the reasons the whole program was acting crazy*/
    for (i=0;i<strlen(s)/2;i++){
     temp=s[i];             /*got a reversed string, turning it around*/
        s[i]=s[strlen(s)-i-1];
        s[strlen(s)-i-1]=temp;
        }
        fprintf(b,"%s\n",s);
    }
}
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main(){
FILE *c,*b;
int a;
c=fopen("C:\\C_fajlovi\\dec.txt","r");
b=fopen("C:\\C_fajlovi\\hex.txt","w");
if (c==NULL){
puts("Error!");
exit(1);
}
if (b==NULL){
puts("Error!");
exit(1);
}
while (fscanf(c,"%d",&a)!=EOF){
 char s[30],temp;
 int i=0;
 if (a==0)
  s[i++]='0';
    while (a>0){                                    /*turning a dec (int) to a hex (string) value*/
        if ((a%16)<=9)
         s[i++]=(a%16)+'0';
        else if ((a%16)==10)
         s[i++]='A';
        else if ((a%16)==11)
         s[i++]='B';
        else if ((a%16)==12)
         s[i++]='C';
        else if ((a%16)==13)
         s[i++]='D';
        else if ((a%16)==14)
         s[i++]='E';
        else
         s[i++]='F';
        a/=16;
        }
    s[i]='\0';                 /*I was missing this part the last time, which is one of the reasons the whole program was acting crazy*/
    for (i=0;i<strlen(s)/2;i++){
     temp=s[i];             /*got a reversed string, turning it around*/
        s[i]=s[strlen(s)-i-1];
        s[strlen(s)-i-1]=temp;
        }
        fprintf(b,"%s\n",s);
    }
}

If someone has any suggestions they're still welcome.

Last edited by Sin-da-cat : Nov 13th, 2006 at 3:20 pm.

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Re: FILE + conversion from dec to hex = I need help

#14

Nov 13th, 2006

>>while (fscanf(c,"%d",&a)!=EOF){

fscanf() does NOT return EOF one eod-of-file. EOF is returned only if there was a conversion error. What you want is this:

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while (fscanf(c,"%d",&a) > 0){

Last edited by Ancient Dragon : Nov 13th, 2006 at 3:28 pm.

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Re: FILE + conversion from dec to hex = I need help

#15

Nov 14th, 2006

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Originally Posted by Ancient Dragon

>>while (fscanf(c,"%d",&a)!=EOF){

fscanf() does NOT return EOF one eod-of-file. EOF is returned only if there was a conversion error.

My thought: the while(fscanf... loop would go through the file line by line untill it gets to EOF, at which point it will stop. It works just fine in every program I write (including the one I posted), never had a problem with that.

What will fscanf return when it gets to the end? What you suggested works too, so I suppose it returns 0, but how come my version always works, then?

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Re: FILE + conversion from dec to hex = I need help

#16

Nov 14th, 2006

Because EOF is actually a maro which is defined in stdio.h as

#define EOF <integer constant expression < 0>

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The macro yields the return value used to signal the end of a stream or to report an error condition

In your case its the end of stream thing which is causing the break of loop.
In Mr. Dragons case it is the 0 which is returned by the fgets( ) which is causing the termination.

Last edited by ~s.o.s~ : Nov 14th, 2006 at 11:03 am.

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Re: FILE + conversion from dec to hex = I need help

#17

Nov 14th, 2006

Here is an example that will illustrate the difference between using EOF and 0. In this example, checking for EOF causes infinite loop because end-of-file is never reached due to conversion error. If you uncomment the while statement that check for 0 then the program will stop when conversion error occurs.

When you wrote your programs for school you probably wrote sample data files that did not contain errors. That will not always be the case in real-world.

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#include <stdlib.h>
#include <stdio.h>
 
int main(int ac, char** av) 
{
	int a;
	int counter = 0;
	FILE* fp = fopen("myfile.txt","r");
	if(fp != NULL)
	{
		while( fscanf(fp,"%d",&a) != EOF)
//		while( fscanf(fp,"%d",&a) > 0)
		{
			printf("%d\n",counter++);
		}
		fclose(fp);

	}
	return 0;
}

This is sample data file

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1
2
40
abc
5a

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Re: FILE + conversion from dec to hex = I need help

#18

Nov 14th, 2006

Ah, I see what you mean. Had to put a 'getchar()' after 'fclose' though so the black screen would stay open more than a milisecond.

Thanks for the answers.