Add various new helper functions

* one_hot(): returns true when slv is one hot coded
  * is_unknown(): return true when slv contains bits with unknown value
  * uint_to_slv(): converts natural to slv (unsigned)
  * slv_to_uint(): converts slv to natural (unsigned)

common/UtilsP.vhd

@@ -1,6 +1,7 @@
 library ieee;
   use ieee.std_logic_1164.all;
   use ieee.numeric_std.all;
+  use ieee.math_real.all;
 
 
 
@@ -20,6 +21,13 @@ package UtilsP is
 
   function count_ones (data : in std_logic_vector) return natural;
 
+  function one_hot (data : in std_logic_vector) return boolean;
+
+  function is_unknown (data : in std_logic_vector) return boolean;
+
+  function uint_to_slv (data: in natural; len : in positive) return std_logic_vector;
+  function slv_to_uint (data: in std_logic_vector) return natural;
+
 
 end package UtilsP;
 
@@ -97,7 +105,47 @@ package body UtilsP is
     for i in data'range loop
       v_return := v_return + 1;
     end loop;
+    return v_return;
   end function count_ones;
 
 
+  function one_hot (data : in std_logic_vector) return boolean is
+  begin
+    return count_ones(data) = 1;
+  end function one_hot;
+
+
+  function is_unknown (data : in std_logic_vector) return boolean is
+  begin
+    for i in data'range loop
+      if (data(i) = 'U') then
+        return true;
+      end if;
+    end loop;
+  end function is_unknown;
+
+
+  function uint_to_slv (data: in natural; len : in positive) return std_logic_vector is
+  begin
+    assert len > integer(trunc(log2(real(data))))
+      report "Warning: std_logic_vector result truncated"
+      severity warning;
+    return std_logic_vector(to_unsigned(data, len));
+  end function uint_to_slv;
+
+  function slv_to_uint (data: in std_logic_vector) return natural is
+  begin
+    if data'ascending then
+      assert data'length <= 31 or or_reduce(data(data'left to data'right-31)) = '0'
+        report "WARNING: integer result overflow"
+        severity warning;
+    else
+      assert data'length <= 31 or or_reduce(data(data'left downto data'right+31)) = '0'
+        report "WARNING: integer result overflow"
+        severity warning;
+    end if;
+    return to_integer(unsigned(data));
+  end function slv_to_uint;
+
+
 end package body UtilsP;