Add keyword spotting for C# (#1105)

scripts/dotnet/.gitignore

@@ -1,8 +1,10 @@
 all
 macos-arm64
 macos-x64
-linux
-windows
+linux-x64
+linux-arm64
+windows-arm64
 windows-x64
 windows-x86
 packages
+tmp

scripts/dotnet/KeywordResult.cs

@@ -0,0 +1,44 @@
+/// Copyright (c)  2024  Xiaomi Corporation
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace SherpaOnnx
+{
+    public class KeywordResult
+    {
+        public KeywordResult(IntPtr handle)
+        {
+            Impl impl = (Impl)Marshal.PtrToStructure(handle, typeof(Impl));
+
+            // PtrToStringUTF8() requires .net standard 2.1
+            // _keyword = Marshal.PtrToStringUTF8(impl.Keyword);
+
+            int length = 0;
+
+            unsafe
+            {
+                byte* buffer = (byte*)impl.Keyword;
+                while (*buffer != 0)
+                {
+                    ++buffer;
+                    length += 1;
+                }
+            }
+
+            byte[] stringBuffer = new byte[length];
+            Marshal.Copy(impl.Keyword, stringBuffer, 0, length);
+            _keyword = Encoding.UTF8.GetString(stringBuffer);
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        struct Impl
+        {
+            public IntPtr Keyword;
+        }
+
+        private String _keyword;
+        public String Keyword => _keyword;
+    }
+}

scripts/dotnet/KeywordSpotter.cs

@@ -0,0 +1,119 @@
+/// Copyright (c)  2024  Xiaomi Corporation (authors: Fangjun Kuang)
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace SherpaOnnx
+{
+    // please see
+    // https://www.mono-project.com/docs/advanced/pinvoke/#gc-safe-pinvoke-code
+    // https://www.mono-project.com/docs/advanced/pinvoke/#properly-disposing-of-resources
+    public class KeywordSpotter : IDisposable
+    {
+        public KeywordSpotter(KeywordSpotterConfig config)
+        {
+            IntPtr h = CreateKeywordSpotter(ref config);
+            _handle = new HandleRef(this, h);
+        }
+
+        public OnlineStream CreateStream()
+        {
+            IntPtr p = CreateKeywordStream(_handle.Handle);
+            return new OnlineStream(p);
+        }
+
+        public OnlineStream CreateStream(string keywords)
+        {
+            byte[] utf8Bytes = Encoding.UTF8.GetBytes(keywords);
+            IntPtr p = CreateKeywordStreamWithKeywords(_handle.Handle, utf8Bytes);
+            return new OnlineStream(p);
+        }
+
+        /// Return true if the passed stream is ready for decoding.
+        public bool IsReady(OnlineStream stream)
+        {
+            return IsReady(_handle.Handle, stream.Handle) != 0;
+        }
+
+        /// You have to ensure that IsReady(stream) returns true before
+        /// you call this method
+        public void Decode(OnlineStream stream)
+        {
+            Decode(_handle.Handle, stream.Handle);
+        }
+
+        // The caller should ensure all passed streams are ready for decoding.
+        public void Decode(IEnumerable<OnlineStream> streams)
+        {
+            // TargetFramework=net20 does not support System.Linq
+            // IntPtr[] ptrs = streams.Select(s => s.Handle).ToArray();
+            List<IntPtr> list = new List<IntPtr>();
+            foreach (OnlineStream s in streams)
+            {
+              list.Add(s.Handle);
+            }
+
+            IntPtr[] ptrs = list.ToArray();
+            Decode(_handle.Handle, ptrs, ptrs.Length);
+        }
+
+        public KeywordResult GetResult(OnlineStream stream)
+        {
+            IntPtr h = GetResult(_handle.Handle, stream.Handle);
+            KeywordResult result = new KeywordResult(h);
+            DestroyResult(h);
+            return result;
+        }
+
+        public void Dispose()
+        {
+            Cleanup();
+            // Prevent the object from being placed on the
+            // finalization queue
+            System.GC.SuppressFinalize(this);
+        }
+
+        ~KeywordSpotter()
+        {
+            Cleanup();
+        }
+
+        private void Cleanup()
+        {
+            DestroyKeywordSpotter(_handle.Handle);
+
+            // Don't permit the handle to be used again.
+            _handle = new HandleRef(this, IntPtr.Zero);
+        }
+
+        private HandleRef _handle;
+
+        [DllImport(Dll.Filename)]
+        private static extern IntPtr CreateKeywordSpotter(ref KeywordSpotterConfig config);
+
+        [DllImport(Dll.Filename)]
+        private static extern void DestroyKeywordSpotter(IntPtr handle);
+
+        [DllImport(Dll.Filename)]
+        private static extern IntPtr CreateKeywordStream(IntPtr handle);
+
+        [DllImport(Dll.Filename)]
+        private static extern IntPtr CreateKeywordStreamWithKeywords(IntPtr handle, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.I1)] byte[] utf8Keywords);
+
+        [DllImport(Dll.Filename, EntryPoint = "IsKeywordStreamReady")]
+        private static extern int IsReady(IntPtr handle, IntPtr stream);
+
+        [DllImport(Dll.Filename, EntryPoint = "DecodeKeywordStream")]
+        private static extern void Decode(IntPtr handle, IntPtr stream);
+
+        [DllImport(Dll.Filename, EntryPoint = "DecodeMultipleKeywordStreams")]
+        private static extern void Decode(IntPtr handle, IntPtr[] streams, int n);
+
+        [DllImport(Dll.Filename, EntryPoint = "GetKeywordResult")]
+        private static extern IntPtr GetResult(IntPtr handle, IntPtr stream);
+
+        [DllImport(Dll.Filename, EntryPoint = "DestroyKeywordResult")]
+        private static extern void DestroyResult(IntPtr result);
+    }
+}

scripts/dotnet/KeywordSpotterConfig.cs

@@ -0,0 +1,32 @@
+/// Copyright (c)  2024  Xiaomi Corporation
+
+using System.Runtime.InteropServices;
+
+namespace SherpaOnnx
+{
+    [StructLayout(LayoutKind.Sequential)]
+    public struct KeywordSpotterConfig
+    {
+        public KeywordSpotterConfig()
+        {
+            FeatConfig = new FeatureConfig();
+            ModelConfig = new OnlineModelConfig();
+
+            MaxActivePaths = 4;
+            NumTrailingBlanks = 1;
+            KeywordsScore = 1.0F;
+            KeywordsThreshold = 0.25F;
+            KeywordsFile = "";
+        }
+        public FeatureConfig FeatConfig;
+        public OnlineModelConfig ModelConfig;
+
+        public int MaxActivePaths;
+        public int NumTrailingBlanks;
+        public float KeywordsScore;
+        public float KeywordsThreshold;
+
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string KeywordsFile;
+    }
+}