text: #include "node.h"
  #include "node_file.h"
  #include "node_buffer.h"
  #include "node_internals.h"
  #include "node_stat_watcher.h"
  
  #include "env.h"
  #include "env-inl.h"
  #include "req-wrap.h"
  #include "req-wrap-inl.h"
  #include "string_bytes.h"
  #include "util.h"
  
  #include <fcntl.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <string.h>
  #include <errno.h>
  #include <limits.h>
  
  #if defined(__MINGW32__) || defined(_MSC_VER)
  # include <io.h>
  #endif
  
  namespace node {
  
  using v8::Array;
  using v8::Context;
  using v8::EscapableHandleScope;
  using v8::Function;
  using v8::FunctionCallbackInfo;
  using v8::FunctionTemplate;
  using v8::Handle;
  using v8::HandleScope;
  using v8::Integer;
  using v8::Local;
  using v8::Number;
  using v8::Object;
  using v8::String;
  using v8::Value;
  
  #ifndef MIN
  # define MIN(a, b) ((a) < (b) ? (a) : (b))
  #endif
  
  #define TYPE_ERROR(msg) env->ThrowTypeError(msg)
  
  #define THROW_BAD_ARGS TYPE_ERROR("Bad argument")
  
  #define GET_OFFSET(a) ((a)->IsNumber() ? (a)->IntegerValue() : -1)
  
  class FSReqWrap: public ReqWrap<uv_fs_t> {
   public:
    enum Ownership { COPY, MOVE };
  
    inline static FSReqWrap* New(Environment* env,
                                 Local<Object> req,
                                 const char* syscall,
                                 const char* data = nullptr,
                                 Ownership ownership = COPY);
  
    inline void Dispose();
  
    void ReleaseEarly() {
      if (data_ != inline_data()) {
        delete[] data_;
        data_ = nullptr;
      }
    }
  
    const char* syscall() const { return syscall_; }
    const char* data() const { return data_; }
  
   private:
    FSReqWrap(Environment* env,
              Local<Object> req,
              const char* syscall,
              const char* data)
        : ReqWrap(env, req, AsyncWrap::PROVIDER_FSREQWRAP),
          syscall_(syscall),
          data_(data) {
      Wrap(object(), this);
    }
  
    ~FSReqWrap() { ReleaseEarly(); }
  
    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); }
  
    const char* syscall_;
    const char* data_;
  
    DISALLOW_COPY_AND_ASSIGN(FSReqWrap);
  };
  
  
  FSReqWrap* FSReqWrap::New(Environment* env,
                            Local<Object> req,
                            const char* syscall,
                            const char* data,
                            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);
    if (copy)
      that->data_ = static_cast<char*>(memcpy(that->inline_data(), data, size));
    return that;
  }
  
  
  void FSReqWrap::Dispose() {
    this->~FSReqWrap();
    delete[] reinterpret_cast<char*>(this);
  }
  
  
  static void NewFSReqWrap(const FunctionCallbackInfo<Value>& args) {
    CHECK(args.IsConstructCall());
  }
  
  
  static inline bool IsInt64(double x) {
    return x == static_cast<double>(static_cast<int64_t>(x));
  }
  
  
  static void After(uv_fs_t *req) {
    FSReqWrap* req_wrap = static_cast<FSReqWrap*>(req->data);
    CHECK_EQ(&req_wrap->req_, req);
    req_wrap->ReleaseEarly();  // Free memory that's no longer used now.
  
    Environment* env = req_wrap->env();
    HandleScope handle_scope(env->isolate());
    Context::Scope context_scope(env->context());
  
    // there is always at least one argument. "error"
    int argc = 1;
  
    // Allocate space for two args. We may only use one depending on the case.
    // (Feel free to increase this if you need more)
    Local<Value> argv[2];
  
    if (req->result < 0) {
      // An error happened.
      argv[0] = UVException(env->isolate(),
                            req->result,
                            req_wrap->syscall(),
                            nullptr,
                            req->path,
                            req_wrap->data());
    } else {
      // error value is empty or null for non-error.
      argv[0] = Null(env->isolate());
  
      // All have at least two args now.
      argc = 2;
  
      switch (req->fs_type) {
        // These all have no data to pass.
        case UV_FS_ACCESS:
        case UV_FS_CLOSE:
        case UV_FS_RENAME:
        case UV_FS_UNLINK:
        case UV_FS_RMDIR:
        case UV_FS_MKDIR:
        case UV_FS_FTRUNCATE:
        case UV_FS_FSYNC:
        case UV_FS_FDATASYNC:
        case UV_FS_LINK:
        case UV_FS_SYMLINK:
        case UV_FS_CHMOD:
        case UV_FS_FCHMOD:
        case UV_FS_CHOWN:
        case UV_FS_FCHOWN:
          // These, however, don't.
          argc = 1;
          break;
  
        case UV_FS_UTIME:
        case UV_FS_FUTIME:
          argc = 0;
          break;
  
        case UV_FS_OPEN:
          argv[1] = Integer::New(env->isolate(), req->result);
          break;
  
        case UV_FS_WRITE:
          argv[1] = Integer::New(env->isolate(), req->result);
          break;
  
        case UV_FS_STAT:
        case UV_FS_LSTAT:
        case UV_FS_FSTAT:
          argv[1] = BuildStatsObject(env,
                                     static_cast<const uv_stat_t*>(req->ptr));
          break;
  
        case UV_FS_READLINK:
          argv[1] = String::NewFromUtf8(env->isolate(),
                                        static_cast<const char*>(req->ptr));
          break;
  
        case UV_FS_READ:
          // Buffer interface
          argv[1] = Integer::New(env->isolate(), req->result);
          break;
  
        case UV_FS_SCANDIR:
          {
            int r;
            Local<Array> names = Array::New(env->isolate(), 0);
  
            for (int i = 0; ; i++) {
              uv_dirent_t ent;
  
              r = uv_fs_scandir_next(req, &ent);
              if (r == UV_EOF)
                break;
              if (r != 0) {
                argv[0] = UVException(r,
                                      nullptr,
                                      req_wrap->syscall(),
                                      static_cast<const char*>(req->path));
                break;
              }
  
              Local<String> name = String::NewFromUtf8(env->isolate(),
                                                       ent.name);
              names->Set(i, name);
            }
  
            argv[1] = names;
          }
          break;
  
        default:
          CHECK(0 && "Unhandled eio response");
      }
    }
  
    req_wrap->MakeCallback(env->oncomplete_string(), argc, argv);
  
    uv_fs_req_cleanup(&req_wrap->req_);
    req_wrap->Dispose();
  }
  
  // This struct is only used on sync fs calls.
  // For async calls FSReqWrap is used.
  struct fs_req_wrap {
    fs_req_wrap() {}
    ~fs_req_wrap() { uv_fs_req_cleanup(&req); }
    uv_fs_t req;
    DISALLOW_COPY_AND_ASSIGN(fs_req_wrap);
  };
  
  
  #define ASYNC_DEST_CALL(func, req, dest, ...)                                 \
    Environment* env = Environment::GetCurrent(args);                           \
    CHECK(req->IsObject());                                                     \
    FSReqWrap* req_wrap = FSReqWrap::New(env, req.As<Object>(), #func, dest);   \
    int err = uv_fs_ ## func(env->event_loop(),                                 \
                             &req_wrap->req_,                                   \
                             __VA_ARGS__,                                       \
                             After);                                            \
    req_wrap->Dispatched();                                                     \
    if (err < 0) {                                                              \
      uv_fs_t* uv_req = &req_wrap->req_;                                        \
      uv_req->result = err;                                                     \
      uv_req->path = nullptr;                                                   \
      After(uv_req);                                                            \
    }                                                                           \
    args.GetReturnValue().Set(req_wrap->persistent());
  
  #define ASYNC_CALL(func, req, ...)                                            \
    ASYNC_DEST_CALL(func, req, nullptr, __VA_ARGS__)                            \
  
  #define SYNC_DEST_CALL(func, path, dest, ...)                                 \
    fs_req_wrap req_wrap;                                                       \
    int err = uv_fs_ ## func(env->event_loop(),                                 \
                           &req_wrap.req,                                       \
                           __VA_ARGS__,                                         \
                           nullptr);                                            \
    if (err < 0) {                                                              \
      return env->ThrowUVException(err, #func, nullptr, path, dest);            \
    }                                                                           \
  
  #define SYNC_CALL(func, path, ...)                                            \
    SYNC_DEST_CALL(func, path, nullptr, __VA_ARGS__)                            \
  
  #define SYNC_REQ req_wrap.req
  
  #define SYNC_RESULT err
  
  
  static void Access(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args.GetIsolate());
    HandleScope scope(env->isolate());
  
    if (args.Length() < 2)
      return THROW_BAD_ARGS;
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
    if (!args[1]->IsInt32())
      return TYPE_ERROR("mode must be an integer");
  
    node::Utf8Value path(env->isolate(), args[0]);
    int mode = static_cast<int>(args[1]->Int32Value());
  
    if (args[2]->IsObject()) {
      ASYNC_CALL(access, args[2], *path, mode);
    } else {
      SYNC_CALL(access, *path, *path, mode);
    }
  }
  
  
  static void Close(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(close, args[1], fd)
    } else {
      SYNC_CALL(close, 0, fd)
    }
  }
  
  
  Local<Value> BuildStatsObject(Environment* env, const uv_stat_t* s) {
    // If you hit this assertion, you forgot to enter the v8::Context first.
    CHECK_EQ(env->context(), env->isolate()->GetCurrentContext());
  
    EscapableHandleScope handle_scope(env->isolate());
  
    // The code below is very nasty-looking but it prevents a segmentation fault
    // when people run JS code like the snippet below. It's apparently more
    // common than you would expect, several people have reported this crash...
    //
    //   function crash() {
    //     fs.statSync('.');
    //     crash();
    //   }
    //
    // We need to check the return value of Integer::New() and Date::New()
    // and make sure that we bail out when V8 returns an empty handle.
  
    // Integers.
  #define X(name)                                                               \
    Local<Value> name = Integer::New(env->isolate(), s->st_##name);             \
    if (name.IsEmpty())                                                         \
      return handle_scope.Escape(Local<Object>());                              \
  
    X(dev)
    X(mode)
    X(nlink)
    X(uid)
    X(gid)
    X(rdev)
  # if defined(__POSIX__)
    X(blksize)
  # else
    Local<Value> blksize = Undefined(env->isolate());
  # endif
  #undef X
  
    // Numbers.
  #define X(name)                                                               \
    Local<Value> name = Number::New(env->isolate(),                             \
                                    static_cast<double>(s->st_##name));         \
    if (name.IsEmpty())                                                         \
      return handle_scope.Escape(Local<Object>());                              \
  
    X(ino)
    X(size)
  # if defined(__POSIX__)
    X(blocks)
  # else
    Local<Value> blocks = Undefined(env->isolate());
  # endif
  #undef X
  
    // Dates.
  #define X(name)                                                               \
    Local<Value> name##_msec =                                                  \
      Number::New(env->isolate(),                                               \
          (static_cast<double>(s->st_##name.tv_sec) * 1000) +                   \
          (static_cast<double>(s->st_##name.tv_nsec / 1000000)));               \
                                                                                \
    if (name##_msec.IsEmpty())                                                  \
      return handle_scope.Escape(Local<Object>());                              \
  
    X(atim)
    X(mtim)
    X(ctim)
    X(birthtim)
  #undef X
  
    // Pass stats as the first argument, this is the object we are modifying.
    Local<Value> argv[] = {
      dev,
      mode,
      nlink,
      uid,
      gid,
      rdev,
      blksize,
      ino,
      size,
      blocks,
      atim_msec,
      mtim_msec,
      ctim_msec,
      birthtim_msec
    };
  
    // Call out to JavaScript to create the stats object.
    Local<Value> stats =
      env->fs_stats_constructor_function()->NewInstance(ARRAY_SIZE(argv), argv);
  
    if (stats.IsEmpty())
      return handle_scope.Escape(Local<Object>());
  
    return handle_scope.Escape(stats);
  }
  
  static void Stat(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(stat, args[1], *path)
    } else {
      SYNC_CALL(stat, *path, *path)
      args.GetReturnValue().Set(
          BuildStatsObject(env, static_cast<const uv_stat_t*>(SYNC_REQ.ptr)));
    }
  }
  
  static void LStat(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(lstat, args[1], *path)
    } else {
      SYNC_CALL(lstat, *path, *path)
      args.GetReturnValue().Set(
          BuildStatsObject(env, static_cast<const uv_stat_t*>(SYNC_REQ.ptr)));
    }
  }
  
  static void FStat(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(fstat, args[1], fd)
    } else {
      SYNC_CALL(fstat, 0, fd)
      args.GetReturnValue().Set(
          BuildStatsObject(env, static_cast<const uv_stat_t*>(SYNC_REQ.ptr)));
    }
  }
  
  static void Symlink(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("dest path required");
    if (len < 2)
      return TYPE_ERROR("src path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("dest path must be a string");
    if (!args[1]->IsString())
      return TYPE_ERROR("src path must be a string");
  
    node::Utf8Value dest(env->isolate(), args[0]);
    node::Utf8Value path(env->isolate(), args[1]);
    int flags = 0;
  
    if (args[2]->IsString()) {
      node::Utf8Value mode(env->isolate(), args[2]);
      if (strcmp(*mode, "dir") == 0) {
        flags |= UV_FS_SYMLINK_DIR;
      } else if (strcmp(*mode, "junction") == 0) {
        flags |= UV_FS_SYMLINK_JUNCTION;
      } else if (strcmp(*mode, "file") != 0) {
        return env->ThrowError("Unknown symlink type");
      }
    }
  
    if (args[3]->IsObject()) {
      ASYNC_DEST_CALL(symlink, args[3], *path, *dest, *path, flags)
    } else {
      SYNC_DEST_CALL(symlink, *dest, *path, *dest, *path, flags)
    }
  }
  
  static void Link(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("dest path required");
    if (len < 2)
      return TYPE_ERROR("src path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("dest path must be a string");
    if (!args[1]->IsString())
      return TYPE_ERROR("src path must be a string");
  
    node::Utf8Value orig_path(env->isolate(), args[0]);
    node::Utf8Value new_path(env->isolate(), args[1]);
  
    if (args[2]->IsObject()) {
      ASYNC_DEST_CALL(link, args[2], *new_path, *orig_path, *new_path)
    } else {
      SYNC_DEST_CALL(link, *orig_path, *new_path, *orig_path, *new_path)
    }
  }
  
  static void ReadLink(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(readlink, args[1], *path)
    } else {
      SYNC_CALL(readlink, *path, *path)
      const char* link_path = static_cast<const char*>(SYNC_REQ.ptr);
      Local<String> rc = String::NewFromUtf8(env->isolate(), link_path);
      args.GetReturnValue().Set(rc);
    }
  }
  
  static void Rename(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("old path required");
    if (len < 2)
      return TYPE_ERROR("new path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("old path must be a string");
    if (!args[1]->IsString())
      return TYPE_ERROR("new path must be a string");
  
    node::Utf8Value old_path(env->isolate(), args[0]);
    node::Utf8Value new_path(env->isolate(), args[1]);
  
    if (args[2]->IsObject()) {
      ASYNC_DEST_CALL(rename, args[2], *new_path, *old_path, *new_path)
    } else {
      SYNC_DEST_CALL(rename, *old_path, *new_path, *old_path, *new_path)
    }
  }
  
  static void FTruncate(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 2 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    // FIXME(bnoordhuis) It's questionable to reject non-ints here but still
    // allow implicit coercion from null or undefined to zero.  Probably best
    // handled in lib/fs.js.
    Local<Value> len_v(args[1]);
    if (!len_v->IsUndefined() &&
        !len_v->IsNull() &&
        !IsInt64(len_v->NumberValue())) {
      return env->ThrowTypeError("Not an integer");
    }
  
    const int64_t len = len_v->IntegerValue();
  
    if (args[2]->IsObject()) {
      ASYNC_CALL(ftruncate, args[2], fd, len)
    } else {
      SYNC_CALL(ftruncate, 0, fd, len)
    }
  }
  
  static void Fdatasync(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(fdatasync, args[1], fd)
    } else {
      SYNC_CALL(fdatasync, 0, fd)
    }
  }
  
  static void Fsync(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(fsync, args[1], fd)
    } else {
      SYNC_CALL(fsync, 0, fd)
    }
  }
  
  static void Unlink(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(unlink, args[1], *path)
    } else {
      SYNC_CALL(unlink, *path, *path)
    }
  }
  
  static void RMDir(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(rmdir, args[1], *path)
    } else {
      SYNC_CALL(rmdir, *path, *path)
    }
  }
  
  static void MKDir(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 2 || !args[0]->IsString() || !args[1]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    node::Utf8Value path(env->isolate(), args[0]);
    int mode = static_cast<int>(args[1]->Int32Value());
  
    if (args[2]->IsObject()) {
      ASYNC_CALL(mkdir, args[2], *path, mode)
    } else {
      SYNC_CALL(mkdir, *path, *path, mode)
    }
  }
  
  static void ReadDir(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 1)
      return TYPE_ERROR("path required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
  
    node::Utf8Value path(env->isolate(), args[0]);
  
    if (args[1]->IsObject()) {
      ASYNC_CALL(scandir, args[1], *path, 0 /*flags*/)
    } else {
      SYNC_CALL(scandir, *path, *path, 0 /*flags*/)
  
      CHECK_GE(SYNC_REQ.result, 0);
      int r;
      Local<Array> names = Array::New(env->isolate(), 0);
  
      for (int i = 0; ; i++) {
        uv_dirent_t ent;
  
        r = uv_fs_scandir_next(&SYNC_REQ, &ent);
        if (r == UV_EOF)
          break;
        if (r != 0)
          return env->ThrowUVException(r, "readdir", "", *path);
  
        Local<String> name = String::NewFromUtf8(env->isolate(),
                                                 ent.name);
        names->Set(i, name);
      }
  
      args.GetReturnValue().Set(names);
    }
  }
  
  static void Open(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("path required");
    if (len < 2)
      return TYPE_ERROR("flags required");
    if (len < 3)
      return TYPE_ERROR("mode required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
    if (!args[1]->IsInt32())
      return TYPE_ERROR("flags must be an int");
    if (!args[2]->IsInt32())
      return TYPE_ERROR("mode must be an int");
  
    node::Utf8Value path(env->isolate(), args[0]);
    int flags = args[1]->Int32Value();
    int mode = static_cast<int>(args[2]->Int32Value());
  
    if (args[3]->IsObject()) {
      ASYNC_CALL(open, args[3], *path, flags, mode)
    } else {
      SYNC_CALL(open, *path, *path, flags, mode)
      args.GetReturnValue().Set(SYNC_RESULT);
    }
  }
  
  
  // Wrapper for write(2).
  //
  // bytesWritten = write(fd, buffer, offset, length, position, callback)
  // 0 fd        integer. file descriptor
  // 1 buffer    the data to write
  // 2 offset    where in the buffer to start from
  // 3 length    how much to write
  // 4 position  if integer, position to write at in the file.
  //             if null, write from the current position
  static void WriteBuffer(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    CHECK(args[0]->IsInt32());
    CHECK(Buffer::HasInstance(args[1]));
  
    int fd = args[0]->Int32Value();
    Local<Object> obj = args[1].As<Object>();
    const char* buf = Buffer::Data(obj);
    size_t buffer_length = Buffer::Length(obj);
    size_t off = args[2]->Uint32Value();
    size_t len = args[3]->Uint32Value();
    int64_t pos = GET_OFFSET(args[4]);
    Local<Value> req = args[5];
  
    if (off > buffer_length)
      return env->ThrowRangeError("offset out of bounds");
    if (len > buffer_length)
      return env->ThrowRangeError("length out of bounds");
    if (off + len < off)
      return env->ThrowRangeError("off + len overflow");
    if (!Buffer::IsWithinBounds(off, len, buffer_length))
      return env->ThrowRangeError("off + len > buffer.length");
  
    buf += off;
  
    uv_buf_t uvbuf = uv_buf_init(const_cast<char*>(buf), len);
  
    if (req->IsObject()) {
      ASYNC_CALL(write, req, fd, &uvbuf, 1, pos)
      return;
    }
  
    SYNC_CALL(write, nullptr, fd, &uvbuf, 1, pos)
    args.GetReturnValue().Set(SYNC_RESULT);
  }
  
  
  // Wrapper for write(2).
  //
  // bytesWritten = write(fd, string, position, enc, callback)
  // 0 fd        integer. file descriptor
  // 1 string    non-buffer values are converted to strings
  // 2 position  if integer, position to write at in the file.
  //             if null, write from the current position
  // 3 enc       encoding of string
  static void WriteString(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (!args[0]->IsInt32())
      return env->ThrowTypeError("First argument must be file descriptor");
  
    Local<Value> req;
    Local<Value> string = args[1];
    int fd = args[0]->Int32Value();
    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(env->isolate(),
                                       string,
                                       const_cast<const char**>(&buf),
                                       &len)) {
      enum encoding enc = ParseEncoding(env->isolate(), args[3], UTF8);
      len = StringBytes::StorageSize(env->isolate(), string, enc);
      buf = new char[len];
      // 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]);
    req = args[4];
  
    uv_buf_t uvbuf = uv_buf_init(const_cast<char*>(buf), len);
  
    if (!req->IsObject()) {
      // SYNC_CALL returns on error.  Make sure to always free the memory.
      struct Delete {
        inline explicit Delete(char* pointer) : pointer_(pointer) {}
        inline ~Delete() { delete[] pointer_; }
        char* const pointer_;
      };
      Delete delete_on_return(ownership == FSReqWrap::MOVE ? buf : nullptr);
      SYNC_CALL(write, nullptr, fd, &uvbuf, 1, pos)
      return args.GetReturnValue().Set(SYNC_RESULT);
    }
  
    FSReqWrap* req_wrap =
        FSReqWrap::New(env, req.As<Object>(), "write", buf, ownership);
    int err = uv_fs_write(env->event_loop(),
                          &req_wrap->req_,
                          fd,
                          &uvbuf,
                          1,
                          pos,
                          After);
    req_wrap->Dispatched();
    if (err < 0) {
      uv_fs_t* uv_req = &req_wrap->req_;
      uv_req->result = err;
      uv_req->path = nullptr;
      After(uv_req);
    }
  
    return args.GetReturnValue().Set(req_wrap->persistent());
  }
  
  
  /*
   * Wrapper for read(2).
   *
   * bytesRead = fs.read(fd, buffer, offset, length, position)
   *
   * 0 fd        integer. file descriptor
   * 1 buffer    instance of Buffer
   * 2 offset    integer. offset to start reading into inside buffer
   * 3 length    integer. length to read
   * 4 position  file position - null for current position
   *
   */
  static void Read(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 2 || !args[0]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
  
    int fd = args[0]->Int32Value();
  
    Local<Value> req;
  
    size_t len;
    int64_t pos;
  
    char * buf = nullptr;
  
    if (!Buffer::HasInstance(args[1])) {
      return env->ThrowError("Second argument needs to be a buffer");
    }
  
    Local<Object> buffer_obj = args[1]->ToObject(env->isolate());
    char *buffer_data = Buffer::Data(buffer_obj);
    size_t buffer_length = Buffer::Length(buffer_obj);
  
    size_t off = args[2]->Int32Value();
    if (off >= buffer_length) {
      return env->ThrowError("Offset is out of bounds");
    }
  
    len = args[3]->Int32Value();
    if (!Buffer::IsWithinBounds(off, len, buffer_length))
      return env->ThrowRangeError("Length extends beyond buffer");
  
    pos = GET_OFFSET(args[4]);
  
    buf = buffer_data + off;
  
    uv_buf_t uvbuf = uv_buf_init(const_cast<char*>(buf), len);
  
    req = args[5];
  
    if (req->IsObject()) {
      ASYNC_CALL(read, req, fd, &uvbuf, 1, pos);
    } else {
      SYNC_CALL(read, 0, fd, &uvbuf, 1, pos)
      args.GetReturnValue().Set(SYNC_RESULT);
    }
  }
  
  
  /* fs.chmod(path, mode);
   * Wrapper for chmod(1) / EIO_CHMOD
   */
  static void Chmod(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 2 || !args[0]->IsString() || !args[1]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
    node::Utf8Value path(env->isolate(), args[0]);
    int mode = static_cast<int>(args[1]->Int32Value());
  
    if (args[2]->IsObject()) {
      ASYNC_CALL(chmod, args[2], *path, mode);
    } else {
      SYNC_CALL(chmod, *path, *path, mode);
    }
  }
  
  
  /* fs.fchmod(fd, mode);
   * Wrapper for fchmod(1) / EIO_FCHMOD
   */
  static void FChmod(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    if (args.Length() < 2 || !args[0]->IsInt32() || !args[1]->IsInt32()) {
      return THROW_BAD_ARGS;
    }
    int fd = args[0]->Int32Value();
    int mode = static_cast<int>(args[1]->Int32Value());
  
    if (args[2]->IsObject()) {
      ASYNC_CALL(fchmod, args[2], fd, mode);
    } else {
      SYNC_CALL(fchmod, 0, fd, mode);
    }
  }
  
  
  /* fs.chown(path, uid, gid);
   * Wrapper for chown(1) / EIO_CHOWN
   */
  static void Chown(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("path required");
    if (len < 2)
      return TYPE_ERROR("uid required");
    if (len < 3)
      return TYPE_ERROR("gid required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
    if (!args[1]->IsUint32())
      return TYPE_ERROR("uid must be an unsigned int");
    if (!args[2]->IsUint32())
      return TYPE_ERROR("gid must be an unsigned int");
  
    node::Utf8Value path(env->isolate(), args[0]);
    uv_uid_t uid = static_cast<uv_uid_t>(args[1]->Uint32Value());
    uv_gid_t gid = static_cast<uv_gid_t>(args[2]->Uint32Value());
  
    if (args[3]->IsObject()) {
      ASYNC_CALL(chown, args[3], *path, uid, gid);
    } else {
      SYNC_CALL(chown, *path, *path, uid, gid);
    }
  }
  
  
  /* fs.fchown(fd, uid, gid);
   * Wrapper for fchown(1) / EIO_FCHOWN
   */
  static void FChown(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("fd required");
    if (len < 2)
      return TYPE_ERROR("uid required");
    if (len < 3)
      return TYPE_ERROR("gid required");
    if (!args[0]->IsInt32())
      return TYPE_ERROR("fd must be an int");
    if (!args[1]->IsUint32())
      return TYPE_ERROR("uid must be an unsigned int");
    if (!args[2]->IsUint32())
      return TYPE_ERROR("gid must be an unsigned int");
  
    int fd = args[0]->Int32Value();
    uv_uid_t uid = static_cast<uv_uid_t>(args[1]->Uint32Value());
    uv_gid_t gid = static_cast<uv_gid_t>(args[2]->Uint32Value());
  
    if (args[3]->IsObject()) {
      ASYNC_CALL(fchown, args[3], fd, uid, gid);
    } else {
      SYNC_CALL(fchown, 0, fd, uid, gid);
    }
  }
  
  
  static void UTimes(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("path required");
    if (len < 2)
      return TYPE_ERROR("atime required");
    if (len < 3)
      return TYPE_ERROR("mtime required");
    if (!args[0]->IsString())
      return TYPE_ERROR("path must be a string");
    if (!args[1]->IsNumber())
      return TYPE_ERROR("atime must be a number");
    if (!args[2]->IsNumber())
      return TYPE_ERROR("mtime must be a number");
  
    const node::Utf8Value path(env->isolate(), args[0]);
    const double atime = static_cast<double>(args[1]->NumberValue());
    const double mtime = static_cast<double>(args[2]->NumberValue());
  
    if (args[3]->IsObject()) {
      ASYNC_CALL(utime, args[3], *path, atime, mtime);
    } else {
      SYNC_CALL(utime, *path, *path, atime, mtime);
    }
  }
  
  static void FUTimes(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);
  
    int len = args.Length();
    if (len < 1)
      return TYPE_ERROR("fd required");
    if (len < 2)
      return TYPE_ERROR("atime required");
    if (len < 3)
      return TYPE_ERROR("mtime required");
    if (!args[0]->IsInt32())
      return TYPE_ERROR("fd must be an int");
    if (!args[1]->IsNumber())
      return TYPE_ERROR("atime must be a number");
    if (!args[2]->IsNumber())
      return TYPE_ERROR("mtime must be a number");
  
    const int fd = args[0]->Int32Value();
    const double atime = static_cast<double>(args[1]->NumberValue());
    const double mtime = static_cast<double>(args[2]->NumberValue());
  
    if (args[3]->IsObject()) {
      ASYNC_CALL(futime, args[3], fd, atime, mtime);
    } else {
      SYNC_CALL(futime, 0, fd, atime, mtime);
    }
  }
  
  void FSInitialize(const FunctionCallbackInfo<Value>& args) {
    Local<Function> stats_constructor = args[0].As<Function>();
    CHECK(stats_constructor->IsFunction());
  
    Environment* env = Environment::GetCurrent(args);
    env->set_fs_stats_constructor_function(stats_constructor);
  }
  
  void InitFs(Handle<Object> target,
              Handle<Value> unused,
              Handle<Context> context,
              void* priv) {
    Environment* env = Environment::GetCurrent(context);
  
    // Function which creates a new Stats object.
    target->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "FSInitialize"),
                env->NewFunctionTemplate(FSInitialize)->GetFunction());
  
    env->SetMethod(target, "access", Access);
    env->SetMethod(target, "close", Close);
    env->SetMethod(target, "open", Open);
    env->SetMethod(target, "read", Read);
    env->SetMethod(target, "fdatasync", Fdatasync);
    env->SetMethod(target, "fsync", Fsync);
    env->SetMethod(target, "rename", Rename);
    env->SetMethod(target, "ftruncate", FTruncate);
    env->SetMethod(target, "rmdir", RMDir);
    env->SetMethod(target, "mkdir", MKDir);
    env->SetMethod(target, "readdir", ReadDir);
    env->SetMethod(target, "stat", Stat);
    env->SetMethod(target, "lstat", LStat);
    env->SetMethod(target, "fstat", FStat);
    env->SetMethod(target, "link", Link);
    env->SetMethod(target, "symlink", Symlink);
    env->SetMethod(target, "readlink", ReadLink);
    env->SetMethod(target, "unlink", Unlink);
    env->SetMethod(target, "writeBuffer", WriteBuffer);
    env->SetMethod(target, "writeString", WriteString);
  
    env->SetMethod(target, "chmod", Chmod);
    env->SetMethod(target, "fchmod", FChmod);
    // env->SetMethod(target, "lchmod", LChmod);
  
    env->SetMethod(target, "chown", Chown);
    env->SetMethod(target, "fchown", FChown);
    // env->SetMethod(target, "lchown", LChown);
  
    env->SetMethod(target, "utimes", UTimes);
    env->SetMethod(target, "futimes", FUTimes);
  
    StatWatcher::Initialize(env, target);
  
    // Create FunctionTemplate for FSReqWrap
    Local<FunctionTemplate> fst =
        FunctionTemplate::New(env->isolate(), NewFSReqWrap);
    fst->InstanceTemplate()->SetInternalFieldCount(1);
    fst->SetClassName(FIXED_ONE_BYTE_STRING(env->isolate(), "FSReqWrap"));
    target->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "FSReqWrap"),
                fst->GetFunction());
  }
  
  }  // end namespace node
  
  NODE_MODULE_CONTEXT_AWARE_BUILTIN(fs, node::InitFs)
  