chore: apply suggestions from CR

core/src/docs/rfcs/3734_buffered_reader.md

@@ -28,7 +28,7 @@ op.reader_with(path).buffer(32 * 1024 * 1024).await
 
 This feature will be implemented in the `CompleteLayer`, with the addition of a `BufferReader` struct in `raw/oio/reader/buffer_reader.rs`. 
 
-The `BufferReader` employs` bytes::BytesMut` as the inner buffer and utilizes `(Option<usize>, Option<usize>)` to track the buffered range of the file.
+The `BufferReader` employs a `tokio::io::ReadBuf` as the inner buffer and uses `offset: Option<u64>` to track the buffered range start of the file, the buffered data should always be `file[offset..offset + buf.len()]`.
 
 
 ```rust
@@ -45,7 +45,7 @@ The `BufferReader` employs` bytes::BytesMut` as the inner buffer and utilizes `(
      ...
 ```
 
-A `buffer` field of type `Option<usize>` will be introduced to `OpRead`. If `buffer` is set to `None`, it functions with default behavior. However, if buffer is set to `Some(n)`, it denotes the maximum buffer capability that the `BufferReader` can utilize, and buffering behaviors introduced below.
+A `buffer` field of type `Option<usize>` will be introduced to `OpRead`. If `buffer` is set to `None`, it functions with default behavior. However, if buffer is set to `Some(n)`, it denotes the maximum buffer capability that the `BufferReader` can utilize. The behavior is similar to [std::io::BufReader](https://doc.rust-lang.org/std/io/struct.BufReader.html), with the only difference being that our implementation always provides the seek_relative if it's available.
 
 **Buffering**
 
@@ -57,11 +57,11 @@ Buffer
 │       │
 └───────┘
 File
-┌───┬───────┬──┐
-│   │       │  │
+┌──────────────┐
+│              │
 └───▲───────▲──┘
     │       │
-    │       │ 2. ReadToEnd(limit), The limit <= Cap(Buffer).
+    │       │ 2. Read(limit), The limit <= Cap(Buffer).
     │
     │ 1. SeekFromStart(128)
 
@@ -81,15 +81,15 @@ File
 
 **Tailing Read**
 
-If a read request attempts to read the trailing bytes of the file, it only reads and buffers the `Min(Max(Limit,Cap(Buffer)),FileEnd-Cursor)` bytes.
+If a read request attempts to read the trailing bytes of the file, it only reads and **without** buffers the `Min(Max(Limit,Cap(Buffer)),FileEnd-Cursor)` bytes.
 
 ```
 File
 ┌──────────────┐
 │              │
 └────────────▲─▲
              │ │
-             │ │ 2. ReadToEnd(limit)
+             │ │ 2. Read(limit)
              │
              │ 1. SeekFromEnd(-8)
 ```
@@ -108,7 +108,7 @@ File
 │*******│      │
 └────▲──┴──▲───┘
      │     │
-     │     │ 2. ReadToEnd(limit), The limit <= Cap(Buffer).
+     │     │ 2. Read(limit), The limit <= Cap(Buffer).
      │
      │ 1. SeekFromStart(128)
 ```
@@ -138,10 +138,10 @@ Buffer
 └───────┘
 File
 ┌───────────┬──┐
-│           │**│
+│           │  │
 └──▲──────▲─┴──┘
    │      │
-   │      │ 2. ReadToEnd(limit), The limit > Cap(Buffer).
+   │      │ 2. Read(limit), The limit > Cap(Buffer).
    │
    │ 1. SeekFromStart(128)
 ```