Use logarithms to calculate number of digits

.github/workflows/build.yaml

@@ -52,7 +52,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - { version: "1.65.0", name: MSRV }
+          - { version: "1.67.0", name: MSRV }
           - { version: stable, name: stable }
         kind:
           - name: no_std
@@ -153,7 +153,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - { version: "1.65.0", name: MSRV }
+          - { version: "1.67.0", name: MSRV }
           - { version: stable, name: stable }
         os:
           - { name: Ubuntu, value: ubuntu-20.04 }

.github/workflows/powerset.yaml

@@ -51,7 +51,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - { version: "1.65.0", name: MSRV }
+          - { version: "1.67.0", name: MSRV }
           - { version: stable, name: stable }
         kind:
           - name: no_std

README.md

@@ -1,6 +1,6 @@
 # time
 
-[![minimum rustc: 1.65](https://img.shields.io/badge/minimum%20rustc-1.65-yellowgreen?logo=rust&style=flat-square)](https://www.whatrustisit.com)
+[![minimum rustc: 1.67](https://img.shields.io/badge/minimum%20rustc-1.67-yellowgreen?logo=rust&style=flat-square)](https://www.whatrustisit.com)
 [![version](https://img.shields.io/crates/v/time?color=blue&logo=rust&style=flat-square)](https://crates.io/crates/time)
 [![build status](https://img.shields.io/github/actions/workflow/status/time-rs/time/build.yaml?branch=main&style=flat-square)](https://github.com/time-rs/time/actions)
 [![codecov](https://codecov.io/gh/time-rs/time/branch/main/graph/badge.svg?token=yt4XSmQNKQ)](https://codecov.io/gh/time-rs/time)

time-core/Cargo.toml

@@ -3,7 +3,7 @@ name = "time-core"
 version = "0.1.1"
 authors = ["Jacob Pratt <[email protected]>", "Time contributors"]
 edition = "2021"
-rust-version = "1.65.0"
+rust-version = "1.67.0"
 repository = "https://github.com/time-rs/time"
 keywords = ["date", "time", "calendar", "duration"]
 categories = ["date-and-time"]

time-macros/Cargo.toml

@@ -3,7 +3,7 @@ name = "time-macros"
 version = "0.2.10"
 authors = ["Jacob Pratt <[email protected]>", "Time contributors"]
 edition = "2021"
-rust-version = "1.65.0"
+rust-version = "1.67.0"
 repository = "https://github.com/time-rs/time"
 keywords = ["date", "time", "calendar", "duration"]
 categories = ["date-and-time"]

time/Cargo.toml

@@ -3,7 +3,7 @@ name = "time"
 version = "0.3.23"
 authors = ["Jacob Pratt <[email protected]>", "Time contributors"]
 edition = "2021"
-rust-version = "1.65.0"
+rust-version = "1.67.0"
 repository = "https://github.com/time-rs/time"
 homepage = "https://time-rs.github.io"
 keywords = ["date", "time", "calendar", "duration"]

time/src/formatting/mod.rs

@@ -47,75 +47,22 @@ pub(crate) trait DigitCount {
     /// The number of digits in the stringified value.
     fn num_digits(self) -> u8;
 }
-impl DigitCount for u8 {
-    fn num_digits(self) -> u8 {
-        // Using a lookup table as with u32 is *not* faster in standalone benchmarks.
-        if self < 10 {
-            1
-        } else if self < 100 {
-            2
-        } else {
-            3
-        }
-    }
-}
-impl DigitCount for u16 {
-    fn num_digits(self) -> u8 {
-        // Using a lookup table as with u32 is *not* faster in standalone benchmarks.
-        if self < 10 {
-            1
-        } else if self < 100 {
-            2
-        } else if self < 1_000 {
-            3
-        } else if self < 10_000 {
-            4
-        } else {
-            5
-        }
-    }
-}
 
-impl DigitCount for u32 {
-    fn num_digits(self) -> u8 {
-        /// Lookup table
-        const TABLE: &[u64] = &[
-            0x0001_0000_0000,
-            0x0001_0000_0000,
-            0x0001_0000_0000,
-            0x0001_FFFF_FFF6,
-            0x0002_0000_0000,
-            0x0002_0000_0000,
-            0x0002_FFFF_FF9C,
-            0x0003_0000_0000,
-            0x0003_0000_0000,
-            0x0003_FFFF_FC18,
-            0x0004_0000_0000,
-            0x0004_0000_0000,
-            0x0004_0000_0000,
-            0x0004_FFFF_D8F0,
-            0x0005_0000_0000,
-            0x0005_0000_0000,
-            0x0005_FFFE_7960,
-            0x0006_0000_0000,
-            0x0006_0000_0000,
-            0x0006_FFF0_BDC0,
-            0x0007_0000_0000,
-            0x0007_0000_0000,
-            0x0007_0000_0000,
-            0x0007_FF67_6980,
-            0x0008_0000_0000,
-            0x0008_0000_0000,
-            0x0008_FA0A_1F00,
-            0x0009_0000_0000,
-            0x0009_0000_0000,
-            0x0009_C465_3600,
-            0x000A_0000_0000,
-            0x000A_0000_0000,
-        ];
-        ((self as u64 + TABLE[31_u32.saturating_sub(self.leading_zeros()) as usize]) >> 32) as _
-    }
+/// A macro to generate implementations of `DigitCount` for unsigned integers.
+macro_rules! impl_digit_count {
+    ($($t:ty),* $(,)?) => {
+        $(impl DigitCount for $t {
+            fn num_digits(self) -> u8 {
+                match self.checked_ilog10() {
+                    Some(n) => (n as u8) + 1,
+                    None => 1,
+                }
+            }
+        })*
+    };
 }
+
+impl_digit_count!(u8, u16, u32);
 // endregion extension trait
 
 /// Write all bytes to the output, returning the number of bytes written.