get rid of inefficient range caching

.changeset/fifty-tips-sit.md

@@ -0,0 +1,10 @@
+---
+"unicode-segmenter": patch
+---
+
+Removed inefficient optimization code from grapheme segmenter.
+
+The single range cache is barely hit after the entire BMP cache is hit.
+So removed it to reduce code size, and to reduce comparison count.
+
+Worth occupying 64KB of linear memory for BMP. It should definitely be acceptable, as it still uses less heap memory size than executing graphemer's uncompressed code.

README.md

@@ -219,7 +219,7 @@ Since [Hermes doesn't support the `Intl.Segmenter` API](https://github.com/faceb
 
 | Name                         | Unicode® | ESM? |   Size    | Size (min) | Size (min+gzip) | Size (min+br) | Size (min+zstd) |
 |------------------------------|----------|------|----------:|-----------:|----------------:|--------------:|----------------:|
-| `unicode-segmenter/grapheme` |   16.0.0 |   ✔️ |    15,730 |     12,199 |           5,113 |         3,787 |           4,807 |
+| `unicode-segmenter/grapheme` |   16.0.0 |   ✔️ |    15,449 |     12,108 |           5,060 |         3,738 |           4,744 |
 | `graphemer`                  |   15.0.0 |   ✖️ ️|   410,435 |     95,104 |          15,752 |        10,660 |          15,911 |
 | `grapheme-splitter`          |   10.0.0 |   ✖️ |   122,254 |     23,682 |           7,852 |         4,802 |           6,753 |
 | `@formatjs/intl-segmenter`*  |   15.0.0 |   ✖️ |   603,301 |    369,576 |          72,225 |        49,483 |          67,964 |
@@ -235,7 +235,7 @@ Since [Hermes doesn't support the `Intl.Segmenter` API](https://github.com/faceb
 
 | Name                         | Bytecode size | Bytecode size (gzip)* |
 |------------------------------|--------------:|----------------------:|
-| `unicode-segmenter/grapheme` |        21,542 |                11,392 |
+| `unicode-segmenter/grapheme` |        21,372 |                11,328 |
 | `graphemer`                  |       134,089 |                31,766 |
 | `grapheme-splitter`          |        63,946 |                19,162 |
 

src/grapheme.js

@@ -56,11 +56,8 @@ export function* graphemeSegments(input) {
   /** Total length of the input string. */
   let len = input.length;
 
-  /** @type {import('./_grapheme_data.js').GraphemeCategoryRange} */
-  let cache = [0, 0, 2 /* GC_Control */];
-
   /** Category of codepoint immediately preceding cursor */
-  let catBefore = cat(cp, cache);
+  let catBefore = cat(cp);
 
   /** @type {GraphemeCategoryNum | null} Category of codepoint immediately preceding cursor. */
   let catAfter = null;
@@ -101,7 +98,7 @@ export function* graphemeSegments(input) {
     }
 
     cp = /** @type {number} */ (input.codePointAt(cursor));
-    catAfter = cat(cp, cache);
+    catAfter = cat(cp);
 
     if (catBefore === 10 /* Regional_Indicator */) {
       risCount++;
@@ -222,30 +219,17 @@ let bmpCursor = (() => {
  * @see https://www.unicode.org/reports/tr29/tr29-43.html#Default_Grapheme_Cluster_Table
  *
  * @param {number} cp
- * @param {import('./_grapheme_data.js').GraphemeCategoryRange} cache
  * @return {GraphemeCategoryNum}
  */
-function cat(cp, cache) {
+function cat(cp) {
   // Fast lookup for BMP (0x0000..0xFFFF) using precomputed table
   if (cp <= BMP_MAX) {
     return /** @type {GraphemeCategoryNum} */ (bmpLookup[cp]);
   }
 
-  // Use cached result
-  if (cp >= cache[0] && cp <= cache[1]) {
-    return cache[2];
-  }
-
   // Binary search, starting from bmpCursor
   let index = findUnicodeRangeIndex(cp, grapheme_ranges, bmpCursor);
-  if (index < 0) {
-    return 0;
-  }
-
-  const range = grapheme_ranges[index];
-  cache[0] = range[0];
-  cache[1] = range[1];
-  return (cache[2] = range[2]);
+  return index < 0 ? 0 : grapheme_ranges[index][2];
 };
 
 /**