Apply clippy::missing_const_for_fn

src/headers.rs

@@ -35,12 +35,12 @@ impl IhdrData {
 
     /// Byte length of IDAT that is correct for this IHDR
     #[must_use]
-    pub fn raw_data_size(&self) -> usize {
+    pub const fn raw_data_size(&self) -> usize {
         let w = self.width as usize;
         let h = self.height as usize;
         let bpp = self.bpp();
 
-        fn bitmap_size(bpp: usize, w: usize, h: usize) -> usize {
+        const fn bitmap_size(bpp: usize, w: usize, h: usize) -> usize {
             (w * bpp).div_ceil(8) * h
         }
 

src/interlace.rs

@@ -149,7 +149,7 @@ fn deinterlace_bytes(png: &PngImage) -> Vec<u8> {
     lines.concat()
 }
 
-fn increment_pass(current_pass: &mut u8, ihdr: &IhdrData) -> bool {
+const fn increment_pass(current_pass: &mut u8, ihdr: &IhdrData) -> bool {
     if *current_pass == 7 {
         return false;
     }

src/lib.rs

@@ -659,7 +659,7 @@ fn recompress_frames(
 }
 
 /// Check if an image was already optimized prior to oxipng's operations
-fn is_fully_optimized(original_size: usize, optimized_size: usize, opts: &Options) -> bool {
+const fn is_fully_optimized(original_size: usize, optimized_size: usize, opts: &Options) -> bool {
     original_size <= optimized_size && !opts.force
 }
 

src/options.rs

@@ -32,7 +32,7 @@ impl OutFile {
     ///
     /// This is a convenience method for `OutFile::Path { path: Some(path), preserve_attrs: false }`.
     #[must_use]
-    pub fn from_path(path: PathBuf) -> Self {
+    pub const fn from_path(path: PathBuf) -> Self {
         Self::Path {
             path: Some(path),
             preserve_attrs: false,
@@ -199,7 +199,7 @@ impl Options {
         self
     }
 
-    fn apply_preset_2(self) -> Self {
+    const fn apply_preset_2(self) -> Self {
         self
     }