Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/ByteStack.cs

@@ -0,0 +1,66 @@
+//------------------------------------------------------------------------------
+// <copyright file="ByteStack.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+using System;
+
+namespace System.Xml {
+
+// This stack is designed to minimize object creation for the
+// objects being stored in the stack by allowing them to be
+// re-used over time.  It basically pushes the objects creating
+// a high water mark then as Pop() is called they are not removed
+// so that next time Push() is called it simply returns the last
+// object that was already on the stack.
+
+    internal class ByteStack {
+        private byte[] stack;
+        private int growthRate;
+        private int top;
+        private int size;
+
+        public ByteStack(int growthRate) {
+            this.growthRate = growthRate;
+            top = 0;
+            stack = new byte[growthRate];
+            size = growthRate; 
+        }
+
+        public void Push(byte data) {
+            if (size == top) {
+                byte[] newstack = new byte[size + growthRate];
+                if (top > 0) {
+                    Buffer.BlockCopy(stack, 0, newstack, 0, top);
+                }
+                stack = newstack;
+                size += growthRate;
+            }
+            stack[top++] = data;
+        }
+
+        public byte Pop() {
+            if (top > 0) {
+                return stack[--top];
+            } else {
+                return 0;
+            }
+        }
+
+        public byte Peek() {
+            if (top > 0) {
+                return stack[top - 1];
+            } else {
+                return 0;
+            }
+        }
+
+        public int Length {
+            get { 
+                return top;
+            }
+        }
+    }
+}