add memory_istream

src/io/memory_istream.hpp

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <istream>
+#include "util/Buffer.hpp"
+
+class memory_istream : public std::istream {
+public:
+    explicit memory_istream(util::Buffer<char> buffer)
+        : std::istream(&buf), buf(std::move(buffer)) {}
+
+private:
+    class memory_streambuf : public std::streambuf {
+    public:
+        explicit memory_streambuf(util::Buffer<char> buffer)
+            : buffer(std::move(buffer)) {
+            char* base = this->buffer.data();
+            char* end = base + this->buffer.size();
+            setg(base, base, end);
+        }
+        
+        memory_streambuf(const memory_streambuf&) = delete;
+        memory_streambuf& operator=(const memory_streambuf&) = delete;
+    
+    protected:
+        int_type underflow() override {
+            return traits_type::eof();
+        }
+    
+    private:
+        util::Buffer<char> buffer;
+    };
+    
+    memory_streambuf buf;
+};