Biggest problems w/ D - strings

[C. Dunn]

Kirk McDonald Wrote:

> C. Dunn wrote:
> > 4) Not enough help for converting between D strings and C char*. 
> > There must be conversion functions which work regardless of whether
> > the D string is dynamic or not, and regardless of whether the C char*
> > is null terminated.  I'm not sure what the answer is, but this has
> > lead to a large number of runtime bugs for me as a novice.
> > 
> 
> The std.string module has the toStringz and toString functions.

I have a field of n chars stored on disk.  It holds a null-terminated string, padded with zeroes.  It is amazingly difficult to compare such a char[n] with some other char[] (which, by the dictates of D, may or may not be null-terminated).


template min(T)
{
   T min( T a, T b ) { if ( a < b ) return a; else return b; }
}

template max(T)
{
   T max( T a, T b ) { if ( a < b ) return b; else return a; }
}

size_t strnlen(char* s, size_t maxlen){
  for(size_t i=0; i<maxlen; ++i){
    if (!s[i]) return i;
  }
  return maxlen;
}

int compare(ConstString lhs, ConstString rhs){
  char* lptr = cast(char*)lhs;
  char* rptr = cast(char*)rhs;
  size_t len_lhs = strnlen(lptr, lhs.length);
  size_t len_rhs = strnlen(rptr, rhs.length);
  int comp = strncmp(lptr, rptr, min!(size_t)(len_lhs, len_rhs));
  if (comp) return comp;
  if (len_lhs < len_rhs) return -1;
  else if (len_lhs > len_rhs) return 1;
  else return 0;
}