stringToNum.diff

   1     A new StringToNum() function without a call to sscanf()
   2
   3     It seems a shame to scan a string twice, as the older version does.
   4
   5 ---
   6
   7  source/interpret.c |   43 +++++++++++++++++++++++++++++++------------
   8  1 file changed, 31 insertions(+), 12 deletions(-)
   9
  10 diff --quilt old/source/interpret.c new/source/interpret.c
  11 --- old/source/interpret.c
  12 +++ new/source/interpret.c
  13 @@ -4053,33 +4053,52 @@ static int execError(const char *s1, con
  14      return STAT_ERROR;
  15  }
  16
  17 +/*
  18 +** read an integer from a string, returning True if successful. The string must
  19 +** not contain anything other than the number (perhaps surrounded by spaces).
  20 +*/
  21  int StringToNum(const char *string, int *number)
  22  {
  23      const char *c = string;
  24 +    int n = 0, new_n;
  25 +    int sign = 1;
  26 +    int haveDigit = False;
  27
  28      while (*c == ' ' || *c == '\t') {
  29          ++c;
  30      }
  31 -    if (*c == '+' || *c == '-') {
  32 +    if (*c == '+') {
  33          ++c;
  34 -    }
  35 -    while (isdigit((unsigned char)*c)) {
  36 +    } else if (*c == '-') {
  37          ++c;
  38 +        sign = -1;
  39      }
  40 -    while (*c == ' ' || *c == '\t') {
  41 -        ++c;
  42 +    if (isdigit((unsigned char)*c)) {
  43 +        haveDigit = True;               /* now pick up any other digits */
  44 +        do {
  45 +            new_n = 10 * n + *c - '0';  /* evaluate the number as we go */
  46 +            if (new_n == INT_MIN) {
  47 +                if (sign != -1) {
  48 +                    return False;       /* special case: INT_MIN must be < 0 */
  49 +                }
  50 +            } else if (new_n < n) {
  51 +                return False;           /* overflow: digit sequence too long! */
  52 +            }
  53 +            n = new_n;
  54 +            ++c;
  55 +        } while (isdigit((unsigned char)*c));
  56 +        while (*c == ' ' || *c == '\t') {
  57 +            ++c;
  58 +        }
  59 +    }
  60 +    if (number) {
  61 +        *number = sign * n;
  62      }
  63      if (*c) {
  64          /* if everything went as expected, we should be at end, but we're not */
  65          return False;
  66      }
  67 -    if (number) {
  68 -        if (sscanf(string, "%d", number) != 1) {
  69 -            /* This case is here to support old behavior */
  70 -           *number = 0;
  71 -        }
  72 -    }
  73 -    return True;
  74 +    return haveDigit;
  75  }
  76
  77  #ifdef DEBUG_DISASSEMBLER   /* dumping values in disassembly or stack dump */