Strtod fast-case that uses DiyFps and cached powers of ten.

src/cached-powers.h

Index: src/cached-powers.h
===================================================================
--- src/cached-powers.h	(revision 5685)
+++ src/cached-powers.h	(working copy)
@@ -33,11 +33,33 @@
 namespace v8 {
 namespace internal {
 
-void GetCachedPowerForBinaryExponentRange(int min_exponent,
-                                          int max_exponent,
-                                          DiyFp* power,
-                                          int* decimal_exponent);
+class PowersOfTenCache {
+ public:
 
+  // Not all powers of ten are cached. The decimal exponent of two neighboring
+  // cached numbers will differ by kDecimalExponentDistance.
+  static const int kDecimalExponentDistance;
+
+  static const int kMinDecimalExponent;
+  static const int kMaxDecimalExponent;
+
+  // Returns a cached power-of-ten with a binary exponent in the range
+  // [min_exponent; max_exponent] (boundaries included).
+  static void GetCachedPowerForBinaryExponentRange(int min_exponent,
+                                                   int max_exponent,
+                                                   DiyFp* power,
+                                                   int* decimal_exponent);
+
+  // Returns a cached power of ten x ~= 10^k such that
+  //   k <= decimal_exponent < k + kCachedPowersDecimalDistance.
+  // The given decimal_exponent must satisfy
+  //   kMinDecimalExponent <= requested_exponent, and
+  //   requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance.
+  static void GetCachedPowerForDecimalExponent(int requested_exponent,
+                                               DiyFp* power,
+                                               int* found_exponent);
+};
+
 } }  // namespace v8::internal
 
 #endif  // V8_CACHED_POWERS_H_