Merge pull request #17 from Dustify/issue-14

basic duplicate detection

Author: Dustify

Pocsag.Plugin/PocsagControl.cs

@@ -4,6 +4,7 @@
     using System;
     using System.ComponentModel;
     using System.Windows.Forms;
+    using System.Linq;
 
     public partial class PocsagControl : UserControl
     {
@@ -52,6 +53,12 @@ private void MessageReceived(Pocsag.Message message)
                     new Action<Pocsag.Message>(
                         (message) =>
                         {
+                            // skip duplicate messages
+                            if (this.bindingList.Any(x => x.Hash == message.Hash))
+                            {
+                                return;
+                            }
+
                             int firstDisplayed = this.dataGridView1.FirstDisplayedScrollingRowIndex;
                             int displayed = this.dataGridView1.DisplayedRowCount(true);
                             int lastVisible = (firstDisplayed + displayed) - 1;

Pocsag/Message.cs

@@ -1,10 +1,9 @@
 namespace Pocsag
 {
     using System;
-    using System.Linq;
-    using System.Collections.Generic;
     using System.Collections;
-    using System.Text;
+    using System.Collections.Generic;
+    using System.Linq;
 
     public class Message
     {
@@ -36,6 +35,8 @@ public class Message
 
         public bool IsValid => !this.HasBchError && !this.HasParityError;
 
+        public string Hash { get; private set; }
+
         public Message(int baud)
         {
             try
@@ -215,6 +216,26 @@ public void ProcessPayload()
                 }
 
                 this.Payload = result;
+
+                var textToHash = this.Payload;
+
+                // skip first 9 characters, typically contains time / date + another number which will mess up duplicate detection
+
+                if (textToHash.Length > 9)
+                {
+                    textToHash = textToHash.Substring(8);
+                }
+
+                var bytesToHash = System.Text.Encoding.ASCII.GetBytes(textToHash);
+
+                var sha256 = new System.Security.Cryptography.SHA256Managed();
+
+                var hashBytes = sha256.ComputeHash(bytesToHash);
+
+                sha256.Dispose();
+                sha256 = null;
+
+                this.Hash = BitConverter.ToString(hashBytes).Replace("-", "");
             }
             catch (Exception exception)
             {