refactored mapped_file to no longer be derived from std::istream

libscio.hpp

@@ -16,7 +16,6 @@
 #include <cstdint>
 #include <cstdlib>
 #include <string>
-#include <sstream>
 
 namespace sc {
 
@@ -282,7 +281,7 @@ namespace sc {
                 byte_order _saved_byte_order {byte_order::undefined};
         };
 
-        class mapped_file : public std::istream {
+        class mapped_file {
             public:
                 mapped_file();
                 mapped_file(const std::string& path);
@@ -295,20 +294,21 @@ namespace sc {
                 mapped_file(mapped_file&& other);
                 mapped_file& operator=(mapped_file&& other);
 
+                // cleanup: mapped_file is RAII class for memory mapping and file descriptor
                 ~mapped_file();
 
                 // it's an error to open an already opened mapped_file
+                // open() is meant to be used after default constructor
                 void open(const std::string& path);
 
                 // direct (read-only) access to mapped memory
-                const char* mapping() const { return _mapping; }
+                char* mapping() const { return _mapping; }
                 size_t size() const { return _length; }
 
             private:
                 int _fd {-1};
                 char* _mapping {nullptr};
                 size_t _length {0};
-                std::stringbuf _membuf;
         };
 
     }

mapped_file.cpp

@@ -18,9 +18,7 @@
 
 using namespace sc::io;
 
-mapped_file::mapped_file() : std::istream {&_membuf} {}
-
-mapped_file::mapped_file(const std::string& path) : std::istream {&_membuf} {
+mapped_file::mapped_file(const std::string& path) {
     open(path);
 }
 
@@ -36,16 +34,14 @@ mapped_file::~mapped_file() {
     }
 }
 
-mapped_file::mapped_file(mapped_file&& other) : std::istream {std::move(other)} {
+mapped_file::mapped_file(mapped_file&& other) {
     _fd = other._fd;
     _mapping = other._mapping;
     _length = other._length;
-    _membuf = std::move(other._membuf);
 
     other._fd = -1;
     other._mapping = nullptr;
     other._length = 0;
-    other._membuf.pubsetbuf(nullptr, 0);
 }
 
 mapped_file& mapped_file::operator=(mapped_file &&other) {
@@ -65,5 +61,4 @@ void mapped_file::open(const std::string& path) {
     _length = st.st_size;
     _mapping = reinterpret_cast<char*>(mmap(nullptr, _length, PROT_READ, MAP_PRIVATE, _fd, 0));
     if (_mapping == MAP_FAILED) throw std::runtime_error("could not map file");
-    _membuf.pubsetbuf(_mapping, _length);
 }