refactor: Avoid doing unnecessary bit operations in rust's const eval

Author: Markus Westerlind

idna/src/make_uts46_mapping_table.py

@@ -162,11 +162,15 @@ def merge_single_char_ranges(ranges):
 
 print("static INDEX_TABLE: &'static [u16] = &[")
 
+SINGLE_MARKER = 1 << 15
+
 offset = 0
 for ranges in optimized_ranges:
+    assert offset < SINGLE_MARKER
+
     block_len = len(ranges)
-    single = (1 << 15) if block_len == 1 else 0 
-    print("    %s | %s, " % (offset, single))
+    single = SINGLE_MARKER if block_len == 1 else 0
+    print("    %s," % (offset | single))
     offset += block_len
 
 print("];\n")

idna/src/uts46.rs

@@ -69,9 +69,12 @@ fn find_char(codepoint: char) -> &'static Mapping {
         }
     });
     r.ok().map(|i| {
+        const SINGLE_MARKER: u16 = 1 << 15;
+
         let x = INDEX_TABLE[i];
-        let single = (x & (1 << 15)) != 0;
-        let offset = !(1 << 15) & x;
+        let single = (x & SINGLE_MARKER) != 0;
+        let offset = !SINGLE_MARKER & x;
+
         if single {
             &MAPPING_TABLE[offset as usize]
         } else {