Function read_buf

modules/llrt_buffer/src/buffer.rs:692–791

(
    this: &This<Object<'js>>,
    ctx: &Ctx<'js>,
    offset: &Opt<usize>,
    endian: Endian,
    kind: NumberKind,
)

                (1i64 << (kind.bits() - 1)) - 1
            } else {
                bit_mask
            };
            let min_val = if kind.is_signed() { -max_val - 1 } else { 0 };

            if int_val < min_val || int_val > max_val {
                return Err(Exception::throw_range(ctx, "Value out of range"));
            }

            let masked = int_val & bit_mask;
            (
                (kind.bits() / 8) as usize,
                shifted_bytes(masked as u64, kind.bits(), endian),
            )
        },
    };

    if offset >= this.0.len() || offset + byte_count > this.0.len() {
        return Err(Exception::throw_range(
            ctx,
            "The specified offset is out of range",
        ));
    }

    let target = ObjectBytes::from(ctx, this.0.as_inner())?;
    let mut writable_length = 0;

    if let Some((array_buffer, target_byte_length, target_byte_offset)) =
        target.get_array_buffer()?
    {
        let target_bytes =
            resolve_view_bytes(ctx, array_buffer, target_byte_length, target_byte_offset)?;

        writable_length = offset + bytes.len();
        target_bytes[offset..writable_length].copy_from_slice(&bytes);
    }

    Ok(writable_length)
}

fn read_buf<'js>(
    this: &This<Object<'js>>,
    ctx: &Ctx<'js>,
    offset: &Opt<usize>,
    endian: Endian,
    kind: NumberKind,
) -> Result<Value<'js>> {
    // Retrieve the array buffer
    let target = ObjectBytes::from(ctx, this.0.as_inner())?;
    let Some((array_buffer, target_byte_length, target_byte_offset)) = target.get_array_buffer()?
    else {
        return Err(Exception::throw_message(ctx, ERROR_MSG_NOT_ARRAY_BUFFER));
    };
    let target_bytes =
        resolve_view_bytes(ctx, array_buffer, target_byte_length, target_byte_offset)?;

    // Enforce the bounds
    let start = offset.0.unwrap_or_default();
    let end = start + (kind.bits() / 8) as usize;