theirix commented on code in PR #9453:
URL: https://github.com/apache/arrow-rs/pull/9453#discussion_r2930127562
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arrow-buffer/src/bigint/mod.rs:
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@@ -614,6 +615,62 @@ impl i256 {
let n = (n.high >> 64) as i64; // throw away the lower 192 bits
(n as f64) * f64::powi(2.0, 192 - (k as i32)) // convert to f64 and
scale it, as we left-shift k bit previous, so we need to scale it by 2^(192-k)
}
+
+ /// Computes the `base` logarithm of the number `self`
+ /// Returns `None` if `self` is less than or equal to zero, or if `base`
is less than 2.
+ #[inline]
+ pub fn checked_ilog(self, base: i256) -> Option<u32> {
+ if self <= Self::ZERO || base < i256::from(2) {
+ None
+ } else {
+ // Invariants are enforced, so this call cannot fail
+ self.to_ext_i256().checked_ilog(base.to_ext_i256())
+ }
+ }
+
+ /// Computes the `base` logarithm of the number `self`
+ /// Panic if `self` is less than or equal to zero, or if `base` is less
than 2.
+ #[inline]
+ pub fn ilog(self, base: i256) -> u32 {
+ self.checked_ilog(base)
+ .unwrap_or_else(|| panic!("ilog overflow with {self} and base
{base}"))
+ }
+
+ /// Computes the decimal logarithm of the number `self`
+ /// Returns `None` if `self` is less than or equal to zero.
+ #[inline]
+ pub fn checked_ilog10(self) -> Option<u32> {
+ // Switch to I256::checked_ilog10 when I256 switches MSRV
+ self.checked_ilog(i256::from(10))
+ }
+
+ /// Computes the decimal logarithm of the number `self`
+ /// Panics if `self` is less than or equal to zero.
+ #[inline]
+ pub fn ilog10(self) -> u32 {
+ self.checked_ilog10()
+ .unwrap_or_else(|| panic!("ilog10 overflow with {self}"))
+ }
+
+ /// Computes the binary logarithm of the number `self`
+ /// Returns `None` if `self` is less than or equal to zero.
+ #[inline]
+ pub fn checked_ilog2(self) -> Option<u32> {
+ // Switch to I256::checked_ilog2 when I256 switches MSRV
Review Comment:
For checked_ilog2 - it exists, updated the call.
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