Rewrite ignores to fix data race, use fewer maps

internal/ignore/cache.go

@@ -0,0 +1,95 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program 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 General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package ignore
+
+import (
+	"sync"
+	"time"
+)
+
+var (
+	caches   = make(map[string]*cache)
+	cacheMut sync.Mutex
+)
+
+func init() {
+	// Periodically go through the cache and remove cache entries that have
+	// not been touched in the last two hours.
+	go cleanIgnoreCaches(2 * time.Hour)
+}
+
+type cache struct {
+	patterns []Pattern
+	entries  map[string]cacheEntry
+	mut      sync.Mutex
+}
+
+type cacheEntry struct {
+	value  bool
+	access time.Time
+}
+
+func newCache(patterns []Pattern) *cache {
+	return &cache{
+		patterns: patterns,
+		entries:  make(map[string]cacheEntry),
+	}
+}
+
+func (c *cache) clean(d time.Duration) {
+	c.mut.Lock()
+	for k, v := range c.entries {
+		if time.Since(v.access) > d {
+			delete(c.entries, k)
+		}
+	}
+	c.mut.Unlock()
+}
+
+func (c *cache) get(key string) (result, ok bool) {
+	c.mut.Lock()
+	res, ok := c.entries[key]
+	if ok {
+		res.access = time.Now()
+		c.entries[key] = res
+	}
+	c.mut.Unlock()
+	return res.value, ok
+}
+
+func (c *cache) set(key string, val bool) {
+	c.mut.Lock()
+	c.entries[key] = cacheEntry{val, time.Now()}
+	c.mut.Unlock()
+}
+
+func (c *cache) len() int {
+	c.mut.Lock()
+	l := len(c.entries)
+	c.mut.Unlock()
+	return l
+}
+
+func cleanIgnoreCaches(dur time.Duration) {
+	for {
+		time.Sleep(dur)
+		cacheMut.Lock()
+		for _, v := range caches {
+			v.clean(dur)
+		}
+		cacheMut.Unlock()
+	}
+}