Phobos addition - std.conv.toInt(char[] s, int base)

[Jarrett Billingsley]

I've been missing the ability to convert any base of string numerical 
literal into an int (i.e. strtol()), so I wrote a new toInt that allows any 
base from 2 to 36 (bases greater than 10 use a-z, case-insensitive).  It 
accomplishes this by using a translation table (generated by 
std.string.maketrans() of course) for easy parsing.  It's written pretty 
much the same way that the existing toInt is.

int toInt(char[] s, int base)
{
 assert(base >= 2 && base <= 36);

 static char[] transTable =
 [
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
  16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
  32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
  48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
  64, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72,
  73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 91, 92, 93, 94, 95,
  96, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72,
  73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 123, 124, 125, 126,
  127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139,
  140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152,
  153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165,
  166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178,
  179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
  192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204,
  205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217,
  218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230,
  231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243,
  244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255
 ];

    int length = s.length;

 if(!length)
  throw new ConvError(s);

 int sign = 0;
 int v = 0;

 char maxDigit = '0' + base - 1;

 for(int i = 0; i < length; i++)
 {
  char c = transTable[s[i]];

  if(c >= '0' && c <= maxDigit)
  {
   uint v1 = v;
   v = v * base + (c - '0');

   if(cast(uint)v < v1)
    throw new ConvOverflowError(s);
  }
  else if(c == '-' && i == 0)
  {
   sign = -1;

   if(length == 1)
    throw new ConvError(s);
  }
  else if(c == '+' && i == 0)
  {
   if(length == 1)
    throw new ConvError(s);
  }
  else
   throw new ConvError(s);
 }

 if(sign == -1)
 {
  if(cast(uint)v > 0x80000000)
   throw new ConvOverflowError(s);

  v = -v;
 }
 else
 {
  if(cast(uint)v > 0x7FFFFFFF)
   throw new ConvOverflowError(s);
 }

 return v;
}