add memory_view_istream

src/io/memory_istream.hpp

@@ -32,3 +32,33 @@ public:
 private:
     memory_streambuf buf;
 };
+
+class memory_view_streambuf : public std::streambuf {
+public:
+    explicit memory_view_streambuf(const util::Buffer<char>& buffer)
+        : buffer(std::move(buffer)) {
+        char* base = const_cast<char*>(this->buffer.data());
+        char* end = base + this->buffer.size();
+        setg(base, base, end);
+    }
+    
+    memory_view_streambuf(const memory_view_streambuf&) = delete;
+    memory_view_streambuf& operator=(const memory_view_streambuf&) = delete;
+
+protected:
+    int_type underflow() override {
+        return traits_type::eof();
+    }
+
+private:
+    const util::Buffer<char>& buffer;
+};
+
+class memory_view_istream : public std::istream {
+public:
+    explicit memory_view_istream(const util::Buffer<char>& buffer)
+        : std::istream(&buf), buf(buffer) {}
+
+private:
+    memory_view_streambuf buf;
+};