internal static int GetCachedPower(int e, int alpha, int gamma, DiyFp cMk)
{
const int kQ = DiyFp.KSignificandSize;
double k = System.Math.Ceiling((alpha - e + kQ - 1) * Kd1Log210);
int index = (GrisuCacheOffset + (int)k - 1) / CachedPowersSpacing + 1;
CachedPower cachedPower = CACHED_POWERS[index];
cMk.F = cachedPower.Significand;
cMk.E = cachedPower.BinaryExponent;
Debug.Assert((alpha <= cMk.E + e) && (cMk.E + e <= gamma));
return(cachedPower.DecimalExponent);
}
public static int GetCachedPower(int e, int alpha, int gamma, NumberDiyFp c_mk)
{
int kQ = NumberDiyFp.kSignificandSize;
double k = Math.Ceiling((alpha - e + kQ - 1) * kD_1_LOG2_10);
int index = (GRISU_CACHE_OFFSET + (int)k - 1) / CACHED_POWERS_SPACING + 1;
CachedPower cachedPower = CACHED_POWERS[index];
c_mk.SetF(cachedPower.significand);
c_mk.SetE(cachedPower.binaryExponent);
Debug.Assert((alpha <= c_mk.E() + e) && (c_mk.E() + e <= gamma));
return(cachedPower.decimalExponent);
}
internal static GetCachedPowerResult GetCachedPowerForBinaryExponentRange(int min_exponent, int max_exponent)
{
const int kQ = DiyFp.KSignificandSize;
double k = System.Math.Ceiling((min_exponent + kQ - 1) * Kd1Log210);
int foo = kCachedPowersOffset;
int index =
(foo + (int)k - 1) / kDecimalExponentDistance + 1;
CachedPower cachedPower = CACHED_POWERS[index];
var cMk = new DiyFp(cachedPower.Significand, cachedPower.BinaryExponent);
return(new GetCachedPowerResult(cachedPower.DecimalExponent, cMk));
}
// 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.
public static void GetCachedPowerForDecimalExponent(int requested_exponent,
out DiyFp power,
out int found_exponent)
{
Debug.Assert(kMinDecimalExponent <= requested_exponent);
Debug.Assert(requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance);
int index =
(requested_exponent + kCachedPowersOffset) / kDecimalExponentDistance;
CachedPower cached_power = kCachedPowers[index];
power = new DiyFp(cached_power.significand, cached_power.binary_exponent);
found_exponent = cached_power.decimal_exponent;
Debug.Assert(found_exponent <= requested_exponent);
Debug.Assert(requested_exponent < found_exponent + kDecimalExponentDistance);
}
// Returns a cached power-of-ten with a binary exponent in the range
// [min_exponent; max_exponent] (boundaries included).
public static void GetCachedPowerForBinaryExponentRange(int min_exponent,
int max_exponent,
out DiyFp power,
out int decimal_exponent)
{
int kQ = DiyFp.kSignificandSize;
double k = Math.Ceiling((min_exponent + kQ - 1) * kD_1_LOG2_10);
int foo = kCachedPowersOffset;
int index =
(foo + (int)(k) - 1) / kDecimalExponentDistance + 1;
Debug.Assert(0 <= index && index < kCachedPowers.Length);
CachedPower cached_power = kCachedPowers[index];
Debug.Assert(min_exponent <= cached_power.binary_exponent);
Debug.Assert(cached_power.binary_exponent <= max_exponent);
decimal_exponent = cached_power.decimal_exponent;
power = new DiyFp(cached_power.significand, cached_power.binary_exponent);
}
