refactor and cleanup [skip ci]

submodules/Postbox/Sources/MessageHistoryUnsentTable.swift

@@ -0,0 +1,57 @@
+import Foundation
+
+enum IntermediateMessageHistoryUnsentOperation {
+    case Insert(MessageId)
+    case Remove(MessageId)
+}
+
+final class MessageHistoryUnsentTable: Table {
+    static func tableSpec(_ id: Int32) -> ValueBoxTable {
+        return ValueBoxTable(id: id, keyType: .binary, compactValuesOnCreation: true)
+    }
+    
+    private let sharedKey = ValueBoxKey(length: 4 + 4 + 8)
+    
+    private func key(_ id: MessageId) -> ValueBoxKey {
+        self.sharedKey.setInt32(0, value: id.namespace)
+        self.sharedKey.setInt32(4, value: id.id)
+        self.sharedKey.setInt64(4 + 4, value: id.peerId.toInt64())
+        
+        return self.sharedKey
+    }
+    
+    private func lowerBound() -> ValueBoxKey {
+        let key = ValueBoxKey(length: 1)
+        key.setInt8(0, value: 0)
+        return key
+    }
+    
+    private func upperBound() -> ValueBoxKey {
+        let key = ValueBoxKey(length: 4 + 4 + 8)
+        memset(key.memory, 0xff, key.length)
+        return key
+    }
+    
+    func add(_ id: MessageId, operations: inout [IntermediateMessageHistoryUnsentOperation]) {
+        self.valueBox.set(self.table, key: self.key(id), value: MemoryBuffer())
+        operations.append(.Insert(id))
+    }
+    
+    func remove(_ id: MessageId, operations: inout [IntermediateMessageHistoryUnsentOperation]) {
+        self.valueBox.remove(self.table, key: self.key(id), secure: false)
+        operations.append(.Remove(id))
+    }
+    
+    func get() -> [MessageId] {
+        var ids: [MessageId] = []
+        self.valueBox.range(self.table, start: self.lowerBound(), end: self.upperBound(), keys: { key in
+            ids.append(MessageId(peerId: PeerId(key.getInt64(4 + 4)), namespace: key.getInt32(0), id: key.getInt32(4)))
+            return true
+        }, limit: 0)
+        return ids
+    }
+    
+    override func beforeCommit() {
+        
+    }
+}