EventReader class

diff --git a/source/io/eventreader.cpp b/source/io/eventreader.cpp
new file mode 100644 (file)
index 0000000..a31a384
--- /dev/null
+++ b/source/io/eventreader.cpp
@@ -0,0 +1,140 @@
+#ifdef WIN32
+#include <windows.h>
+#endif
+#include <algorithm>
+#include <msp/core/systemerror.h>
+#include "eventreader.h"
+#include "handle_private.h"
+
+using namespace std;
+
+namespace Msp {
+namespace IO {
+
+struct EventReader::Private
+{
+#ifdef WIN32
+       OVERLAPPED *overlapped;
+       Handle event;
+       unsigned buf_size;
+       char *buffer;
+       unsigned buf_avail;
+       char *buf_next;
+#endif
+};
+
+
+EventReader::EventReader(Handle &h, unsigned size):
+       handle(h),
+       priv(0)
+{
+#ifdef WIN32
+       priv = new Private;
+
+       priv->overlapped = 0;
+       *priv->event = CreateEvent(0, true, false, 0);
+       priv->buf_size = size;
+       priv->buffer = new char[priv->buf_size];
+       priv->buf_avail = 0;
+       priv->buf_next = priv->buffer;
+
+       start();
+#else
+       (void)size;
+#endif
+}
+
+EventReader::~EventReader()
+{
+#ifdef WIN32
+       CloseHandle(*priv->event);
+       delete priv->overlapped;
+       delete[] priv->buffer;
+#endif
+       delete priv;
+}
+
+const Handle &EventReader::get_event() const
+{
+#ifdef WIN32
+       return priv->event;
+#else
+       return handle;
+#endif
+}
+
+void EventReader::start()
+{
+#ifdef WIN32
+       if(priv->buf_avail || priv->overlapped)
+               return;
+
+       priv->overlapped = new OVERLAPPED;
+       memset(priv->overlapped, 0, sizeof(OVERLAPPED));
+       priv->overlapped->hEvent = *priv->event;
+
+       DWORD ret;
+       priv->buf_next = priv->buffer;
+       if(!ReadFile(*handle, priv->buffer, priv->buf_size, &ret, priv->overlapped))
+       {
+               unsigned err = GetLastError();
+               if(err!=ERROR_IO_PENDING)
+                       throw system_error("ReadFile");
+       }
+       else
+       {
+               priv->buf_avail = ret;
+               delete priv->overlapped;
+               priv->overlapped = 0;
+               SetEvent(*priv->event);
+       }
+#endif
+}
+
+void EventReader::wait()
+{
+#ifdef WIN32
+       if(!priv->overlapped)
+               return;
+
+       DWORD ret;
+       if(!GetOverlappedResult(*handle, priv->overlapped, &ret, true))
+               throw system_error("GetOverlappedResult");
+       else
+       {
+               priv->buf_avail = ret;
+               delete priv->overlapped;
+               priv->overlapped = 0;
+       }
+#endif
+}
+
+unsigned EventReader::read(char *buf, unsigned len)
+{
+#ifdef WIN32
+       if(!priv->buf_avail)
+       {
+               // No data in buffer, try to get some
+               start();
+               wait();
+       }
+
+       len = min(len, priv->buf_avail);
+       memcpy(buf, priv->buf_next, len);
+       priv->buf_next += len;
+       priv->buf_avail -= len;
+
+       if(!priv->buf_avail)
+       {
+               ResetEvent(*priv->event);
+               start();
+       }
+
+       return len;
+#else
+       return sys_read(handle, buf, len);
+#endif
+}
+
+} // namespace IO
+} // namespace Msp

diff --git a/source/io/eventreader.h b/source/io/eventreader.h
new file mode 100644 (file)
index 0000000..b3acdb9
--- /dev/null
+++ b/source/io/eventreader.h
@@ -0,0 +1,43 @@
+#ifndef MSP_IO_EVENTREADER_H_
+#define MSP_IO_EVENTREADER_H_
+
+#include "handle.h"
+
+namespace Msp {
+namespace IO {
+
+/**
+Helper class for reading data in a way that supports events.  For internal use
+only.
+
+On Windows, overlapped reads are used.  Data is read to an internal buffer and
+handed out from there.  An event object is kept synchronized with the buffer
+state to get level-triggered semantics for poll.  Whenever the buffer becomes
+empty, a new overlapped read is started.
+
+Unix-based systems can poll the fd directly, so this class reduces to a simple
+passthrough to sys_read.
+*/
+class EventReader
+{
+private:
+       struct Private;
+
+       Handle &handle;
+       Private *priv;
+
+public:
+       EventReader(Handle &, unsigned);
+       ~EventReader();
+
+       const Handle &get_event() const;
+
+       void start();
+       void wait();
+       unsigned read(char *, unsigned);
+};
+
+} // namespace IO
+} // namespace Msp
+
+#endif