add：添加get_len接口。

include/of_util.h

@@ -4,6 +4,7 @@
 #include <iostream>
 #include <memory>
 #include <mutex>
+#include <vector>
 #include <algorithm>
 #include <cstring>
 
@@ -40,6 +41,7 @@ public:
     void push(const char* data, int len);
     int index_of(const char* data, int len, int start_pos = 0);
     const char* get_data() const;
+    int get_len() const;
     void remove_of(int start_pos, int len);
     void clear();
 private:

src/of_util.cpp

@@ -33,6 +33,11 @@ const char* CMutBuffer::get_data() const
     return buffer_.data();
 }
 
+int CMutBuffer::get_len() const
+{
+    return static_cast<int>(buffer_.size());
+}
+
 void CMutBuffer::clear()
 {
     std::lock_guard<std::mutex> lock(mutex_);