1 files changed, 257 insertions, 0 deletions
diff --git a/toolkit/components/telemetry/other/CombinedStacks.cpp b/toolkit/components/telemetry/other/CombinedStacks.cpp
new file mode 100644
index 0000000000..61248f9b40
--- /dev/null
+++ b/toolkit/components/telemetry/other/CombinedStacks.cpp
@@ -0,0 +1,257 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CombinedStacks.h"
+
+#include "jsapi.h"
+#include "js/Array.h"               // JS::NewArrayObject
+#include "js/PropertyAndElement.h"  // JS_DefineElement, JS_DefineProperty
+#include "js/String.h"
+
+namespace mozilla::Telemetry {
+
+// The maximum number of chrome hangs stacks that we're keeping.
+const size_t kMaxChromeStacksKept = 50;
+
+CombinedStacks::CombinedStacks() : CombinedStacks(kMaxChromeStacksKept) {}
+
+CombinedStacks::CombinedStacks(size_t aMaxStacksCount)
+    : mNextIndex(0), mMaxStacksCount(aMaxStacksCount) {}
+
+size_t CombinedStacks::GetMaxStacksCount() const { return mMaxStacksCount; }
+size_t CombinedStacks::GetModuleCount() const { return mModules.size(); }
+
+const Telemetry::ProcessedStack::Module& CombinedStacks::GetModule(
+    unsigned aIndex) const {
+  return mModules[aIndex];
+}
+
+void CombinedStacks::AddFrame(
+    size_t aStackIndex, const ProcessedStack::Frame& aFrame,
+    const std::function<const ProcessedStack::Module&(int)>& aModuleGetter) {
+  uint16_t modIndex;
+  if (aFrame.mModIndex == std::numeric_limits<uint16_t>::max()) {
+    modIndex = aFrame.mModIndex;
+  } else {
+    const ProcessedStack::Module& module = aModuleGetter(aFrame.mModIndex);
+    auto modIterator = std::find(mModules.begin(), mModules.end(), module);
+    if (modIterator == mModules.end()) {
+      mModules.push_back(module);
+      modIndex = mModules.size() - 1;
+    } else {
+      modIndex = modIterator - mModules.begin();
+    }
+  }
+  mStacks[aStackIndex].push_back(
+      ProcessedStack::Frame{aFrame.mOffset, modIndex});
+}
+
+size_t CombinedStacks::AddStack(const Telemetry::ProcessedStack& aStack) {
+  size_t index = mNextIndex;
+  // Advance the indices of the circular queue holding the stacks.
+  mNextIndex = (mNextIndex + 1) % mMaxStacksCount;
+  // Grow the vector up to the maximum size, if needed.
+  if (mStacks.size() < mMaxStacksCount) {
+    mStacks.resize(mStacks.size() + 1);
+  }
+
+  // Clear the old stack before set.
+  mStacks[index].clear();
+
+  size_t stackSize = aStack.GetStackSize();
+  for (size_t i = 0; i < stackSize; ++i) {
+    // Need to specify a return type in the following lambda,
+    // otherwise it's incorrectly deduced to be a non-reference type.
+    AddFrame(index, aStack.GetFrame(i),
+             [&aStack](int aIdx) -> const ProcessedStack::Module& {
+               return aStack.GetModule(aIdx);
+             });
+  }
+  return index;
+}
+
+void CombinedStacks::AddStacks(const CombinedStacks& aStacks) {
+  mStacks.resize(
+      std::min(mStacks.size() + aStacks.GetStackCount(), mMaxStacksCount));
+
+  for (const auto& stack : aStacks.mStacks) {
+    size_t index = mNextIndex;
+    // Advance the indices of the circular queue holding the stacks.
+    mNextIndex = (mNextIndex + 1) % mMaxStacksCount;
+
+    // Clear the old stack before set.
+    mStacks[index].clear();
+
+    for (const auto& frame : stack) {
+      // Need to specify a return type in the following lambda,
+      // otherwise it's incorrectly deduced to be a non-reference type.
+      AddFrame(index, frame,
+               [&aStacks](int aIdx) -> const ProcessedStack::Module& {
+                 return aStacks.mModules[aIdx];
+               });
+    }
+  }
+}
+
+const CombinedStacks::Stack& CombinedStacks::GetStack(unsigned aIndex) const {
+  return mStacks[aIndex];
+}
+
+size_t CombinedStacks::GetStackCount() const { return mStacks.size(); }
+
+size_t CombinedStacks::SizeOfExcludingThis() const {
+  // This is a crude approximation. We would like to do something like
+  // aMallocSizeOf(&mModules[0]), but on linux aMallocSizeOf will call
+  // malloc_usable_size which is only safe on the pointers returned by malloc.
+  // While it works on current libstdc++, it is better to be safe and not assume
+  // that &vec[0] points to one. We could use a custom allocator, but
+  // it doesn't seem worth it.
+  size_t n = 0;
+  n += mModules.capacity() * sizeof(Telemetry::ProcessedStack::Module);
+  n += mStacks.capacity() * sizeof(Stack);
+  for (const auto& s : mStacks) {
+    n += s.capacity() * sizeof(Telemetry::ProcessedStack::Frame);
+  }
+  return n;
+}
+
+void CombinedStacks::RemoveStack(unsigned aIndex) {
+  MOZ_ASSERT(aIndex < mStacks.size());
+
+  mStacks.erase(mStacks.begin() + aIndex);
+
+  if (aIndex < mNextIndex) {
+    if (mNextIndex == 0) {
+      mNextIndex = mStacks.size();
+    } else {
+      mNextIndex--;
+    }
+  }
+
+  if (mNextIndex > mStacks.size()) {
+    mNextIndex = mStacks.size();
+  }
+}
+
+void CombinedStacks::Swap(CombinedStacks& aOther) {
+  mModules.swap(aOther.mModules);
+  mStacks.swap(aOther.mStacks);
+
+  size_t nextIndex = aOther.mNextIndex;
+  aOther.mNextIndex = mNextIndex;
+  mNextIndex = nextIndex;
+
+  size_t maxStacksCount = aOther.mMaxStacksCount;
+  aOther.mMaxStacksCount = mMaxStacksCount;
+  mMaxStacksCount = maxStacksCount;
+}
+
+void CombinedStacks::Clear() {
+  mNextIndex = 0;
+  mStacks.clear();
+  mModules.clear();
+}
+
+JSObject* CreateJSStackObject(JSContext* cx, const CombinedStacks& stacks) {
+  JS::Rooted<JSObject*> ret(cx, JS_NewPlainObject(cx));
+  if (!ret) {
+    return nullptr;
+  }
+
+  JS::Rooted<JSObject*> moduleArray(cx, JS::NewArrayObject(cx, 0));
+  if (!moduleArray) {
+    return nullptr;
+  }
+  bool ok =
+      JS_DefineProperty(cx, ret, "memoryMap", moduleArray, JSPROP_ENUMERATE);
+  if (!ok) {
+    return nullptr;
+  }
+
+  const size_t moduleCount = stacks.GetModuleCount();
+  for (size_t moduleIndex = 0; moduleIndex < moduleCount; ++moduleIndex) {
+    // Current module
+    const Telemetry::ProcessedStack::Module& module =
+        stacks.GetModule(moduleIndex);
+
+    JS::Rooted<JSObject*> moduleInfoArray(cx, JS::NewArrayObject(cx, 0));
+    if (!moduleInfoArray) {
+      return nullptr;
+    }
+    if (!JS_DefineElement(cx, moduleArray, moduleIndex, moduleInfoArray,
+                          JSPROP_ENUMERATE)) {
+      return nullptr;
+    }
+
+    unsigned index = 0;
+
+    // Module name
+    JS::Rooted<JSString*> str(cx, JS_NewUCStringCopyZ(cx, module.mName.get()));
+    if (!str || !JS_DefineElement(cx, moduleInfoArray, index++, str,
+                                  JSPROP_ENUMERATE)) {
+      return nullptr;
+    }
+
+    // Module breakpad identifier
+    JS::Rooted<JSString*> id(cx,
+                             JS_NewStringCopyZ(cx, module.mBreakpadId.get()));
+    if (!id ||
+        !JS_DefineElement(cx, moduleInfoArray, index, id, JSPROP_ENUMERATE)) {
+      return nullptr;
+    }
+  }
+
+  JS::Rooted<JSObject*> reportArray(cx, JS::NewArrayObject(cx, 0));
+  if (!reportArray) {
+    return nullptr;
+  }
+  ok = JS_DefineProperty(cx, ret, "stacks", reportArray, JSPROP_ENUMERATE);
+  if (!ok) {
+    return nullptr;
+  }
+
+  const size_t length = stacks.GetStackCount();
+  for (size_t i = 0; i < length; ++i) {
+    // Represent call stack PCs as (module index, offset) pairs.
+    JS::Rooted<JSObject*> pcArray(cx, JS::NewArrayObject(cx, 0));
+    if (!pcArray) {
+      return nullptr;
+    }
+
+    if (!JS_DefineElement(cx, reportArray, i, pcArray, JSPROP_ENUMERATE)) {
+      return nullptr;
+    }
+
+    const CombinedStacks::Stack& stack = stacks.GetStack(i);
+    const uint32_t pcCount = stack.size();
+    for (size_t pcIndex = 0; pcIndex < pcCount; ++pcIndex) {
+      const Telemetry::ProcessedStack::Frame& frame = stack[pcIndex];
+      JS::Rooted<JSObject*> framePair(cx, JS::NewArrayObject(cx, 0));
+      if (!framePair) {
+        return nullptr;
+      }
+      int modIndex = (std::numeric_limits<uint16_t>::max() == frame.mModIndex)
+                         ? -1
+                         : frame.mModIndex;
+      if (!JS_DefineElement(cx, framePair, 0, modIndex, JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+      if (!JS_DefineElement(cx, framePair, 1,
+                            static_cast<double>(frame.mOffset),
+                            JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+      if (!JS_DefineElement(cx, pcArray, pcIndex, framePair,
+                            JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+    }
+  }
+
+  return ret;
+}
+
+}  // namespace mozilla::Telemetry