Avoid the possibility of stack overflow in spliceArray helper

benchmarks/helpers.js

@@ -1,9 +1,10 @@
 const WORDS = require('../spec/helpers/words')
 const Random = require('random-seed')
 const random = new Random(Date.now())
+const {Point, Range} = require('..')
 
 exports.getRandomText = function (sizeInKB) {
-  const goalLength = sizeInKB * 1024
+  const goalLength = Math.round(sizeInKB * 1024)
 
   let length = 0
   let lines = []
@@ -41,3 +42,19 @@ exports.getRandomText = function (sizeInKB) {
 
   return lines.join('\n') + '\n'
 }
+
+exports.getRandomRange = function (buffer) {
+  const start = getRandomPoint(buffer)
+  const end = getRandomPoint(buffer)
+  if (end.isLessThan(start)) {
+    return new Range(end, start)
+  } else {
+    return new Range(start, end)
+  }
+}
+
+function getRandomPoint (buffer) {
+  const row = random(buffer.getLineCount())
+  const column = random(buffer.lineLengthForRow(row))
+  return new Point(row, column)
+}

benchmarks/index.js

@@ -1,3 +1,4 @@
 #!/usr/bin/env node
 
 require('./construction')
+require('./mutation')

benchmarks/mutation.js

@@ -0,0 +1,21 @@
+const helpers = require('./helpers')
+const TextBuffer = require('..')
+
+let text = helpers.getRandomText(100)
+let buffer = new TextBuffer({text})
+let displayLayer = buffer.addDisplayLayer({})
+
+let t0 = Date.now()
+
+for (let i = 0; i < 1000; i++) {
+  buffer.setTextInRange(
+    helpers.getRandomRange(buffer),
+    helpers.getRandomText(0.5)
+  )
+}
+
+let t1 = Date.now()
+
+console.log('Mutation')
+console.log('------------')
+console.log('TextBuffer:    %s ms', t1 - t0)

src/helpers.coffee

@@ -1,20 +1,27 @@
 Point = require './point'
 
-SpliceArrayChunkSize = 100000
-
 MULTI_LINE_REGEX_REGEX = /\\r|\\n|\r|\n|^\[\^|[^\\]\[\^/
 
 module.exports =
-  spliceArray: (originalArray, start, length, insertedArray=[]) ->
-    if insertedArray.length < SpliceArrayChunkSize
-      originalArray.splice(start, length, insertedArray...)
+  spliceArray: (array, start, removedCount, insertedItems=[]) ->
+    oldLength = array.length
+    insertedCount = insertedItems.length
+    removedCount = Math.min(removedCount, oldLength - start)
+    lengthDelta = insertedCount - removedCount
+    newLength = oldLength + lengthDelta
+
+    if lengthDelta > 0
+      array.length = newLength
+      for i in [(newLength - 1)..(start + insertedCount)] by -1
+        array[i] = array[i - lengthDelta]
     else
-      removedValues = originalArray.splice(start, length)
-      for chunkStart in [0..insertedArray.length] by SpliceArrayChunkSize
-        chunkEnd = chunkStart + SpliceArrayChunkSize
-        chunk = insertedArray.slice(chunkStart, chunkEnd)
-        originalArray.splice(start + chunkStart, 0, chunk...)
-      removedValues
+      for i in [(start + insertedCount)...newLength] by 1
+        array[i] = array[i - lengthDelta]
+      array.length = newLength
+
+    for value, i in insertedItems by 1
+      array[start + i] = insertedItems[i]
+    return
 
   newlineRegex: /\r\n|\n|\r/g