Use a manual loop to scan for line ends

FIX: Use a loop to find line breaks, because the existing regexp search
would overrun the end of the searched range and waste a lot of time
in minified code.

Closes #1083

Author: marijnh

acorn/src/locutil.js

@@ -1,4 +1,4 @@
-import {lineBreakG} from "./whitespace.js"
+import {nextLineBreak} from "./whitespace.js"
 
 // These are used when `options.locations` is on, for the
 // `startLoc` and `endLoc` properties.
@@ -30,13 +30,9 @@ export class SourceLocation {
 
 export function getLineInfo(input, offset) {
   for (let line = 1, cur = 0;;) {
-    lineBreakG.lastIndex = cur
-    let match = lineBreakG.exec(input)
-    if (match && match.index < offset) {
-      ++line
-      cur = match.index + match[0].length
-    } else {
-      return new Position(line, offset - cur)
-    }
+    let nextBreak = nextLineBreak(input, cur, offset)
+    if (nextBreak < 0) return new Position(line, offset - cur)
+    ++line
+    cur = nextBreak
   }
 }

acorn/src/tokenize.js

@@ -3,7 +3,7 @@ import {types as tt, keywords as keywordTypes} from "./tokentype.js"
 import {Parser} from "./state.js"
 import {SourceLocation} from "./locutil.js"
 import {RegExpValidationState} from "./regexp.js"
-import {lineBreak, lineBreakG, isNewLine, nonASCIIwhitespace} from "./whitespace.js"
+import {lineBreak, nextLineBreak, isNewLine, nonASCIIwhitespace} from "./whitespace.js"
 
 // Object type used to represent tokens. Note that normally, tokens
 // simply exist as properties on the parser object. This is only
@@ -100,11 +100,9 @@ pp.skipBlockComment = function() {
   if (end === -1) this.raise(this.pos - 2, "Unterminated comment")
   this.pos = end + 2
   if (this.options.locations) {
-    lineBreakG.lastIndex = start
-    let match
-    while ((match = lineBreakG.exec(this.input)) && match.index < this.pos) {
+    for (let nextBreak, pos = start; (nextBreak = nextLineBreak(this.input, pos, this.pos)) > -1;) {
       ++this.curLine
-      this.lineStart = match.index + match[0].length
+      pos = this.lineStart = nextBreak
     }
   }
   if (this.options.onComment)

acorn/src/whitespace.js

@@ -8,6 +8,15 @@ export function isNewLine(code) {
   return code === 10 || code === 13 || code === 0x2028 || code === 0x2029
 }
 
+export function nextLineBreak(code, from, end = code.length) {
+  for (let i = from; i < end; i++) {
+    let next = code.charCodeAt(i)
+    if (isNewLine(next))
+      return i < end - 1 && next === 13 && code.charCodeAt(i + 1) === 10 ? i + 2 : i + 1
+  }
+  return -1
+}
+
 export const nonASCIIwhitespace = /[\u1680\u2000-\u200a\u202f\u205f\u3000\ufeff]/
 
 export const skipWhiteSpace = /(?:\s|\/\/.*|\/\*[^]*?\*\/)*/g