Greatly reduced the number of memcpy operations done on the media plug-in message output pipe

by removing 's = s.substr()' type operations.  The output string is now cleared via 's.clear()'
when its entire contents have been pumped and the beginning of the data is stored as an index
when necessary, rather than modifying the initial string.

Reviewed by davep.

2 files changed, 35 insertions, 17 deletions

diff --git a/indra/llplugin/llpluginmessagepipe.cpp b/indra/llplugin/llpluginmessagepipe.cpp
index 8d13e38ad5..091e93ea4b 100644
--- a/indra/llplugin/llpluginmessagepipe.cpp
+++ b/indra/llplugin/llpluginmessagepipe.cpp
@@ -94,10 +94,10 @@ void LLPluginMessagePipeOwner::killMessagePipe(void)
 LLPluginMessagePipe::LLPluginMessagePipe(LLPluginMessagePipeOwner *owner, LLSocket::ptr_t socket):
 	mInputMutex(gAPRPoolp),
 	mOutputMutex(gAPRPoolp),
+	mOutputStartIndex(0),
 	mOwner(owner),
 	mSocket(socket)
 {
-	
 	mOwner->setMessagePipe(this);
 }
 
@@ -113,6 +113,14 @@ bool LLPluginMessagePipe::addMessage(const std::string &message)
 {
 	// queue the message for later output
 	LLMutexLock lock(&mOutputMutex);
+
+	// If we're starting to use up too much memory, clear
+	if (mOutputStartIndex > 1024 * 1024)
+	{
+		mOutput = mOutput.substr(mOutputStartIndex);
+		mOutputStartIndex = 0;
+	}
+		
 	mOutput += message;
 	mOutput += MESSAGE_DELIMITER;	// message separator
 	
@@ -165,35 +173,44 @@ bool LLPluginMessagePipe::pumpOutput()
 	if(mSocket)
 	{
 		apr_status_t status;
-		apr_size_t size;
+		apr_size_t in_size, out_size;
 		
 		LLMutexLock lock(&mOutputMutex);
-		if(!mOutput.empty())
+
+		const char * output_data = &(mOutput.data()[mOutputStartIndex]);
+		if(*output_data != '\0')
 		{
 			// write any outgoing messages
-			size = (apr_size_t)mOutput.size();
+			in_size = (apr_size_t) (mOutput.size() - mOutputStartIndex);
+			out_size = in_size;
 			
 			setSocketTimeout(0);
 			
 //			LL_INFOS("Plugin") << "before apr_socket_send, size = " << size << LL_ENDL;
 
-			status = apr_socket_send(
-					mSocket->getSocket(),
-					(const char*)mOutput.data(),
-					&size);
+			status = apr_socket_send(mSocket->getSocket(),
+									 output_data,
+									 &out_size);
 
 //			LL_INFOS("Plugin") << "after apr_socket_send, size = " << size << LL_ENDL;
 			
-			if(status == APR_SUCCESS)
+			if((status == APR_SUCCESS) || APR_STATUS_IS_EAGAIN(status))
 			{
-				// success
-				mOutput = mOutput.substr(size);
-			}
-			else if(APR_STATUS_IS_EAGAIN(status))
-			{
-				// Socket buffer is full... 
-				// remove the written part from the buffer and try again later.
-				mOutput = mOutput.substr(size);
+				// Success or Socket buffer is full... 
+				
+				// If we've pumped the entire string, clear it
+				if (out_size == in_size)
+				{
+					mOutputStartIndex = 0;
+					mOutput.clear();
+				}
+				else
+				{
+					llassert(in_size > out_size);
+					
+					// Remove the written part from the buffer and try again later.
+					mOutputStartIndex += out_size;
+				}
 			}
 			else if(APR_STATUS_IS_EOF(status))
 			{
diff --git a/indra/llplugin/llpluginmessagepipe.h b/indra/llplugin/llpluginmessagepipe.h
index beb942c0fe..059943cc90 100644
--- a/indra/llplugin/llpluginmessagepipe.h
+++ b/indra/llplugin/llpluginmessagepipe.h
@@ -86,6 +86,7 @@ protected:
 	std::string mInput;
 	LLMutex mOutputMutex;
 	std::string mOutput;
+	std::string::size_type mOutputStartIndex;
 
 	LLPluginMessagePipeOwner *mOwner;
 	LLSocket::ptr_t mSocket;