[Feature] Add write_bytes and write_slice Methods to Buffer

[vmarcella]

Overview

Extend the high-level Buffer API with methods for writing raw bytes and typed slices, complementing the existing single-value write_value<T>

Current State

Buffer currently only exposes write_value<T> for uploading a single piece of data value:

// crates/lambda-rs/src/render/buffer.rs
impl Buffer {
  /// Write a single plain-old-data value into this buffer at the specified
  /// byte offset.
  pub fn write_value<T: Copy>(
    &self,
    render_context: &RenderContext,
    offset: u64,
    data: &T,
  ) {
    let bytes = unsafe {
      std::slice::from_raw_parts(
        (data as *const T) as *const u8,
        std::mem::size_of::<T>(),
      )
    };
    self.buffer.write_bytes(render_context.gpu(), offset, bytes);
  }
}

Common use cases however require writing arrays of vertices, instance data, or raw byte buffers.

Scope

• Add write_bytes(&self, ctx, offset, &[u8]) for raw byte uploads
• Add write_slice<T: Copy>(&self, ctx, offset, &[T]) for typed array uploads

Proposed API

impl Buffer {
  /// Write raw bytes into this buffer at the specified byte offset.
  pub fn write_bytes(
    &self,
    render_context: &RenderContext,
    offset: u64,
    data: &[u8],
  );

  /// Write a slice of plain-old-data values into this buffer at the
  /// specified byte offset.
  pub fn write_slice<T: Copy>(
    &self,
    render_context: &RenderContext,
    offset: u64,
    data: &[T],
  );
}

Example Usage

// Update instance transforms each frame
let transforms: Vec<InstanceTransform> = compute_transforms();
instance_buffer.write_slice(&render_context, 0, &transforms);

// Or raw bytes from an external source
let raw_data: &[u8] = load_binary_data();
buffer.write_bytes(&render_context, 0, raw_data);

Acceptance criteria

• Buffer::write_bytes method
• Buffer::write_slice<T> method
• Unit tests for each implementation
• Documentation with examples