add Chapter08

Chapter08/tmpt_crtp.cpp

@@ -0,0 +1,56 @@
+#include <span> 
+#include <cstdio> 
+#include <cstdint> 
+
+template<typename U> 
+class uart_interface { 
+public: 
+    void init(std::uint32_t baudrate = 9600) { 
+       static_cast<U*>(this)->initImpl(baudrate); 
+    } 
+
+    void write(std::span<const char> data) { 
+       static_cast<U*>(this)->writeImpl(data); 
+    } 
+}; 
+
+class uart_stm32 : public uart_interface<uart_stm32> { 
+public: 
+    void initImpl(std::uint32_t baudrate = 9600) { 
+        printf("uart_stm32::init: setting baudrate to %d\r\n", baudrate); 
+    } 
+
+    void writeImpl(std::span<const char> data) { 
+        printf("uart_stm32::write: "); 
+        for(auto ch: data) { 
+            putc(ch, stdout); 
+        } 
+    } 
+}; 
+
+template<typename T> 
+concept TheUart = std::derived_from<T, uart_interface<T>>; 
+
+template<TheUart T> 
+class gsm_lib{ 
+public: 
+    gsm_lib(T &u) : uart_(u) {} 
+
+    void init() {
+        printf("gsm_lib::init: sending AT command\r\n"); 
+        uart_.write("AT"); 
+    } 
+
+private: 
+    T &uart_; 
+}; 
+
+int main() { 
+    uart_stm32 uart_stm32_obj; 
+    uart_stm32_obj.init(115200); 
+
+    gsm_lib gsm(uart_stm32_obj); 
+    gsm.init(); 
+
+    return 0; 
+}