From 79ee8c1c814a156a9460dff29e77f83d7dd8d875 Mon Sep 17 00:00:00 2001
From: "Peter S. May" <me@psmay.com>
Date: Thu, 23 Apr 2015 12:50:28 -0400
Subject: [PATCH] Block+timeout CanRead/CanWrite/DataAvailable EzSockets
 methods.

A minor change to the code exposes the timeout parameter of `select()`, which was already in use for CanRead()/CanWrite(). The timeout parameter is used to block the current thread until data (for read) or space (for write) is available on the underlying socket.

A timeout of 0 suppresses any blocking (the original methods fix the timeout to 0).

The timeout value is supplied in milliseconds as an `unsigned int`; this is converted internally to the equivalent `timeval`.

An in-progress addition to my SextetStream input driver is implemented with non-blocking reads on a TCP socket. Without the block+timeout functionality, it must busy-wait for new input. Changing the reads to blocking works during a game but can cause the program to hang when exiting. The changes in this commit provide a solution to both issues without disrupting any existing code.
---
 src/ezsockets.cpp | 46 ++++++++++++++++++++++++++++++++++++++++------
 src/ezsockets.h   |  3 +++
 2 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/src/ezsockets.cpp b/src/ezsockets.cpp
index 5b3bc56423..18a4d8ee3e 100644
--- a/src/ezsockets.cpp
+++ b/src/ezsockets.cpp
@@ -33,6 +33,16 @@
 #define INVALID_SOCKET -1
 #endif
 
+// Returns a timeval set to the given number of milliseconds.
+inline timeval timevalFromMs(unsigned int ms)
+{
+	timeval tv;
+	tv.tv_sec = ms / 1000;
+	tv.tv_usec = (ms % 1000) * 1000;
+	return tv;
+}
+
+
 EzSockets::EzSockets()
 {
 	MAXCON = 5;
@@ -185,12 +195,24 @@ bool EzSockets::connect(const std::string& host, unsigned short port)
 	return true;
 }
 
+inline bool checkCanRead(int sock, timeval& timeout)
+{
+	fd_set fds;
+	FD_ZERO(&fds);
+	FD_SET((unsigned)sock, &fds);
+
+	return select(sock+1, &fds, NULL, NULL, &timeout) > 0;
+}
+
 bool EzSockets::CanRead()
 {
-	FD_ZERO(scks);
-	FD_SET((unsigned)sock, scks);
+	return checkCanRead(sock, *times);
+}
 
-	return select(sock+1,scks,NULL,NULL,times) > 0;
+bool EzSockets::CanRead(unsigned int msTimeout)
+{
+	timeval tv = timevalFromMs(msTimeout);
+	return checkCanRead(sock, tv);
 }
 
 bool EzSockets::IsError()
@@ -208,12 +230,24 @@ bool EzSockets::IsError()
 	return true;
 }
 
+inline bool checkCanWrite(int sock, timeval& timeout)
+{
+	fd_set fds;
+	FD_ZERO(&fds);
+	FD_SET((unsigned)sock, &fds);
+
+	return select(sock+1, NULL, &fds, NULL, &timeout) > 0;
+}
+
 bool EzSockets::CanWrite()
 {
-	FD_ZERO(scks);
-	FD_SET((unsigned)sock, scks);
+	return checkCanWrite(sock, *times);
+}
 
-	return select(sock+1, NULL, scks, NULL, times) > 0;
+bool EzSockets::CanWrite(unsigned int msTimeout)
+{
+	timeval tv = timevalFromMs(msTimeout);
+	return checkCanWrite(sock, tv);
 }
 
 void EzSockets::update()
diff --git a/src/ezsockets.h b/src/ezsockets.h
index 6e90313d67..a679cd4e94 100644
--- a/src/ezsockets.h
+++ b/src/ezsockets.h
@@ -60,9 +60,12 @@ public:
 	long uAddr();
 
 	bool CanRead();
+	bool CanRead(unsigned int msTimeout);
 	bool DataAvailable() { return ( ( inBuffer.length()>0 ) || CanRead() ); }
+	bool DataAvailable(unsigned int msTimeout) { return ( ( inBuffer.length()>0 ) || CanRead(msTimeout) ); }
 	bool IsError();
 	bool CanWrite();
+	bool CanWrite(unsigned int msTimeout);
 
 	void update();