Improve C# string input performance

Encode input strings directly to UTF8 unmanaged memory instead of managed byte array.

Apply string typemap to `void* callback_data`

Author: Mbucari

swig/csharp/apps/GDALTestUtf8.cs

@@ -1,6 +1,7 @@
 using System;
 
 using OSGeo.GDAL;
+using OSGeo.OSR;
 
 namespace testapp
 {

swig/include/csharp/csharp_strings.i

@@ -101,17 +101,6 @@ static CSharpUtf8StringHelperCallback SWIG_csharp_string_callback = NULL;
 
     return unmanagedString;
   }
-  
-  public static byte[] StringToUtf8Bytes(string str)
-  {
-    if (str == null)
-      return null;
-
-    int bytecount = System.Text.Encoding.UTF8.GetByteCount(str);
-    byte[] bytes = new byte[bytecount + 1];
-    System.Text.Encoding.UTF8.GetBytes(str, 0, str.Length, bytes, 0);
-    return bytes;
-  }
 %}
 
 %insert(runtime) %{
@@ -129,18 +118,35 @@ SWIGEXPORT void SWIGSTDCALL RegisterUtf8StringCallback_$module(CSharpUtf8StringH
 
 /* Changing csin and imtype typemaps for string types defined by SWIG in csharp.swg */
 
-%typemap(imtype, out="IntPtr") (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) "byte[]"
+%typemap(cstype) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) "string"
+%typemap(imtype) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) "IntPtr"
 
 %typemap(in) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) %{
   $1 = ($1_ltype)$input;
 %}
 
-%typemap(out) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string)
-%{
+%typemap(out) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) %{
   $result = SWIG_csharp_string_callback((const char *)$1);
 %}
 
-%typemap(csin) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) "$modulePINVOKE.StringToUtf8Bytes($csinput)"
+%typemap(csin, 
+         pre="    IntPtr temp$csinput = $modulePINVOKE.StringToUtf8Unmanaged($csinput);", 
+         post="    Marshal.FreeHGlobal(temp$csinput);",
+         cshin="$csinput"
+        ) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string)
+         "temp$csinput"
+
+%typemap(csvarin, excode=SWIGEXCODE2) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) %{
+  /* %typemap(csvarin) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string) */
+  set {
+    IntPtr temp$csinput = $modulePINVOKE.StringToUtf8Unmanaged($csinput);
+    try {
+      $imcall;$excode
+    }
+    finally {
+      Marshal.FreeHGlobal(temp$csinput);
+    }
+  } %}
 
 %typemap(csout, excode=SWIGEXCODE) (char *), (char *&), (char[ANY]), (char[]), (const char *utf8_string)
   {

swig/include/csharp/ogr_csharp.i

@@ -71,7 +71,7 @@ DEFINE_EXTERNAL_CLASS(GDALMajorObjectShadow, OSGeo.GDAL.MajorObject)
      return new $csclassname(wkbGeometryType.wkbUnknown, null, 0, IntPtr.Zero, gml);
   }
 
-  public Geometry(wkbGeometryType type) : this(OgrPINVOKE.new_Geometry((int)type, null, 0, IntPtr.Zero, null), true, null) {
+  public Geometry(wkbGeometryType type) : this(OgrPINVOKE.new_Geometry((int)type, IntPtr.Zero, 0, IntPtr.Zero, IntPtr.Zero), true, null) {
     if (OgrPINVOKE.SWIGPendingException.Pending) throw OgrPINVOKE.SWIGPendingException.Retrieve();
   }
 }

swig/include/csharp/typemaps_csharp.i

@@ -600,9 +600,7 @@ CSHARP_OBJECT_ARRAYS_PINNED(GDALRasterBandShadow, Band)
       return ret;
     } %}
 %typemap(in) (GDALProgressFunc callback) %{ $1 = ($1_ltype)$input; %}
-%typemap(imtype) (void* callback_data) "string"
-%typemap(cstype) (void* callback_data) "string"
-%typemap(csin) (void* callback_data) "$csinput"
+%apply (const char *utf8_string) {(void* callback_data)};
 
 %ignore SWIGTYPE_p_GDALProgressFunc;