Implement Double.{toString, toStringAsExponential, toStringAsPrecision}

runtime/vm/double_conversion.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/double_conversion.h"
 
 #include "third_party/double-conversion/src/double-conversion.h"
 
 #include "vm/exceptions.h"
 #include "vm/globals.h"
 #include "vm/object.h"
 
 namespace dart {
 
 static const char kDoubleToStringCommonExponentChar = 'e';
 static const char* kDoubleToStringCommonInfinitySymbol = "Infinity";
 static const char* kDoubleToStringCommonNaNSymbol = "NaN";
 
-bool DoubleToString(double d, String& result) {
+bool DoubleToCString(double d, char* buffer, int buffer_size,

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

Nit: We do either all parameters on new line or one parameter on its own line.

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

Done.

+                     int* result_length) {
   static const int kDecimalLow = -6;
   static const int kDecimalHigh = 21;
+
+  // The output contains the sign, at most kDecimalHigh - 1 digits,
+  // the decimal point followed by a 0 plus the \0.
+  ASSERT(buffer_size >= 1 + (kDecimalHigh - 1) + 1 + 1 + 1);
+  // Or it contains the sign, a 0, the decimal point, kDecimalLow '0's,
+  // 17 digits (the precision needed for doubles), plus the \0.
+  ASSERT(buffer_size >= 1 + 1 + 1 + kDecimalLow + 17 + 1);
+  // Alternatively it contains a sign, at most 17 digits (precision needed for
+  // any double), the decimal point, the exponent character, the exponent's
+  // sign, at most three exponent digits, plus the \0.
+  ASSERT(buffer_size >= 1 + 17 + 1 + 1 + 1 + 3 + 1);
+
   static const int kConversionFlags =
       double_conversion::DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN |
       double_conversion::DoubleToStringConverter::EMIT_TRAILING_DECIMAL_POINT |
      double_conversion::DoubleToStringConverter::EMIT_TRAILING_ZERO_AFTER_POINT;
-  const int kBufferSize = 128;
-  // The output contains the sign, at most kDecimalHigh - 1 digits,
-  // the decimal point followed by a 0 plus the \0.
-  ASSERT(kBufferSize >= 1 + (kDecimalHigh - 1) + 1 + 1 + 1);
-  // Or it contains the sign, a 0, the decimal point, kDecimalLow '0's,
-  // 17 digits (the precision needed for doubles), plus the \0.
-  ASSERT(kBufferSize >= 1 + 1 + 1 + kDecimalLow + 17 + 1);
-  // Alternatively it contains a sign, at most 17 digits (precision needed for
-  // any double), the decimal point, the exponent character, the exponent's
-  // sign, at most three exponent digits, plus the \0.
-  ASSERT(kBufferSize >= 1 + 17 + 1 + 1 + 1 + 3 + 1);
 
   const double_conversion::DoubleToStringConverter converter(
       kConversionFlags,
       kDoubleToStringCommonInfinitySymbol,
       kDoubleToStringCommonNaNSymbol,
       kDoubleToStringCommonExponentChar,
       kDecimalLow,
       kDecimalHigh,
       0, 0);  // Last two values are ignored in shortest mode.
 
-  UNIMPLEMENTED();
-  return false;
+  double_conversion::StringBuilder builder(buffer, buffer_size);
+  bool status = converter.ToShortest(d, &builder);
+  if (!status) return false;
+  *result_length = builder.position() + 1;  // Include trailing \0 character.
+  char* result = builder.Finalize();
+  ASSERT(result == buffer);
+  return true;
 }
 
-bool DoubleToStringAsFixed(double d, int fraction_digits, String& result) {
+RawString* DoubleToStringAsFixed(double d, int fraction_digits) {
   static const int kMinFractionDigits = 0;
   static const int kMaxFractionDigits = 20;
   static const int kMaxDigitsBeforePoint = 20;
   // The boundaries are exclusive.
   static const double kLowerBoundary = -1e21;
   static const double kUpperBoundary = 1e21;
   // TODO(floitsch): remove the UNIQUE_ZERO flag when the test is updated.
   static const int kConversionFlags =
-      double_conversion::DoubleToStringConverter::UNIQUE_ZERO;
+      double_conversion::DoubleToStringConverter::NO_FLAGS;
   const int kBufferSize = 128;
+
+  USE(kMaxDigitsBeforePoint);
+  USE(kMaxFractionDigits);
+  USE(kLowerBoundary);
+  USE(kUpperBoundary);
+  USE(kMinFractionDigits);
+  USE(kMaxFractionDigits);
   // The output contains the sign, at most kMaxDigitsBeforePoint digits,
   // the decimal point followed by at most fraction_digits digits plus the \0.
   ASSERT(kBufferSize >= 1 + kMaxDigitsBeforePoint + 1 + kMaxFractionDigits + 1);
 
-  if (d <= kLowerBoundary || d >= kUpperBoundary) {
-    return false;
-  }
-  if (fraction_digits < kMinFractionDigits ||
-      fraction_digits > kMaxFractionDigits) {
-    return false;
-  }
+  ASSERT(kLowerBoundary < d && d < kUpperBoundary);
+
+  ASSERT(kMinFractionDigits <= fraction_digits &&
+         fraction_digits <= kMaxFractionDigits);
 
   const double_conversion::DoubleToStringConverter converter(
       kConversionFlags,
       kDoubleToStringCommonInfinitySymbol,
       kDoubleToStringCommonNaNSymbol,
       kDoubleToStringCommonExponentChar,
       0, 0, 0, 0);  // Last four values are ignored in fixed mode.
 
   char buffer[kBufferSize];
   double_conversion::StringBuilder builder(buffer, kBufferSize);
   bool status = converter.ToFixed(d, fraction_digits, &builder);
-  if (!status) return false;
+  if (!status) return String::null();
   int length = builder.position();
-  result ^= String::New(reinterpret_cast<uint8_t*>(builder.Finalize()), length);
-  return true;
+  return String::New(reinterpret_cast<uint8_t*>(builder.Finalize()), length);
 }
 
 
-bool DoubleToStringAsExponential(double d,
-                                 int fraction_digits,
-                                 String& result) {
-  static const int kMinFractionDigits = 0;
+RawString* DoubleToStringAsExponential(double d, int fraction_digits) {
+  static const int kMinFractionDigits = -1;  // -1 represents shortest mode.
   static const int kMaxFractionDigits = 20;
   static const int kConversionFlags =
       double_conversion::DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN;
   const int kBufferSize = 128;
+
+  USE(kMinFractionDigits);
+  USE(kMaxFractionDigits);
   // The output contains the sign, at most 1 digits, the decimal point followed
   // by at most kMaxFractionDigits digits, the exponent-character, the
   // exponent-sign and three exponent digits plus \0.
   ASSERT(kBufferSize >= 1 + 1 + kMaxFractionDigits + 1 + 1 + 3 + 1);
 
-  if (!(kMinFractionDigits <= fraction_digits &&
-        fraction_digits <= kMaxFractionDigits)) {
-    return false;
-  }
+  ASSERT(kMinFractionDigits <= fraction_digits &&
+         fraction_digits <= kMaxFractionDigits);
 
   const double_conversion::DoubleToStringConverter converter(
       kConversionFlags,
       kDoubleToStringCommonInfinitySymbol,
       kDoubleToStringCommonNaNSymbol,
       kDoubleToStringCommonExponentChar,
       0, 0, 0, 0);  // Last four values are ignored in exponential mode.
 
-  UNIMPLEMENTED();
-  return false;
+  char buffer[kBufferSize];
+  double_conversion::StringBuilder builder(buffer, kBufferSize);
+  bool status = converter.ToExponential(d, fraction_digits, &builder);
+  if (!status) return String::null();
+  int length = builder.position();
+  return String::New(reinterpret_cast<uint8_t*>(builder.Finalize()), length);
 }
 
 
-bool DoubleToStringAsPrecision(double d, int precision, String& result) {
+RawString* DoubleToStringAsPrecision(double d, int precision) {
   static const int kMinPrecisionDigits = 1;
   static const int kMaxPrecisionDigits = 21;
   static const int kMaxLeadingPaddingZeroes = 6;
   static const int kMaxTrailingPaddingZeroes = 0;
   static const int kConversionFlags =
       double_conversion::DoubleToStringConverter::EMIT_POSITIVE_EXPONENT_SIGN;
   const int kBufferSize = 128;
-  // The output contains the sign, the decimal point, precision digits,
+
+  USE(kMinPrecisionDigits);
+  USE(kMaxPrecisionDigits);
+  // The output contains the sign, a potential leading 0, the decimal point,
+  // at most kMax{Leading|Trailing} padding zeroes, precision digits,
   // the exponent-character, the exponent-sign, three exponent digits
   // plus the \0.
-  ASSERT(kBufferSize >= 1 + 1 + kMaxPrecisionDigits + 1 + 1 + 3 + 1);
+  // Note that padding and exponent are exclusive. We still add them up.
+  ASSERT(kBufferSize >= 1 + 1 + 1 + kMaxLeadingPaddingZeroes +
+         kMaxTrailingPaddingZeroes + kMaxPrecisionDigits + 1 + 1 + 3 + 1);
 
-  if (!(kMinPrecisionDigits <= precision && precision <= kMaxPrecisionDigits)) {
-    return false;
-  }
+  ASSERT(kMinPrecisionDigits <= precision && precision <= kMaxPrecisionDigits);
 
   const double_conversion::DoubleToStringConverter converter(
       kConversionFlags,
       kDoubleToStringCommonInfinitySymbol,
       kDoubleToStringCommonNaNSymbol,
       kDoubleToStringCommonExponentChar,
       0, 0,  // Ignored in precision mode.
       kMaxLeadingPaddingZeroes,
       kMaxTrailingPaddingZeroes);
 
-  UNIMPLEMENTED();
-  return false;
+  char buffer[kBufferSize];
+  double_conversion::StringBuilder builder(buffer, kBufferSize);
+  bool status = converter.ToPrecision(d, precision, &builder);
+  if (!status) return String::null();
+  int length = builder.position();
+  return String::New(reinterpret_cast<uint8_t*>(builder.Finalize()), length);
 }
 
 }  // namespace dart