added note on datastructure selection

src/main.rs

@@ -29,9 +29,17 @@ pub struct Blob {
     // where n is number of bytes
     // and m is number of ranges
     // -------------------------
+    // Selected VecDeque<Box<[u8;N]>>> for fast push/pop/access
+    // pop_front may re-allocate, but better than vector most of time
+    // also since we use box, we are only copying pointers to the arrays, not each u8
+    // -------------------------
     // also tried using LinkedList, but slow reading when ranges were inside nodes
     // and indexing into LinkedList nodes doesn't seem to jive well with Rust's ownership model
     // especially when considering multi-threaded access
+    // -------------------------
+    // Vec<Option<Box<[u8;N]>>> also worth considering, but instead of pop
+    // using None slots to maintain indexes, if arrays are likely to be sparse
+    // this would probably be preferrable
     arrays: VecDeque<Box<[u8; ARRAY_SIZE]>>, // complexity variable n
     dropped: usize,
     ranges: Vec<Range>, // valid, global   // complexity variable m