Basic parsing for Archive II file

wxdata/source/scwx/util/rangebuf.cpp

@@ -0,0 +1,30 @@
+#include <scwx/util/rangebuf.hpp>
+
+namespace scwx
+{
+namespace util
+{
+
+rangebuf::rangebuf(std::streambuf* sbuf, size_t size) :
+    size_(size), sbuf_(sbuf), data_()
+{
+   size_t bufferSize = std::max<size_t>(size, 4096u);
+   data_.reserve(bufferSize);
+}
+
+int rangebuf::underflow()
+{
+   char*     buf     = data_.data();
+   ptrdiff_t bufSize = data_.capacity();
+
+   // Read from underlying stream buffer into own buffer until needed characters
+   // have been consumed
+   size_t r(sbuf_->sgetn(buf, std::min<size_t>(bufSize, size_)));
+   size_ -= r;
+   setg(buf, buf, buf + r);
+   return gptr() == egptr() ? traits_type::eof() :
+                              traits_type::to_int_type(*gptr());
+}
+
+} // namespace util
+} // namespace scwx