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+// Adapted from https://github.com/Alexhuszagh/rust-lexical.
+
+//! Cached powers trait for extended-precision floats.
+
+use super::cached_float80;
+use super::float::ExtendedFloat;
+
+// POWERS
+
+/// Precalculated powers that uses two-separate arrays for memory-efficiency.
+#[doc(hidden)]
+pub(crate) struct ExtendedFloatArray {
+ // Pre-calculated mantissa for the powers.
+ pub mant: &'static [u64],
+ // Pre-calculated binary exponents for the powers.
+ pub exp: &'static [i32],
+}
+
+/// Allow indexing of values without bounds checking
+impl ExtendedFloatArray {
+ #[inline]
+ pub fn get_extended_float(&self, index: usize) -> ExtendedFloat {
+ let mant = self.mant[index];
+ let exp = self.exp[index];
+ ExtendedFloat { mant, exp }
+ }
+
+ #[inline]
+ pub fn len(&self) -> usize {
+ self.mant.len()
+ }
+}
+
+// MODERATE PATH POWERS
+
+/// Precalculated powers of base N for the moderate path.
+#[doc(hidden)]
+pub(crate) struct ModeratePathPowers {
+ // Pre-calculated small powers.
+ pub small: ExtendedFloatArray,
+ // Pre-calculated large powers.
+ pub large: ExtendedFloatArray,
+ /// Pre-calculated small powers as 64-bit integers
+ pub small_int: &'static [u64],
+ // Step between large powers and number of small powers.
+ pub step: i32,
+ // Exponent bias for the large powers.
+ pub bias: i32,
+}
+
+/// Allow indexing of values without bounds checking
+impl ModeratePathPowers {
+ #[inline]
+ pub fn get_small(&self, index: usize) -> ExtendedFloat {
+ self.small.get_extended_float(index)
+ }
+
+ #[inline]
+ pub fn get_large(&self, index: usize) -> ExtendedFloat {
+ self.large.get_extended_float(index)
+ }
+
+ #[inline]
+ pub fn get_small_int(&self, index: usize) -> u64 {
+ self.small_int[index]
+ }
+}
+
+// CACHED EXTENDED POWERS
+
+/// Cached powers as a trait for a floating-point type.
+pub(crate) trait ModeratePathCache {
+ /// Get cached powers.
+ fn get_powers() -> &'static ModeratePathPowers;
+}
+
+impl ModeratePathCache for ExtendedFloat {
+ #[inline]
+ fn get_powers() -> &'static ModeratePathPowers {
+ cached_float80::get_powers()
+ }
+}