From 38227e92898a049412ddaab6c8596218d32db650 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Mon, 5 Aug 2024 16:23:30 -0700
Subject: [PATCH] fuzzer web UI: render PCs with red or green depending on
 coverage

---
 lib/fuzzer/index.html    | 19 ++++++++++++++-----
 lib/fuzzer/main.js       | 19 +++++++++++++++----
 lib/fuzzer/wasm/main.zig | 27 +++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/lib/fuzzer/index.html b/lib/fuzzer/index.html
index 0f62f58e6d..16fa879913 100644
--- a/lib/fuzzer/index.html
+++ b/lib/fuzzer/index.html
@@ -53,11 +53,14 @@
       }
 
       .l {
-          display: inline-block;
-          background: white;
-          width: 1em;
-          height: 1em;
-          border-radius: 1em;
+        display: inline-block;
+        background: red;
+        width: 1em;
+        height: 1em;
+        border-radius: 1em;
+      }
+      .c {
+        background-color: green;
       }
 
       .tok-kw {
@@ -104,6 +107,12 @@
         code a {
           color: #ccc;
         }
+        .l {
+          background-color: red;
+        }
+        .c {
+          background-color: green;
+        }
         .tok-kw {
             color: #eee;
         }
diff --git a/lib/fuzzer/main.js b/lib/fuzzer/main.js
index 42bd72cef5..773cdfe902 100644
--- a/lib/fuzzer/main.js
+++ b/lib/fuzzer/main.js
@@ -172,12 +172,20 @@
   }
 
   function renderCoverage() {
+    if (curNavLocation == null) return;
+    const sourceLocationIndex = curNavLocation;
+
     for (let i = 0; i < domSourceText.children.length; i += 1) {
       const childDom = domSourceText.children[i];
       if (childDom.id != null && childDom.id[0] == "l") {
         childDom.classList.add("l");
+        childDom.classList.remove("c");
       }
     }
+    const coveredList = unwrapInt32Array(wasm_exports.sourceLocationFileCoveredList(sourceLocationIndex));
+    for (let i = 0; i < coveredList.length; i += 1) {
+      document.getElementById("l" + coveredList[i]).classList.add("c");
+    }
   }
 
   function resizeDomList(listDom, desiredLen, templateHtml) {
@@ -203,10 +211,13 @@
 
     domSectSource.classList.remove("hidden");
 
-    const slDom = document.getElementById("l" + sourceLocationIndex);
-    slDom.scrollIntoView({
-      behavior: "smooth",
-      block: "center",
+    // Empirically, Firefox needs this requestAnimationFrame in order for the scrollIntoView to work.
+    requestAnimationFrame(function() {
+      const slDom = document.getElementById("l" + sourceLocationIndex);
+      slDom.scrollIntoView({
+        behavior: "smooth",
+        block: "center",
+      });
     });
   }
 
diff --git a/lib/fuzzer/wasm/main.zig b/lib/fuzzer/wasm/main.zig
index 5d8edf768a..a352458afc 100644
--- a/lib/fuzzer/wasm/main.zig
+++ b/lib/fuzzer/wasm/main.zig
@@ -395,3 +395,30 @@ export fn sourceLocationFileHtml(sli: SourceLocationIndex) String {
     };
     return String.init(string_result.items);
 }
+
+export fn sourceLocationFileCoveredList(sli_file: SourceLocationIndex) Slice(SourceLocationIndex) {
+    const global = struct {
+        var result: std.ArrayListUnmanaged(SourceLocationIndex) = .{};
+        fn add(i: u32, want_file: Coverage.File.Index) void {
+            const src_loc_index: SourceLocationIndex = @enumFromInt(i);
+            if (src_loc_index.ptr().file == want_file) result.appendAssumeCapacity(src_loc_index);
+        }
+    };
+    const want_file = sli_file.ptr().file;
+    global.result.clearRetainingCapacity();
+    const covered_bits = recent_coverage_update.items[@sizeOf(abi.CoverageUpdateHeader)..];
+    var sli: u32 = 0;
+    for (covered_bits) |byte| {
+        global.result.ensureUnusedCapacity(gpa, 8) catch @panic("OOM");
+        if ((byte & 0b0000_0001) != 0) global.add(sli + 0, want_file);
+        if ((byte & 0b0000_0010) != 0) global.add(sli + 1, want_file);
+        if ((byte & 0b0000_0100) != 0) global.add(sli + 2, want_file);
+        if ((byte & 0b0000_1000) != 0) global.add(sli + 3, want_file);
+        if ((byte & 0b0001_0000) != 0) global.add(sli + 4, want_file);
+        if ((byte & 0b0010_0000) != 0) global.add(sli + 5, want_file);
+        if ((byte & 0b0100_0000) != 0) global.add(sli + 6, want_file);
+        if ((byte & 0b1000_0000) != 0) global.add(sli + 7, want_file);
+        sli += 8;
+    }
+    return Slice(SourceLocationIndex).init(global.result.items);
+}