1 files changed, 38 insertions, 12 deletions
diff --git a/butl/fdstream b/butl/fdstream
index 01a19b7..2814d4b 100644
--- a/butl/fdstream
+++ b/butl/fdstream
@@ -6,18 +6,19 @@
 #define BUTL_FDSTREAM
 
 #include <istream>
+#include <ostream>
 
 namespace butl
 {
-  // An input stream that is initialized with a file descriptor
-  // rather than a file name.
+  // An iostream that is initialized with a file descriptor rather than
+  // a file name.
   //
   // Notes and limitations:
   //
   // - char only
-  // - input only
+  // - input or output but not both
   // - no support for put back
-  // - throws std::system_error in case of a read() error
+  // - throws std::system_error in case of a read()/write() error
   // - not movable, though can be easily supported
   //
   class fdbuf: public std::basic_streambuf<char>
@@ -35,17 +36,18 @@ namespace butl
     close ();
 
     void
-    open (int fd) {close (); fd_ = fd; setg (buf_, buf_, buf_);}
+    open (int fd);
 
     bool
     is_open () const {return fd_ != -1;}
 
-    // basic_streambuf input interface.
-    //
   public:
     using int_type = std::basic_streambuf<char>::int_type;
     using traits_type = std::basic_streambuf<char>::traits_type;
 
+    // basic_streambuf input interface.
+    //
+  public:
     virtual std::streamsize
     showmanyc ();
 
@@ -56,26 +58,50 @@ namespace butl
     bool
     load ();
 
+    // basic_streambuf output interface.
+    //
+  public:
+    virtual int_type
+    overflow (int_type);
+
+    virtual int
+    sync ();
+
+  private:
+    bool
+    save ();
+
   private:
     int fd_ = -1;
     char buf_[2048];
   };
 
-  class ifdstream_base
+  class fdstream_base
   {
   protected:
-    ifdstream_base () = default;
-    ifdstream_base (int fd): buf_ (fd) {}
+    fdstream_base () = default;
+    fdstream_base (int fd): buf_ (fd) {}
 
   protected:
     fdbuf buf_;
   };
 
-  class ifdstream: ifdstream_base, public std::istream
+  class ifdstream: fdstream_base, public std::istream
   {
   public:
     ifdstream (): std::istream (&buf_) {}
-    ifdstream (int fd): ifdstream_base (fd), std::istream (&buf_) {}
+    ifdstream (int fd): fdstream_base (fd), std::istream (&buf_) {}
+
+    void close () {buf_.close ();}
+    void open (int fd) {buf_.open (fd);}
+    bool is_open () const {return buf_.is_open ();}
+  };
+
+  class ofdstream: fdstream_base, public std::ostream
+  {
+  public:
+    ofdstream (): std::ostream (&buf_) {}
+    ofdstream (int fd): fdstream_base (fd), std::ostream (&buf_) {}
 
     void close () {buf_.close ();}
     void open (int fd) {buf_.open (fd);}