From caa2f6ca5d0a803e47d6efb4858c92c505520527 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 12 Jun 2011 18:02:56 +0300
Subject: [PATCH] EventReader class

---
 source/io/eventreader.cpp | 140 ++++++++++++++++++++++++++++++++++++++
 source/io/eventreader.h   |  43 ++++++++++++
 2 files changed, 183 insertions(+)
 create mode 100644 source/io/eventreader.cpp
 create mode 100644 source/io/eventreader.h

diff --git a/source/io/eventreader.cpp b/source/io/eventreader.cpp
new file mode 100644
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
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
-- 
2.43.0