Improve testability and add tests to the way that blocks of coefficie…

…nts are encoded (#69)

Cargo.toml

@@ -43,6 +43,7 @@ thread-priority = "1.0.0"
 [dev-dependencies]
 rstest = "0.19"
 rand = "0.8"
+siphasher = "1"
 
 [[bin]]
 name = "lepton_jpeg_util"

src/structs/block_context.rs

@@ -5,7 +5,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 use super::block_based_image::{AlignedBlock, BlockBasedImage, EMPTY_BLOCK};
-use super::neighbor_summary::NeighborSummary;
+use super::neighbor_summary::{NeighborSummary, NEIGHBOR_DATA_EMPTY};
 use super::probability_tables::ProbabilityTables;
 
 pub struct BlockContext {
@@ -17,6 +17,13 @@ pub struct BlockContext {
     cur_num_non_zeros_index: i32,
     above_num_non_zero_index: i32,
 }
+pub struct NeighborData<'a> {
+    pub above: &'a AlignedBlock,
+    pub left: &'a AlignedBlock,
+    pub above_left: &'a AlignedBlock,
+    pub neighbor_context_above: &'a NeighborSummary,
+    pub neighbor_context_left: &'a NeighborSummary,
+}
 
 impl BlockContext {
     // for debugging
@@ -72,60 +79,46 @@ impl BlockContext {
         return retval;
     }
 
-    pub fn get_neighbors<'a, const ALL_PRESENT: bool>(
+    pub fn get_neighbor_data<'a, const ALL_PRESENT: bool>(
         &self,
         image_data: &'a BlockBasedImage,
+        neighbor_summary: &'a [NeighborSummary],
         pt: &ProbabilityTables,
-    ) -> (&'a AlignedBlock, &'a AlignedBlock, &'a AlignedBlock) {
-        (
-            if ALL_PRESENT {
+    ) -> NeighborData<'a> {
+        NeighborData::<'a> {
+            above_left: if ALL_PRESENT {
                 image_data.get_block(self.above_block_index - 1)
             } else {
                 &EMPTY_BLOCK
             },
-            if ALL_PRESENT || pt.is_above_present() {
+            above: if ALL_PRESENT || pt.is_above_present() {
                 image_data.get_block(self.above_block_index)
             } else {
                 &EMPTY_BLOCK
             },
-            if ALL_PRESENT || pt.is_left_present() {
+            left: if ALL_PRESENT || pt.is_left_present() {
                 image_data.get_block(self.cur_block_index - 1)
             } else {
                 &EMPTY_BLOCK
             },
-        )
-    }
-
-    pub fn non_zeros_here(&self, num_non_zeros: &[NeighborSummary]) -> u8 {
-        return num_non_zeros[self.cur_num_non_zeros_index as usize].get_num_non_zeros();
-    }
-
-    pub fn get_non_zeros_above(&self, num_non_zeros: &[NeighborSummary]) -> u8 {
-        return num_non_zeros[self.above_num_non_zero_index as usize].get_num_non_zeros();
-    }
-
-    pub fn get_non_zeros_left(&self, num_non_zeros: &[NeighborSummary]) -> u8 {
-        return num_non_zeros[(self.cur_num_non_zeros_index - 1) as usize].get_num_non_zeros();
+            neighbor_context_above: if ALL_PRESENT || pt.is_above_present() {
+                &neighbor_summary[self.above_num_non_zero_index as usize]
+            } else {
+                &NEIGHBOR_DATA_EMPTY
+            },
+            neighbor_context_left: if ALL_PRESENT || pt.is_left_present() {
+                &neighbor_summary[(self.cur_num_non_zeros_index - 1) as usize]
+            } else {
+                &NEIGHBOR_DATA_EMPTY
+            },
+        }
     }
 
-    pub fn neighbor_context_here<'a>(
+    pub fn set_neighbor_summary_here(
         &mut self,
-        num_non_zeros: &'a mut [NeighborSummary],
-    ) -> &'a mut NeighborSummary {
-        return &mut num_non_zeros[self.cur_num_non_zeros_index as usize];
-    }
-
-    pub fn neighbor_context_above<'a>(
-        &self,
-        num_non_zeros: &'a [NeighborSummary],
-    ) -> &'a NeighborSummary {
-        return &num_non_zeros[self.above_num_non_zero_index as usize];
-    }
-
-    pub fn neighbor_context_left<'a>(
-        &self,
-        num_non_zeros: &'a [NeighborSummary],
-    ) -> &'a NeighborSummary {
-        return &num_non_zeros[(self.cur_num_non_zeros_index - 1) as usize];
+        neighbor_summary_cache: &mut [NeighborSummary],
+        neighbor_summary: NeighborSummary,
+    ) {
+        neighbor_summary_cache[self.cur_num_non_zeros_index as usize] = neighbor_summary;
     }
 }

src/structs/branch.rs

@@ -51,6 +51,18 @@ impl Branch {
         Branch { counts: 0x0101 }
     }
 
+    /// used for testing to set counts to a specific value
+    #[cfg(test)]
+    pub fn set_count(&mut self, count: u16) {
+        self.counts = count;
+    }
+
+    /// used for testing to set counts to a specific value
+    #[cfg(test)]
+    pub fn get_count(&self) -> u16 {
+        self.counts
+    }
+
     /// used for debugging to keep the state for hashing
     #[allow(dead_code)]
     pub fn get_u64(&self) -> u64 {