1 files changed, 170 insertions, 0 deletions
diff --git a/xpcom/io/nsSegmentedBuffer.cpp b/xpcom/io/nsSegmentedBuffer.cpp
new file mode 100644
index 0000000000..01d075368a
--- /dev/null
+++ b/xpcom/io/nsSegmentedBuffer.cpp
@@ -0,0 +1,170 @@
+/* -*- 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 "nsSegmentedBuffer.h"
+#include "nsNetCID.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+#include "mozilla/ScopeExit.h"
+
+nsresult nsSegmentedBuffer::Init(uint32_t aSegmentSize) {
+  if (mSegmentArrayCount != 0) {
+    return NS_ERROR_FAILURE;  // initialized more than once
+  }
+  mSegmentSize = aSegmentSize;
+  mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
+  return NS_OK;
+}
+
+char* nsSegmentedBuffer::AppendNewSegment() {
+  if (!mSegmentArray) {
+    uint32_t bytes = mSegmentArrayCount * sizeof(char*);
+    mSegmentArray = (char**)moz_xmalloc(bytes);
+    memset(mSegmentArray, 0, bytes);
+  }
+
+  if (IsFull()) {
+    mozilla::CheckedInt<uint32_t> newArraySize =
+        mozilla::CheckedInt<uint32_t>(mSegmentArrayCount) * 2;
+    mozilla::CheckedInt<uint32_t> bytes = newArraySize * sizeof(char*);
+    if (!bytes.isValid()) {
+      return nullptr;
+    }
+
+    mSegmentArray = (char**)moz_xrealloc(mSegmentArray, bytes.value());
+    // copy wrapped content to new extension
+    if (mFirstSegmentIndex > mLastSegmentIndex) {
+      // deal with wrap around case
+      memcpy(&mSegmentArray[mSegmentArrayCount], mSegmentArray,
+             mLastSegmentIndex * sizeof(char*));
+      memset(mSegmentArray, 0, mLastSegmentIndex * sizeof(char*));
+      mLastSegmentIndex += mSegmentArrayCount;
+      memset(&mSegmentArray[mLastSegmentIndex], 0,
+             (newArraySize.value() - mLastSegmentIndex) * sizeof(char*));
+    } else {
+      memset(&mSegmentArray[mLastSegmentIndex], 0,
+             (newArraySize.value() - mLastSegmentIndex) * sizeof(char*));
+    }
+    mSegmentArrayCount = newArraySize.value();
+  }
+
+  char* seg = (char*)malloc(mSegmentSize);
+  if (!seg) {
+    return nullptr;
+  }
+  mSegmentArray[mLastSegmentIndex] = seg;
+  mLastSegmentIndex = ModSegArraySize(mLastSegmentIndex + 1);
+  return seg;
+}
+
+bool nsSegmentedBuffer::DeleteFirstSegment() {
+  NS_ASSERTION(mSegmentArray[mFirstSegmentIndex] != nullptr,
+               "deleting bad segment");
+  FreeOMT(mSegmentArray[mFirstSegmentIndex]);
+  mSegmentArray[mFirstSegmentIndex] = nullptr;
+  int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
+  if (mFirstSegmentIndex == last) {
+    mLastSegmentIndex = last;
+    return true;
+  } else {
+    mFirstSegmentIndex = ModSegArraySize(mFirstSegmentIndex + 1);
+    return false;
+  }
+}
+
+bool nsSegmentedBuffer::DeleteLastSegment() {
+  int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
+  NS_ASSERTION(mSegmentArray[last] != nullptr, "deleting bad segment");
+  FreeOMT(mSegmentArray[last]);
+  mSegmentArray[last] = nullptr;
+  mLastSegmentIndex = last;
+  return (bool)(mLastSegmentIndex == mFirstSegmentIndex);
+}
+
+bool nsSegmentedBuffer::ReallocLastSegment(size_t aNewSize) {
+  int32_t last = ModSegArraySize(mLastSegmentIndex - 1);
+  NS_ASSERTION(mSegmentArray[last] != nullptr, "realloc'ing bad segment");
+  char* newSegment = (char*)realloc(mSegmentArray[last], aNewSize);
+  if (newSegment) {
+    mSegmentArray[last] = newSegment;
+    return true;
+  }
+  return false;
+}
+
+void nsSegmentedBuffer::Empty() {
+  auto clearMembers = mozilla::MakeScopeExit([&] {
+    mSegmentArray = nullptr;
+    mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
+    mFirstSegmentIndex = mLastSegmentIndex = 0;
+  });
+
+  // If mSegmentArray is null, there's no need to actually free anything
+  if (!mSegmentArray) {
+    return;
+  }
+
+  // Dispatch a task that frees up the array. This may run immediately or on
+  // a background thread.
+  FreeOMT([segmentArray = mSegmentArray, arrayCount = mSegmentArrayCount]() {
+    for (uint32_t i = 0; i < arrayCount; i++) {
+      if (segmentArray[i]) {
+        free(segmentArray[i]);
+      }
+    }
+    free(segmentArray);
+  });
+}
+
+void nsSegmentedBuffer::FreeOMT(void* aPtr) {
+  FreeOMT([aPtr]() { free(aPtr); });
+}
+
+void nsSegmentedBuffer::FreeOMT(std::function<void()>&& aTask) {
+  if (!NS_IsMainThread()) {
+    aTask();
+    return;
+  }
+
+  if (mFreeOMT) {
+    // There is a runnable pending which will handle this object
+    if (mFreeOMT->AddTask(std::move(aTask)) > 1) {
+      return;
+    }
+  } else {
+    mFreeOMT = mozilla::MakeRefPtr<FreeOMTPointers>();
+    mFreeOMT->AddTask(std::move(aTask));
+  }
+
+  if (!mIOThread) {
+    mIOThread = do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+  }
+
+  // During the shutdown we are not able to obtain the IOThread and/or the
+  // dispatching of runnable fails.
+  if (!mIOThread || NS_FAILED(mIOThread->Dispatch(NS_NewRunnableFunction(
+                        "nsSegmentedBuffer::FreeOMT",
+                        [obj = mFreeOMT]() { obj->FreeAll(); })))) {
+    mFreeOMT->FreeAll();
+  }
+}
+
+void nsSegmentedBuffer::FreeOMTPointers::FreeAll() {
+  // Take all the tasks from the object. If AddTask is called after we release
+  // the lock, then another runnable will be dispatched for that task. This is
+  // necessary to avoid blocking the main thread while memory is being freed.
+  nsTArray<std::function<void()>> tasks = [this]() {
+    auto t = mTasks.Lock();
+    return std::move(*t);
+  }();
+
+  // Finally run all the tasks to free memory.
+  for (auto& task : tasks) {
+    task();
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////