src: port memory-tracking allocator from QUIC repo

This implements a memory-tracking allocator that can be used to
provide memory allocation facilities to several thread-safe C
libraries, including nghttp2, nghttp3, ngtcp3 and uvwasi.

Refs: https://github.com/nodejs/quic/blob/34ee0bc96f804c73cb22b2945a1a78f780938492/src/node_mem.h
Co-authored-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/30745
Refs: https://github.com/nodejs/quic/pull/126
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

2 files changed, 153 insertions, 0 deletions

diff --git a/src/node_mem-inl.h b/src/node_mem-inl.h
new file mode 100644
index 0000000000..ad6fc45b36
--- /dev/null
+++ b/src/node_mem-inl.h
@@ -0,0 +1,112 @@
+#ifndef SRC_NODE_MEM_INL_H_
+#define SRC_NODE_MEM_INL_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include "node_mem.h"
+#include "node_internals.h"
+
+namespace node {
+namespace mem {
+
+template <typename Class, typename AllocatorStruct>
+AllocatorStruct NgLibMemoryManager<Class, AllocatorStruct>::MakeAllocator() {
+  return AllocatorStruct {
+    static_cast<void*>(static_cast<Class*>(this)),
+    MallocImpl,
+    FreeImpl,
+    CallocImpl,
+    ReallocImpl
+  };
+}
+
+template <typename Class, typename T>
+void* NgLibMemoryManager<Class, T>::ReallocImpl(void* ptr,
+                                             size_t size,
+                                             void* user_data) {
+  Class* manager = static_cast<Class*>(user_data);
+
+  size_t previous_size = 0;
+  char* original_ptr = nullptr;
+
+  // We prepend each allocated buffer with a size_t containing the full
+  // size of the allocation.
+  if (size > 0) size += sizeof(size_t);
+
+  if (ptr != nullptr) {
+    // We are free()ing or re-allocating.
+    original_ptr = static_cast<char*>(ptr) - sizeof(size_t);
+    previous_size = *reinterpret_cast<size_t*>(original_ptr);
+    // This means we called StopTracking() on this pointer before.
+    if (previous_size == 0) {
+      // Fall back to the standard Realloc() function.
+      char* ret = UncheckedRealloc(original_ptr, size);
+      if (ret != nullptr)
+        ret += sizeof(size_t);
+      return ret;
+    }
+  }
+
+  manager->CheckAllocatedSize(previous_size);
+
+  char* mem = UncheckedRealloc(original_ptr, size);
+
+  if (mem != nullptr) {
+    // Adjust the memory info counter.
+    // TODO(addaleax): Avoid the double bookkeeping we do with
+    // current_nghttp2_memory_ + AdjustAmountOfExternalAllocatedMemory
+    // and provide versions of our memory allocation utilities that take an
+    // Environment*/Isolate* parameter and call the V8 method transparently.
+    const int64_t new_size = size - previous_size;
+    manager->IncreaseAllocatedSize(new_size);
+    manager->env()->isolate()->AdjustAmountOfExternalAllocatedMemory(
+        new_size);
+    *reinterpret_cast<size_t*>(mem) = size;
+    mem += sizeof(size_t);
+  } else if (size == 0) {
+    manager->DecreaseAllocatedSize(previous_size);
+    manager->env()->isolate()->AdjustAmountOfExternalAllocatedMemory(
+        -static_cast<int64_t>(previous_size));
+  }
+  return mem;
+}
+
+template <typename Class, typename T>
+void* NgLibMemoryManager<Class, T>::MallocImpl(size_t size, void* user_data) {
+  return ReallocImpl(nullptr, size, user_data);
+}
+
+template <typename Class, typename T>
+void NgLibMemoryManager<Class, T>::FreeImpl(void* ptr, void* user_data) {
+  if (ptr == nullptr) return;
+  CHECK_NULL(ReallocImpl(ptr, 0, user_data));
+}
+
+template <typename Class, typename T>
+void* NgLibMemoryManager<Class, T>::CallocImpl(size_t nmemb,
+                                            size_t size,
+                                            void* user_data) {
+  size_t real_size = MultiplyWithOverflowCheck(nmemb, size);
+  void* mem = MallocImpl(real_size, user_data);
+  if (mem != nullptr)
+    memset(mem, 0, real_size);
+  return mem;
+}
+
+template <typename Class, typename T>
+void NgLibMemoryManager<Class, T>::StopTrackingMemory(void* ptr) {
+  size_t* original_ptr = reinterpret_cast<size_t*>(
+      static_cast<char*>(ptr) - sizeof(size_t));
+  Class* manager = static_cast<Class*>(this);
+  manager->DecreaseAllocatedSize(*original_ptr);
+  manager->env()->isolate()->AdjustAmountOfExternalAllocatedMemory(
+      -static_cast<int64_t>(*original_ptr));
+  *original_ptr = 0;
+}
+
+}  // namespace mem
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_NODE_MEM_INL_H_
diff --git a/src/node_mem.h b/src/node_mem.h
new file mode 100644
index 0000000000..0d3388ad47
--- /dev/null
+++ b/src/node_mem.h
@@ -0,0 +1,41 @@
+#ifndef SRC_NODE_MEM_H_
+#define SRC_NODE_MEM_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include <cstddef>
+
+namespace node {
+namespace mem {
+
+// Both ngtcp2 and nghttp2 allow custom allocators that
+// follow exactly the same structure and behavior, but
+// use different struct names. To allow for code re-use,
+// the NgLibMemoryManager template class can be used for both.
+
+template <typename Class, typename AllocatorStructName>
+class NgLibMemoryManager {
+ public:
+  // Class needs to provide these methods:
+  // void CheckAllocatedSize(size_t previous_size) const;
+  // void IncreaseAllocatedSize(size_t size);
+  // void DecreaseAllocatedSize(size_t size);
+  // Environment* env() const;
+
+  AllocatorStructName MakeAllocator();
+
+  void StopTrackingMemory(void* ptr);
+
+ private:
+  static void* ReallocImpl(void* ptr, size_t size, void* user_data);
+  static void* MallocImpl(size_t size, void* user_data);
+  static void FreeImpl(void* ptr, void* user_data);
+  static void* CallocImpl(size_t nmemb, size_t size, void* user_data);
+};
+
+}  // namespace mem
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_NODE_MEM_H_