Faster and smaller write/writeln for integrals

andralex · Jun 7, 2011 · 0812b4f · 0812b4f
1 parent 44fc065
commit 0812b4f
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Showing 2 changed files with 55 additions and 5 deletions.
diff --git a/std/conv.d b/std/conv.d
@@ -3301,7 +3301,7 @@ if (staticIndexOf!(Unqual!S, int, long) >= 0 && isSomeString!T)
         return to!T(cast(Unsigned!(S)) value);
     alias Unqual!(typeof(T.init[0])) Char;
 
-    // Cache read-only data only for const and immutable - mutable
+    // Cache read-only data only for const and immutable; mutable
     // data is supposed to use allocation in all cases
     static if (is(ElementType!T == const) || is(ElementType!T == immutable))
     {
@@ -4229,3 +4229,39 @@ unittest
     emplace!Foo(&foo, 2U);
     assert(foo.num == 2);
 }
+
+// Undocumented for the time being
+void toTextRange(T, W)(T value, W writer)
+if (isIntegral!T && isOutputRange!(W, char))
+{
+    Unqual!(Unsigned!T) v = void;
+    if (value < 0)
+    {
+        put(writer, '-');
+        v = -value;
+    }
+    else
+    {
+        v = value;
+    }
+
+    if (v < 10 && v < hexdigits.length)
+    {
+        put(writer, hexdigits[cast(size_t) v]);
+        return;
+    }
+
+    char[v.sizeof * 4] buffer = void;
+    auto i = buffer.length;
+
+    do
+    {
+        auto c = cast(ubyte) (v % 10);
+        v = v / 10;
+        i--;
+        buffer[i] = cast(char) (c + '0');
+    } while (v);
+
+    put(writer, buffer[i .. $]);
+}
+
diff --git a/std/stdio.d b/std/stdio.d
@@ -651,12 +651,26 @@ arguments in text format to the file. */
         auto w = lockingTextWriter();
         foreach (arg; args)
         {
-            static if (isSomeString!(typeof(arg)))
+            alias typeof(arg) A;
+            static if (isSomeString!A)
+            {
+                put(w, arg);
+            }
+            else static if (isIntegral!A)
+            {
+                toTextRange(arg, w);
+            }
+            else static if (is(A : char))
+            {
+                put(w, arg);
+            }
+            else static if (isSomeChar!A)
             {
-                w.put(arg);
+                put(w, arg);
             }
             else
             {
+                // Most general case
                 std.format.formattedWrite(w, "%s", arg);
             }
         }
@@ -1473,7 +1487,7 @@ unittest
     if (false) writeln();
 }
 
-/// ditto
+// Specialization for strings - a very frequent case
 void writeln(T...)(T args)
 if (T.length == 1 && is(typeof(args[0]) : const(char)[]))
 {
@@ -1486,7 +1500,7 @@ unittest
     if (false) writeln("wyda");
 }
 
-/// Ditto
+// Most general instance
 void writeln(T...)(T args)
 if (T.length > 1 || T.length == 1 && !is(typeof(args[0]) : const(char)[]))
 {