reserve some extra builtins, add encoding uniqueness test

vortex-array/src/encoding.rs

@@ -10,9 +10,9 @@ use crate::{Array, ArrayDef, ArrayTrait};
 /// EncodingId is a unique name and numerical code of the array
 ///
 /// 0x0000 - reserved marker encoding
-/// 0x0001 - 0x04FF - vortex internal encodings
-/// 0x0401 - 0x7FFF - well known extension encodings
-/// 0x8000 - 0xFFFF - custom extension encodings
+/// 0x0001 - 0x0400 - vortex internal encodings (1 - 1024)
+/// 0x0401 - 0x7FFF - well known extension encodings (1025 - 32767)
+/// 0x8000 - 0xFFFF - custom extension encodings (32768 - 65535)
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 pub struct EncodingId(&'static str, u16);
 
@@ -98,27 +98,91 @@ pub trait ArrayEncodingRef {
 
 #[doc = "Encoding ID constants for all Vortex-provided encodings"]
 pub mod ids {
+    // reserved - 0x0000
+    pub const RESERVED: u16 = 0;
+
+    // Vortex built-in encodings (1 - 15)
+    // built-ins first
     pub const NULL: u16 = 1;
     pub const BOOL: u16 = 2;
     pub const PRIMITIVE: u16 = 3;
-    pub const VAR_BIN: u16 = 4;
-    pub const VAR_BIN_VIEW: u16 = 5;
-    pub const EXTENSION: u16 = 6;
-    pub const STRUCT: u16 = 7;
+    pub const STRUCT: u16 = 4;
+    pub const VAR_BIN: u16 = 5;
+    pub const VAR_BIN_VIEW: u16 = 6;
+    pub const EXTENSION: u16 = 7;
     pub const SPARSE: u16 = 8;
     pub const CONSTANT: u16 = 9;
     pub const CHUNKED: u16 = 10;
-    pub const BYTE_BOOL: u16 = 11;
-    pub const ALP: u16 = 12;
-    pub const FL_BITPACKED: u16 = 13;
-    pub const FL_FOR: u16 = 14;
-    pub const FL_DELTA: u16 = 15;
-    pub const ROARING_BOOL: u16 = 16;
-    pub const ROARING_INT: u16 = 17;
-    pub const RUN_END: u16 = 18;
-    pub const DICT: u16 = 19;
-    pub const ZIGZAG: u16 = 20;
-    pub const DATE_TIME_PARTS: u16 = 21;
-    pub const RUN_END_BOOL: u16 = 22;
-    pub const FSST: u16 = 23;
+
+    // currently unused, saved for future built-ins
+    // e.g., List, FixedList, Union, Tensor, etc.
+    pub const RESERVED_11: u16 = 11;
+    pub const RESERVED_12: u16 = 12;
+    pub const RESERVED_13: u16 = 13;
+    pub const RESERVED_14: u16 = 14;
+    pub const RESERVED_15: u16 = 15;
+    pub const RESERVED_16: u16 = 16;
+
+    // bundled extensions
+    pub const ALP: u16 = 17;
+    pub const BYTE_BOOL: u16 = 18;
+    pub const DATE_TIME_PARTS: u16 = 19;
+    pub const DICT: u16 = 20;
+    pub const FL_BITPACKED: u16 = 21;
+    pub const FL_DELTA: u16 = 22;
+    pub const FL_FOR: u16 = 23;
+    pub const FSST: u16 = 24;
+    pub const ROARING_BOOL: u16 = 25;
+    pub const ROARING_INT: u16 = 26;
+    pub const RUN_END: u16 = 27;
+    pub const RUN_END_BOOL: u16 = 28;
+    pub const ZIGZAG: u16 = 29;
 }
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashSet;
+
+    use super::ids;
+
+    #[test]
+    fn test_encoding_id() {
+        let all_ids = [
+            ids::RESERVED,
+            ids::NULL,
+            ids::BOOL,
+            ids::PRIMITIVE,
+            ids::STRUCT,
+            ids::VAR_BIN,
+            ids::VAR_BIN_VIEW,
+            ids::EXTENSION,
+            ids::SPARSE,
+            ids::CONSTANT,
+            ids::CHUNKED,
+            ids::RESERVED_11,
+            ids::RESERVED_12,
+            ids::RESERVED_13,
+            ids::RESERVED_14,
+            ids::RESERVED_15,
+            ids::RESERVED_16,
+            ids::ALP,
+            ids::BYTE_BOOL,
+            ids::DATE_TIME_PARTS,
+            ids::DICT,
+            ids::FL_BITPACKED,
+            ids::FL_DELTA,
+            ids::FL_FOR,
+            ids::FSST,
+            ids::ROARING_BOOL,
+            ids::ROARING_INT,
+            ids::RUN_END,
+            ids::RUN_END_BOOL,
+            ids::ZIGZAG,
+        ];
+
+        let mut ids_set = HashSet::with_capacity(all_ids.len());
+        ids_set.extend(all_ids);
+        assert_eq!(ids_set.len(), all_ids.len());
+        assert!(ids_set.iter().max().unwrap() <= &0x0400);
+    }
+}