rpc, whisper, xeth: polish whisper RPC interface

xeth/whisper_filter.go

@@ -0,0 +1,26 @@
+// Contains the external API side message filter for watching, pooling and polling
+// matched whisper messages.
+
+package xeth
+
+import "time"
+
+// whisperFilter is the message cache matching a specific filter, accumulating
+// inbound messages until the are requested by the client.
+type whisperFilter struct {
+	id      int              // Filter identifier
+	cache   []WhisperMessage // Cache of messages not yet polled
+	timeout time.Time        // Time when the last message batch was queries
+}
+
+// insert injects a new batch of messages into the filter cache.
+func (w *whisperFilter) insert(msgs ...WhisperMessage) {
+	w.cache = append(w.cache, msgs...)
+}
+
+// retrieve fetches all the cached messages from the filter.
+func (w *whisperFilter) retrieve() (messages []WhisperMessage) {
+	messages, w.cache = w.cache, nil
+	w.timeout = time.Now()
+	return
+}