add BufferReader in rust-src

rust-src/src/adapters/damage.rs

-use wasm_bindgen::prelude::wasm_bindgen;
 use std::convert::TryInto;
+use wasm_bindgen::prelude::wasm_bindgen;
 
 #[wasm_bindgen]
 pub struct MsgUpdateHp {

rust-src/src/buffer.rs

-// TODO
+//! Raw Buffer 解析工具
+//!
+//! 在Javascript/Typescript中数字类型只有`numbuer`，
+//! 要做二进制数组的解析需要用[`DataView`]，比较复杂，且性能不佳。
+//! 因此这里用WASM实现两个基础的二进制数据解析模块[`BufferReader`]和[`BufferWriter`]。
+
+use wasm_bindgen::prelude::wasm_bindgen;
+
+const OFFSET_UINT8: usize = 1;
+const OFFSET_INT8: usize = 1;
+const OFFSET_UINT16: usize = 2;
+const OFFSET_UINT32: usize = 4;
+const OFFSET_INT32: usize = 4;
+
+#[wasm_bindgen]
+pub struct BufferReader {
+    array: Vec<u8>,
+    offset: usize,
+}
+
+#[wasm_bindgen]
+impl BufferReader {
+    #[wasm_bindgen(constructor)]
+    pub fn new(array: js_sys::Uint8Array) -> Self {
+        Self {
+            array: array.to_vec(),
+            offset: 0,
+        }
+    }
+
+    pub fn readUint8(&mut self) -> u8 {
+        let ret = self.array[self.offset];
+        self.offset += OFFSET_UINT8;
+
+        ret
+    }
+
+    pub fn readInt8(&mut self) -> i8 {
+        let ret = self.array[self.offset] as i8;
+        self.offset += OFFSET_INT8;
+
+        ret
+    }
+
+    pub fn readUint16(&mut self) -> u16 {
+        let ret = self.array[self.offset..self.offset + OFFSET_UINT16]
+            .try_into()
+            .map(u16::from_le_bytes)
+            .unwrap();
+        self.offset += OFFSET_UINT16;
+
+        ret
+    }
+
+    pub fn readUint32(&mut self) -> u32 {
+        let ret = self.array[self.offset..self.offset + OFFSET_UINT32]
+            .try_into()
+            .map(u32::from_le_bytes)
+            .unwrap();
+        self.offset += OFFSET_UINT32;
+
+        ret
+    }
+
+    pub fn readInt32(&mut self) -> i32 {
+        let ret = self.array[self.offset..self.offset + OFFSET_INT32]
+            .try_into()
+            .map(i32::from_le_bytes)
+            .unwrap();
+        self.offset += OFFSET_INT32;
+
+        ret
+    }
+}

rust-src/src/lib.rs

 #![allow(non_snake_case)]
 
+mod adapters;
 mod buffer;
 mod utils;
-mod adapters;
 
-pub use utils::set_panic_hook;
 pub use adapters::*;
+pub use buffer::BufferReader;
+pub use utils::set_panic_hook;
 
 // When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
 // allocator.