update samples for stackalloc (dotnet#14)

* update samples for stackalloc Moved samples from the snippets folder in the dotnet/docs repo. Add project file and main program to run snippets. Add second sample that uses stackalloc initializers. * respond to feedback.
karelz · Aug 31, 2018 · 3ef2d3c · 3ef2d3c
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diff --git a/snippets/csharp/keywords/Program.cs b/snippets/csharp/keywords/Program.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace keywords
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            StackAllocExamples.Examples();
+        }
+    }
+}
diff --git a/snippets/csharp/keywords/StackAllocExamples.cs b/snippets/csharp/keywords/StackAllocExamples.cs
@@ -0,0 +1,102 @@
+using System;
+
+namespace keywords
+{
+    public static class StackAllocExamples
+    {
+        public static void Examples()
+        {
+            FibonacciGeneration();
+            Console.WriteLine("=========================");
+            InitializeBitMasks();
+        }
+
+        private static unsafe void InitializeBitMasks()
+        {
+            // <Snippet2>
+            int* mask = stackalloc[] {
+                0b_0000_0000_0000_0001,
+                0b_0000_0000_0000_0010,
+                0b_0000_0000_0000_0100,
+                0b_0000_0000_0000_1000,
+                0b_0000_0000_0001_0000,
+                0b_0000_0000_0010_0000,
+                0b_0000_0000_0100_0000,
+                0b_0000_0000_1000_0000,
+                0b_0000_0001_0000_0000,
+                0b_0000_0010_0000_0000,
+                0b_0000_0100_0000_0000,
+                0b_0000_1000_0000_0000,
+                0b_0001_0000_0000_0000,
+                0b_0010_0000_0000_0000,
+                0b_0100_0000_0000_0000,
+                0b_1000_0000_0000_0000
+            };
+
+            for (int i = 0; i < 16; i++)
+                Console.WriteLine(mask[i]);
+            /* Output:
+               1
+               2
+               4
+               8
+               16
+               32
+               64
+               128
+               256
+               512
+               1024
+               2048
+               4096
+               8192
+               16384
+               32768
+             */
+
+            // </Snippet2>
+        }
+
+        private static unsafe void FibonacciGeneration()
+        {
+            // <Snippet1>
+            const int arraySize = 20;
+            int* fib = stackalloc int[arraySize];
+            int* p = fib;
+            // The sequence begins with 1, 1.
+            *p++ = *p++ = 1;
+            for (int i = 2; i < arraySize; ++i, ++p)
+            {
+                // Sum the previous two numbers.
+                *p = p[-1] + p[-2];
+            }
+            for (int i = 0; i < arraySize; ++i)
+            {
+                Console.WriteLine(fib[i]);
+            }
+            /* Output:
+               1
+               1
+               2
+               3
+               5
+               8
+               13
+               21
+               34
+               55
+               89
+               144
+               233
+               377
+               610
+               987
+               1597
+               2584
+               4181
+               6765
+             */
+            // </Snippet1>
+        }
+    }
+}
diff --git a/snippets/csharp/keywords/keywords.csproj b/snippets/csharp/keywords/keywords.csproj
@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <LangVersion>7.3</LangVersion>
+  </PropertyGroup>
+</Project>