From: Ben Burwell <ben@benburwell.com>
To: ~sircmpwn/aerc@lists.sr.ht
Cc: Ben Burwell <ben@benburwell.com>
Subject: [PATCH v2 1/5] Create UIDStore package
Date: Thu, 11 Jul 2019 09:44:50 -0400
Message-Id: <20190711134454.80318-2-ben@benburwell.com>
In-Reply-To: <20190711134454.80318-1-ben@benburwell.com>
References: <20190711134454.80318-1-ben@benburwell.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable

This package can be used to provide a source for mapping mock UIDs back
to relevant keys for alternate backends. For example, for the Maildir
backend, we need to map between UID and message file names.
---
 lib/uidstore/uidstore.go | 62 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 lib/uidstore/uidstore.go

diff --git a/lib/uidstore/uidstore.go b/lib/uidstore/uidstore.go
new file mode 100644
index 0000000..11c5e47
--- /dev/null
+++ b/lib/uidstore/uidstore.go
@@ -0,0 +1,62 @@
+// Package uidstore provides a concurrency-safe two-way mapping between =
UIDs
+// used by the UI and arbitrary string keys as used by different mail ba=
ckends.
+//
+// Multiple Store instances can safely be created and the UIDs that they
+// generate will be globally unique.
+package uidstore
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+var nextUID uint32 =3D 1
+
+// Store holds a mapping between application keys and globally-unique UI=
Ds.
+type Store struct {
+	keyByUID map[uint32]string
+	uidByKey map[string]uint32
+	m        sync.Mutex
+}
+
+// NewStore creates a new, empty Store.
+func NewStore() *Store {
+	return &Store{
+		keyByUID: make(map[uint32]string),
+		uidByKey: make(map[string]uint32),
+	}
+}
+
+// GetOrInsert returns the UID for the provided key. If the key was alre=
ady
+// present in the store, the same UID value is returned. Otherwise, the =
key is
+// inserted and the newly generated UID is returned.
+func (s *Store) GetOrInsert(key string) uint32 {
+	s.m.Lock()
+	defer s.m.Unlock()
+	if uid, ok :=3D s.uidByKey[key]; ok {
+		return uid
+	}
+	uid :=3D atomic.AddUint32(&nextUID, 1)
+	s.keyByUID[uid] =3D key
+	s.uidByKey[key] =3D uid
+	return uid
+}
+
+// GetKey returns the key for the provided UID, if available.
+func (s *Store) GetKey(uid uint32) (string, bool) {
+	s.m.Lock()
+	defer s.m.Unlock()
+	key, ok :=3D s.keyByUID[uid]
+	return key, ok
+}
+
+// RemoveUID removes the specified UID from the store.
+func (s *Store) RemoveUID(uid uint32) {
+	s.m.Lock()
+	defer s.m.Unlock()
+	key, ok :=3D s.keyByUID[uid]
+	if ok {
+		delete(s.uidByKey, key)
+	}
+	delete(s.keyByUID, uid)
+}
--=20
2.22.0