Add C API for streaming HLG decoding (#734)

scripts/dotnet/examples/streaming-hlg-decoding.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>streaming_hlg_decoding</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <RestoreSources>/tmp/packages;$(RestoreSources);https://api.nuget.org/v3/index.json</RestoreSources>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="org.k2fsa.sherpa.onnx" Version="*" />
+  </ItemGroup>
+
+</Project>

scripts/dotnet/online.cs

@@ -116,6 +116,21 @@ namespace SherpaOnnx
     public int FeatureDim;
   }
 
+  [StructLayout(LayoutKind.Sequential)]
+  public struct OnlineCtcFstDecoderConfig
+  {
+    public OnlineCtcFstDecoderConfig()
+    {
+      Graph = "";
+      MaxActive = 3000;
+    }
+
+    [MarshalAs(UnmanagedType.LPStr)]
+    public string Graph;
+
+    public int MaxActive;
+  }
+
   [StructLayout(LayoutKind.Sequential)]
   public struct OnlineRecognizerConfig
   {
@@ -131,6 +146,7 @@ namespace SherpaOnnx
       Rule3MinUtteranceLength = 20.0F;
       HotwordsFile = "";
       HotwordsScore = 1.5F;
+      CtcFstDecoderConfig = new OnlineCtcFstDecoderConfig();
     }
     public FeatureConfig FeatConfig;
     public OnlineModelConfig ModelConfig;
@@ -167,6 +183,8 @@ namespace SherpaOnnx
 
     /// Bonus score for each token in hotwords.
     public float HotwordsScore;
+
+    public OnlineCtcFstDecoderConfig CtcFstDecoderConfig;
   }
 
   public class OnlineRecognizerResult