some fixes

- commenting the bit shifts
- switching to Uint32Array
- conditional for TypedArray
- fixing Math.floor slowdown in bisearch

src/InputHandler.ts

@@ -1553,7 +1553,7 @@ export const wcwidth = (function(opts) {
       if (ucs < data[0][0] || ucs > data[max][1])
         return false;
       while (max >= min) {
-            mid = Math.floor((min + max) / 2);
+        mid = (min + max) >> 1;
         if (ucs > data[mid][1])
           min = mid + 1;
         else if (ucs < data[mid][0])
@@ -1600,22 +1600,43 @@ export const wcwidth = (function(opts) {
       }
       return 1;
     }
-    let table = new Uint8Array(16384);
-    for (let i = 0; i < 16384; ++i) {
-        let j = i * 4;
+    // lookup table for BMP
+    const CODEPOINTS = 65536;  // BMP holds 65536 codepoints
+    const BITWIDTH = 2;        // a codepoint can have a width of 0, 1 or 2
+    const ITEMSIZE = 32;       // using uint32_t
+    const CONTAINERSIZE = CODEPOINTS * BITWIDTH / ITEMSIZE;
+    const CODEPOINTS_PER_ITEM = ITEMSIZE / BITWIDTH;
+    const table = (typeof Uint32Array === 'undefined')
+      ? new Array(CONTAINERSIZE)
+      : new Uint32Array(CONTAINERSIZE);
+    for (let i = 0; i < CONTAINERSIZE; ++i) {
       let num = 0;
-        num |= (wcwidthBMP(j + 3));
-        num <<= 2;
-        num |= (wcwidthBMP(j + 2));
-        num <<= 2;
-        num |= (wcwidthBMP(j + 1));
-        num <<= 2;
-        num |= (wcwidthBMP(j));
+      let pos = CODEPOINTS_PER_ITEM;
+      while (pos--)
+        num = (num << 2) | wcwidthBMP(CODEPOINTS_PER_ITEM * i + pos);
       table[i] = num;
     }
+    // get width from lookup table for num < 65536:
+    //   position in container   : num / CODEPOINTS_PER_ITEM
+    //     ==> n = table[Math.floor(num / 16)]
+    //     ==> n = table[num >> 4]
+    //   16 codepoints per number:       FFEEDDCCBBAA99887766554433221100
+    //   position in number      : (num % CODEPOINTS_PER_ITEM) * BITWIDTH
+    //     ==> m = (n % 16) * 2
+    //     ==> m = (num & 15) << 1
+    //   right shift to position m
+    //     ==> n = n >> m     e.g. m=12  000000000000FFEEDDCCBBAA99887766
+    //   we are only interested in 2 LSBs, cut off higher
+    //     ==> n = n & 3      e.g.       000000000000000000000000000000XX
     return function (num) {
-        num = num | 0;
-        return (num < 65536) ? (table[num >> 2] >> ((num & 3) * 2)) & 3 : wcwidthHigh(num);
+      num = num | 0;  // get asm.js like optimization under V8
+      if (num < 32)
+        return opts.control;
+      else if (num < 127)
+        return 1;
+      else if (num < 65536)
+        return table[num >> 4] >> ((num & 15) << 1) & 3;
+      // do a full search for high codepoints
+      else return wcwidthHigh(num);
     };
 })({nul: 0, control: 0});  // configurable options
-