Address comments.

Author: lrhn

pkgs/characters/lib/src/grapheme_clusters/table.dart

@@ -1130,6 +1130,7 @@ const String _start = '\u1132\u166c\u166c\u206f\u11c0\u13fb\u166c\u166c\u166c'
 @pragma('vm:prefer-inline')
 @pragma('wasm:prefer-inline')
 int low(int codeUnit) {
+  assert(codeUnit <= 0xFFFF);
   var chunkStart = _start.codeUnitAt(codeUnit >> 5);
   var index = chunkStart + (codeUnit & 31);
   return _data.codeUnitAt(index);
@@ -1139,10 +1140,11 @@ int low(int codeUnit) {
 @pragma('vm:prefer-inline')
 @pragma('wasm:prefer-inline')
 int high(int lead, int tail) {
-  var offset = (tail >> 8) + (lead << 2);
-  tail &= 255;
-  var chunkStart = _start.codeUnitAt(2048 + offset);
-  return _data.codeUnitAt(chunkStart + tail);
+  assert(lead <= 0x3FF && tail <= 0x3FF);
+  var chunkIndex = (tail >> 8) + (lead << 2);
+  var byteIndex = tail & 255;
+  var chunkStart = _start.codeUnitAt(2048 + chunkIndex);
+  return _data.codeUnitAt(chunkStart + byteIndex);
 }
 
 const _stateMachine = '\x15\x01)))µ\x8d\x01=QeyeyÉ)))ñð\x15\x01)))µ\x8d\x00=Qey'

pkgs/characters/pubspec.yaml

@@ -10,8 +10,8 @@ topics:
   - unicode
 
 environment:
-  sdk: ^3.4.0
+  sdk: ^3.8.0
 
 dev_dependencies:
-  dart_flutter_team_lints: ^3.1.0
-  test: ^1.16.6
+  dart_flutter_team_lints: ^3.5.0
+  test: ^1.26.0

pkgs/characters/test/characters_test.dart

@@ -115,28 +115,29 @@ void main([List<String>? args]) {
         var zwj = '\u200d'; // U+200D, ZWJ
         var rainbow = '\u{1f308}'; // U+1F308, Rainbow. Category Pictogram
 
-        var rbflag = '$flag$white$zwj$rainbow';
-        var string = '-$rbflag-';
+        var rainbowFlag = '$flag$white$zwj$rainbow';
+        var string = '-$rainbowFlag-';
         var range = CharacterRange.at(string, 1);
         expect(range.isEmpty, true);
         expect(range.moveNext(), true);
-        expect(range.current, rbflag);
+        expect(range.current, rainbowFlag);
 
         range = range = CharacterRange.at(string, 2);
         expect(range.isEmpty, false);
-        expect(range.current, rbflag);
+        expect(range.current, rainbowFlag);
 
         range = range = CharacterRange.at(string, 0, 2);
         expect(range.isEmpty, false);
-        expect(range.current, '-$rbflag');
+        expect(range.current, '-$rainbowFlag');
 
         range = range = CharacterRange.at(string, 0, 2);
         expect(range.isEmpty, false);
-        expect(range.current, '-$rbflag');
+        expect(range.current, '-$rainbowFlag');
 
-        range = range = CharacterRange.at(string, 2, '-$rbflag'.length - 1);
+        range =
+            range = CharacterRange.at(string, 2, '-$rainbowFlag'.length - 1);
         expect(range.isEmpty, false);
-        expect(range.current, rbflag);
+        expect(range.current, rainbowFlag);
         expect(range.stringBeforeLength, 1);
 
         range = range = CharacterRange.at(string, 0, string.length);

pkgs/characters/tool/benchmark.dart

@@ -16,8 +16,8 @@ void main(List<String> args) {
   if (args.isNotEmpty) {
     count = int.parse(args[0]);
   }
-  var gcsf = 0;
-  var gcsb = 0;
+  var gcSumForward = 0;
+  var gcSumBackwards = 0;
 
   var text = genesis +
       hangul +
@@ -29,19 +29,19 @@ void main(List<String> args) {
   var codeUnits = text.length;
   var codePoints = text.runes.length;
   for (var i = 0; i < count; i++) {
-    gcsf = benchForward(text, i, codePoints, codeUnits);
-    gcsb = benchBackward(text, i, codePoints, codeUnits);
+    gcSumForward = benchForward(text, i, codePoints, codeUnits);
+    gcSumBackwards = benchBackward(text, i, codePoints, codeUnits);
   }
   print('gc: Grapheme Clusters, cp: Code Points, cu: Code Units.');
-  if (gcsf != gcsb) {
+  if (gcSumForward != gcSumBackwards) {
     print(
       'ERROR: Did not count the same number of grapheme clusters: '
-      '$gcsf forward vs. $gcsb backward.',
+      '$gcSumForward forward vs. $gcSumBackwards backward.',
     );
   } else {
-    print('Total: $gcsf gc, $codePoints cp, $codeUnits cu');
-    print('Avg ${(codePoints / gcsf).toStringAsFixed(3)} cp/gc');
-    print('Avg ${(codeUnits / gcsf).toStringAsFixed(3)} cu/gc');
+    print('Total: $gcSumForward gc, $codePoints cp, $codeUnits cu');
+    print('Avg ${(codePoints / gcSumForward).toStringAsFixed(3)} cp/gc');
+    print('Avg ${(codeUnits / gcSumForward).toStringAsFixed(3)} cu/gc');
   }
 }
 

pkgs/characters/tool/bin/generate_tables.dart

@@ -307,6 +307,7 @@ String _lookupMethod(
     '''
 $preferInline
 int $name(int codeUnit) {
+  assert(codeUnit <= 0xFFFF);
   var chunkStart = $startName.codeUnitAt(codeUnit >> ${chunkSize.bitLength - 1});
   var index = chunkStart + (codeUnit & ${chunkSize - 1});
   return $dataName.codeUnitAt(index);
@@ -326,6 +327,7 @@ String _lookupSurrogatesMethod(
     return '''
 $preferInline
 int $name(int lead, int tail) {
+  assert(lead <= 0x3FF && tail <= 0x3FF);
   var chunkStart = $startName.codeUnitAt($startOffset + lead);
   return $dataName.codeUnitAt(chunkStart + tail);
 }
@@ -335,15 +337,17 @@ int $name(int lead, int tail) {
     return '''
 $preferInline
 int $name(int lead, int tail) {
-  var offset = (tail >> $shift) + (lead << ${10 - shift});
-  tail &= ${chunkSize - 1};
-  var chunkStart = $startName.codeUnitAt($startOffset + offset);
-  return $dataName.codeUnitAt(chunkStart + tail);
+  assert(lead <= 0x3FF && tail <= 0x3FF);
+  var chunkIndex = (tail >> $shift) + (lead << ${10 - shift});
+  var byteIndex = tail & ${chunkSize - 1};
+  var chunkStart = $startName.codeUnitAt($startOffset + chunkIndex);
+  return $dataName.codeUnitAt(chunkStart + byteIndex);
 }
 ''';
   }
   // Add code if shift > 10 ever becomes optimal for table size.
-  // Example code:
+  // Fx: chunkIndex = lead >> ${20 - shift};
+  //     byteIndex = tail + ((lead & ${(chunkSize >> 10) - 1}) << 10);
   throw UnimplementedError('No code for chunk sizes > 10 bits');
 }
 

pkgs/characters/tool/src/grapheme_category_loader.dart

@@ -291,9 +291,6 @@ Uint8List _parseInCBCategories(String file, {required bool verbose}) {
 }
 
 // --------------------------------------------------------------------
-// TODO: Use a sparse table?
-// Likely not worth it.
-
 /// Fixed length table for Unicode properties.
 class UnicodePropertyTable {
   static const int _unicodeCodePoints = 0x110000;