dotnet · BillWagner · Feb 22, 2022 · Feb 20, 2022
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+// <Snippet1>
+#nowarn "9"
+open System
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ =
+    let mutable arr = 
+        [| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]
+
+    use parr = fixed arr
+
+    let ptr = NativePtr.toNativeInt parr
+
+    // Get the size of an array element.
+    let size = sizeof<int>
+    for i = 0 to arr.Length - 1 do
+        let newPtr = IntPtr.Add(ptr, i * size)
+        printf $"{Marshal.ReadInt32 newPtr}   "
+    0
+
+// The example displays the following output:
+//       2   4   6   8   10   12   14   16   18   20
+// </Snippet1>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="add1.fs" />
+  </ItemGroup>
+</Project>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="topointer.fs" />
+  </ItemGroup>
+</Project>
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+//<snippet1>
+#nowarn "9"
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ =
+    let stringA = "I seem to be turned around!"
+    let mutable copylen = stringA.Length
+
+    // Allocate HGlobal memory for source and destination strings
+    let sptr = Marshal.StringToHGlobalAnsi stringA
+    let dptr = Marshal.AllocHGlobal(copylen + 1)
+
+    let mutable src: byte nativeptr = sptr.ToPointer() |> NativePtr.ofVoidPtr
+    let mutable dst: byte nativeptr = dptr.ToPointer() |> NativePtr.ofVoidPtr
+
+    if copylen > 0 then
+        // set the source pointer to the end of the string
+        // to do a reverse copy.
+        src <- 
+            NativePtr.toNativeInt src + nativeint (copylen - 1) 
+            |> NativePtr.ofNativeInt
+
+        while copylen > 0 do
+            copylen <- copylen - 1
+            NativePtr.read src |> NativePtr.write dst
+            dst <- NativePtr.toNativeInt dst + 1n |> NativePtr.ofNativeInt
+            src <- NativePtr.toNativeInt src - 1n |> NativePtr.ofNativeInt
+        NativePtr.write dst 0uy
+
+    let stringB = Marshal.PtrToStringAnsi dptr
+
+    printfn $"Original:\n{stringA}\n"
+    printfn $"Reversed:\n{stringB}"
+
+    // Free HGlobal memory
+    Marshal.FreeHGlobal dptr
+    Marshal.FreeHGlobal sptr
+    0
+
+// The progam has the following output:
+//
+// Original:
+// I seem to be turned around!
+//
+// Reversed:
+// !dnuora denrut eb ot mees I
+//</snippet1>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="subtract1.fs" />
+  </ItemGroup>
+</Project>
@@ -0,0 +1,24 @@
+// <Snippet1>
+#nowarn "9"
+open System
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ =
+    let arr =
+        [| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]
+
+    // Get the size of a single array element.
+    let size = sizeof<int>
+
+    use pend = fixed &arr[arr.GetUpperBound 0]
+    let ptr = NativePtr.toNativeInt pend 
+    for i = 0 to arr.Length - 1 do
+        let newPtr = IntPtr.Subtract(ptr, i * size)
+        printf $"{Marshal.ReadInt32 newPtr}   "
+    0
+
+// The example displays the following output:
+//       20   18   16   14   12   10   8   6   4   2
+// </Snippet1>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="topointer.fs" />
+  </ItemGroup>
+</Project>
@@ -0,0 +1,49 @@
+//<snippet1>
+#nowarn "9"
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ = 
+    let stringA = "I seem to be turned around!"
+    let mutable copylen = stringA.Length
+
+    // Allocate HGlobal memory for source and destination strings
+    let sptr = Marshal.StringToHGlobalAnsi stringA
+    let dptr = Marshal.AllocHGlobal(copylen + 1)
+
+    let mutable src: byte nativeptr = sptr.ToPointer() |> NativePtr.ofVoidPtr
+    let mutable dst: byte nativeptr = dptr.ToPointer() |> NativePtr.ofVoidPtr
+
+    if copylen > 0 then
+        // set the source pointer to the end of the string
+        // to do a reverse copy.
+        src <- 
+            NativePtr.toNativeInt src + nativeint (copylen - 1) 
+            |> NativePtr.ofNativeInt
+
+        while copylen > 0 do
+            copylen <- copylen - 1
+            NativePtr.read src |> NativePtr.write dst
+            dst <- NativePtr.toNativeInt dst + 1n |> NativePtr.ofNativeInt
+            src <- NativePtr.toNativeInt src - 1n |> NativePtr.ofNativeInt
+        NativePtr.write dst 0uy
+
+    let stringB = Marshal.PtrToStringAnsi dptr
+
+    printfn $"Original:\n{stringA}\n"
+    printfn $"Reversed:\n{stringB}"
+
+    // Free HGlobal memory
+    Marshal.FreeHGlobal dptr
+    Marshal.FreeHGlobal sptr
+    0
+
+// The progam has the following output:
+//
+// Original:
+// I seem to be turned around!
+//
+// Reversed:
+// !dnuora denrut eb ot mees I
+//</snippet1>
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="zero2.fs" />
+    <Compile Include="zero4.fs" />
+  </ItemGroup>
+</Project>
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+module zero2
+
+// <Snippet1>
+open System
+open System.Runtime.InteropServices
+
+let GW_OWNER = 4
+
+[<DllImport("user32", CharSet=CharSet.Auto, SetLastError=true, ExactSpelling=true)>]
+extern IntPtr GetWindow(nativeint hwnd, int wFlag)
+
+let hwnd = IntPtr 3
+let hOwner = GetWindow(hwnd, GW_OWNER)
+if hOwner = IntPtr.Zero then
+    printfn "Window not found."
+
+// The example displays the following output:
+//        Window not found.
+// </Snippet1>
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+// <Snippet2>
+open Microsoft.Win32.SafeHandles
+open System
+open System.Runtime.InteropServices
+
+let GENERIC_READ = 0x80000000u
+let OPEN_EXISTING = 3u
+let FILE_ATTRIBUTE_NORMAL = 128u
+let FILE_FLAG_OVERLAPPED = 0x40000000u
+
+[<DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)>]
+extern SafeFileHandle CreateFile(
+            string lpFileName, uint dwDesiredAccess, uint dwShareMode,
+            nativeint pSecurityAttributes, uint dwCreationDisposition,
+            uint dwFlagsAndAttributes, nativeint hTemplateFile)
+
+let hnd = 
+    CreateFile("CallOfTheWild.txt", GENERIC_READ, 0u,
+               IntPtr.Zero, OPEN_EXISTING,
+               FILE_ATTRIBUTE_NORMAL ||| FILE_FLAG_OVERLAPPED,
+               IntPtr.Zero)
+
+if hnd.IsInvalid then
+    let ex = Marshal.GetExceptionForHR(Marshal.GetHRForLastWin32Error())
+    printfn $"Attempt to open file failed:\n  {ex.Message}"
+else
+    printfn "File successfully opened."
+    hnd.Close()
+
+// If the file cannot be found, the example displays the following output:
+//    Attempt to open file failed:
+//      The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
+// </Snippet2>
@@ -0,0 +1,22 @@
+// <Snippet1>
+#nowarn "9"
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ =
+    let arr =
+        [| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]
+
+    use parr = fixed arr
+
+    let ptr = NativePtr.toNativeInt parr
+
+    for i = 0 to arr.Length - 1 do
+        let newPtr = ptr + nativeint i * nativeint sizeof<int>
+        printf $"{Marshal.ReadInt32 newPtr}   "
+    0
+
+    // The example displays the following output:
+    //       2   4   6   8   10   12   14   16   18   20
+    // </Snippet1>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="addition1.fs" />
+  </ItemGroup>
+</Project>
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\op_subtraction1.fs" />
+  </ItemGroup>
+</Project>
@@ -0,0 +1,22 @@
+// <Snippet2>
+#nowarn "9"
+open System.Runtime.InteropServices
+open FSharp.NativeInterop
+
+[<EntryPoint>]
+let main _ =
+    let arr =
+        [| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]
+
+    use parr = fixed &arr[arr.GetUpperBound 0]
+
+    let ptr = NativePtr.toNativeInt parr
+
+    for i = 0 to arr.GetUpperBound 0 do
+        let newPtr = ptr - nativeint i * nativeint sizeof<int>
+        printf $"{Marshal.ReadInt32 newPtr}   "
+    0
+
+    // The example displays the following output:
+    //       20   18   16   14   12   10   8   6   4   2
+    // </Snippet2>