fs: encapsulate FSReqWrap more

In further preparation for the Promises enabled fs API,
further encapsulate FSReqWrap details.

The intent here is to isolate, as much as possible, the
functionality of the various fs functions from the details
of how the results are notified. The promises implementation
will use a `FSReqPromise` alternative to `FSReqWrap` that
will use the same API so that both models can be used without
changing any of the actual implementation details for the
various methods.

PR-URL: https://github.com/nodejs/node/pull/18112
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

2 files changed, 66 insertions, 113 deletions

diff --git a/src/node_file.cc b/src/node_file.cc
index c9bbea1ee5..c8cdc79591 100644
--- a/src/node_file.cc
+++ b/src/node_file.cc
@@ -94,6 +94,7 @@ using v8::MaybeLocal;
 using v8::Number;
 using v8::Object;
 using v8::String;
+using v8::Undefined;
 using v8::Value;
 
 #ifndef MIN
@@ -102,32 +103,16 @@ using v8::Value;
 
 #define GET_OFFSET(a) ((a)->IsNumber() ? (a)->IntegerValue() : -1)
 
-FSReqWrap* FSReqWrap::New(Environment* env,
-                          Local<Object> req,
-                          const char* syscall,
-                          const char* data,
-                          enum encoding encoding,
-                          Ownership ownership) {
-  const bool copy = (data != nullptr && ownership == COPY);
-  const size_t size = copy ? 1 + strlen(data) : 0;
-  FSReqWrap* that;
-  char* const storage = new char[sizeof(*that) + size];
-  that = new(storage) FSReqWrap(env, req, syscall, data, encoding);
-  if (copy)
-    that->data_ = static_cast<char*>(memcpy(that->inline_data(), data, size));
-  return that;
+void FSReqWrap::Reject(Local<Value> reject) {
+  MakeCallback(env()->oncomplete_string(), 1, &reject);
 }
 
-
-void FSReqWrap::Dispose() {
-  this->~FSReqWrap();
-  delete[] reinterpret_cast<char*>(this);
+void FSReqWrap::FillStatsArray(const uv_stat_t* stat) {
+  node::FillStatsArray(env()->fs_stats_field_array(), stat);
 }
 
-
-void FSReqWrap::Reject(Local<Value> reject) {
-  Local<Value> argv[1] { reject };
-  MakeCallback(env()->oncomplete_string(), arraysize(argv), argv);
+void FSReqWrap::ResolveStat() {
+  Resolve(Undefined(env()->isolate()));
 }
 
 void FSReqWrap::Resolve(Local<Value> value) {
@@ -138,9 +123,26 @@ void FSReqWrap::Resolve(Local<Value> value) {
   MakeCallback(env()->oncomplete_string(), arraysize(argv), argv);
 }
 
+void FSReqWrap::Init(const char* syscall,
+                     const char* data,
+                     size_t len,
+                     enum encoding encoding) {
+  syscall_ = syscall;
+  encoding_ = encoding;
+
+  if (data != nullptr) {
+    CHECK_EQ(data_, nullptr);
+    buffer_.AllocateSufficientStorage(len + 1);
+    buffer_.SetLengthAndZeroTerminate(len);
+    memcpy(*buffer_, data, len);
+    data_ = *buffer_;
+  }
+}
+
 void NewFSReqWrap(const FunctionCallbackInfo<Value>& args) {
   CHECK(args.IsConstructCall());
-  ClearWrap(args.This());
+  Environment* env = Environment::GetCurrent(args.GetIsolate());
+  new FSReqWrap(env, args.This());
 }
 
 
@@ -150,12 +152,11 @@ FSReqAfterScope::FSReqAfterScope(FSReqWrap* wrap, uv_fs_t* req)
       handle_scope_(wrap->env()->isolate()),
       context_scope_(wrap->env()->context()) {
   CHECK_EQ(wrap_->req(), req);
-  wrap_->ReleaseEarly();  // Free memory that's no longer used now.
 }
 
 FSReqAfterScope::~FSReqAfterScope() {
   uv_fs_req_cleanup(wrap_->req());
-  wrap_->Dispose();
+  delete wrap_;
 }
 
 // TODO(joyeecheung): create a normal context object, and
@@ -195,12 +196,10 @@ void AfterNoArgs(uv_fs_t* req) {
 void AfterStat(uv_fs_t* req) {
   FSReqWrap* req_wrap = static_cast<FSReqWrap*>(req->data);
   FSReqAfterScope after(req_wrap, req);
-  Environment* env = req_wrap->env();
 
   if (after.Proceed()) {
-    FillStatsArray(env->fs_stats_field_array(),
-                   static_cast<const uv_stat_t*>(req->ptr));
-    req_wrap->Resolve(Undefined(req_wrap->env()->isolate()));
+    req_wrap->FillStatsArray(&req->statbuf);
+    req_wrap->ResolveStat();
   }
 }
 
@@ -222,7 +221,7 @@ void AfterStringPath(uv_fs_t* req) {
   if (after.Proceed()) {
     link = StringBytes::Encode(req_wrap->env()->isolate(),
                                static_cast<const char*>(req->path),
-                               req_wrap->encoding_,
+                               req_wrap->encoding(),
                                &error);
     if (link.IsEmpty())
       req_wrap->Reject(error);
@@ -241,7 +240,7 @@ void AfterStringPtr(uv_fs_t* req) {
   if (after.Proceed()) {
     link = StringBytes::Encode(req_wrap->env()->isolate(),
                                static_cast<const char*>(req->ptr),
-                               req_wrap->encoding_,
+                               req_wrap->encoding(),
                                &error);
     if (link.IsEmpty())
       req_wrap->Reject(error);
@@ -278,7 +277,7 @@ void AfterScanDir(uv_fs_t* req) {
       MaybeLocal<Value> filename =
           StringBytes::Encode(env->isolate(),
                               ent.name,
-                              req_wrap->encoding_,
+                              req_wrap->encoding(),
                               &error);
       if (filename.IsEmpty())
         return req_wrap->Reject(error);
@@ -317,12 +316,12 @@ class fs_req_wrap {
 template <typename Func, typename... Args>
 inline FSReqWrap* AsyncDestCall(Environment* env,
     const FunctionCallbackInfo<Value>& args,
-    const char* syscall, const char* dest,
-    enum encoding enc, FSReqWrap::Ownership ownership,
-    uv_fs_cb after, Func fn, Args... fn_args) {
+    const char* syscall, const char* dest, size_t len,
+    enum encoding enc, uv_fs_cb after, Func fn, Args... fn_args) {
   Local<Object> req = args[args.Length() - 1].As<Object>();
-  FSReqWrap* req_wrap = FSReqWrap::New(env, req,
-                                       syscall, dest, enc, ownership);
+  FSReqWrap* req_wrap = Unwrap<FSReqWrap>(req);
+  CHECK_NE(req_wrap, nullptr);
+  req_wrap->Init(syscall, dest, len, enc);
   int err = fn(env->event_loop(), req_wrap->req(), fn_args..., after);
   req_wrap->Dispatched();
   if (err < 0) {
@@ -339,38 +338,16 @@ inline FSReqWrap* AsyncDestCall(Environment* env,
   return req_wrap;
 }
 
-// Defaults to COPY ownership.
-template <typename Func, typename... Args>
-inline FSReqWrap* AsyncDestCall(Environment* env,
-    const FunctionCallbackInfo<Value>& args,
-    const char* syscall, const char* dest, enum encoding enc,
-    uv_fs_cb after, Func fn, Args... fn_args) {
-  return AsyncDestCall(env, args,
-                       syscall, dest, enc, FSReqWrap::COPY,
-                       after, fn, fn_args...);
-}
-
 template <typename Func, typename... Args>
 inline FSReqWrap* AsyncCall(Environment* env,
     const FunctionCallbackInfo<Value>& args,
-    const char* syscall, enum encoding enc, FSReqWrap::Ownership ownership,
+    const char* syscall, enum encoding enc,
     uv_fs_cb after, Func fn, Args... fn_args) {
   return AsyncDestCall(env, args,
-                       syscall, nullptr, enc, ownership,
+                       syscall, nullptr, 0, enc,
                        after, fn, fn_args...);
 }
 
-// Defaults to COPY ownership.
-template <typename Func, typename... Args>
-inline FSReqWrap* AsyncCall(Environment* env,
-    const FunctionCallbackInfo<Value>& args,
-    const char* syscall, enum encoding enc,
-    uv_fs_cb after, Func fn, Args... fn_args) {
-  return AsyncCall(env, args,
-                   syscall, enc, FSReqWrap::COPY,
-                   after, fn, fn_args...);
-}
-
 // Template counterpart of SYNC_CALL, except that it only puts
 // the error number and the syscall in the context instead of
 // creating an error in the C++ land.
@@ -623,8 +600,8 @@ static void Symlink(const FunctionCallbackInfo<Value>& args) {
 
   if (args[3]->IsObject()) {  // symlink(target, path, flags, req)
     CHECK_EQ(args.Length(), 4);
-    AsyncDestCall(env, args, "symlink", *path, UTF8, AfterNoArgs,
-                  uv_fs_symlink, *target, *path, flags);
+    AsyncDestCall(env, args, "symlink", *path, path.length(), UTF8,
+                  AfterNoArgs, uv_fs_symlink, *target, *path, flags);
   } else {  // symlink(target, path, flags)
     SYNC_DEST_CALL(symlink, *target, *path, *target, *path, flags)
   }
@@ -643,8 +620,8 @@ static void Link(const FunctionCallbackInfo<Value>& args) {
 
   if (args[2]->IsObject()) {  // link(src, dest, req)
     CHECK_EQ(args.Length(), 3);
-    AsyncDestCall(env, args, "link", *dest, UTF8, AfterNoArgs,
-                  uv_fs_link, *src, *dest);
+    AsyncDestCall(env, args, "link", *dest, dest.length(), UTF8,
+                  AfterNoArgs, uv_fs_link, *src, *dest);
   } else {  // link(src, dest)
     SYNC_DEST_CALL(link, *src, *dest, *src, *dest)
   }
@@ -695,8 +672,8 @@ static void Rename(const FunctionCallbackInfo<Value>& args) {
 
   if (args[2]->IsObject()) {
     CHECK_EQ(args.Length(), 3);
-    AsyncDestCall(env, args, "rename", *new_path, UTF8, AfterNoArgs,
-                  uv_fs_rename, *old_path, *new_path);
+    AsyncDestCall(env, args, "rename", *new_path, new_path.length(),
+                  UTF8, AfterNoArgs, uv_fs_rename, *old_path, *new_path);
   } else {
     SYNC_DEST_CALL(rename, *old_path, *new_path, *old_path, *new_path)
   }
@@ -1041,7 +1018,6 @@ static void WriteString(const FunctionCallbackInfo<Value>& args) {
   char* buf = nullptr;
   int64_t pos;
   size_t len;
-  FSReqWrap::Ownership ownership = FSReqWrap::COPY;
 
   // will assign buf and len if string was external
   if (!StringBytes::GetExternalParts(string,
@@ -1053,7 +1029,6 @@ static void WriteString(const FunctionCallbackInfo<Value>& args) {
     // StorageSize may return too large a char, so correct the actual length
     // by the write size
     len = StringBytes::Write(env->isolate(), buf, len, args[1], enc);
-    ownership = FSReqWrap::MOVE;
   }
   pos = GET_OFFSET(args[2]);
 
@@ -1061,8 +1036,7 @@ static void WriteString(const FunctionCallbackInfo<Value>& args) {
 
   if (args[4]->IsObject()) {
     CHECK_EQ(args.Length(), 5);
-    AsyncCall(env, args,
-              "write", UTF8, ownership, AfterInteger,
+    AsyncCall(env, args, "write", UTF8, AfterInteger,
               uv_fs_write, fd, &uvbuf, 1, pos);
   } else {
     // SYNC_CALL returns on error.  Make sure to always free the memory.
@@ -1071,7 +1045,7 @@ static void WriteString(const FunctionCallbackInfo<Value>& args) {
       inline ~Delete() { delete[] pointer_; }
       char* const pointer_;
     };
-    Delete delete_on_return(ownership == FSReqWrap::MOVE ? buf : nullptr);
+    Delete delete_on_return(buf);
     SYNC_CALL(write, nullptr, fd, &uvbuf, 1, pos)
     return args.GetReturnValue().Set(SYNC_RESULT);
   }
@@ -1373,7 +1347,7 @@ void InitFs(Local<Object> target,
   Local<String> wrapString =
       FIXED_ONE_BYTE_STRING(env->isolate(), "FSReqWrap");
   fst->SetClassName(wrapString);
-  target->Set(wrapString, fst->GetFunction());
+  target->Set(context, wrapString, fst->GetFunction()).FromJust();
 }
 
 }  // namespace fs
diff --git a/src/node_file.h b/src/node_file.h
index db85451b67..878d02c8ba 100644
--- a/src/node_file.h
+++ b/src/node_file.h
@@ -17,60 +17,39 @@ using v8::Value;
 
 namespace fs {
 
-class FSReqWrap: public ReqWrap<uv_fs_t> {
+class FSReqWrap : public ReqWrap<uv_fs_t> {
  public:
-  enum Ownership { COPY, MOVE };
+  FSReqWrap(Environment* env, Local<Object> req)
+      : ReqWrap(env, req, AsyncWrap::PROVIDER_FSREQWRAP) {
+    Wrap(object(), this);
+  }
 
-  inline static FSReqWrap* New(Environment* env,
-                               Local<Object> req,
-                               const char* syscall,
-                               const char* data = nullptr,
-                               enum encoding encoding = UTF8,
-                               Ownership ownership = COPY);
+  virtual ~FSReqWrap() {
+    ClearWrap(object());
+  }
 
-  inline void Dispose();
+  void Init(const char* syscall,
+            const char* data = nullptr,
+            size_t len = 0,
+            enum encoding encoding = UTF8);
 
+  virtual void FillStatsArray(const uv_stat_t* stat);
   virtual void Reject(Local<Value> reject);
   virtual void Resolve(Local<Value> value);
-
-  void ReleaseEarly() {
-    if (data_ != inline_data()) {
-      delete[] data_;
-      data_ = nullptr;
-    }
-  }
+  virtual void ResolveStat();
 
   const char* syscall() const { return syscall_; }
   const char* data() const { return data_; }
-  const enum encoding encoding_;
+  enum encoding encoding() const { return encoding_; }
 
   size_t self_size() const override { return sizeof(*this); }
 
- protected:
-  FSReqWrap(Environment* env,
-            Local<Object> req,
-            const char* syscall,
-            const char* data,
-            enum encoding encoding)
-      : ReqWrap(env, req, AsyncWrap::PROVIDER_FSREQWRAP),
-        encoding_(encoding),
-        syscall_(syscall),
-        data_(data) {
-    Wrap(object(), this);
-  }
-
-  virtual ~FSReqWrap() {
-    ReleaseEarly();
-    ClearWrap(object());
-  }
-
-  void* operator new(size_t size) = delete;
-  void* operator new(size_t size, char* storage) { return storage; }
-  char* inline_data() { return reinterpret_cast<char*>(this + 1); }
-
  private:
+  enum encoding encoding_ = UTF8;
   const char* syscall_;
-  const char* data_;
+
+  const char* data_ = nullptr;
+  MaybeStackBuffer<char> buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(FSReqWrap);
 };