Store shared private images by content hash

[onechat] / memory.go

diff --git a/memory.go b/memory.go
index c9fe1c567504c11f0a94be48fdb581298cde510c..a240b6c16d1d898e3051f3e0a0c7a19434061b3e 100644 (file)
--- a/memory.go
+++ b/memory.go
@@ -149,6 +149,11 @@ func (m *Memory) AppendDated(kind, text, date string) (Message, error) {
        m.mutex.Lock()
        defer m.mutex.Unlock()
 
+       return m.appendDated(kind, text, date)
+}
+
+// appendDated appends under the memory lock and updates the views and builds.
+func (m *Memory) appendDated(kind, text, date string) (Message, error) {
        message, err := m.log.AppendDated(kind, text, date)
        if err != nil {
                return Message{}, fmt.Errorf("append dated log message: %w", err)
@@ -172,6 +177,44 @@ func (m *Memory) AppendDated(kind, text, date string) (Message, error) {
        return message, nil
 }
 
+// AppendOnce appends a queued message. prepare saves its log ID before the
+// append, under the memory lock. A saved ID permits recovery after a stop
+// between that save and the append, without a second log entry. prepare must
+// not call Memory. The caller stops delivery after a failed append.
+func (m *Memory) AppendOnce(kind, text string, id *int, prepare func(int) error) (Message, error) {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       if id != nil && *id < m.log.Len() {
+               message, err := m.log.Message(*id)
+               if err != nil {
+                       return Message{}, fmt.Errorf("read queued message: %w", err)
+               }
+
+               if message.Kind != kind || message.Text != text {
+                       return Message{}, errors.New("queued message does not match its log entry")
+               }
+
+               return message, nil
+       }
+
+       if id != nil && *id != m.log.Len() {
+               return Message{}, errors.New("queued message is beyond the log")
+       }
+
+       err := prepare(m.log.Len())
+       if err != nil {
+               return Message{}, fmt.Errorf("prepare queued message: %w", err)
+       }
+
+       message, err := m.appendDated(kind, text, "")
+       if err != nil {
+               return Message{}, fmt.Errorf("append queued message: %w", err)
+       }
+
+       return message, nil
+}
+
 // children reads the two children of the node key.
 func (m *Memory) children(key NodeKey) (Node, Node, error) {
        var children [2]Node