From 8c882817c0b2e47001737c2b3105978b162f7518 Mon Sep 17 00:00:00 2001
From: Kevin <nekevss@gmail.com>
Date: Thu, 24 Nov 2022 00:51:31 +0000
Subject: [PATCH] `JsArrayBuffer` take method and docs (#2454)

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This Pull Request is related to the #2058 and the discussion in the discord chat.

It changes the following:

- Adds a `take` method to `JsArrayBuffer`
- Builds out `JsArrayBuffer` docs
- Adds a `JsArrayBuffer::take()` example to `jsarraybuffer.rs` in `boa_examples`
---
 .../src/object/builtins/jsarraybuffer.rs      | 97 +++++++++++++++++++
 boa_examples/src/bin/jsarraybuffer.rs         | 10 ++
 2 files changed, 107 insertions(+)

diff --git a/boa_engine/src/object/builtins/jsarraybuffer.rs b/boa_engine/src/object/builtins/jsarraybuffer.rs
index a24f92170e..abfa187d74 100644
--- a/boa_engine/src/object/builtins/jsarraybuffer.rs
+++ b/boa_engine/src/object/builtins/jsarraybuffer.rs
@@ -19,6 +19,23 @@ pub struct JsArrayBuffer {
 
 impl JsArrayBuffer {
     /// Create a new array buffer with byte length.
+    ///
+    /// ```
+    /// # use boa_engine::{
+    /// # object::builtins::JsArrayBuffer,
+    /// # Context, JsResult
+    /// # };
+    /// # fn main() -> JsResult<()> {
+    /// # // Initialize context
+    /// # let context = &mut Context::default();
+    /// // Creates a blank array buffer of n bytes
+    /// let array_buffer = JsArrayBuffer::new(4, context)?;
+    ///
+    /// assert_eq!(array_buffer.take()?, vec![0_u8; 4]);
+    ///
+    /// # Ok(())
+    /// # }
+    /// ```
     #[inline]
     pub fn new(byte_length: usize, context: &mut Context) -> JsResult<Self> {
         let inner = ArrayBuffer::allocate(
@@ -40,6 +57,24 @@ impl JsArrayBuffer {
     /// This uses the passed byte block as the internal storage, it does not clone it!
     ///
     /// The `byte_length` will be set to `byte_block.len()`.
+    ///  
+    /// ```
+    /// # use boa_engine::{
+    /// # object::builtins::JsArrayBuffer,
+    /// # Context, JsResult,
+    /// # };
+    /// # fn main() -> JsResult<()> {
+    /// # // Initialize context
+    /// # let context = &mut Context::default();
+    ///
+    /// // Create a buffer from a chunk of data
+    /// let data_block: Vec<u8> = (0..5).collect();
+    /// let array_buffer = JsArrayBuffer::from_byte_block(data_block, context)?;
+    ///
+    /// assert_eq!(array_buffer.take()?, (0..5).collect::<Vec<u8>>());
+    /// # Ok(())
+    /// # }
+    /// ```
     #[inline]
     pub fn from_byte_block(byte_block: Vec<u8>, context: &mut Context) -> JsResult<Self> {
         let byte_length = byte_block.len();
@@ -92,6 +127,26 @@ impl JsArrayBuffer {
     }
 
     /// Returns the byte length of the array buffer.
+    ///
+    /// ```
+    /// # use boa_engine::{
+    /// # object::builtins::JsArrayBuffer,
+    /// # Context, JsResult,
+    /// # };
+    /// # fn main() -> JsResult<()> {
+    /// # // Initialize context
+    /// # let context = &mut Context::default();
+    /// // Create a buffer from a chunk of data
+    /// let data_block: Vec<u8> = (0..5).collect();
+    /// let array_buffer = JsArrayBuffer::from_byte_block(data_block, context)?;
+    ///
+    /// // Take the inner buffer
+    /// let buffer_length = array_buffer.byte_length(context);
+    ///
+    /// assert_eq!(buffer_length, 5);
+    /// # Ok(())
+    /// # }
+    ///  ```
     #[inline]
     pub fn byte_length(&self, context: &mut Context) -> usize {
         ArrayBuffer::get_byte_length(&self.inner.clone().into(), &[], context)
@@ -99,6 +154,48 @@ impl JsArrayBuffer {
             .as_number()
             .expect("expected a number") as usize
     }
+
+    /// Take the inner `ArrayBuffer`'s `array_buffer_data` field and replace it with `None`
+    ///
+    /// Note: This causes the pre-existing `JsArrayBuffer` to become detached.
+    ///
+    /// ```
+    /// # use boa_engine::{
+    /// # object::builtins::JsArrayBuffer,
+    /// # Context, JsResult,
+    /// # };
+    /// # fn main() -> JsResult<()> {
+    /// # // Initialize context
+    /// # let context = &mut Context::default();
+    /// // Create a buffer from a chunk of data
+    /// let data_block: Vec<u8> = (0..5).collect();
+    /// let array_buffer = JsArrayBuffer::from_byte_block(data_block, context)?;
+    ///
+    /// // Take the inner buffer
+    /// let internal_buffer = array_buffer.take()?;
+    ///
+    /// assert_eq!(internal_buffer, (0..5).collect::<Vec<u8>>());
+    ///
+    /// // Anymore interaction with the buffer will return an error
+    /// let detached_err = array_buffer.take();
+    /// assert!(detached_err.is_err());
+    /// # Ok(())
+    /// # }
+    /// ```
+    #[inline]
+    pub fn take(&self) -> JsResult<Vec<u8>> {
+        self.inner
+            .borrow_mut()
+            .as_array_buffer_mut()
+            .expect("inner must be an ArrayBuffer")
+            .array_buffer_data
+            .take()
+            .ok_or_else(|| {
+                JsNativeError::typ()
+                    .with_message("ArrayBuffer is detached")
+                    .into()
+            })
+    }
 }
 
 impl From<JsArrayBuffer> for JsObject {
diff --git a/boa_examples/src/bin/jsarraybuffer.rs b/boa_examples/src/bin/jsarraybuffer.rs
index f0c0d8306e..c6987df25d 100644
--- a/boa_examples/src/bin/jsarraybuffer.rs
+++ b/boa_examples/src/bin/jsarraybuffer.rs
@@ -56,5 +56,15 @@ fn main() -> JsResult<()> {
         Attribute::WRITABLE | Attribute::ENUMERABLE | Attribute::CONFIGURABLE,
     );
 
+    // We can also take the inner data from a JsArrayBuffer
+    let data_block: Vec<u8> = (0..5).collect();
+    let array_buffer = JsArrayBuffer::from_byte_block(data_block, context)?;
+
+    let internal_buffer = array_buffer.take()?;
+
+    assert_eq!(internal_buffer, (0..5).collect::<Vec<u8>>());
+    let detached_err = array_buffer.take();
+    assert!(detached_err.is_err());
+
     Ok(())
 }