# Buffer
Class `Napi::Buffer` inherits from class [`Napi::Uint8Array`][].
The `Napi::Buffer` class creates a projection of raw data that can be consumed by
script.
## Methods
### New
Allocates a new `Napi::Buffer` object with a given length.
```cpp
static Napi::Buffer<T> Napi::Buffer::New(napi_env env, size_t length);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] length`: The number of `T` elements to allocate.
Returns a new `Napi::Buffer` object.
### New
Wraps the provided external data into a new `Napi::Buffer` object.
The `Napi::Buffer` object does not assume ownership for the data and expects it to be
valid for the lifetime of the object. Since the `Napi::Buffer` is subject to garbage
collection this overload is only suitable for data which is static and never
needs to be freed.
```cpp
static Napi::Buffer<T> Napi::Buffer::New(napi_env env, T* data, size_t length);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] data`: The pointer to the external data to expose.
- `[in] length`: The number of `T` elements in the external data.
Returns a new `Napi::Buffer` object.
### New
Wraps the provided external data into a new `Napi::Buffer` object.
The `Napi::Buffer` object does not assume ownership for the data and expects it
to be valid for the lifetime of the object. The data can only be freed once the
`finalizeCallback` is invoked to indicate that the `Napi::Buffer` has been released.
```cpp
template <typename Finalizer>
static Napi::Buffer<T> Napi::Buffer::New(napi_env env,
T* data,
size_t length,
Finalizer finalizeCallback);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] data`: The pointer to the external data to expose.
- `[in] length`: The number of `T` elements in the external data.
- `[in] finalizeCallback`: The function to be called when the `Napi::Buffer` is
destroyed. It must implement `operator()`, accept a `T*` (which is the
external data pointer), and return `void`.
Returns a new `Napi::Buffer` object.
### New
Wraps the provided external data into a new `Napi::Buffer` object.
The `Napi::Buffer` object does not assume ownership for the data and expects it to be
valid for the lifetime of the object. The data can only be freed once the
`finalizeCallback` is invoked to indicate that the `Napi::Buffer` has been released.
```cpp
template <typename Finalizer, typename Hint>
static Napi::Buffer<T> Napi::Buffer::New(napi_env env,
T* data,
size_t length,
Finalizer finalizeCallback,
Hint* finalizeHint);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] data`: The pointer to the external data to expose.
- `[in] length`: The number of `T` elements in the external data.
- `[in] finalizeCallback`: The function to be called when the `Napi::Buffer` is
destroyed. It must implement `operator()`, accept a `T*` (which is the
external data pointer) and `Hint*`, and return `void`.
- `[in] finalizeHint`: The hint to be passed as the second parameter of the
finalize callback.
Returns a new `Napi::Buffer` object.
### Copy
Allocates a new `Napi::Buffer` object and copies the provided external data into it.
```cpp
static Napi::Buffer<T> Napi::Buffer::Copy(napi_env env, const T* data, size_t length);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] data`: The pointer to the external data to copy.
- `[in] length`: The number of `T` elements in the external data.
Returns a new `Napi::Buffer` object containing a copy of the data.
### Constructor
Initializes an empty instance of the `Napi::Buffer` class.
```cpp
Napi::Buffer::Buffer();
```
### Constructor
Initializes the `Napi::Buffer` object using an existing Uint8Array.
```cpp
Napi::Buffer::Buffer(napi_env env, napi_value value);
```
- `[in] env`: The environment in which to create the `Napi::Buffer` object.
- `[in] value`: The Uint8Array reference to wrap.
### Data
```cpp
T* Napi::Buffer::Data() const;
```
Returns a pointer the external data.
### Length
```cpp
size_t Napi::Buffer::Length() const;
```
Returns the number of `T` elements in the external data.
[`Napi::Uint8Array`]: ./typed_array_of.md
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