Fast algorithm for double->string conversion.

src/conversions.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <stdarg.h>
 
 #include "v8.h"
 
 #include "conversions-inl.h"
 #include "factory.h"
 #include "scanner.h"
 
+#include "grisu3.h"
+
 namespace v8 {
 namespace internal {
 
 int HexValue(uc32 c) {
   if ('0' <= c && c <= '9')
     return c - '0';
   if ('a' <= c && c <= 'f')
     return c - 'a' + 10;
   if ('A' <= c && c <= 'F')
     return c - 'A' + 10;
@@ skipping 329 matching lines @@
       break;
 
     case FP_ZERO:
       builder.AddCharacter('0');
       break;
 
     default: {
       int decimal_point;
       int sign;
 
-      char* decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);
-      int length = StrLength(decimal_rep);
+      char* decimal_rep;
+      bool used_dtoa = false;
+      char grisu_buffer[kGrisu3MaximalLength + 1];
+      int length;
+      if (grisu3(v, grisu_buffer, &sign, &length, &decimal_point)) {
+        decimal_rep = &grisu_buffer[0];

[fschneider, 2010/02/22 16:25:24]

You can just write: decimal_rep = grisu_buffer;

[Florian Loitsch, 2010/02/23 09:05:10]

Done.

+      } else {
+        decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);
+        used_dtoa = true;
+        length = StrLength(decimal_rep);
+      }
 
       if (sign) builder.AddCharacter('-');
 
       if (length <= decimal_point && decimal_point <= 21) {
         // ECMA-262 section 9.8.1 step 6.
         builder.AddString(decimal_rep);
         builder.AddPadding('0', decimal_point - length);
 
       } else if (0 < decimal_point && decimal_point <= 21) {
         // ECMA-262 section 9.8.1 step 7.
@@ skipping 14 matching lines @@
           builder.AddCharacter('.');
           builder.AddString(decimal_rep + 1);
         }
         builder.AddCharacter('e');
         builder.AddCharacter((decimal_point >= 0) ? '+' : '-');
         int exponent = decimal_point - 1;
         if (exponent < 0) exponent = -exponent;
         builder.AddFormatted("%d", exponent);
       }
 
-      freedtoa(decimal_rep);
+      if (used_dtoa) freedtoa(decimal_rep);
     }
   }
   return builder.Finalize();
 }
 
 
 const char* IntToCString(int n, Vector<char> buffer) {
   bool negative = false;
   if (n < 0) {
     // We must not negate the most negative int.
@@ skipping 268 matching lines @@
   // Allocate result and fill in the parts.
   StringBuilder builder(result_size + 1);
   builder.AddSubstring(integer_buffer + integer_pos + 1, integer_part_size);
   if (decimal_pos > 0) builder.AddCharacter('.');
   builder.AddSubstring(decimal_buffer, decimal_pos);
   return builder.Finalize();
 }
 
 
 } }  // namespace v8::internal