Performance add exist

hikyuu_cpp/hikyuu/trade_manage/Performance.cpp

@@ -72,6 +72,17 @@ Performance::Performance() {
 
 Performance::~Performance() {}
 
+bool Performance::exist(const string& key) {
+    bool ret = false;
+    for (const auto& item : ms_keys) {
+        if (item == key) {
+            ret = true;
+            break;
+        }
+    }
+    return ret;
+}
+
 Performance& Performance::operator=(const Performance& other) {
     HKU_IF_RETURN(this == &other, *this);
     m_result = other.m_result;

hikyuu_cpp/hikyuu/trade_manage/Performance.h

@@ -29,6 +29,9 @@ public:
     Performance& operator=(const Performance& other);
     Performance& operator=(Performance&& other);
 
+    /** 是否为合法的统计项 */
+    static bool exist(const string& key);
+
     /** 复位，清除已计算的结果 */
     void reset();