[libhttpseverywhere] context: add a cache for most recent targets

[Daniel Brendle <elbren src gnome org>]

commit 0e8fb0742b4072ef344efaad7d65d32ba0ef2908
Author: grindhold <grindhold gmx net>
Date:   Mon Dec 12 17:39:48 2016 +0100

    context: add a cache for most recent targets
    
    pages that load many resources via https tend to generate
    many queries for the same target. by caching the results we
    can accellerate recurring queries to the same host approx 2k times.

 src/context.vala |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)
---
diff --git a/src/context.vala b/src/context.vala
index 29e2dbb..91a3a1d 100644
--- a/src/context.vala
+++ b/src/context.vala
@@ -39,6 +39,10 @@ namespace HTTPSEverywhere {
         private Gee.HashMap<Target, Gee.ArrayList<uint>> targets;
         private Gee.HashMap<uint, Ruleset> rulesets;
 
+        // Cache for recently used targets
+        private Gee.ArrayList<Target> cache;
+        private const int CACHE_SIZE = 20;
+
         /**
          * Indicates whether the library has been successfully
          * initialized. Be careful: this property will become //false//
@@ -81,6 +85,7 @@ namespace HTTPSEverywhere {
 
             targets = new Gee.HashMap<Target,Gee.ArrayList<uint>>();
             rulesets = new Gee.HashMap<int, Ruleset>();
+            cache = new Gee.ArrayList<Target>();
 
             var datapaths = new Gee.ArrayList<string>();
 
@@ -149,7 +154,8 @@ namespace HTTPSEverywhere {
                     p_url += "/";
             }
             Ruleset? rs = null;
-            foreach (Target target in targets.keys) {
+
+            foreach (Target target in this.cache) {
                 if (target.matches(p_url)) {
                     foreach (uint ruleset_id in targets.get(target)) {
                         if (!rulesets.has_key(ruleset_id))
@@ -159,6 +165,23 @@ namespace HTTPSEverywhere {
                     break;
                 }
             }
+
+            if (rs == null) {
+                foreach (Target target in targets.keys) {
+                    if (target.matches(p_url)) {
+                        foreach (uint ruleset_id in targets.get(target)) {
+                            if (!rulesets.has_key(ruleset_id))
+                                load_ruleset(ruleset_id);
+                            rs = rulesets.get(ruleset_id);
+                        }
+                        if (cache.size >= Context.CACHE_SIZE)
+                            cache.remove_at(Context.CACHE_SIZE-1);
+                        cache.add(target);
+                        break;
+                    }
+                }
+            }
+
             if (rs == null) {
                 last_rewrite_state = RewriteResult.NO_RULESET;
                 return p_url;