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After converting the hexstr to Hex and storing the Hex in a char*


 
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# 1  
Old 08-09-2009
CPU & Memory After converting the hexstr to Hex and storing the Hex in a char*

Hi All,

My main intension of is to convert the Hexstring stored in a char* into hex and then prefixing it with "0x" and suffix it with ','

This has to be done for all the hexstring char* is NULL.

Store the result prefixed with "0x" and suffixed with ',' in another char* and pass it to another module.

I just want to print and see the values in the result char* to see if it is stored as 0x30, (say when the input char* a = "30" )

How can I verify the values stored in the char*...?

I cannot print it neither as %s nor %x both gives junk values.. %s gives junk because it is hex and %x gives junk because i have formatted with "0x30," i think.. But am not clear and don't know how to check if the values got stored in this format. 0x30,


- Thanks






Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>


int hexstr2bin(const char *hex_input, char *buf_output, size_t len);
static int hex2byte(const char *hex);
static int hex2num(char c);

main()
{
	int len;
	char* buf;

	const char* hex ="abcd1234567890";

	buf = (char*)malloc(100);

	len = strlen(hex);

	hexstr2bin(hex,buf,len);

	printf("Values in hex %s",buf);
}


int hexstr2bin(const char *hex_input, char *buf_output, size_t len)
{
	size_t i;
	int a;
	const char *ipos = hex;
	char *opos = buf;
	char *prefix = "0x";

	for (i = 0; i < len; i++) {
		a = hex2byte(ipos);
		if (a < 0)
			return -1;
		*opos++ = prefix[0];
		*opos++ = prefix[1];

			
		*opos++ = a;

		
		*opos++ = ',';
		ipos += 2;
	}
	return 0;
}


static int hex2byte(const char *hex)
{
	int a, b;
	a = hex2num(*hex++);
	if (a < 0)
		return -1;
	b = hex2num(*hex++);
	if (b < 0)
		return -1;
	return (a << 4) | b;
}


static int hex2num(char c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;
	return -1;
}

# 2  
Old 08-09-2009
> convert the Hexstring stored in a char* into hex and then prefixing it with "0x" and suffix it with ','
I'm not really sure what you're trying to accomplish with that. A C-string in hex format is *one* printable representation of a number. In the computer's storage there is no such thing as hex format, it's just bits and bytes.

So, without reading your code, the only sane thing regarding number conversion is to switch between representations. I would suggest something like this:
> snprintf(string, sizeof(string)-1, "%x", (unsigned int)n)

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