feat(codi-core): no_std support

Add [no_std] support using "libm" crate, which implements all the necessary functions for float operations like sqrt, pow, hypot, etc. Add build for the "thumbv6m-none-eabi" target to CI, although I'm still not 100% sure that no_std will work. This is first time I did this.
woojiq · Apr 7, 2024 · 4606881 · 4606881
1 parent 38b21d6
commit 4606881
Show file tree

Hide file tree

Showing 8 changed files with 42 additions and 27 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/README.md b/README.md
@@ -64,6 +64,3 @@ $ nix develop ./nix # devShell
 $ direnv allow # direnv with devShell
 $ nix flake check ./nix # run CI locally
 ```
-
-## TODO
-- [ ] No-std support: not easy because no_std doesn't have common float operations (thumbv6m-none-eabi target)
diff --git a/codi-core/Cargo.toml b/codi-core/Cargo.toml
@@ -10,7 +10,12 @@ description.workspace = true
 readme.workspace = true
 
 [dependencies]
-ordered-float = { version = "4.2.0" }
+libm = "0.2.8"
+ordered-float = { version = "4.2.0", default-features = false }
+
+[features]
+default = ["std"]
+std = []
 
 [lints]
 workspace = true
diff --git a/codi-core/src/color_dist.rs b/codi-core/src/color_dist.rs
@@ -1,3 +1,4 @@
+use libm::{hypotf, powf, sqrtf};
 use ordered_float::NotNan;
 
 use crate::color_space::{Cielab, Rgb};
@@ -30,9 +31,9 @@ pub struct Euclidean;
 
 impl ColorDistance for Euclidean {
     fn dist(&self, c1: Rgb, c2: Rgb) -> NotNan<f32> {
-        let dist = (f32::from(c1.r) - f32::from(c2.r)).powi(2)
-            + (f32::from(c1.g) - f32::from(c2.g)).powi(2)
-            + (f32::from(c1.b) - f32::from(c2.b)).powi(2);
+        let dist = powf(f32::from(c1.r) - f32::from(c2.r), 2.0)
+            + powf(f32::from(c1.g) - f32::from(c2.g), 2.0)
+            + powf(f32::from(c1.b) - f32::from(c2.b), 2.0);
         NotNan::new(dist).unwrap()
     }
 }
@@ -55,9 +56,9 @@ impl ColorDistance for EuclideanImproved {
             (f32::from(c1.g) - f32::from(c2.g)),
             (f32::from(c1.b) - f32::from(c2.b)),
         );
-        let dist: f32 = (2.0 + red_mean / 256.0) * d_r.powi(2)
-            + 4.0 * d_g.powi(2)
-            + (2.0 + (255.0 - red_mean) / 256.0) * d_b.powi(2);
+        let dist: f32 = powf((2.0 + red_mean / 256.0) * d_r, 2.0)
+            + 4.0 * powf(d_g, 2.0)
+            + powf((2.0 + (255.0 - red_mean) / 256.0) * d_b, 2.0);
         NotNan::new(dist).unwrap()
     }
 }
@@ -81,20 +82,19 @@ impl ColorDistance for CIE94 {
 
         let (delta_l, delta_a, delta_b) = (lab1.l - lab2.l, lab1.a - lab2.a, lab1.b - lab2.b);
 
-        let C1 = lab1.a.hypot(lab1.b.into_inner());
-        let C2 = lab2.a.hypot(lab2.b.into_inner());
+        let C1 = hypotf(*lab1.a, *lab1.b);
+        let C2 = hypotf(*lab2.a, *lab2.b);
 
         let Cab = C1 - C2;
         let Sl = 1.0;
         let Sc = 1.0 + K1 * C1;
         let Sh = 1.0 + K2 * C1;
         // https://github.com/zschuessler/DeltaE/issues/9
-        let Hab = (delta_a.powi(2) + delta_b.powi(2) - Cab.powi(2))
-            .max(0.0)
-            .sqrt();
+        let Hab = sqrtf((powf(*delta_a, 2.0) + powf(*delta_b, 2.0) - powf(Cab, 2.0)).max(0.0));
 
-        let dist =
-            (delta_l / (kL * Sl)).powi(2) + (Cab / (kC * Sc)).powi(2) + (Hab / (kH * Sh)).powi(2);
+        let dist = powf(*delta_l / (kL * Sl), 2.0)
+            + powf(Cab / (kC * Sc), 2.0)
+            + powf(Hab / (kH * Sh), 2.0);
         NotNan::new(dist).unwrap()
     }
 }

diff --git a/codi-core/src/color_space.rs b/codi-core/src/color_space.rs
@@ -1,3 +1,4 @@
+use libm::{cbrtf, powf, roundf};
 use ordered_float::NotNan;
 
 const HEX_COLOR_LEN: usize = 6;
@@ -33,6 +34,7 @@ impl core::fmt::Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for Error {}
 
 type Result<T> = core::result::Result<T, Error>;
@@ -134,7 +136,7 @@ impl From<Xyz> for Rgb {
             if col <= 0.003_130_8 {
                 col * 12.92
             } else {
-                col.powf(1.0 / 2.4) * 1.055 - 0.055
+                powf(col, 1.0 / 2.4) * 1.055 - 0.055
             }
         };
 
@@ -147,9 +149,9 @@ impl From<Xyz> for Rgb {
         );
 
         Self {
-            r: (corrected.0).round() as u8,
-            g: (corrected.1).round() as u8,
-            b: (corrected.2).round() as u8,
+            r: roundf(corrected.0) as u8,
+            g: roundf(corrected.1) as u8,
+            b: roundf(corrected.2) as u8,
         }
     }
 }
@@ -203,7 +205,7 @@ impl From<Rgb> for Xyz {
             if col <= 0.04045 {
                 col / 12.92
             } else {
-                ((col + 0.055) / 1.055).powf(2.4)
+                powf((col + 0.055) / 1.055, 2.4)
             }
         };
 
@@ -231,7 +233,7 @@ impl From<Cielab> for Xyz {
     fn from(value: Cielab) -> Self {
         let f_inv = |t: f32| {
             if t > LAB_XYZ_DELTA {
-                t.powi(3)
+                powf(t, 3.0)
             } else {
                 3.0 * LAB_XYZ_DELTA_POW2 * (t - 4.0 / 29.0)
             }
@@ -265,9 +267,9 @@ impl From<Xyz> for Cielab {
     fn from(value: Xyz) -> Self {
         let f = |t: f32| {
             if t > LAB_XYZ_DELTA_POW3 {
-                t.cbrt()
+                cbrtf(t)
             } else {
-                1.0 / 3.0 * t * LAB_XYZ_DELTA.powi(-2) + 4.0 / 29.0
+                1.0 / 3.0 * t * powf(LAB_XYZ_DELTA, -2.0) + 4.0 / 29.0
             }
         };
 

diff --git a/codi-core/src/lib.rs b/codi-core/src/lib.rs
@@ -1,3 +1,5 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
 pub mod color_dist;
 pub mod color_space;
 pub mod html_color;

diff --git a/codi-core/src/math_utils.rs b/codi-core/src/math_utils.rs
@@ -6,7 +6,7 @@ pub fn matrix_mul<T, const I: usize, const J: usize, const K: usize>(
     m2: &[[T; J]; K],
 ) -> [[T; J]; I]
 where
-    T: std::ops::Mul<Output = T> + std::ops::Add<Output = T> + Default + Copy,
+    T: core::ops::Mul<Output = T> + core::ops::Add<Output = T> + Default + Copy,
 {
     let mut res: [[T; J]; I] = [[T::default(); J]; I];
 

diff --git a/nix/flake.nix b/nix/flake.nix
@@ -17,7 +17,7 @@
       rust =
         (pkgs.rust-bin.fromRustupToolchainFile ../rust-toolchain.toml)
         .override {
-          targets = [];
+          targets = ["thumbv6m-none-eabi"];
           extensions = [];
         };
       rust-nightly = pkgs.rust-bin.nightly."2024-02-01".default;
@@ -66,6 +66,8 @@
           doCheck = true;
 
           postCheck = ''
+            cargo build -p codi-core --target thumbv6m-none-eabi --no-default-features
+
             cargo clippy --all-targets
             cargo fmt --check
             cargo doc