private static bool DoubleToShortestAscii(ref GrisuDouble v, char[] buffer, out int length, out int point)
{
Debug.Assert(!v.IsSpecial);
Debug.Assert(v.Value >= 0.0);
double value = v.Value;
if (value == 0.0)
{
buffer[0] = '0';
buffer[1] = '\0';
length = 1;
point = 1;
return(true);
}
int decimal_exponent = 0;
bool result = Grisu3(ref v, buffer, out length, out decimal_exponent);
if (result)
{
point = length + decimal_exponent;
}
else
{
point = 0;
}
return(result);
}
private static void HandleSpecialValues(
ref GrisuDouble double_inspect,
TextWriter resultBuilder)
{
if (double_inspect.IsInfinite)
{
if (double_inspect.Value < 0)
{
resultBuilder.Write('-');
}
resultBuilder.Write(infinity_symbol_);
return;
}
if (double_inspect.IsNaN)
{
resultBuilder.Write(nan_symbol_);
return;
}
}
// Provides a decimal representation of v.
// Returns true if it succeeds, otherwise the result cannot be trusted.
// There will be *length digits inside the buffer (not null-terminated).
// If the function returns true then
// v == (double) (buffer * 10^decimal_exponent).
// The digits in the buffer are the shortest representation possible: no
// 0.09999999999999999 instead of 0.1. The shorter representation will even be
// chosen even if the longer one would be closer to v.
// The last digit will be closest to the actual v. That is, even if several
// digits might correctly yield 'v' when read again, the closest will be
// computed.
private static bool Grisu3(ref GrisuDouble v,
char[] buffer,
out int length,
out int decimal_exponent)
{
DiyFp w = v.AsNormalizedDiyFp();
// boundary_minus and boundary_plus are the boundaries between v and its
// closest floating-point neighbors. Any number strictly between
// boundary_minus and boundary_plus will round to v when convert to a double.
// Grisu3 will never output representations that lie exactly on a boundary.
DiyFp boundary_minus, boundary_plus;
v.NormalizedBoundaries(out boundary_minus, out boundary_plus);
Debug.Assert(boundary_plus.E == w.E);
DiyFp ten_mk; // Cached power of ten: 10^-k
int mk; // -k
int ten_mk_minimal_binary_exponent =
kMinimalTargetExponent - (w.E + DiyFp.kSignificandSize);
int ten_mk_maximal_binary_exponent =
kMaximalTargetExponent - (w.E + DiyFp.kSignificandSize);
PowersOfTenCache.GetCachedPowerForBinaryExponentRange(
ten_mk_minimal_binary_exponent,
ten_mk_maximal_binary_exponent,
out ten_mk, out mk);
Debug.Assert((kMinimalTargetExponent <= w.E + ten_mk.E +
DiyFp.kSignificandSize) &&
(kMaximalTargetExponent >= w.E + ten_mk.E +
DiyFp.kSignificandSize));
// Note that ten_mk is only an approximation of 10^-k. A DiyFp only contains a
// 64 bit significand and ten_mk is thus only precise up to 64 bits.
// The DiyFp.Times procedure rounds its result, and ten_mk is approximated
// too. The variable scaled_w (as well as scaled_boundary_minus/plus) are now
// off by a small amount.
// In fact: scaled_w - w*10^k < 1ulp (unit in the last place) of scaled_w.
// In other words: let f = scaled_w.f() and e = scaled_w.e(), then
// (f-1) * 2^e < w*10^k < (f+1) * 2^e
//DiyFp scaled_w = DiyFp.Times(ref w, ref ten_mk);
w.Multiply(ref ten_mk);
Debug.Assert(w.E ==
boundary_plus.E + ten_mk.E + DiyFp.kSignificandSize);
// In theory it would be possible to avoid some recomputations by computing
// the difference between w and boundary_minus/plus (a power of 2) and to
// compute scaled_boundary_minus/plus by subtracting/adding from
// scaled_w. However the code becomes much less readable and the speed
// enhancements are not terriffic.
//DiyFp scaled_boundary_minus = DiyFp.Times(ref boundary_minus, ref ten_mk);
boundary_minus.Multiply(ref ten_mk);
//DiyFp scaled_boundary_plus = DiyFp.Times(ref boundary_plus, ref ten_mk);
boundary_plus.Multiply(ref ten_mk);
// DigitGen will generate the digits of scaled_w. Therefore we have
// v == (double) (scaled_w * 10^-mk).
// Set decimal_exponent == -mk and pass it to DigitGen. If scaled_w is not an
// integer than it will be updated. For instance if scaled_w == 1.23 then
// the buffer will be filled with "123" und the decimal_exponent will be
// decreased by 2.
int kappa;
bool result = DigitGen(ref boundary_minus, ref w, ref boundary_plus,
buffer, out length, out kappa);
decimal_exponent = -mk + kappa;
return result;
}
private static bool DoubleToShortestAscii(ref GrisuDouble v, char[] buffer, out int length, out int point)
{
Debug.Assert(!v.IsSpecial);
Debug.Assert(v.Value >= 0.0);
double value = v.Value;
if (value == 0.0)
{
buffer[0] = '0';
buffer[1] = '\0';
length = 1;
point = 1;
return true;
}
int decimal_exponent = 0;
bool result = Grisu3(ref v, buffer, out length, out decimal_exponent);
if (result)
{
point = length + decimal_exponent;
}
else
{
point = 0;
}
return result;
}
public static void DoubleToString(double value, TextWriter resultBuilder)
{
if (value < 0.0)
{
resultBuilder.Write('-');
value = -value;
}
GrisuDouble grisuDouble = new GrisuDouble(value);
if (grisuDouble.IsSpecial)
{
HandleSpecialValues(ref grisuDouble, resultBuilder);
return;
}
char[] decimal_rep = ts_decimal_rep;
if (decimal_rep == null)
decimal_rep = ts_decimal_rep = new char[kBase10MaximalLength + 1];
int decimal_point;
int decimal_rep_length;
if (!DoubleToShortestAscii(ref grisuDouble, decimal_rep, out decimal_rep_length, out decimal_point))
{
resultBuilder.Write("{0:R}", value);
return;
}
int decimalRepLength = decimal_rep_length + 1;
if (decimal_point < 1)
{
decimalRepLength += -decimal_point + 1;
}
else if (decimal_point >= decimal_rep_length)
{
decimalRepLength += decimal_point - decimal_rep_length + 1;
}
int exponent = decimal_point - 1;
int absExponent = Math.Abs(exponent);
int exponentRepLength = decimal_rep_length + 3;
if (exponent < 0)
++exponentRepLength;
if (absExponent >= 10)
{
++exponentRepLength;
if (absExponent >= 100)
++exponentRepLength;
}
if (decimalRepLength <= exponentRepLength)
{
CreateDecimalRepresentation(decimal_rep, decimal_rep_length,
decimal_point,
Math.Max(0, decimal_rep_length - decimal_point),
resultBuilder);
}
else
{
CreateExponentialRepresentation(decimal_rep, decimal_rep_length, exponent,
resultBuilder);
}
}
private static void HandleSpecialValues(
ref GrisuDouble double_inspect,
TextWriter resultBuilder)
{
if (double_inspect.IsInfinite)
{
if (double_inspect.Value < 0)
{
resultBuilder.Write('-');
}
resultBuilder.Write(infinity_symbol_);
return;
}
if (double_inspect.IsNaN)
{
resultBuilder.Write(nan_symbol_);
return;
}
}
// Provides a decimal representation of v.
// Returns true if it succeeds, otherwise the result cannot be trusted.
// There will be *length digits inside the buffer (not null-terminated).
// If the function returns true then
// v == (double) (buffer * 10^decimal_exponent).
// The digits in the buffer are the shortest representation possible: no
// 0.09999999999999999 instead of 0.1. The shorter representation will even be
// chosen even if the longer one would be closer to v.
// The last digit will be closest to the actual v. That is, even if several
// digits might correctly yield 'v' when read again, the closest will be
// computed.
private static bool Grisu3(ref GrisuDouble v,
char[] buffer,
out int length,
out int decimal_exponent)
{
DiyFp w = v.AsNormalizedDiyFp();
// boundary_minus and boundary_plus are the boundaries between v and its
// closest floating-point neighbors. Any number strictly between
// boundary_minus and boundary_plus will round to v when convert to a double.
// Grisu3 will never output representations that lie exactly on a boundary.
DiyFp boundary_minus, boundary_plus;
v.NormalizedBoundaries(out boundary_minus, out boundary_plus);
Debug.Assert(boundary_plus.E == w.E);
DiyFp ten_mk; // Cached power of ten: 10^-k
int mk; // -k
int ten_mk_minimal_binary_exponent =
kMinimalTargetExponent - (w.E + DiyFp.kSignificandSize);
int ten_mk_maximal_binary_exponent =
kMaximalTargetExponent - (w.E + DiyFp.kSignificandSize);
PowersOfTenCache.GetCachedPowerForBinaryExponentRange(
ten_mk_minimal_binary_exponent,
ten_mk_maximal_binary_exponent,
out ten_mk, out mk);
Debug.Assert((kMinimalTargetExponent <= w.E + ten_mk.E +
DiyFp.kSignificandSize) &&
(kMaximalTargetExponent >= w.E + ten_mk.E +
DiyFp.kSignificandSize));
// Note that ten_mk is only an approximation of 10^-k. A DiyFp only contains a
// 64 bit significand and ten_mk is thus only precise up to 64 bits.
// The DiyFp.Times procedure rounds its result, and ten_mk is approximated
// too. The variable scaled_w (as well as scaled_boundary_minus/plus) are now
// off by a small amount.
// In fact: scaled_w - w*10^k < 1ulp (unit in the last place) of scaled_w.
// In other words: let f = scaled_w.f() and e = scaled_w.e(), then
// (f-1) * 2^e < w*10^k < (f+1) * 2^e
//DiyFp scaled_w = DiyFp.Times(ref w, ref ten_mk);
w.Multiply(ref ten_mk);
Debug.Assert(w.E ==
boundary_plus.E + ten_mk.E + DiyFp.kSignificandSize);
// In theory it would be possible to avoid some recomputations by computing
// the difference between w and boundary_minus/plus (a power of 2) and to
// compute scaled_boundary_minus/plus by subtracting/adding from
// scaled_w. However the code becomes much less readable and the speed
// enhancements are not terriffic.
//DiyFp scaled_boundary_minus = DiyFp.Times(ref boundary_minus, ref ten_mk);
boundary_minus.Multiply(ref ten_mk);
//DiyFp scaled_boundary_plus = DiyFp.Times(ref boundary_plus, ref ten_mk);
boundary_plus.Multiply(ref ten_mk);
// DigitGen will generate the digits of scaled_w. Therefore we have
// v == (double) (scaled_w * 10^-mk).
// Set decimal_exponent == -mk and pass it to DigitGen. If scaled_w is not an
// integer than it will be updated. For instance if scaled_w == 1.23 then
// the buffer will be filled with "123" und the decimal_exponent will be
// decreased by 2.
int kappa;
bool result = DigitGen(ref boundary_minus, ref w, ref boundary_plus,
buffer, out length, out kappa);
decimal_exponent = -mk + kappa;
return(result);
}
public static void DoubleToString(double value, TextWriter resultBuilder)
{
if (value < 0.0)
{
resultBuilder.Write('-');
value = -value;
}
GrisuDouble grisuDouble = new GrisuDouble(value);
if (grisuDouble.IsSpecial)
{
HandleSpecialValues(ref grisuDouble, resultBuilder);
return;
}
char[] decimal_rep = ts_decimal_rep;
if (decimal_rep == null)
{
decimal_rep = ts_decimal_rep = new char[kBase10MaximalLength + 1];
}
int decimal_point;
int decimal_rep_length;
if (!DoubleToShortestAscii(ref grisuDouble, decimal_rep, out decimal_rep_length, out decimal_point))
{
resultBuilder.Write("{0:R}", value);
return;
}
int decimalRepLength = decimal_rep_length + 1;
if (decimal_point < 1)
{
decimalRepLength += -decimal_point + 1;
}
else if (decimal_point >= decimal_rep_length)
{
decimalRepLength += decimal_point - decimal_rep_length + 1;
}
int exponent = decimal_point - 1;
int absExponent = Math.Abs(exponent);
int exponentRepLength = decimal_rep_length + 3;
if (exponent < 0)
{
++exponentRepLength;
}
if (absExponent >= 10)
{
++exponentRepLength;
if (absExponent >= 100)
{
++exponentRepLength;
}
}
if (decimalRepLength <= exponentRepLength)
{
CreateDecimalRepresentation(decimal_rep, decimal_rep_length,
decimal_point,
Math.Max(0, decimal_rep_length - decimal_point),
resultBuilder);
}
else
{
CreateExponentialRepresentation(decimal_rep, decimal_rep_length, exponent,
resultBuilder);
}
}