From a36566b3486b30ab15e3336033ca3a4ce7bd5ed8 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Thu, 19 Mar 2020 13:16:41 -0400
Subject: [PATCH] Allow empty needle in BidiTrieContainer.lastIndexOf()

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/882

Related commit:
- https://github.com/gorhill/uBlock/commit/7c0294bd5f54

The changes in the commit above have been reverted, and
the new fix is to add the ability to handle an empty
needle in BidiTrieContainer.lastIndexOf() -- in which
case the method will return the end of the currently
matched pattern.
---
 src/js/static-net-filtering.js |  14 --------------
 src/js/strie.js                |   1 +
 src/js/wasm/biditrie.wasm      | Bin 981 -> 990 bytes
 src/js/wasm/biditrie.wat       |   7 +++++++
 4 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/src/js/static-net-filtering.js b/src/js/static-net-filtering.js
index f726881fa..57314b6af 100644
--- a/src/js/static-net-filtering.js
+++ b/src/js/static-net-filtering.js
@@ -2599,20 +2599,6 @@ const FilterParser = class {
         this.token = matches[0];
         this.tokenHash = urlTokenizer.tokenHashFromString(this.token);
         this.tokenBeg = matches.index;
-
-        // https://www.reddit.com/r/uBlockOrigin/comments/dpcvfx/
-        //   Since we found a valid token, we can get rid of trailing
-        //   wildcards if any.
-        if ( this.firstWildcardPos !== -1 ) {
-            const lastCharPos = this.f.length - 1;
-            if ( this.firstWildcardPos === lastCharPos ) {
-                this.f = this.f.slice(0, -1);
-                this.firstWildcardPos = -1;
-            } else if ( this.secondWildcardPos === lastCharPos ) {
-                this.f = this.f.slice(0, -1);
-                this.secondWildcardPos = -1;
-            }
-        }
     }
 
     findGoodToken() {
diff --git a/src/js/strie.js b/src/js/strie.js
index b7c62f27e..c084eb1a3 100644
--- a/src/js/strie.js
+++ b/src/js/strie.js
@@ -666,6 +666,7 @@ const roundToPageSize = v => (v + PAGE_SIZE-1) & ~(PAGE_SIZE-1);
     // Find the right-most instance of substring in main string.
     // WASMable.
     lastIndexOf(haystackBeg, haystackEnd, needleLeft, needleLen) {
+        if ( needleLen === 0 ) { return haystackBeg; }
         let haystackLeft = haystackEnd - needleLen;
         if ( haystackLeft < haystackBeg ) { return -1; }
         needleLeft += this.buf32[CHAR0_SLOT];
diff --git a/src/js/wasm/biditrie.wasm b/src/js/wasm/biditrie.wasm
index a5d3aef9eed6ceb3bdb4ea2fd728ab446eb9083b..e1de9312c791266c644351b10c0a287b8ea10b37 100644
GIT binary patch
delta 30
mcmcc0evf@Z2ji8Eop+gd%Nbeg6_{OF926M%xhH2aX9EDLnh7ER

delta 21
dcmcb|ewBSf2jl6Dop+g7@)%j`Cl@nk0{~;A2r2*o

diff --git a/src/js/wasm/biditrie.wat b/src/js/wasm/biditrie.wat
index 5f7ec5e46..3cd76a618 100644
--- a/src/js/wasm/biditrie.wat
+++ b/src/js/wasm/biditrie.wat
@@ -639,6 +639,13 @@
     (local $i i32)
     (local $j i32)
     (local $c0 i32)
+    ;; if ( needleLen === 0 ) { return haystackBeg; }
+    get_local $needleLen
+    i32.eqz
+    if
+        get_local $haystackBeg
+        return
+    end
     block $fail
     block $succeed
     ;; let haystackLeft = haystackEnd - needleLen;