1 files changed, 186 insertions, 0 deletions
diff --git a/xpcom/string/nsStringBuffer.cpp b/xpcom/string/nsStringBuffer.cpp
new file mode 100644
index 0000000000..b5d506333f
--- /dev/null
+++ b/xpcom/string/nsStringBuffer.cpp
@@ -0,0 +1,186 @@
+/* -*- 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 "nsStringBuffer.h"
+
+#include "mozilla/MemoryReporting.h"
+#include "nsISupportsImpl.h"
+#include "nsString.h"
+
+#ifdef DEBUG
+#  include "nsStringStats.h"
+#else
+#  define STRING_STAT_INCREMENT(_s)
+#endif
+
+void nsStringBuffer::AddRef() {
+  // Memory synchronization is not required when incrementing a
+  // reference count.  The first increment of a reference count on a
+  // thread is not important, since the first use of the object on a
+  // thread can happen before it.  What is important is the transfer
+  // of the pointer to that thread, which may happen prior to the
+  // first increment on that thread.  The necessary memory
+  // synchronization is done by the mechanism that transfers the
+  // pointer between threads.
+#ifdef NS_BUILD_REFCNT_LOGGING
+  uint32_t count =
+#endif
+      mRefCount.fetch_add(1, std::memory_order_relaxed)
+#ifdef NS_BUILD_REFCNT_LOGGING
+      + 1
+#endif
+      ;
+  STRING_STAT_INCREMENT(Share);
+  NS_LOG_ADDREF(this, count, "nsStringBuffer", sizeof(*this));
+}
+
+void nsStringBuffer::Release() {
+  // Since this may be the last release on this thread, we need
+  // release semantics so that prior writes on this thread are visible
+  // to the thread that destroys the object when it reads mValue with
+  // acquire semantics.
+  uint32_t count = mRefCount.fetch_sub(1, std::memory_order_release) - 1;
+  NS_LOG_RELEASE(this, count, "nsStringBuffer");
+  if (count == 0) {
+    // We're going to destroy the object on this thread, so we need
+    // acquire semantics to synchronize with the memory released by
+    // the last release on other threads, that is, to ensure that
+    // writes prior to that release are now visible on this thread.
+    count = mRefCount.load(std::memory_order_acquire);
+
+    STRING_STAT_INCREMENT(Free);
+    free(this);  // we were allocated with |malloc|
+  }
+}
+
+/**
+ * Alloc returns a pointer to a new string header with set capacity.
+ */
+already_AddRefed<nsStringBuffer> nsStringBuffer::Alloc(size_t aSize) {
+  NS_ASSERTION(aSize != 0, "zero capacity allocation not allowed");
+  NS_ASSERTION(sizeof(nsStringBuffer) + aSize <= size_t(uint32_t(-1)) &&
+                   sizeof(nsStringBuffer) + aSize > aSize,
+               "mStorageSize will truncate");
+
+  auto* hdr = (nsStringBuffer*)malloc(sizeof(nsStringBuffer) + aSize);
+  if (hdr) {
+    STRING_STAT_INCREMENT(Alloc);
+
+    hdr->mRefCount = 1;
+    hdr->mStorageSize = aSize;
+    NS_LOG_ADDREF(hdr, 1, "nsStringBuffer", sizeof(*hdr));
+  }
+  return already_AddRefed(hdr);
+}
+
+template <typename CharT>
+static already_AddRefed<nsStringBuffer> DoCreate(const CharT* aData,
+                                                 size_t aLength) {
+  RefPtr<nsStringBuffer> buffer =
+      nsStringBuffer::Alloc((aLength + 1) * sizeof(CharT));
+  if (MOZ_UNLIKELY(!buffer)) {
+    return nullptr;
+  }
+  auto* data = reinterpret_cast<CharT*>(buffer->Data());
+  memcpy(data, aData, aLength * sizeof(CharT));
+  data[aLength] = 0;
+  return buffer.forget();
+}
+
+already_AddRefed<nsStringBuffer> nsStringBuffer::Create(const char* aData,
+                                                        size_t aLength) {
+  return DoCreate(aData, aLength);
+}
+
+already_AddRefed<nsStringBuffer> nsStringBuffer::Create(const char16_t* aData,
+                                                        size_t aLength) {
+  return DoCreate(aData, aLength);
+}
+
+nsStringBuffer* nsStringBuffer::Realloc(nsStringBuffer* aHdr, size_t aSize) {
+  STRING_STAT_INCREMENT(Realloc);
+
+  NS_ASSERTION(aSize != 0, "zero capacity allocation not allowed");
+  NS_ASSERTION(sizeof(nsStringBuffer) + aSize <= size_t(uint32_t(-1)) &&
+                   sizeof(nsStringBuffer) + aSize > aSize,
+               "mStorageSize will truncate");
+
+  // no point in trying to save ourselves if we hit this assertion
+  NS_ASSERTION(!aHdr->IsReadonly(), "|Realloc| attempted on readonly string");
+
+  // Treat this as a release and addref for refcounting purposes, since we
+  // just asserted that the refcount is 1.  If we don't do that, refcount
+  // logging will claim we've leaked all sorts of stuff.
+  NS_LOG_RELEASE(aHdr, 0, "nsStringBuffer");
+
+  aHdr = (nsStringBuffer*)realloc(aHdr, sizeof(nsStringBuffer) + aSize);
+  if (aHdr) {
+    NS_LOG_ADDREF(aHdr, 1, "nsStringBuffer", sizeof(*aHdr));
+    aHdr->mStorageSize = aSize;
+  }
+
+  return aHdr;
+}
+
+nsStringBuffer* nsStringBuffer::FromString(const nsAString& aStr) {
+  if (!(aStr.mDataFlags & nsAString::DataFlags::REFCOUNTED)) {
+    return nullptr;
+  }
+
+  return FromData(aStr.mData);
+}
+
+nsStringBuffer* nsStringBuffer::FromString(const nsACString& aStr) {
+  if (!(aStr.mDataFlags & nsACString::DataFlags::REFCOUNTED)) {
+    return nullptr;
+  }
+
+  return FromData(aStr.mData);
+}
+
+void nsStringBuffer::ToString(uint32_t aLen, nsAString& aStr,
+                              bool aMoveOwnership) {
+  char16_t* data = static_cast<char16_t*>(Data());
+
+  MOZ_DIAGNOSTIC_ASSERT(data[aLen] == char16_t(0),
+                        "data should be null terminated");
+
+  nsAString::DataFlags flags =
+      nsAString::DataFlags::REFCOUNTED | nsAString::DataFlags::TERMINATED;
+
+  if (!aMoveOwnership) {
+    AddRef();
+  }
+  aStr.Finalize();
+  aStr.SetData(data, aLen, flags);
+}
+
+void nsStringBuffer::ToString(uint32_t aLen, nsACString& aStr,
+                              bool aMoveOwnership) {
+  char* data = static_cast<char*>(Data());
+
+  MOZ_DIAGNOSTIC_ASSERT(data[aLen] == char(0),
+                        "data should be null terminated");
+
+  nsACString::DataFlags flags =
+      nsACString::DataFlags::REFCOUNTED | nsACString::DataFlags::TERMINATED;
+
+  if (!aMoveOwnership) {
+    AddRef();
+  }
+  aStr.Finalize();
+  aStr.SetData(data, aLen, flags);
+}
+
+size_t nsStringBuffer::SizeOfIncludingThisIfUnshared(
+    mozilla::MallocSizeOf aMallocSizeOf) const {
+  return IsReadonly() ? 0 : aMallocSizeOf(this);
+}
+
+size_t nsStringBuffer::SizeOfIncludingThisEvenIfShared(
+    mozilla::MallocSizeOf aMallocSizeOf) const {
+  return aMallocSizeOf(this);
+}