Read a unicode character from the terminal

[Ali Çehreli]

On 03/31/2012 11:53 AM, Ali Çehreli wrote:

 > The solution is to use ranges when pulling Unicode characters out of
 > strings. std.stdin does not provide this yet, but it will eventually
 > happen (so I've heard :)).

Here is a Unicode character range, which is unfortunately pretty 
inefficient because it relies on an exception that is thrown from 
isValidDchar! :p

import std.stdio;
import std.utf;
import std.array;

struct UnicodeRange
{
     File file;
     char[4] codes;
     bool ready;

     this(File file)
     {
         this.file = file;
         this.ready = false;
     }

     bool empty() const @property
     {
         return file.eof();
     }

     dchar front() const @property
     {
         if (!ready) {
             // Sorry, no 'mutable' in D! :p
             UnicodeRange * mutable_this = cast(UnicodeRange*)&this;
             mutable_this.readNext();
         }
         return codes.front;
     }

     void popFront()
     {
         codes = codes.init;
         ready = false;
     }

     void readNext()
     {
         foreach (ref code; codes) {
             file.readf("%s", &code);

             if (file.eof()) {
                 codes[] = '\0';
                 ready = false;
                 break;
             }

             // Expensive way of determining "ready"!
             try {
                 if (isValidDchar(codes.front)) {
                     ready = true;
                     break;
                 }

             } catch (Exception) {
                 // not ready
             }
         }
     }
}

UnicodeRange byUnicode(File file = stdin)
{
     return UnicodeRange(file);
}

void main()
{
     foreach(c; byUnicode()) {
         writeln(c);
     }
}

Ali