Add IntPtrExtension

To manage PtrToString conversions

Author: SignalRT

LLama/Extensions/IModelParamsExtensions.cs

@@ -115,7 +115,7 @@ private static IReadOnlyDictionary<string, IntPtr> GetAvailableBufferTypes()
             var dev = NativeApi.ggml_backend_dev_get(i);
             var buft = NativeApi.ggml_backend_dev_buffer_type(dev);
 
-            var name = Marshal.PtrToStringAnsi(NativeApi.ggml_backend_buft_name(buft));
+            var name = NativeApi.ggml_backend_buft_name(buft).PtrToString();
             if (string.IsNullOrEmpty(name))
                 continue;
 
@@ -165,4 +165,4 @@ private static IReadOnlyDictionary<string, IntPtr> GetAvailableBufferTypes()
 
         return (LLamaModelTensorBufferOverride*)overrideArrayPin.Pointer;
     }
-}
+}

LLama/Extensions/IntPtrExtensions.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace LLama.Extensions;
+
+public static class IntPtrExtensions
+{
+
+    /// <summary>
+    /// Converts a native UTF-8 string pointer to a managed string, returning a fallback value when no data is available.
+    /// </summary>
+    /// <param name="ptr">Pointer to a null-terminated UTF-8 string.</param>
+    /// <param name="defaultValue">Value to return when the pointer is <see cref="IntPtr.Zero"/> or when the string is empty.</param>
+    /// <returns>Managed string representation of the native data, or <paramref name="defaultValue"/> when unavailable.</returns>
+    public static string PtrToStringWithDefault(this IntPtr ptr, string defaultValue="")
+    {
+        return ptr.PtrToString() ?? defaultValue;
+    }
+
+    /// <summary>
+    /// Converts a pointer to a null-terminated UTF-8 string into a managed string.
+    /// </summary>
+    /// <param name="ptr">Pointer to the first byte of a null-terminated UTF-8 string.</param>
+    /// <returns>Managed string representation, or <c>null</c> when the pointer is zero or the string is empty.</returns>
+    public static string? PtrToString(this IntPtr ptr )
+    {
+        if (ptr == IntPtr.Zero)
+            return null;
+
+#if NETSTANDARD2_0
+        unsafe
+        {
+            var length = 0;
+            var current = (byte*)ptr;
+            while (current[length] != 0)
+                length++;
+
+            if (length == 0)
+                return null;
+
+            var buffer = new byte[length];
+            Marshal.Copy(ptr, buffer, 0, length);
+            return Encoding.UTF8.GetString(buffer);
+        }
+#else
+        return Marshal.PtrToStringUTF8(ptr);
+#endif
+    }        
+    
+}

LLama/Native/MtmdContextParams.cs

@@ -51,35 +51,11 @@ public static MtmdContextParams Default()
             PrintTimings = native.print_timings,
             NThreads = native.n_threads,
             Verbosity = native.verbosity,
-            ImageMarker = PtrToString(native.image_marker),
-            MediaMarker = PtrToString(native.media_marker)
+            ImageMarker = native.image_marker.PtrToString(),
+            MediaMarker = native.media_marker.PtrToString()
         };
     }
 
-    private static string? PtrToString(IntPtr ptr)
-    {
-        if (ptr == IntPtr.Zero)
-            return null;
-
-#if NETSTANDARD2_0
-        unsafe
-        {
-            var length = 0;
-            var current = (byte*)ptr;
-            while (current[length] != 0)
-                length++;
-
-            if (length == 0)
-                return string.Empty;
-
-            var buffer = new byte[length];
-            Marshal.Copy(ptr, buffer, 0, length);
-            return Encoding.UTF8.GetString(buffer);
-        }
-#else
-        return Marshal.PtrToStringUTF8(ptr);
-#endif
-    }
 
     /// <summary>
     /// Convert the managed representation to a native structure, pinning strings for the duration of the scope.

LLama/Native/NativeApi.Mtmd.cs

@@ -9,35 +9,7 @@ namespace LLama.Native;
 /// </summary>
 public static partial class NativeApi
 {
-    /// <summary>
-    /// Convert a UTF-8 encoded native string pointer into a managed <see cref="string"/>.
-    /// Returns <c>null</c> when the pointer is zero.
-    /// </summary>
-    public static string? PtrToStringUtf8(IntPtr ptr)
-    {
-        if (ptr == IntPtr.Zero)
-            return null;
-
-#if NETSTANDARD2_0
-        unsafe
-        {
-            var current = (byte*)ptr;
-            var length = 0;
-            while (current[length] != 0)
-                length++;
-
-            if (length == 0)
-                return string.Empty;
-
-            var buffer = new byte[length];
-            Marshal.Copy(ptr, buffer, 0, length);
-            return Encoding.UTF8.GetString(buffer);
-        }
-#else
-        return Marshal.PtrToStringUTF8(ptr);
-#endif
-    }
-
+    
     /// <summary>
     /// Native context parameters returned by <see cref="mtmd_context_params_default"/>.
     /// </summary>
@@ -59,7 +31,7 @@ internal struct mtmd_context_params
     /// Retrieve the default multimodal marker text.
     /// </summary>
     public static string? MtmdDefaultMarker()
-        => PtrToStringUtf8(mtmd_default_marker());
+        => mtmd_default_marker().PtrToString();
 
     [DllImport(mtmdLibraryName, EntryPoint = "mtmd_context_params_default", CallingConvention = CallingConvention.Cdecl)]
     internal static extern mtmd_context_params mtmd_context_params_default();

LLama/Native/SafeLLamaSamplerHandle.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Text;
+using LLama.Extensions;
 
 namespace LLama.Native;
 
@@ -119,7 +121,7 @@ public string GetName(int index)
         if (index < 0 || index >= Count)
             throw new ArgumentOutOfRangeException(nameof(index));
 
-        return Marshal.PtrToStringAnsi(llama_sampler_name(llama_sampler_chain_get(this, index))) ?? "Unknown Name";
+        return llama_sampler_name(llama_sampler_chain_get(this, index)).PtrToStringWithDefault("Unknown Name");
 
         [DllImport(NativeApi.libraryName, CallingConvention = CallingConvention.Cdecl)]
         static extern IntPtr llama_sampler_name(IntPtr smpl);
@@ -904,4 +906,4 @@ public interface ICustomSampler
     /// Create a clone of this sampler
     /// </summary>
     ICustomSampler Clone();
-}
+}

LLama/Native/SafeMtmdEmbed.cs

@@ -195,7 +195,7 @@ public string? Id
                 return WithHandle(ptr =>
                 {
                     var idPtr = NativeApi.mtmd_bitmap_get_id(ptr);
-                    return NativeApi.PtrToStringUtf8(idPtr);
+                    return idPtr.PtrToString();
                 });
             }
             set

LLama/Native/SafeMtmdInputChunk.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Runtime.InteropServices;
+using LLama.Extensions;
 
 namespace LLama.Native;
 
@@ -91,7 +91,7 @@ public string Id
             return WithHandle(ptr =>
             {
                 var idPtr = NativeApi.mtmd_input_chunk_get_id(ptr);
-                return Marshal.PtrToStringAnsi(idPtr) ?? string.Empty;
+                return idPtr.PtrToStringWithDefault(string.Empty);
             });
         }
     }