sync up to viewer-developer

1 files changed, 822 insertions, 0 deletions

diff --git a/indra/llmessage/llavatarnamecache.cpp b/indra/llmessage/llavatarnamecache.cpp
new file mode 100644
index 0000000000..2f2d9099a3
--- /dev/null
+++ b/indra/llmessage/llavatarnamecache.cpp
@@ -0,0 +1,822 @@
+/** 
+ * @file llavatarnamecache.cpp
+ * @brief Provides lookup of avatar SLIDs ("bobsmith123") and display names
+ * ("James Cook") from avatar UUIDs.
+ *
+ * $LicenseInfo:firstyear=2010&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2010, Linden Research, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+#include "linden_common.h"
+
+#include "llavatarnamecache.h"
+
+#include "llcachename.h"		// we wrap this system
+#include "llframetimer.h"
+#include "llhttpclient.h"
+#include "llsd.h"
+#include "llsdserialize.h"
+
+#include <boost/tokenizer.hpp>
+
+#include <map>
+#include <set>
+
+namespace LLAvatarNameCache
+{
+	use_display_name_signal_t mUseDisplayNamesSignal;
+
+	// Manual override for display names - can disable even if the region
+	// supports it.
+	bool sUseDisplayNames = true;
+
+	// Cache starts in a paused state until we can determine if the
+	// current region supports display names.
+	bool sRunning = false;
+	
+	// Base lookup URL for name service.
+	// On simulator, loaded from indra.xml
+	// On viewer, usually a simulator capability (at People API team's request)
+	// Includes the trailing slash, like "http://pdp60.lindenlab.com:8000/agents/"
+	std::string sNameLookupURL;
+
+	// accumulated agent IDs for next query against service
+	typedef std::set<LLUUID> ask_queue_t;
+	ask_queue_t sAskQueue;
+
+	// agent IDs that have been requested, but with no reply
+	// maps agent ID to frame time request was made
+	typedef std::map<LLUUID, F64> pending_queue_t;
+	pending_queue_t sPendingQueue;
+
+	// Callbacks to fire when we received a name.
+	// May have multiple callbacks for a single ID, which are
+	// represented as multiple slots bound to the signal.
+	// Avoid copying signals via pointers.
+	typedef std::map<LLUUID, callback_signal_t*> signal_map_t;
+	signal_map_t sSignalMap;
+
+	// names we know about
+	typedef std::map<LLUUID, LLAvatarName> cache_t;
+	cache_t sCache;
+
+	// Send bulk lookup requests a few times a second at most
+	// only need per-frame timing resolution
+	LLFrameTimer sRequestTimer;
+
+	// Periodically clean out expired entries from the cache
+	//LLFrameTimer sEraseExpiredTimer;
+
+	//-----------------------------------------------------------------------
+	// Internal methods
+	//-----------------------------------------------------------------------
+
+	// Handle name response off network.
+	// Optionally skip adding to cache, used when this is a fallback to the
+	// legacy name system.
+	void processName(const LLUUID& agent_id,
+					 const LLAvatarName& av_name,
+					 bool add_to_cache);
+
+	void requestNamesViaCapability();
+
+	// Legacy name system callback
+	void legacyNameCallback(const LLUUID& agent_id,
+		const std::string& full_name,
+		bool is_group);
+
+	void requestNamesViaLegacy();
+
+	// Fill in an LLAvatarName with the legacy name data
+	void buildLegacyName(const std::string& full_name,
+						 LLAvatarName* av_name);
+
+	// Do a single callback to a given slot
+	void fireSignal(const LLUUID& agent_id,
+					const callback_slot_t& slot,
+					const LLAvatarName& av_name);
+	
+	// Is a request in-flight over the network?
+	bool isRequestPending(const LLUUID& agent_id);
+
+	// Erase expired names from cache
+	void eraseExpired();
+
+	bool expirationFromCacheControl(LLSD headers, F64 *expires);
+}
+
+/* Sample response:
+<?xml version="1.0"?>
+<llsd>
+  <map>
+    <key>agents</key>
+    <array>
+      <map>
+        <key>display_name_next_update</key>
+        <date>2010-04-16T21:34:02+00:00Z</date>
+        <key>display_name_expires</key>
+        <date>2010-04-16T21:32:26.142178+00:00Z</date>
+        <key>display_name</key>
+        <string>MickBot390 LLQABot</string>
+        <key>sl_id</key>
+        <string>mickbot390.llqabot</string>
+        <key>id</key>
+        <string>0012809d-7d2d-4c24-9609-af1230a37715</string>
+        <key>is_display_name_default</key>
+        <boolean>false</boolean>
+      </map>
+      <map>
+        <key>display_name_next_update</key>
+        <date>2010-04-16T21:34:02+00:00Z</date>
+        <key>display_name_expires</key>
+        <date>2010-04-16T21:32:26.142178+00:00Z</date>
+        <key>display_name</key>
+        <string>Bjork Gudmundsdottir</string>
+        <key>sl_id</key>
+        <string>sardonyx.linden</string>
+        <key>id</key>
+        <string>3941037e-78ab-45f0-b421-bd6e77c1804d</string>
+        <key>is_display_name_default</key>
+        <boolean>true</boolean>
+      </map>
+    </array>
+  </map>
+</llsd>
+*/
+
+class LLAvatarNameResponder : public LLHTTPClient::Responder
+{
+private:
+	// need to store agent ids that are part of this request in case of
+	// an error, so we can flag them as unavailable
+	std::vector<LLUUID> mAgentIDs;
+
+	// Need the headers to look up Expires: and Retry-After:
+	LLSD mHeaders;
+	
+public:
+	LLAvatarNameResponder(const std::vector<LLUUID>& agent_ids)
+	:	mAgentIDs(agent_ids),
+		mHeaders()
+	{ }
+	
+	/*virtual*/ void completedHeader(U32 status, const std::string& reason, 
+		const LLSD& headers)
+	{
+		mHeaders = headers;
+	}
+
+	/*virtual*/ void result(const LLSD& content)
+	{
+		// Pull expiration out of headers if available
+		F64 expires = LLAvatarNameCache::nameExpirationFromHeaders(mHeaders);
+
+		LLSD agents = content["agents"];
+		LLSD::array_const_iterator it = agents.beginArray();
+		for ( ; it != agents.endArray(); ++it)
+		{
+			const LLSD& row = *it;
+			LLUUID agent_id = row["id"].asUUID();
+
+			LLAvatarName av_name;
+			av_name.fromLLSD(row);
+
+			// Use expiration time from header
+			av_name.mExpires = expires;
+
+			// Some avatars don't have explicit display names set
+			if (av_name.mDisplayName.empty())
+			{
+				av_name.mDisplayName = av_name.mUsername;
+			}
+
+			// cache it and fire signals
+			LLAvatarNameCache::processName(agent_id, av_name, true);
+		}
+
+		// Same logic as error response case
+		LLSD unresolved_agents = content["bad_ids"];
+		if (unresolved_agents.size() > 0)
+		{
+			const std::string DUMMY_NAME("\?\?\?");
+			LLAvatarName av_name;
+			av_name.mUsername = DUMMY_NAME;
+			av_name.mDisplayName = DUMMY_NAME;
+			av_name.mIsDisplayNameDefault = false;
+			av_name.mIsDummy = true;
+			av_name.mExpires = expires;
+
+			it = unresolved_agents.beginArray();
+			for ( ; it != unresolved_agents.endArray(); ++it)
+			{
+				const LLUUID& agent_id = *it;
+				// cache it and fire signals
+				LLAvatarNameCache::processName(agent_id, av_name, true);
+			}
+		}
+	}
+
+	/*virtual*/ void error(U32 status, const std::string& reason)
+	{
+		// We're going to construct a dummy record and cache it for a while,
+		// either briefly for a 503 Service Unavailable, or longer for other
+		// errors.
+		F64 retry_timestamp = errorRetryTimestamp(status);
+
+		// *NOTE: "??" starts trigraphs in C/C++, escape the question marks.
+		const std::string DUMMY_NAME("\?\?\?");
+		LLAvatarName av_name;
+		av_name.mUsername = DUMMY_NAME;
+		av_name.mDisplayName = DUMMY_NAME;
+		av_name.mIsDisplayNameDefault = false;
+		av_name.mIsDummy = true;
+		av_name.mExpires = retry_timestamp;
+
+		// Add dummy records for all agent IDs in this request
+		std::vector<LLUUID>::const_iterator it = mAgentIDs.begin();
+		for ( ; it != mAgentIDs.end(); ++it)
+		{
+			const LLUUID& agent_id = *it;
+			// cache it and fire signals
+			LLAvatarNameCache::processName(agent_id, av_name, true);
+		}
+	}
+
+	// Return time to retry a request that generated an error, based on
+	// error type and headers.  Return value is seconds-since-epoch.
+	F64 errorRetryTimestamp(S32 status)
+	{
+		F64 now = LLFrameTimer::getTotalSeconds();
+
+		// Retry-After takes priority
+		LLSD retry_after = mHeaders["retry-after"];
+		if (retry_after.isDefined())
+		{
+			// We only support the delta-seconds type
+			S32 delta_seconds = retry_after.asInteger();
+			if (delta_seconds > 0)
+			{
+				// ...valid delta-seconds
+				return now + F64(delta_seconds);
+			}
+		}
+
+		// If no Retry-After, look for Cache-Control max-age
+		F64 expires = 0.0;
+		if (LLAvatarNameCache::expirationFromCacheControl(mHeaders, &expires))
+		{
+			return expires;
+		}
+
+		// No information in header, make a guess
+		if (status == 503)
+		{
+			// ...service unavailable, retry soon
+			const F64 SERVICE_UNAVAILABLE_DELAY = 600.0; // 10 min
+			return now + SERVICE_UNAVAILABLE_DELAY;
+		}
+		else
+		{
+			// ...other unexpected error
+			const F64 DEFAULT_DELAY = 3600.0; // 1 hour
+			return now + DEFAULT_DELAY;
+		}
+	}
+};
+
+void LLAvatarNameCache::processName(const LLUUID& agent_id,
+									const LLAvatarName& av_name,
+									bool add_to_cache)
+{
+	if (add_to_cache)
+	{
+		sCache[agent_id] = av_name;
+	}
+
+	sPendingQueue.erase(agent_id);
+
+	// signal everyone waiting on this name
+	signal_map_t::iterator sig_it =	sSignalMap.find(agent_id);
+	if (sig_it != sSignalMap.end())
+	{
+		callback_signal_t* signal = sig_it->second;
+		(*signal)(agent_id, av_name);
+
+		sSignalMap.erase(agent_id);
+
+		delete signal;
+		signal = NULL;
+	}
+}
+
+void LLAvatarNameCache::requestNamesViaCapability()
+{
+	F64 now = LLFrameTimer::getTotalSeconds();
+
+	// URL format is like:
+	// http://pdp60.lindenlab.com:8000/agents/?ids=3941037e-78ab-45f0-b421-bd6e77c1804d&ids=0012809d-7d2d-4c24-9609-af1230a37715&ids=0019aaba-24af-4f0a-aa72-6457953cf7f0
+	//
+	// Apache can handle URLs of 4096 chars, but let's be conservative
+	const U32 NAME_URL_MAX = 4096;
+	const U32 NAME_URL_SEND_THRESHOLD = 3000;
+	std::string url;
+	url.reserve(NAME_URL_MAX);
+
+	std::vector<LLUUID> agent_ids;
+	agent_ids.reserve(128);
+	
+	ask_queue_t::const_iterator it = sAskQueue.begin();
+	for ( ; it != sAskQueue.end(); ++it)
+	{
+		const LLUUID& agent_id = *it;
+
+		if (url.empty())
+		{
+			// ...starting new request
+			url += sNameLookupURL;
+			url += "?ids=";
+		}
+		else
+		{
+			// ...continuing existing request
+			url += "&ids=";
+		}
+		url += agent_id.asString();
+		agent_ids.push_back(agent_id);
+
+		// mark request as pending
+		sPendingQueue[agent_id] = now;
+
+		if (url.size() > NAME_URL_SEND_THRESHOLD)
+		{
+			//llinfos << "requestNames " << url << llendl;
+			LLHTTPClient::get(url, new LLAvatarNameResponder(agent_ids));
+			url.clear();
+			agent_ids.clear();
+		}
+	}
+
+	if (!url.empty())
+	{
+		//llinfos << "requestNames " << url << llendl;
+		LLHTTPClient::get(url, new LLAvatarNameResponder(agent_ids));
+		url.clear();
+		agent_ids.clear();
+	}
+
+	// We've moved all asks to the pending request queue
+	sAskQueue.clear();
+}
+
+void LLAvatarNameCache::legacyNameCallback(const LLUUID& agent_id,
+										   const std::string& full_name,
+										   bool is_group)
+{
+	// Construct a dummy record for this name.  By convention, SLID is blank
+	// Never expires, but not written to disk, so lasts until end of session.
+	LLAvatarName av_name;
+	buildLegacyName(full_name, &av_name);
+
+	// Don't add to cache, the data already exists in the legacy name system
+	// cache and we don't want or need duplicate storage, because keeping the
+	// two copies in sync is complex.
+	processName(agent_id, av_name, false);
+}
+
+void LLAvatarNameCache::requestNamesViaLegacy()
+{
+	F64 now = LLFrameTimer::getTotalSeconds();
+	std::string full_name;
+	ask_queue_t::const_iterator it = sAskQueue.begin();
+	for (; it != sAskQueue.end(); ++it)
+	{
+		const LLUUID& agent_id = *it;
+
+		// Mark as pending first, just in case the callback is immediately
+		// invoked below.  This should never happen in practice.
+		sPendingQueue[agent_id] = now;
+
+		gCacheName->get(agent_id, false,  // legacy compatibility
+			boost::bind(&LLAvatarNameCache::legacyNameCallback,
+				_1, _2, _3));
+	}
+
+	// We've either answered immediately or moved all asks to the
+	// pending queue
+	sAskQueue.clear();
+}
+
+void LLAvatarNameCache::initClass(bool running)
+{
+	sRunning = running;
+}
+
+void LLAvatarNameCache::cleanupClass()
+{
+}
+
+void LLAvatarNameCache::importFile(std::istream& istr)
+{
+	LLSD data;
+	S32 parse_count = LLSDSerialize::fromXMLDocument(data, istr);
+	if (parse_count < 1) return;
+
+	// by convention LLSD storage is a map
+	// we only store one entry in the map
+	LLSD agents = data["agents"];
+
+	LLUUID agent_id;
+	LLAvatarName av_name;
+	LLSD::map_const_iterator it = agents.beginMap();
+	for ( ; it != agents.endMap(); ++it)
+	{
+		agent_id.set(it->first);
+		av_name.fromLLSD( it->second );
+		sCache[agent_id] = av_name;
+	}
+	// entries may have expired since we last ran the viewer, just
+	// clean them out now
+	eraseExpired();
+	llinfos << "loaded " << sCache.size() << llendl;
+}
+
+void LLAvatarNameCache::exportFile(std::ostream& ostr)
+{
+	LLSD agents;
+	cache_t::const_iterator it = sCache.begin();
+	for ( ; it != sCache.end(); ++it)
+	{
+		const LLUUID& agent_id = it->first;
+		const LLAvatarName& av_name = it->second;
+		if (!av_name.mIsDummy)
+		{
+			// key must be a string
+			agents[agent_id.asString()] = av_name.asLLSD();
+		}
+	}
+	LLSD data;
+	data["agents"] = agents;
+	LLSDSerialize::toPrettyXML(data, ostr);
+}
+
+void LLAvatarNameCache::setNameLookupURL(const std::string& name_lookup_url)
+{
+	sNameLookupURL = name_lookup_url;
+}
+
+bool LLAvatarNameCache::hasNameLookupURL()
+{
+	return !sNameLookupURL.empty();
+}
+
+void LLAvatarNameCache::idle()
+{
+	// By convention, start running at first idle() call
+	sRunning = true;
+
+	// *TODO: Possibly re-enabled this based on People API load measurements
+	// 100 ms is the threshold for "user speed" operations, so we can
+	// stall for about that long to batch up requests.
+	//const F32 SECS_BETWEEN_REQUESTS = 0.1f;
+	//if (!sRequestTimer.checkExpirationAndReset(SECS_BETWEEN_REQUESTS))
+	//{
+	//	return;
+	//}
+
+	// Must be large relative to above
+
+	// No longer deleting expired entries, just re-requesting in the get
+	// this way first synchronous get call on an expired entry won't return
+	// legacy name.  LF
+
+	//const F32 ERASE_EXPIRED_TIMEOUT = 60.f; // seconds
+	//if (sEraseExpiredTimer.checkExpirationAndReset(ERASE_EXPIRED_TIMEOUT))
+	//{
+	//	eraseExpired();
+	//}
+
+	if (sAskQueue.empty())
+	{
+		return;
+	}
+
+	if (useDisplayNames())
+	{
+		requestNamesViaCapability();
+	}
+	else
+	{
+		// ...fall back to legacy name cache system
+		requestNamesViaLegacy();
+	}
+}
+
+bool LLAvatarNameCache::isRequestPending(const LLUUID& agent_id)
+{
+	const F64 PENDING_TIMEOUT_SECS = 5.0 * 60.0;
+	F64 now = LLFrameTimer::getTotalSeconds();
+	F64 expire_time = now - PENDING_TIMEOUT_SECS;
+
+	pending_queue_t::const_iterator it = sPendingQueue.find(agent_id);
+	if (it != sPendingQueue.end())
+	{
+		bool request_expired = (it->second < expire_time);
+		return !request_expired;
+	}
+	return false;
+}
+
+void LLAvatarNameCache::eraseExpired()
+{
+	F64 now = LLFrameTimer::getTotalSeconds();
+	cache_t::iterator it = sCache.begin();
+	while (it != sCache.end())
+	{
+		cache_t::iterator cur = it;
+		++it;
+		const LLAvatarName& av_name = cur->second;
+		if (av_name.mExpires < now)
+		{
+			sCache.erase(cur);
+		}
+	}
+}
+
+void LLAvatarNameCache::buildLegacyName(const std::string& full_name,
+										LLAvatarName* av_name)
+{
+	llassert(av_name);
+	av_name->mUsername = "";
+	av_name->mDisplayName = full_name;
+	av_name->mIsDisplayNameDefault = true;
+	av_name->mIsDummy = true;
+	av_name->mExpires = F64_MAX;
+}
+
+// fills in av_name if it has it in the cache, even if expired (can check expiry time)
+// returns bool specifying  if av_name was filled, false otherwise
+bool LLAvatarNameCache::get(const LLUUID& agent_id, LLAvatarName *av_name)
+{
+	if (sRunning)
+	{
+		// ...only do immediate lookups when cache is running
+		if (useDisplayNames())
+		{
+			// ...use display names cache
+			std::map<LLUUID,LLAvatarName>::iterator it = sCache.find(agent_id);
+			if (it != sCache.end())
+			{
+				*av_name = it->second;
+
+				// re-request name if entry is expired
+				if (av_name->mExpires < LLFrameTimer::getTotalSeconds())
+				{
+					if (!isRequestPending(agent_id))
+					{
+						sAskQueue.insert(agent_id);
+					}
+				}
+				
+				return true;
+			}
+		}
+		else
+		{
+			// ...use legacy names cache
+			std::string full_name;
+			if (gCacheName->getFullName(agent_id, full_name))
+			{
+				buildLegacyName(full_name, av_name);
+				return true;
+			}
+		}
+	}
+
+	if (!isRequestPending(agent_id))
+	{
+		sAskQueue.insert(agent_id);
+	}
+
+	return false;
+}
+
+void LLAvatarNameCache::fireSignal(const LLUUID& agent_id,
+								   const callback_slot_t& slot,
+								   const LLAvatarName& av_name)
+{
+	callback_signal_t signal;
+	signal.connect(slot);
+	signal(agent_id, av_name);
+}
+
+void LLAvatarNameCache::get(const LLUUID& agent_id, callback_slot_t slot)
+{
+	if (sRunning)
+	{
+		// ...only do immediate lookups when cache is running
+		if (useDisplayNames())
+		{
+			// ...use new cache
+			std::map<LLUUID,LLAvatarName>::iterator it = sCache.find(agent_id);
+			if (it != sCache.end())
+			{
+				const LLAvatarName& av_name = it->second;
+				
+				if (av_name.mExpires > LLFrameTimer::getTotalSeconds())
+				{
+					// ...name already exists in cache, fire callback now
+					fireSignal(agent_id, slot, av_name);
+
+					return;
+				}
+			}
+		}
+		else
+		{
+			// ...use old name system
+			std::string full_name;
+			if (gCacheName->getFullName(agent_id, full_name))
+			{
+				LLAvatarName av_name;
+				buildLegacyName(full_name, &av_name);
+				fireSignal(agent_id, slot, av_name);
+				return;
+			}
+		}
+	}
+
+	// schedule a request
+	if (!isRequestPending(agent_id))
+	{
+		sAskQueue.insert(agent_id);
+	}
+
+	// always store additional callback, even if request is pending
+	signal_map_t::iterator sig_it = sSignalMap.find(agent_id);
+	if (sig_it == sSignalMap.end())
+	{
+		// ...new callback for this id
+		callback_signal_t* signal = new callback_signal_t();
+		signal->connect(slot);
+		sSignalMap[agent_id] = signal;
+	}
+	else
+	{
+		// ...existing callback, bind additional slot
+		callback_signal_t* signal = sig_it->second;
+		signal->connect(slot);
+	}
+}
+
+
+void LLAvatarNameCache::setUseDisplayNames(bool use)
+{
+	if (use != sUseDisplayNames)
+	{
+		sUseDisplayNames = use;
+		// flush our cache
+		sCache.clear();
+
+		mUseDisplayNamesSignal();
+	}
+}
+
+bool LLAvatarNameCache::useDisplayNames()
+{
+	// Must be both manually set on and able to look up names.
+	return sUseDisplayNames && !sNameLookupURL.empty();
+}
+
+void LLAvatarNameCache::erase(const LLUUID& agent_id)
+{
+	sCache.erase(agent_id);
+}
+
+void LLAvatarNameCache::fetch(const LLUUID& agent_id)
+{
+	// re-request, even if request is already pending
+	sAskQueue.insert(agent_id);
+}
+
+void LLAvatarNameCache::insert(const LLUUID& agent_id, const LLAvatarName& av_name)
+{
+	// *TODO: update timestamp if zero?
+	sCache[agent_id] = av_name;
+}
+
+F64 LLAvatarNameCache::nameExpirationFromHeaders(LLSD headers)
+{
+	F64 expires = 0.0;
+	if (expirationFromCacheControl(headers, &expires))
+	{
+		return expires;
+	}
+	else
+	{
+		// With no expiration info, default to an hour
+		const F64 DEFAULT_EXPIRES = 60.0 * 60.0;
+		F64 now = LLFrameTimer::getTotalSeconds();
+		return now + DEFAULT_EXPIRES;
+	}
+}
+
+bool LLAvatarNameCache::expirationFromCacheControl(LLSD headers, F64 *expires)
+{
+	// Allow the header to override the default
+	LLSD cache_control_header = headers["cache-control"];
+	if (cache_control_header.isDefined())
+	{
+		S32 max_age = 0;
+		std::string cache_control = cache_control_header.asString();
+		if (max_age_from_cache_control(cache_control, &max_age))
+		{
+			F64 now = LLFrameTimer::getTotalSeconds();
+			*expires = now + (F64)max_age;
+			return true;
+		}
+	}
+	return false;
+}
+
+
+void LLAvatarNameCache::addUseDisplayNamesCallback(const use_display_name_signal_t::slot_type& cb) 
+{ 
+	mUseDisplayNamesSignal.connect(cb); 
+}
+
+
+static const std::string MAX_AGE("max-age");
+static const boost::char_separator<char> EQUALS_SEPARATOR("=");
+static const boost::char_separator<char> COMMA_SEPARATOR(",");
+
+bool max_age_from_cache_control(const std::string& cache_control, S32 *max_age)
+{
+	// Split the string on "," to get a list of directives
+	typedef boost::tokenizer<boost::char_separator<char> > tokenizer;
+	tokenizer directives(cache_control, COMMA_SEPARATOR);
+
+	tokenizer::iterator token_it = directives.begin();
+	for ( ; token_it != directives.end(); ++token_it)
+	{
+		// Tokens may have leading or trailing whitespace
+		std::string token = *token_it;
+		LLStringUtil::trim(token);
+
+		if (token.compare(0, MAX_AGE.size(), MAX_AGE) == 0)
+		{
+			// ...this token starts with max-age, so let's chop it up by "="
+			tokenizer subtokens(token, EQUALS_SEPARATOR);
+			tokenizer::iterator subtoken_it = subtokens.begin();
+
+			// Must have a token
+			if (subtoken_it == subtokens.end()) return false;
+			std::string subtoken = *subtoken_it;
+
+			// Must exactly equal "max-age"
+			LLStringUtil::trim(subtoken);
+			if (subtoken != MAX_AGE) return false;
+
+			// Must have another token
+			++subtoken_it;
+			if (subtoken_it == subtokens.end()) return false;
+			subtoken = *subtoken_it;
+
+			// Must be a valid integer
+			// *NOTE: atoi() returns 0 for invalid values, so we have to
+			// check the string first.
+			// *TODO: Do servers ever send "0000" for zero?  We don't handle it
+			LLStringUtil::trim(subtoken);
+			if (subtoken == "0")
+			{
+				*max_age = 0;
+				return true;
+			}
+			S32 val = atoi( subtoken.c_str() );
+			if (val > 0 && val < S32_MAX)
+			{
+				*max_age = val;
+				return true;
+			}
+			return false;
+		}
+	}
+	return false;
+}
+