From d11a624a340d34c9b836a268562c5dac53a52563 Mon Sep 17 00:00:00 2001
From: Christian Luksch <luksch@vrvis.at>
Date: Mon, 13 May 2024 18:14:13 +0200
Subject: [PATCH] [IO] using spans in all Read/WriteArray functions with net6.0

---
 src/Aardvark.Base.IO/StreamCodeReader.cs | 54 ++++++++++++++++++++----
 src/Aardvark.Base.IO/StreamCodeWriter.cs | 25 ++++++-----
 2 files changed, 60 insertions(+), 19 deletions(-)

diff --git a/src/Aardvark.Base.IO/StreamCodeReader.cs b/src/Aardvark.Base.IO/StreamCodeReader.cs
index 7a37a6de..79e62821 100644
--- a/src/Aardvark.Base.IO/StreamCodeReader.cs
+++ b/src/Aardvark.Base.IO/StreamCodeReader.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -178,6 +179,25 @@ public long ReadArray<T>(T[,] array, long count)
             where T : struct
         {
             if (count < 1) return 0;
+
+#if NET6_0_OR_GREATER
+            var sizeOfT = Marshal.SizeOf(typeof(T));
+            var span = MemoryMarshal.CreateSpan(ref MemoryMarshal.GetArrayDataReference(array), (int)count * sizeOfT);
+
+            var bytesToRead = span.Length;
+            var offset = 0;
+
+            do
+            {
+                int finished = base.Read(span);
+                if (finished == 0) break;
+                offset += finished; bytesToRead -= finished;
+                span = span.Slice(offset, bytesToRead);
+            }
+            while (bytesToRead > 0);
+
+            return offset / sizeOfT;
+#else
             unsafe
             {
                 var sizeOfT = Marshal.SizeOf(typeof(T));
@@ -185,11 +205,9 @@ public long ReadArray<T>(T[,] array, long count)
                 hack.structs = array;
 
                 var bytesToRead = (int)(sizeOfT * count);
-                #if __MonoCS__
-                var skip = 0;
-                #else
+
                 var skip = 2 * 2 * sizeof(int);
-                #endif
+
                 IntPtr byteLen = (IntPtr)(array.Length * sizeOfT + skip);
                 var offset = skip;
 
@@ -212,12 +230,31 @@ public long ReadArray<T>(T[,] array, long count)
                 }
                 return (long)((offset - skip) / sizeOfT);
             }
+#endif
         }
 
         public long ReadArray<T>(T[, ,] array, long count)
             where T : struct
         {
             if (count < 1) return 0;
+#if NET6_0_OR_GREATER
+            var sizeOfT = Marshal.SizeOf(typeof(T));
+            var span = MemoryMarshal.CreateSpan(ref MemoryMarshal.GetArrayDataReference(array), (int)count * sizeOfT);
+
+            var bytesToRead = span.Length;
+            var offset = 0;
+
+            do
+            {
+                int finished = base.Read(span);
+                if (finished == 0) break;
+                offset += finished; bytesToRead -= finished;
+                span = span.Slice(offset, bytesToRead);
+            }
+            while (bytesToRead > 0);
+
+            return offset / sizeOfT;
+#else
             unsafe
             {
                 var sizeOfT = Marshal.SizeOf(typeof(T));
@@ -225,11 +262,9 @@ public long ReadArray<T>(T[, ,] array, long count)
                 hack.structs = array;
 
                 var bytesToRead = (int)(sizeOfT * count);
-                #if __MonoCS__
-                var skip = 0;
-                #else
+
                 var skip = 3 * 2 * sizeof(int);
-                #endif
+
                 IntPtr byteLen = (IntPtr)(array.Length * sizeOfT + skip);
                 var offset = skip;
 
@@ -252,6 +287,7 @@ public long ReadArray<T>(T[, ,] array, long count)
                 }
                 return (long)((offset - skip) / sizeOfT);
             }
+#endif
         }
 
         public int ReadList<T>(List<T> buffer, int index, int count)
@@ -264,7 +300,7 @@ public int ReadList<T>(List<T> buffer, int index, int count)
             return (int)ReadArray(arrayValue, (long)index, (long)count);
         }
 
-        #endregion
+#endregion
 
         #region Close
 
diff --git a/src/Aardvark.Base.IO/StreamCodeWriter.cs b/src/Aardvark.Base.IO/StreamCodeWriter.cs
index 9cbfe925..f4d07215 100644
--- a/src/Aardvark.Base.IO/StreamCodeWriter.cs
+++ b/src/Aardvark.Base.IO/StreamCodeWriter.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -165,6 +166,11 @@ public void WriteArray<T>(T[,] array, long count)
                     where T : struct
         {
             if (count < 1) return;
+#if NET6_0_OR_GREATER
+            var sizeOfT = Marshal.SizeOf(typeof(T));
+            var byteSpan = MemoryMarshal.CreateSpan(ref MemoryMarshal.GetArrayDataReference(array), (int)count * sizeOfT);
+            base.Write(byteSpan);
+#else
             unsafe
             {
                 var sizeOfT = Marshal.SizeOf(typeof(T));
@@ -174,11 +180,7 @@ public void WriteArray<T>(T[,] array, long count)
 
                 fixed (byte* pBytes = hack.bytes)
                 {
-                    #if __MonoCS__
-                    long offset = 0;
-                    #else
                     long offset = 2 * 2 * sizeof(int);
-                    #endif
 
                     int itemsPerBlock = c_bufferSize / sizeOfT;
                     do
@@ -198,12 +200,18 @@ public void WriteArray<T>(T[,] array, long count)
                     while (count > 0);
                 }
             }
+#endif
         }
 
         public void WriteArray<T>(T[, ,] array, long count)
                     where T : struct
         {
             if (count < 1) return;
+#if NET6_0_OR_GREATER
+            var sizeOfT = Marshal.SizeOf(typeof(T));
+            var byteSpan = MemoryMarshal.CreateSpan(ref MemoryMarshal.GetArrayDataReference(array), (int)count * sizeOfT);
+            base.Write(byteSpan);
+#else
             unsafe
             {
                 var sizeOfT = Marshal.SizeOf(typeof(T));
@@ -213,12 +221,8 @@ public void WriteArray<T>(T[, ,] array, long count)
 
                 fixed (byte* pBytes = hack.bytes)
                 {
-                    #if __MonoCS__
-                    long offset = 0;
-                    #else
                     long offset = 3 * 2 * sizeof(int);
-                    #endif
-
+                    
                     int itemsPerBlock = c_bufferSize / sizeOfT;
                     do
                     {
@@ -237,6 +241,7 @@ public void WriteArray<T>(T[, ,] array, long count)
                     while (count > 0);
                 }
             }
+#endif
         }
 
         public void WriteList<T>(List<T> buffer, int index, int count)
@@ -247,7 +252,7 @@ public void WriteList<T>(List<T> buffer, int index, int count)
             WriteArray(arrayValue, (long)index, (long)count);
         }
 
-        #endregion
+#endregion
 
         #region Close