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Annotation of 42BSD/ingres/source/gutil/atol.c, revision 1.1

1.1     ! root        1: # include      <sccs.h>
        !             2: 
        !             3: SCCSID(@(#)atol.c      7.1     2/5/81)
        !             4: 
        !             5: /*
        !             6: **  ASCII CHARACTER STRING TO 32-BIT INTEGER CONVERSION
        !             7: **
        !             8: **     `a' is a pointer to the character string, `i' is a
        !             9: **     pointer to the doubleword which is to contain the result.
        !            10: **
        !            11: **     The return value of the function is:
        !            12: **             zero:   succesful conversion; `i' contains the integer
        !            13: **             +1:     numeric overflow; `i' is unchanged
        !            14: **             -1:     syntax error; `i' is unchanged
        !            15: **
        !            16: **     A valid string is of the form:
        !            17: **             <space>* [+-] <space>* <digit>* <space>*
        !            18: */
        !            19: 
        !            20: atol(a, i)
        !            21: register char  *a;
        !            22: long   *i;
        !            23: {
        !            24:        register int    sign;   /* flag to indicate the sign */
        !            25:        long            x;      /* holds the integer being formed */
        !            26:        register char   c;
        !            27: 
        !            28:        sign = 0;
        !            29:        /* skip leading blanks */
        !            30:        while (*a == ' ')
        !            31:                a++;
        !            32:        /* check for sign */
        !            33:        switch (*a)
        !            34:        {
        !            35: 
        !            36:          case '-':
        !            37:                sign = -1;
        !            38: 
        !            39:          case '+':
        !            40:                while (*++a == ' ');
        !            41:        }
        !            42: 
        !            43:        /* at this point everything had better be numeric */
        !            44:        x = 0;
        !            45:        while ((c = *a) <= '9' && c >= '0')
        !            46:        {
        !            47:                /* check for overflow */
        !            48:                /* 2 ** 31 = 2147483648 */
        !            49:                if (x > 0x7fffffffL / 10)
        !            50:                        return (1);
        !            51:                x = x * 10 + (c - '0');
        !            52:                if (x < 0)      /* check if new digit caused overflow */
        !            53:                        return (1);
        !            54:                a++;
        !            55:        }
        !            56: 
        !            57:        /* eaten all the numerics; better be all blanks */
        !            58:        while (c = *a++)
        !            59:                if(c != ' ')                    /* syntax error */
        !            60:                        return (-1);
        !            61:        *i = sign ? -x : x;
        !            62:        return (0);             /* successful termination */
        !            63: }

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