add memory_istream

test/io/memory_istream.cpp

@@ -0,0 +1,19 @@
+#include <gtest/gtest.h>
+
+#include "io/memory_istream.hpp"
+
+TEST(io, memory_istream) {
+    const char data[] = "Hello, world!";
+    const int n = std::strlen(data);
+
+    util::Buffer<char> buffer(data, n);
+    memory_istream stream(std::move(buffer));
+
+    ASSERT_TRUE(stream.good());
+
+    std::string text(n, '\0');
+    stream.read(text.data(), n);
+    ASSERT_EQ(text, std::string(data));
+    stream.read(text.data(), 1);
+    ASSERT_TRUE(stream.eof());
+}