Delta lookback (#248)

docs/benchmark_results/mbp_m3_max.csv

@@ -1,16 +1,16 @@
 input,codec,compress_dt,decompress_dt,compressed_size
 air_quality,blosc:cname=zstd:level=3,0.104805835,0.028497249,8429280
 air_quality,parquet:compression=zstd1,0.2296,0.02594,11156819
-air_quality,pco,0.10299417,0.021796916,4283105
+air_quality,pco,0.11510511,0.022027887,4283153
 air_quality,spdp,0.09585233,0.10599508,22560633
 air_quality,tpfor,0.029559456,0.002875309,19114630
 r_place,blosc:cname=zstd:level=3,11.372147,3.3396413,976973046
 r_place,parquet:compression=zstd1,15.389868,1.9258637,961718183
-r_place,pco,10.476611,1.5533803,661664577
+r_place,pco,11.368066,1.5747843,661665164
 r_place,spdp,11.464923,12.225844,3306514546
 r_place,tpfor,2.5569496,0.5739353,2023272462
 taxi,blosc:cname=zstd:level=3,6.3025703,1.8824589,841110760
 taxi,parquet:compression=zstd1,5.600355,0.9174722,464867099
-taxi,pco,5.3043575,0.8830483,333004373
+taxi,pco,5.6141233,0.8759089,333004631
 taxi,spdp,4.5603795,5.0574136,1636214754
 taxi,tpfor,1.0123023,0.24857067,1452549995

dtype_dispatch/src/lib.rs

@@ -1,4 +1,5 @@
 #![doc = include_str!("../README.md")]
+#![allow(unreachable_patterns)]
 
 /// Produces two macros: an enum definer and an enum matcher.
 ///
@@ -15,17 +16,38 @@ macro_rules! build_dtype_macros {
   ) => {
     $(#[$definer_attrs])*
     macro_rules! $definer {
+      (#[$enum_attrs: meta] $vis: vis $name: ident) => {
+        #[$enum_attrs]
+        #[non_exhaustive]
+        $vis enum $name {
+          $($variant,)+
+        }
+
+        impl $name {
+          #[inline]
+          pub fn new<T: $constraint>() -> Option<Self> {
+            let type_id = std::any::TypeId::of::<T>();
+            $(
+              if type_id == std::any::TypeId::of::<$t>() {
+                return Some($name::$variant);
+              }
+            )+
+            None
+          }
+        }
+      };
       (#[$enum_attrs: meta] #[repr($desc_t: ty)] $vis: vis $name: ident = $desc_val: ident) => {
         #[$enum_attrs]
         #[repr($desc_t)]
+        #[non_exhaustive]
         $vis enum $name {
           $($variant = <$t>::$desc_val,)+
         }
 
         impl $name {
           #[inline]
-          pub fn new<S: $constraint>() -> Option<Self> {
-            let type_id = std::any::TypeId::of::<S>();
+          pub fn new<T: $constraint>() -> Option<Self> {
+            let type_id = std::any::TypeId::of::<T>();
             $(
               if type_id == std::any::TypeId::of::<$t>() {
                 return Some($name::$variant);
@@ -50,6 +72,7 @@ macro_rules! build_dtype_macros {
         }
 
         #[$enum_attrs]
+        #[non_exhaustive]
         $vis enum $name {
           $($variant($container<$t>),)+
         }
@@ -106,26 +129,26 @@ macro_rules! build_dtype_macros {
             None
           }
 
-          pub fn downcast<S: $constraint>(self) -> Option<$container<S>> {
+          pub fn downcast<T: $constraint>(self) -> Option<$container<T>> {
             match self {
               $(
-                Self::$variant(inner) => inner.downcast::<S>(),
+                Self::$variant(inner) => inner.downcast::<T>(),
               )+
             }
           }
 
-          pub fn downcast_ref<S: $constraint>(&self) -> Option<&$container<S>> {
+          pub fn downcast_ref<T: $constraint>(&self) -> Option<&$container<T>> {
             match self {
               $(
-                Self::$variant(inner) => inner.downcast_ref::<S>(),
+                Self::$variant(inner) => inner.downcast_ref::<T>(),
               )+
             }
           }
 
-          pub fn downcast_mut<S: $constraint>(&mut self) -> Option<&mut $container<S>> {
+          pub fn downcast_mut<T: $constraint>(&mut self) -> Option<&mut $container<T>> {
             match self {
               $(
-                Self::$variant(inner) => inner.downcast_mut::<S>(),
+                Self::$variant(inner) => inner.downcast_mut::<T>(),
               )+
             }
           }
@@ -141,6 +164,7 @@ macro_rules! build_dtype_macros {
             type $generic = $t;
             $block
           })+
+          _ => unreachable!()
         }
       };
       ($value: expr, $enum_: ident<$generic: ident>($inner: ident) => $block: block) => {
@@ -149,6 +173,7 @@ macro_rules! build_dtype_macros {
             type $generic = $t;
             $block
           })+
+          _ => unreachable!()
         }
       };
     }