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Problem with "atoi"

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fbtech

Joined: 25 Mar 2015
Posts: 7

Problem with "atoi"

Posted: Thu Apr 30, 2015 5:42 am

Hello,
I'm using "atoi" as follows:

Code:

#include <main.h>

char date_mday[2] = "", date_mon[2] = "", date_year[2] = "", date_hour[2] = "", date_min[2] = "", tm_sec[2] = "";
unsigned int date_mday_v = 0, date_mon_v = 0, date_year_v = 0, date_hour_v = 0, date_min_v = 0, tm_sec_v = 0;

void initisialisation()
{
PORTA = 0x00;
PORTB = 0x00;
PORTC = 0x00;

TRISA = 0xF7;
TRISB = 0x01;
TRISC = 0x8C;

SETUP_ADC_PORTS(NO_ANALOGS);

}

void main()
{
initisialisation();

// badge_config();

// COMMENT DATE
char comment_date[17] = "16:30:50 30/14/15";

date_hour[0] = comment_date[0];
date_hour[1] = comment_date[1];
date_hour_v = atoi(date_hour);
printf("hour : %d \n\r",date_hour_v);

date_min[0] = comment_date[3];
date_min[1] = comment_date[4];
date_min_v = atoi(date_min);
printf("min : %d \n\r",date_min_v);

tm_sec[0] = comment_date[6];
tm_sec[1] = comment_date[7];
tm_sec_v = atoi(tm_sec);
printf("sec : %d \n\r",tm_sec_v);

date_mday[0] = comment_date[9];
date_mday[1] = comment_date[10];
date_mday_v = atoi(date_mday);
printf("day : %d \n\r",date_mday_v);

date_mon[0] = comment_date[12];
date_mon[1] = comment_date[13];
date_mon_v = atoi(date_mon);
printf("month : %d \n\r",date_mon_v);

date_year[0] = comment_date[15];
date_year[1] = comment_date[16];

date_year_v = atoi(date_year);
printf("year : %c%c \n\r",date_year[0],date_year[1]);
printf("year : %d \n\r",date_year_v);

delay_ms(200);

while(true);

} //Main

The problem is that I have this result:
http://www.4shared.com/download/JtLKh36Ece/atoi_Problem.jpg?lgfp=3000

for the "year" the conversion is wrong.

I dont undestand the problem.

Thanks.

asmboy

Joined: 20 Nov 2007
Posts: 2128
Location: albany ny

Posted: Thu Apr 30, 2015 7:02 am

from the CCS manual
re ATOI() INPUT...

Quote:

string is a pointer to a null terminated string of characters.

where is your NULL char ?? ie ascii Z terminator ?

RF_Developer

Joined: 07 Feb 2011
Posts: 839

Re: Problem with "atoi"

Posted: Thu Apr 30, 2015 7:16 am

fbtech wrote:

Hello,
I'm using "atoi" as follows:

Code:

#include <main.h>

char date_mday[2] = "", date_mon[2] = "", date_year[2] = "", date_hour[2] = "", date_min[2] = "", tm_sec[2] = "";
unsigned int date_mday_v = 0, date_mon_v = 0, date_year_v = 0, date_hour_v = 0, date_min_v = 0, tm_sec_v = 0;

...

date_hour[0] = comment_date[0];
date_hour[1] = comment_date[1];
date_hour_v = atoi(date_hour);
printf("hour : %d \n\r",date_hour_v);

...

date_year[0] = comment_date[15];
date_year[1] = comment_date[16];

date_year_v = atoi(date_year);
printf("year : %c%c \n\r",date_year[0],date_year[1]);
printf("year : %d \n\r",date_year_v);

...

atoi() takes a null-terinated string as its input. When you intialise, you empty all the strings. That means all they have is a null (0) as their first character, the second character is undefined. You then overwrite the null with actual characters.

Think about your two character strings, and the way they are placed in memory. When you set the two characters of the hour, the null in the string after it in memory, the minutes, terminates the hour string and atoi() works. That happen for all the strings until you get to the last one, the year, as then there is no following null, and atoi() does the best it can, but clearly won't produce the right result. I am sure that if you repeat the same code, then the first time around you wil get the result you have now, but it'll be even more confused the second time as the nulls will have been replaced by numeric characters from the first time through.

To convert a two character string, you need three characters space, to allow for the terminating null.

fbtech

Joined: 25 Mar 2015
Posts: 7


Posted: Thu Apr 30, 2015 7:26 am

Every thing is fine now. BIG THANKS.

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