stringToNum.diff

   1 From: Tony Balinski <ajbj@free.fr>
   2 Subject: A new StringToNum() function without a call to sscanf()
   3
   4 It seems a shame to scan a string twice, as the older version does.
   5
   6 ---
   7
   8  source/interpret.c |   43 +++++++++++++++++++++++++++++++------------
   9  1 file changed, 31 insertions(+), 12 deletions(-)
  10
  11 diff --quilt old/source/interpret.c new/source/interpret.c
  12 --- old/source/interpret.c
  13 +++ new/source/interpret.c
  14 @@ -4088,33 +4088,52 @@ static int execError(const char *s1, con
  15      return STAT_ERROR;
  16  }
  17
  18 +/*
  19 +** read an integer from a string, returning True if successful. The string must
  20 +** not contain anything other than the number (perhaps surrounded by spaces).
  21 +*/
  22  int StringToNum(const char *string, int *number)
  23  {
  24      const char *c = string;
  25 +    int n = 0, new_n;
  26 +    int sign = 1;
  27 +    int haveDigit = False;
  28
  29      while (*c == ' ' || *c == '\t') {
  30          ++c;
  31      }
  32 -    if (*c == '+' || *c == '-') {
  33 +    if (*c == '+') {
  34          ++c;
  35 -    }
  36 -    while (isdigit((unsigned char)*c)) {
  37 +    } else if (*c == '-') {
  38          ++c;
  39 +        sign = -1;
  40      }
  41 -    while (*c == ' ' || *c == '\t') {
  42 -        ++c;
  43 +    if (isdigit((unsigned char)*c)) {
  44 +        haveDigit = True;               /* now pick up any other digits */
  45 +        do {
  46 +            new_n = 10 * n + *c - '0';  /* evaluate the number as we go */
  47 +            if (new_n == INT_MIN) {
  48 +                if (sign != -1) {
  49 +                    return False;       /* special case: INT_MIN must be < 0 */
  50 +                }
  51 +            } else if (new_n < n) {
  52 +                return False;           /* overflow: digit sequence too long! */
  53 +            }
  54 +            n = new_n;
  55 +            ++c;
  56 +        } while (isdigit((unsigned char)*c));
  57 +        while (*c == ' ' || *c == '\t') {
  58 +            ++c;
  59 +        }
  60 +    }
  61 +    if (number) {
  62 +        *number = sign * n;
  63      }
  64      if (*c) {
  65          /* if everything went as expected, we should be at end, but we're not */
  66          return False;
  67      }
  68 -    if (number) {
  69 -        if (sscanf(string, "%d", number) != 1) {
  70 -            /* This case is here to support old behavior */
  71 -           *number = 0;
  72 -        }
  73 -    }
  74 -    return True;
  75 +    return haveDigit;
  76  }
  77
  78