Feature #891

- Added feature #891, which allows for leftmost partial matches of UUID values.
  Makes direct comparisons for full-length values, and regular expressions for
  partial values.  Note that there is a minimum length of 8 hex digits.
- Added safety parsing mechanism that fails a partial UUID if immediately
  followed by a hex digit.  This allows for numbers longer than 8 digits to not
  be misinterpreted as a UUID.
- Implemented Nibbler::getPartialUUID.
- Implemented unit tests.
@@ -1145,12 +1145,23 @@ const A3 A3::sequence (const A3& input) const

   for (unsigned int i = 0; i < uuids.size (); ++i)
   {
-    if (ids.size ())
+    if (ids.size () + i > 0)
       sequenced.push_back (Arg ("or", Arg::cat_op));

-    sequenced.push_back (Arg ("uuid",        Arg::type_string, Arg::cat_dom));
-    sequenced.push_back (Arg ("=",                             Arg::cat_op));
-    sequenced.push_back (Arg (uuids[i],      Arg::type_string, Arg::cat_literal));
+    // A full-length UUID requires a string comparison.
+    if (uuids[i].length () == 36)
+    {
+      sequenced.push_back (Arg ("uuid",         Arg::type_string, Arg::cat_dom));
+      sequenced.push_back (Arg ("=",                              Arg::cat_op));
+      sequenced.push_back (Arg (uuids[i],       Arg::type_string, Arg::cat_literal));
+    }
+    // A UUID fragment is a leftmost comparison.
+    else
+    {
+      sequenced.push_back (Arg ("uuid",         Arg::type_string, Arg::cat_dom));
+      sequenced.push_back (Arg ("~",                              Arg::cat_op));
+      sequenced.push_back (Arg ("^" + uuids[i], Arg::type_string, Arg::cat_rx));
+    }
   }

   sequenced.push_back (Arg (")", Arg::cat_op));
@@ -1674,11 +1685,11 @@ bool A3::is_uuid (Nibbler& n, std::string& result)
   n.save ();
   result = "";
   std::string uuid;
-  if (n.getUUID (uuid))
+  if (n.getPartialUUID (uuid))
   {
     result += uuid;
     while (n.skip (',') &&
-           n.getUUID (uuid))
+           n.getPartialUUID (uuid))
     {
       result += ',' + uuid;
     }
@@ -1997,13 +2008,13 @@ bool A3::extract_uuid (
   Nibbler n (input);

   std::string uuid;
-  if (n.getUUID (uuid))
+  if (n.getPartialUUID (uuid))
   {
     sequence.push_back (uuid);

     while (n.skip (','))
     {
-      if (!n.getUUID (uuid))
+      if (!n.getPartialUUID (uuid))
         throw std::string (STRING_A3_UUID_AFTER_COMMA);

       sequence.push_back (uuid);

src/Nibbler.cpp

@@ -38,7 +38,8 @@
 #include <RX.h>
 #endif
 
-const char* c_digits = "0123456789"; // TODO Not used?
+static const char*        _uuid_pattern    = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";
+static const unsigned int _uuid_min_length = 8;
 
 ////////////////////////////////////////////////////////////////////////////////
 Nibbler::Nibbler ()
@@ -613,6 +614,36 @@ bool Nibbler::getUUID (std::string& result)
   return false;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+bool Nibbler::getPartialUUID (std::string& result)
+{
+  std::string::size_type i;
+  for (i = 0; i < 36 && i < (_length - _cursor); i++)
+  {
+    if (_uuid_pattern[i] == 'x' && !isxdigit (_input[_cursor + i]))
+      break;
+
+    else if (_uuid_pattern[i] == '-' && _input[_cursor + i] != '-')
+      break;
+  }
+
+  // If the partial match found is long enough, consider it a match.
+  if (i >= _uuid_min_length)
+  {
+    // Fail if there is another hex digit.
+    if (_cursor + i < _length &&
+        isxdigit (_input[_cursor + i]))
+      return false;
+
+    result = _input.substr (_cursor, i);
+    _cursor += i;
+
+    return true;
+  }
+
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // 19980119T070000Z =  YYYYMMDDThhmmssZ
 bool Nibbler::getDateISO (time_t& t)