atoi.c File Reference

#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>

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Functions
int	atoi (const char *str)
	Interprets an integer value in a byte string pointed to by str. More...

Function Documentation

atoi()

int atoi

(

const char *

str

)

Interprets an integer value in a byte string pointed to by str.

Interprets an integer value in a byte string pointed to by str. Discards any whitespace characters until the first non-whitespace character is found, then takes as many characters as possible to form a valid integer number representation and converts them to an integer value. The valid integer value consists of the following parts: a) (optional) plus or minus sign b) numeric digits

Parameters

str	pointer to the null-terminated byte string to be interpreted

Returns

Integer value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, the return value is undefined. If no conversion can be performed, ​0​ is returned.

Definition at line 5 of file atoi.c.

{
    bool neg = false;
    int val = 0;

    switch(*str)
    {
        case '-':
            neg = true;
        // intentional fallthrough to advance str
        case '+':
            str++;
    }

    while(isdigit(*str))
    {
        val = (10 * val) + (*str++ - '0');
    }

    return (neg ? -val : val);
}

References isdigit().