Implement Double.{toString, toStringAsExponential, toStringAsPrecision}

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 9662afe3d7c30277410764a8cc1f9a68b2b7be96..55b48501adb8ce9fab6b7885642c5dc42b76ae0a 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -18,6 +18,7 @@
 #include "vm/dart_api_state.h"
 #include "vm/dart_entry.h"
 #include "vm/debuginfo.h"
+#include "vm/double_conversion.h"
 #include "vm/exceptions.h"
 #include "vm/growable_array.h"
 #include "vm/heap.h"
@@ -6085,21 +6086,15 @@ const char* Double::ToCString() const {
   if (isinf(value())) {
     return value() < 0 ? "-Infinity" : "Infinity";
   }
-  const char* kFormat = "%f";
-  // Calculate the size of the string.
-  intptr_t len = OS::SNPrint(NULL, 0, kFormat, value()) + 1;
+  const int kBufferSize = 128;
+  char buffer[kBufferSize];

[Ivan Posva, 2012/02/27 14:47:14]

Please avoid stack allocated buffers that are being printed into under "user"
control. Instead you can allocate this straight zone and avoid the copying
around below.

[floitsch, 2012/02/27 19:55:40]

Done.

+  int len;
+  bool status = DoubleToCString(value(), buffer, kBufferSize, &len);
+  ASSERT(status);
+
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len));
-  OS::SNPrint(chars, len, kFormat, value());
-  // Eliminate trailing 0s, but leave one digit after '.'.
-  // 'chars' is null terminated.
-  for (intptr_t i = len - 2; i >= 1; i--) {
-    if ((chars[i] == '0') && (chars[i - 1] != '.')) {
-      chars[i] = '\0';
-    } else {
-      break;
-    }
-  }
+  memmove(chars, buffer, len);
   return chars;
 }