Divide lib into multiple internal modules

src/bmpdepth.rs

@@ -0,0 +1,74 @@
+//===========================================================================//
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) enum BmpDepth {
+    One,
+    Four,
+    Eight,
+    Sixteen,
+    TwentyFour,
+    ThirtyTwo,
+}
+
+impl BmpDepth {
+    pub(crate) fn from_bits_per_pixel(
+        bits_per_pixel: u16,
+    ) -> Option<BmpDepth> {
+        match bits_per_pixel {
+            1 => Some(BmpDepth::One),
+            4 => Some(BmpDepth::Four),
+            8 => Some(BmpDepth::Eight),
+            16 => Some(BmpDepth::Sixteen),
+            24 => Some(BmpDepth::TwentyFour),
+            32 => Some(BmpDepth::ThirtyTwo),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn bits_per_pixel(&self) -> u16 {
+        match *self {
+            BmpDepth::One => 1,
+            BmpDepth::Four => 4,
+            BmpDepth::Eight => 8,
+            BmpDepth::Sixteen => 16,
+            BmpDepth::TwentyFour => 24,
+            BmpDepth::ThirtyTwo => 32,
+        }
+    }
+
+    pub(crate) fn num_colors(&self) -> usize {
+        match *self {
+            BmpDepth::One => 2,
+            BmpDepth::Four => 16,
+            BmpDepth::Eight => 256,
+            _ => 0,
+        }
+    }
+}
+
+//===========================================================================//
+
+#[cfg(test)]
+mod tests {
+    use super::BmpDepth;
+
+    #[test]
+    fn bmp_depth_round_trip() {
+        let depths = &[
+            BmpDepth::One,
+            BmpDepth::Four,
+            BmpDepth::Eight,
+            BmpDepth::Sixteen,
+            BmpDepth::TwentyFour,
+            BmpDepth::ThirtyTwo,
+        ];
+        for &depth in depths.iter() {
+            assert_eq!(
+                BmpDepth::from_bits_per_pixel(depth.bits_per_pixel()),
+                Some(depth)
+            );
+        }
+    }
+}
+
+//===========================================================================//