Fix an issue where growing the ByteBuffer would fail (#167)

* Fix an issue where growing a buffer when the read water mark = 0 would fail

* Simplify fix

tests/KubernetesClient.Tests/ByteBufferTests.cs

@@ -1,4 +1,6 @@
+using Nito.AsyncEx;
 using System;
+using System.Security.Cryptography;
 using System.Threading;
 using System.Threading.Tasks;
 using Xunit;
@@ -341,5 +343,151 @@ namespace k8s.Tests
             read = buffer.Read(readData, 0, 0x10);
             Assert.Equal(0, read);
         }
+
+        /// <summary>
+        /// Tests growing the byte buffer on the first write. This is a special case where
+        /// ReadWaterMark = WriteWaterMark = 0
+        /// </summary>
+        [Fact]
+        public void GrowOnFirstWriteTest()
+        {
+            // In the current implementation, the minimum size of the buffer will be 16 bytes,
+            // but that's not guaranteed.
+            ByteBuffer buffer = new ByteBuffer(1, 128);
+
+            byte[] data = new byte[buffer.Size + 1];
+            RandomNumberGenerator.Create().GetBytes(data);
+
+            byte[] output = new byte[buffer.Size + 1];
+
+            buffer.Write(data, 0, data.Length);
+
+            Assert.Equal(data.Length, buffer.AvailableReadableBytes);
+            buffer.Read(output, 0, output.Length);
+            Assert.Equal(data, output);
+        }
+
+        /// <summary>
+        /// Tests growing the byte buffer on the second write.
+        /// </summary>
+        [Fact]
+        public void GrowOnSecondFirstWriteTest()
+        {
+            // In the current implementation, the minimum size of the buffer will be 16 bytes,
+            // but that's not guaranteed.
+            ByteBuffer buffer = new ByteBuffer(1, 128);
+
+            byte[] data = new byte[buffer.Size + 1];
+            RandomNumberGenerator.Create().GetBytes(data);
+
+            byte[] output = new byte[buffer.Size + 1];
+
+            buffer.Write(data, 0, 1);
+            buffer.Write(data, 0, data.Length);
+
+            Assert.Equal(data.Length + 1, buffer.AvailableReadableBytes);
+            buffer.Read(output, 0, 1);
+            buffer.Read(output, 0, output.Length);
+            Assert.Equal(data, output);
+        }
+
+        /// <summary>
+        /// Tests reading from the buffer before data has been written, and makes sure
+        /// data is read correctly.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="Task"/> which represents the asynchronous operation.
+        /// </returns>
+        [Fact]
+        public async Task ReadFirstTest()
+        {
+            ByteBuffer buffer = new ByteBuffer(1, 128);
+
+            byte[] data = new byte[buffer.Size + 1];
+            RandomNumberGenerator.Create().GetBytes(data);
+
+            byte[] output = new byte[buffer.Size + 1];
+
+            var readTask = Task.Run(() => buffer.Read(output, 0, output.Length));
+            await Task.Delay(TimeSpan.FromSeconds(1));
+
+            buffer.Write(data, 0, data.Length);
+            await readTask;
+        }
+
+#if NETCOREAPP2_0
+        /// <summary>
+        /// A simpel test which will use a random number generator to write lots of data to
+        /// the buffer, and read that data using another thread. Makes sure the hashes of the
+        /// data written and read matches.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="Task"/> which represents the asynchronous operation.
+        /// </returns>
+        [Fact]
+        public async Task RandomReadWriteTest()
+        {
+            ByteBuffer buffer = new ByteBuffer(1, 1024 * 1024);
+
+            var generatorTask = Task.Run(() => this.Generate(buffer, SHA256.Create()));
+            var consumerTask = Task.Run(() => this.Consume(buffer, SHA256.Create()));
+
+            await Task.WhenAll(generatorTask, consumerTask);
+
+            var generatorHash = await generatorTask;
+            var consumerHash = await consumerTask;
+
+            Assert.Equal(generatorHash, consumerHash);
+        }
+
+        private byte[] Generate(ByteBuffer buffer, HashAlgorithm hash)
+        {
+            RandomNumberGenerator g = RandomNumberGenerator.Create();
+
+            byte[] next = new byte[32];
+
+            int iterations = 0;
+            while (buffer.Size < buffer.MaximumSize)
+            {
+                iterations++;
+
+                g.GetBytes(next);
+                buffer.Write(next, 0, next.Length);
+                hash.TransformBlock(next, 0, next.Length, null, 0);
+            }
+
+            buffer.WriteEnd();
+            hash.TransformFinalBlock(next, 0, 0);
+            return hash.Hash;
+        }
+
+        private byte[] Consume(ByteBuffer buffer, HashAlgorithm hash)
+        {
+            byte[] data = new byte[32];
+
+            AsyncAutoResetEvent onBufferResized = new AsyncAutoResetEvent();
+            buffer.OnResize += (sender, e) => onBufferResized.Set();
+
+            int read;
+            int iterations = 0;
+            while ((read = buffer.Read(data, 0, data.Length)) > 0)
+            {
+                iterations++;
+
+                hash.TransformBlock(data, 0, read, null, 0);
+
+                // The reader task is probably much faster than the writer, as the writer should also generate
+                // random data. Wait at specific intervals for the writer to catch up and to force a resize
+                // of the buffer.
+                if (iterations % 1024 == 0 && buffer.Size < buffer.MaximumSize)
+                {
+                    onBufferResized.Wait();
+                }
+            }
+
+            hash.TransformFinalBlock(data, 0, 0);
+            return hash.Hash;
+        }
+#endif
     }
 }