fix: lower lookbehind size to needleLength - 1

deps/streamsearch/sbmh.js

@@ -40,6 +40,7 @@ function SBMH (needle) {
   }
 
   const needleLength = needle.length
+  const needleLastCharIndex = needleLength - 1
 
   if (needleLength === 0) {
     throw new Error('The needle cannot be an empty String/Buffer.')
@@ -52,18 +53,17 @@ function SBMH (needle) {
   this.maxMatches = Infinity
   this.matches = 0
 
+  this._needle = needle
   this._occ = new Array(256)
     .fill(needleLength) // Initialize occurrence table.
+  this._lookbehind = Buffer.alloc(needleLastCharIndex)
   this._lookbehind_size = 0
-  this._needle = needle
   this._bufpos = 0
 
-  this._lookbehind = Buffer.alloc(needleLength)
-
   // Populate occurrence table with analysis of the needle,
   // ignoring last letter.
-  for (var i = 0; i < needleLength - 1; ++i) { // eslint-disable-line no-var
-    this._occ[needle[i]] = needleLength - 1 - i
+  for (let i = 0; i < needleLastCharIndex; ++i) {
+    this._occ[needle[i]] = needleLastCharIndex - i
   }
 }
 inherits(SBMH, EventEmitter)
@@ -89,7 +89,8 @@ SBMH.prototype._sbmh_feed = function (data) {
   const len = data.length
   const needle = this._needle
   const needleLength = needle.length
-  const lastNeedleChar = needle[needleLength - 1]
+  const needleLastCharIndex = needleLength - 1
+  const lastNeedleChar = needle[needleLastCharIndex]
 
   // Positive: points to a position in `data`
   //           pos == 3 points to data[3]
@@ -112,11 +113,11 @@ SBMH.prototype._sbmh_feed = function (data) {
     // or until
     //   the character to look at lies outside the haystack.
     while (pos < 0 && pos <= len - needleLength) {
-      ch = this._sbmh_lookup_char(data, pos + needleLength - 1)
+      ch = this._sbmh_lookup_char(data, pos + needleLastCharIndex)
 
       if (
         ch === lastNeedleChar &&
-        this._sbmh_memcmp(data, pos, needleLength - 1)
+        this._sbmh_memcmp(data, pos, needleLastCharIndex)
       ) {
         this._lookbehind_size = 0
         ++this.matches

test/streamsearch.test.js

@@ -244,7 +244,7 @@ test('streamsearch', async t => {
 
     const expected = [
       [false, Buffer.from('bar\r'), 0, 3],
-      [false, Buffer.from('\r\0\0'), 0, 1],
+      [false, Buffer.from('\r\0'), 0, 1],
       [false, Buffer.from('\n\r\nhello'), 0, 8]
     ]
     const needle = '\r\n\n'
@@ -339,7 +339,7 @@ test('streamsearch', async t => {
     t.plan(13)
 
     const expected = [
-      [false, Buffer.from('\n\n\0'), 0, 1],
+      [false, Buffer.from('\n\n'), 0, 1],
       [true, undefined, undefined, undefined],
       [false, Buffer.from('\r\nhello'), 1, 7]
     ]
@@ -374,8 +374,8 @@ test('streamsearch', async t => {
 
     const expected = [
       [false, Buffer.from('bar\r'), 0, 3],
-      [false, Buffer.from('\r\n\0'), 0, 2],
-      [false, Buffer.from('\r\n\0'), 0, 1],
+      [false, Buffer.from('\r\n'), 0, 2],
+      [false, Buffer.from('\r\n'), 0, 1],
       [false, Buffer.from('hello'), 0, 5]
     ]
     const needle = '\r\n\n'