Change struct to grab input iterator, not slice

I want to iterate over the input elements, and I couldn't figure out how
to get the slice lifetime to be specified properly. I've swapped the
slice for any Iterator that emits u8's.

src/main.rs

@@ -27,16 +27,16 @@ const QOI_OP_DIFF: u8 = 0b0100_0000;
 const QOI_OP_LUMA: u8 = 0b1000_0000;
 const QOI_OP_RUN: u8 = 0b1100_0000;
 
-struct Decoder<'input> {
+struct Decoder<I: Iterator<Item=u8>> {
     // QOI codec state information
     back_buffer: [PixelRGBA; 64],
     prev_pixel: PixelRGBA,
 
-    bytes: &'input [u8], // input byte slice
+    bytes: I,
 }
 
-impl<'input> Decoder<'input> {
+impl <I> Decoder <I> where I: Iterator<Item=u8> {
-    fn new(qoi_bytes: &'input [u8]) -> Self {
+    fn new(bytes: I) -> Self {
         Self {
             back_buffer: [PixelRGBA::zero(); 64],
             prev_pixel: PixelRGBA {
@@ -45,7 +45,7 @@ impl<'input> Decoder<'input> {
                 b: 0,
                 a: 255,
             },
-            bytes: qoi_bytes,
+            bytes,
         }
     }
 
@@ -54,27 +54,29 @@ impl<'input> Decoder<'input> {
     // then extracting back-referenced data out of it. A complete test should
     // feed in other valid operations that populate the backbuffer, and then index
     // op codes to demonstrate the indexing operations.
-    fn new_with_backbuffer(qoi_bytes: &'input [u8], back_buffer: [PixelRGBA; 64]) -> Self {
+    fn new_with_backbuffer(bytes: I, back_buffer: [PixelRGBA; 64]) -> Self {
         Self {
             back_buffer,
             prev_pixel: PixelRGBA {
                 r: 0, g: 0, b: 0, a: 255,
             },
-            bytes: qoi_bytes
+            bytes
         }
     }
 
     // A hack to unit test the run behavior. Same idea as the new_with_backbuffer()
     // function, but for testing a run of pixels.
-    fn new_with_previous_pixel(qoi_bytes: &'input [u8], prev_pixel: PixelRGBA) -> Self {
+    fn new_with_previous_pixel(bytes: I, prev_pixel: PixelRGBA) -> Self {
         Self {
             back_buffer: [PixelRGBA::zero(); 64],
             prev_pixel,
-            bytes: qoi_bytes,
+            bytes,
         }
     }
-
+}
-    fn hash(pixel: PixelRGBA) -> u8 {
+mod codec_utils {
+    use super::PixelRGBA;
+    pub(crate) fn hash(pixel: PixelRGBA) -> u8 {
         pixel
             .r
             .wrapping_mul(3)
@@ -85,11 +87,12 @@ impl<'input> Decoder<'input> {
     }
 }
 
-impl<'input> Iterator for Decoder<'input> {
+impl<'input, I> Iterator for Decoder<I> where I: Iterator<Item=u8> {
     type Item = PixelRGBA;
 
     fn next(&mut self) -> Option<Self::Item> {
-        todo!("Implement the Iterator trait for Decoder")
+        let byte = self.bytes.next()?;
+        todo!();
     }
 }
 
@@ -106,7 +109,7 @@ mod test {
             a: 255,
         };
         let expected = 39;
-        assert_eq!(Decoder::hash(pixel), expected);
+        assert_eq!(codec_utils::hash(pixel), expected);
     }
 
     #[test]
@@ -125,7 +128,7 @@ mod test {
             PixelRGBA{ r: 0x00, g: 0x00, b: 0x00, a: 0xFF}
         ];
 
-        let decoder = Decoder::new(&compressed);
+        let decoder = Decoder::new(compressed.into_iter());
         let result = decoder.collect::<Vec<PixelRGBA>>();
         assert_eq!(result, expected);
     }
@@ -144,7 +147,7 @@ mod test {
             PixelRGBA{ r: 0x10, g: 0x20, b: 0x30, a: 0x40 },
         ];
 
-        let decoder = Decoder::new(&compressed);
+        let decoder = Decoder::new(compressed.into_iter());
         let result: Vec<PixelRGBA> = decoder.collect();
         assert_eq!(result, expected);
     }
@@ -179,7 +182,7 @@ mod test {
             PixelRGBA::zero(),
         ];
 
-        let decoder = Decoder::new_with_backbuffer(&compressed, backbuffer);
+        let decoder = Decoder::new_with_backbuffer(compressed.into_iter(), backbuffer);
         let result: Vec<PixelRGBA> = decoder.collect();
         assert_eq!(result, expected);
     }
@@ -210,7 +213,7 @@ mod test {
             PixelRGBA::new(0, 0, 0, 255),
         ];
 
-        let decoder = Decoder::new(&compressed);
+        let decoder = Decoder::new(compressed.into_iter());
         let result: Vec<PixelRGBA> = decoder.collect();
         assert_eq!(result, expected);
     }
@@ -235,7 +238,7 @@ mod test {
             PixelRGBA::new(37, 19, 28, 255),
         ];
 
-        let decoder = Decoder::new(&compressed);
+        let decoder = Decoder::new(compressed.into_iter());
         let result: Vec<PixelRGBA> = decoder.collect();
         assert_eq!(result, expected);
     }
@@ -254,7 +257,7 @@ mod test {
         // lets pretend an encoder did this for some reason. The decoder can still
         // unpack this correctly, it's just a sub-optimal compression is all.
         
-        let decoder = Decoder::new_with_previous_pixel(&compressed, init_pixel);
+        let decoder = Decoder::new_with_previous_pixel(compressed.into_iter(), init_pixel);
         let result: Vec<PixelRGBA> = decoder.collect();
         assert_eq!(result, expected);
     }