diff --git a/src/libscio.hpp b/src/libscio.hpp
index 3b4c582..0ccbe14 100644
--- a/src/libscio.hpp
+++ b/src/libscio.hpp
@@ -327,8 +327,8 @@ namespace sc {
 
             protected:
                 // input
+                int_type underflow() override;
                 int_type uflow() override;
-                std::streamsize xsgetn(char* s, std::streamsize n) override;
 
                 // output
                 int_type overflow(int_type c) override;
diff --git a/src/memstreambuf.cpp b/src/memstreambuf.cpp
index eb29e35..7e0a85f 100644
--- a/src/memstreambuf.cpp
+++ b/src/memstreambuf.cpp
@@ -12,6 +12,11 @@ void sc::io::memstreambuf::init(char* mem, size_t size) {
 	setg(_mem, _mem, _mem + _size);
 }
 
+std::streambuf::int_type sc::io::memstreambuf::underflow() {
+	if (gptr() == _mem + _size) return EOF;
+	return *gptr();
+}
+
 std::streambuf::int_type sc::io::memstreambuf::uflow() {
 	if (gptr() == _mem + _size) return EOF;
 	char c = *gptr();
@@ -19,14 +24,6 @@ std::streambuf::int_type sc::io::memstreambuf::uflow() {
 	return c;
 }
 
-std::streamsize sc::io::memstreambuf::xsgetn(char* s, std::streamsize n) {
-	std::streamsize left = _mem + _size - gptr();
-	std::streamsize tot_read = std::min(left, n);
-	if (tot_read == 0) return EOF;
-	std::memcpy(s, gptr(), tot_read);
-	return tot_read;
-}
-
 std::streambuf::int_type sc::io::memstreambuf::overflow(std::streambuf::int_type c) {
 	// TODO
 	// if (c != EOF) {
@@ -43,7 +40,7 @@ std::streambuf::int_type sc::io::memstreambuf::overflow(std::streambuf::int_type
 	return c;
 }
 
-std::streamsize sc::io::memstreambuf::xsputn(const char* s, std::streamsize num) {
+std::streamsize sc::io::memstreambuf::xsputn(const char* /*s*/, std::streamsize num) {
 	// TODO
 // 	int res = write(_fd, s, num);
 // 	if (res != num) {
@@ -55,25 +52,53 @@ std::streamsize sc::io::memstreambuf::xsputn(const char* s, std::streamsize num)
 }
 
 std::streambuf::pos_type sc::io::memstreambuf::seekoff(std::streambuf::off_type off,
-												  std::ios_base::seekdir dir,
-												  std::ios_base::openmode /*which*/) {
-	switch (dir) {
-		case std::ios_base::beg: setg(_mem, _mem + off, _mem + _size); break;
-		case std::ios_base::end: setg(_mem, _mem + _size - off, _mem + _size); break;
-		case std::ios_base::cur: setg(_mem, gptr() + off, _mem + _size); break;
-		default: throw std::runtime_error("invalid seekdir");
+													   std::ios_base::seekdir dir,
+													   std::ios_base::openmode which) {
+	if (which & std::ios::in) { // reading
+		switch (dir) {
+			case std::ios::beg:
+				if (off < 0 || static_cast<size_t>(off) > _size) return EOF;
+				setg(_mem, _mem + off, _mem + _size);
+				break;
+			case std::ios::cur: {
+				int64_t pos = gptr() - _mem + off;
+				if (pos < 0 || static_cast<size_t>(pos) > _size) return EOF;
+				setg(_mem, gptr() + off, _mem + _size);
+				break;
+			}
+			case std::ios::end:
+				if (off > 0 || static_cast<size_t>(off) < -_size) return EOF;
+				setg(_mem, _mem + _size + off - 1, _mem + _size);
+				break;
+		}
+		return gptr() - _mem;
+	} else if (which & std::ios::out) { // writing
+		switch (dir) { // TODO
+			case std::ios::beg:
+				break;
+			case std::ios::cur:
+				break;
+			case std::ios::end:
+				break;
+		}
+		return pptr() - _mem;
 	}
-	return gptr() - _mem;
+	return EOF;
 }
 
 std::streambuf::pos_type sc::io::memstreambuf::seekpos(std::streambuf::pos_type pos,
-												  std::ios_base::openmode /*which*/) {
-	setg(_mem, _mem + pos, _mem + _size);
-	return gptr() - _mem;
+													   std::ios_base::openmode which) {
+	if (which & std::ios::in) {
+		if (pos < 0 || static_cast<size_t>(pos) > _size) return EOF;
+		setg(_mem, _mem + pos, _mem + _size);
+		return pos;
+	} else if (which & std::ios::out) {
+		// TODO
+		return pos;
+	}
+	return EOF;
 }
 
 std::streambuf::int_type sc::io::memstreambuf::pbackfail(std::streambuf::int_type /*c*/) {
-	setg(_mem, gptr() - 1, _mem + _size);
-	if (gptr() < _mem) return EOF;
-	return 0;
+	return EOF;
 }