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C language => Tips & tricks => Topic started by: TimoVJL on May 02, 2016, 06:27:56 PM

Title: Hex2Int() example
Post by: TimoVJL on May 02, 2016, 06:27:56 PM

Ispired by masm32 forum topic here (http://masm32.com/board/index.php?topic=5323.msg57148#msg57148)

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int Hex2Int(char *s)
{
int n = 0;
unsigned char ch;
while (*s) {
ch = *s - '0';
if (ch >= 49 && ch <= 55) ch -= 39; // 'a' - '0'
else if (ch >= 17 && ch <= 22) ch -= 7; // 'A' - '0'
else if (ch < 0 || ch > 16) break;
n = n<<4;
n += ch;
s++;
}
return n;
}

Title: Re: Hex2Int() example
Post by: jj2007 on May 07, 2016, 08:37:52 AM

Hi Timo,
Does this work for you? I always get zero...

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#include <stdio.h>

#pragma warn(disable:2216)    // retval never used
#pragma warn(disable:2007)    // assembly not portable
#pragma warn(disable:2018)    // _getch
#pragma comment(linker, "/subsystem:console" )

int Hex2Int(char *s)
{
int n = 0;
unsigned char ch;
// _asm int 3;
while (*s) {
ch = *s - '0'; /// <- sure?
if (ch >= 49 && ch <= 55) ch -= 39; // 'a' - '0'
else if (ch >= 17 && ch <= 22) ch -= 7; // 'A' - '0'
else break;
n = n<<4;
n += ch;
s++;
}
return n;
}
int main(void) {
  printf("%i\n", Hex2Int("123h"));
  _getch();
}

Title: Re: Hex2Int() example
Post by: TimoVJL on May 07, 2016, 09:06:45 AM

My mistake :(
value check should be

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...
else if (ch < 0 || ch > 16) break;
...not

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else break;