Fix NativeStringContext: fixed 8MB pool, malloc fallback, and proper free (#1264)

* Initial plan

* Add NativeStringContext::free and fix pool allocation in NativeString

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---------

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Co-authored-by: uNetworkingAB <110806833+uNetworkingAB@users.noreply.github.com>

Author: Copilot

src/Utilities.h

@@ -22,6 +22,7 @@
 #include <openssl/x509.h>
 #include <v8.h>
 #include <vector>
+#include <cstdlib>
 using namespace v8;
 
 /* Unfortunately we _have_ to depend on Node.js crap */
@@ -125,20 +126,29 @@ class NativeStringContext {
 public:
     char *alloc(size_t size) {
         if (pool_offset + size > pool.size()) {
-            pool.resize(pool_offset + size);
+            return (char *) malloc(size);
         }
         char *ptr = pool.data() + pool_offset;
         pool_offset += size;
         return ptr;
     }
+
+    void free(char *ptr) {
+        if (ptr >= pool.data() && ptr < pool.data() + pool.size()) {
+            return;
+        }
+        ::free(ptr);
+    }
 };
 
 class NativeString {
     char *data;
     size_t length;
     bool invalid = false;
+    bool allocated = false;
+    NativeStringContext *ctx = nullptr;
 public:
-    NativeString(NativeStringContext &ctx, Isolate *isolate, const Local<Value> &value) {
+    NativeString(NativeStringContext &ctx, Isolate *isolate, const Local<Value> &value) : ctx(&ctx) {
         if (value->IsUndefined()) {
             data = nullptr;
             length = 0;
@@ -154,11 +164,13 @@ class NativeString {
                     // utf16: copy and convert to utf8
                     length = string->Utf8LengthV2(isolate);
                     data = ctx.alloc(length);
+                    allocated = true;
                     string->WriteUtf8V2(isolate, data, length);
                 }
             #else // Fallback Node.js < 24
                 length = string->Utf8Length(isolate);
                 data = ctx.alloc(length);
+                allocated = true;
                 string->WriteUtf8(isolate, data, length, nullptr, String::WriteOptions::NO_NULL_TERMINATION);
             #endif
         } else if (value->IsArrayBufferView()) { /* DataView or TypedArray */
@@ -181,6 +193,15 @@ class NativeString {
         }
     }
 
+    ~NativeString() noexcept {
+        if (allocated) {
+            ctx->free(data);
+        }
+    }
+
+    NativeString(const NativeString &) = delete;
+    NativeString &operator=(const NativeString &) = delete;
+
     bool isInvalid(const FunctionCallbackInfo<Value> &args) {
         if (invalid) {
             args.GetReturnValue().Set(args.GetIsolate()->ThrowException(v8::Exception::Error(String::NewFromUtf8(args.GetIsolate(), "Text and data can only be passed by String, ArrayBuffer, SharedArrayBuffer or ArrayBufferView.", NewStringType::kNormal).ToLocalChecked())));