Fix native collector subscription inventory and Unicode readback

modules/WecSubscriptionInventory.cs

@@ -0,0 +1,52 @@
+// Read-only WEC names, returned only after complete bounded native enumeration.
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+namespace Wela.WecInventory {
+ public static class Reader {
+  public const string SourceSha256="__WELA_SOURCE_SHA256__";
+  const uint Capacity=1024;
+  [DllImport("wecapi.dll",SetLastError=true)] static extern IntPtr EcOpenSubscriptionEnum(uint flags);
+  [DllImport("wecapi.dll",SetLastError=true)] [return:MarshalAs(UnmanagedType.Bool)] static extern bool EcEnumNextSubscription(IntPtr enumeration,uint size,IntPtr name,out uint used);
+  [DllImport("wecapi.dll",SetLastError=true)] [return:MarshalAs(UnmanagedType.Bool)] static extern bool EcClose(IntPtr handle);
+  // Public only for safe allocated-buffer ABI and boundary regression tests.
+  public static string DecodeName(IntPtr buffer,uint used,uint capacity) {
+   if(buffer==IntPtr.Zero||capacity<2||capacity>Capacity||used<2||used>capacity)throw new InvalidDataException("Invalid native subscription-name buffer.");
+   if(Marshal.ReadInt16(buffer,checked((int)(used-1)*2))!=0)throw new InvalidDataException("Native subscription name is not terminated.");
+   byte[] bytes=new byte[checked((int)(used-1)*2)];Marshal.Copy(buffer,bytes,0,bytes.Length);
+   string name=new UnicodeEncoding(false,false,true).GetString(bytes);
+   if(name.IndexOf('\0')>=0)throw new InvalidDataException("Native subscription name contains an embedded terminator.");
+   return name;
+  }
+  // Public so duplicate, count and aggregate bounds can be tested without Windows.
+  public static string[] ValidateNames(string[] names) {
+   if(names==null||names.Length>4096)throw new InvalidDataException("Native subscription inventory exceeds 4096 entries.");
+   var unique=new HashSet<string>(StringComparer.OrdinalIgnoreCase);long characters=0;
+   foreach(string name in names) {
+    if(String.IsNullOrEmpty(name)||name.Length>=Capacity||name.IndexOf('\0')>=0||!unique.Add(name))throw new InvalidDataException("Native subscription inventory contains an invalid or duplicate name.");
+    new UnicodeEncoding(false,false,true).GetBytes(name);
+    characters+=name.Length+1;if(characters>1048576)throw new InvalidDataException("Native subscription inventory exceeds its total character bound.");
+   }
+   string[] result=(string[])names.Clone();Array.Sort(result,StringComparer.Ordinal);return result;
+  }
+  public static string[] ReadNames() {
+   IntPtr handle=EcOpenSubscriptionEnum(0);if(handle==IntPtr.Zero)throw new Win32Exception(Marshal.GetLastWin32Error());
+   try {
+    IntPtr buffer=Marshal.AllocHGlobal(checked((int)Capacity*2));
+    try {
+     var names=new List<string>();long characters=0;
+     while(true) {
+      uint used;
+      if(!EcEnumNextSubscription(handle,Capacity,buffer,out used)) {int error=Marshal.GetLastWin32Error();if(error==259)return ValidateNames(names.ToArray());throw new Win32Exception(error);}
+      string name=DecodeName(buffer,used,Capacity);characters+=name.Length+1;
+      if(names.Count>=4096||characters>1048576)throw new InvalidDataException("Native subscription inventory exceeded its bounds; no absence is established.");
+      names.Add(name);
+     }
+    }finally {Marshal.FreeHGlobal(buffer);}
+   }finally {EcClose(handle);}
+  }
+ }
+}