はじまりの大地

packages/transcription-devtools/src/levenshtein.ts

@@ -0,0 +1,101 @@
+function min (d0: number, d1: number, d2: number, bx: number, ay: number) {
+  return d0 < d1 || d2 < d1
+    ? d0 > d2
+      ? d2 + 1
+      : d0 + 1
+    : bx === ay
+      ? d1
+      : d1 + 1
+}
+
+/**
+ * @see https://github.com/gustf/js-levenshtein
+ */
+export function levenshteinDistance (a: string, b: string): number {
+  if (a === b) {
+    return 0
+  }
+
+  if (a.length > b.length) {
+    const tmp = a
+    a = b
+    b = tmp
+  }
+
+  let la = a.length
+  let lb = b.length
+
+  while (la > 0 && (a.charCodeAt(la - 1) === b.charCodeAt(lb - 1))) {
+    la--
+    lb--
+  }
+
+  let offset = 0
+
+  while (offset < la && (a.charCodeAt(offset) === b.charCodeAt(offset))) {
+    offset++
+  }
+
+  la -= offset
+  lb -= offset
+
+  if (la === 0 || lb < 3) {
+    return lb
+  }
+
+  let x = 0
+  let y: number
+  let d0: number
+  let d1: number
+  let d2: number
+  let d3: number
+  let dd: number
+  let dy: number
+  let ay: number
+  let bx0: number
+  let bx1: number
+  let bx2: number
+  let bx3: number
+
+  const vector: number[] = []
+
+  for (y = 0; y < la; y++) {
+    vector.push(y + 1)
+    vector.push(a.charCodeAt(offset + y))
+  }
+
+  const len = vector.length - 1
+
+  for (; x < lb - 3;) {
+    bx0 = b.charCodeAt(offset + (d0 = x))
+    bx1 = b.charCodeAt(offset + (d1 = x + 1))
+    bx2 = b.charCodeAt(offset + (d2 = x + 2))
+    bx3 = b.charCodeAt(offset + (d3 = x + 3))
+    dd = (x += 4)
+    for (y = 0; y < len; y += 2) {
+      dy = vector[y]
+      ay = vector[y + 1]
+      d0 = min(dy, d0, d1, bx0, ay)
+      d1 = min(d0, d1, d2, bx1, ay)
+      d2 = min(d1, d2, d3, bx2, ay)
+      dd = min(d2, d3, dd, bx3, ay)
+      vector[y] = dd
+      d3 = d2
+      d2 = d1
+      d1 = d0
+      d0 = dy
+    }
+  }
+
+  for (; x < lb;) {
+    bx0 = b.charCodeAt(offset + (d0 = x))
+    dd = ++x
+    for (y = 0; y < len; y += 2) {
+      dy = vector[y]
+      vector[y] = dd = min(dy, d0, dd, bx0, vector[y + 1])
+      d0 = dy
+    }
+  }
+
+  return dd
+}