Ad:

C Discussion Thread
Marked Solved
Views: 6212

Page 1
2
Next

You are currently viewing page 1 of this multi-page discussion thread

Jun 20th, 2008

Sprintf and hex dumps

Expand Post »

Hey Guys,

I am new to C programming and I got a task of storing hex dumps in character array and then use them as a string. I use the sprintf function for the job but it is giving me incorrect results. Please help me out. I am writing a prototype of the functionality I want to use.

c Syntax (Toggle Plain Text)
#include<stdio.h>
int main()
{
	char a[25];
	int i;
	sprintf(a,"%d%d%d",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("\n%d",a[i]);
	}
	return 0;
}
#include<stdio.h>
int main()
{
	char a[25];
	int i;
	sprintf(a,"%d%d%d",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("\n%d",a[i]);
	}
	return 0;
}

Last edited by Ancient Dragon; Jun 20th, 2008 at 8:13 am. Reason: add code tags

gargg321

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

21 posts
since Jun 2008

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

"%d" will produce decimal. If you want hex then use "%x"

Try this:

C Syntax (Toggle Plain Text)
int main()
{
	char a[25];
	int i;
	sprintf(a,"%x%x%x",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("%c\n",a[i]);
	}
	return 0;
}
int main()
{
	char a[25];
	int i;
	sprintf(a,"%x%x%x",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("%c\n",a[i]);
	}
	return 0;
}

Last edited by Ancient Dragon; Jun 20th, 2008 at 8:20 am.

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 5608

Solved Threads: 2282

Retired and Enjoying Life

Offline

21,947 posts
since Aug 2005

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

I have tried it already. 1F should return the value 31 but instead it is returning 33. Same with all hex dumps. they all are returning incorrect results.

gargg321

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

21 posts
since Jun 2008

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

Change the %x to %d with the sprintf()
use %c when printing the chars

this code:

c Syntax (Toggle Plain Text)
int main()
{
	char a[25];
	int i;
	sprintf(a,"%d%d%d",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("%c",a[i]);
	}
	return 0;
}
int main()
{
	char a[25];
	int i;
	sprintf(a,"%d%d%d",0x0000001F,0x00000001,0x00271418);
	for(i=0;i<8;i++)
	{
		printf("%c",a[i]);
	}
	return 0;
}

works fine for me..

Last edited by Nick Evan; Jun 20th, 2008 at 8:40 am.

Nick Evan

Moderator

Featured Poster

Reputation Points: 4142

Solved Threads: 394

Industrious Poster

Offline

4,132 posts
since Oct 2006

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

sprintf() doesn't work that way. Each digit of the number will be placed in a different element of the character array. So for 0x1f the a[0] == '1' and a[1] == 'f' (assuming "%x")

C Syntax (Toggle Plain Text)
#include<stdio.h>
int main()
{
    char a[25] = {0};
	int i;
    a[0] = 0x1f;
    a[1] = 0x01;
    a[2] = 0x00271418;
	//sprintf(a,"%4d%4d%4d",0x0000001F,0x00000001,0x00271418);
	for(i=0; i <3; i++)
	{
		printf("%d\n",a[i]);
	}
    return 0;
}
}
#include<stdio.h>
int main()
{
    char a[25] = {0};
	int i;
    a[0] = 0x1f;
    a[1] = 0x01;
    a[2] = 0x00271418;
	//sprintf(a,"%4d%4d%4d",0x0000001F,0x00000001,0x00271418);
	for(i=0; i <3; i++)
	{
		printf("%d\n",a[i]);
	}
    return 0;
}
}

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 5608

Solved Threads: 2282

Retired and Enjoying Life

Offline

21,947 posts
since Aug 2005

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

@AD:

But that's not what he wants right? I thought he wanted the decimal values of the hex numbers stored as a string in a char-array?
So my code should be OK

Last edited by Nick Evan; Jun 20th, 2008 at 8:43 am.

Nick Evan

Moderator

Featured Poster

Reputation Points: 4142

Solved Threads: 394

Industrious Poster

Offline

4,132 posts
since Oct 2006

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

Click to Expand / Collapse Quote originally posted by niek_e ...

Change the %x to %d with the sprintf()
use %c when printing the chars

this code:

works fine for me..

But I think he was expending a[0] to be 31.

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 5608

Solved Threads: 2282

Retired and Enjoying Life

Offline

21,947 posts
since Aug 2005

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

Click to Expand / Collapse Quote originally posted by Ancient Dragon ...

But I think he was expending a[0] to be 31.

Hmm. Let's ask:

@gargg321:

Do you want an array like this:
a[0] = 31
a[1] = 1
etc

or like this:
a[0] = '3'
a[1] = '1'
a[2] = '1'
etc

Nick Evan

Moderator

Featured Poster

Reputation Points: 4142

Solved Threads: 394

Industrious Poster

Offline

4,132 posts
since Oct 2006

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

Guys I like the array to be of first option. I think the solution given by Ancient Dragon is OK with me but he is not using the sprintf function, instead he's given every element of array indidually. The string of hex dumps I have to use is real long and giving individual values is simply not possible. When I am using sprintf the problem still persists.

gargg321

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

21 posts
since Jun 2008

Permalink

Jun 20th, 2008

Re: Sprintf and hex dumps

You didn't answer Niek's question. Which way do you expect to see the data ? If you want it similiar to what I posted then you can't use sprintf(). And the way I posted, one char can only hold a value up to 127 decimal (signed integer). If the values are larger than that then you can't do it my way.

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 5608

Solved Threads: 2282

Retired and Enjoying Life

Offline

21,947 posts
since Aug 2005

Page 1
2
Next

This thread is solved

Either the thread starter or a moderator has marked this thread as solved. You can most likely trust the responses and answers given. There is most likely no reason for any further responses to be posted here. If you have a related question, please start a new thread in this forum instead.

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in C Forum Timeline: How to use timer in C?

Next Thread in C Forum Timeline: Help in taking input

DaniWeb Message

Cancel Changes

User Name
Password