public void IfCanSeekIsFalseLengthAndPositionShouldNotBeCalled()
        {
            var baseStream = new DelegateStream(
                canReadFunc: () => true,
                canSeekFunc: () => false,
                readFunc: (buffer, offset, count) => 0);
            var trackingStream = new CallTrackingStream(baseStream);

            var dest = Stream.Null;

            trackingStream.CopyTo(dest);

            Assert.InRange(trackingStream.TimesCalled(nameof(trackingStream.CanSeek)), 0, 1);
            Assert.Equal(0, trackingStream.TimesCalled(nameof(trackingStream.Length)));
            Assert.Equal(0, trackingStream.TimesCalled(nameof(trackingStream.Position)));
            // We can't override CopyTo since it's not virtual, so checking TimesCalled
            // for CopyTo will result in 0. Instead, we check that Read was called,
            // and validate the parameters passed there.
            Assert.Equal(1, trackingStream.TimesCalled(nameof(trackingStream.Read)));

            byte[] outerBuffer = trackingStream.ReadBuffer;
            int    outerOffset = trackingStream.ReadOffset;
            int    outerCount  = trackingStream.ReadCount;

            Assert.NotNull(outerBuffer);
            Assert.InRange(outerOffset, 0, outerBuffer.Length - outerCount);
            Assert.InRange(outerCount, 1, int.MaxValue); // the buffer can't be size 0
        }
        public void IfLengthMinusPositionPositiveOverflowsBufferSizeShouldStillBePositive(long length, long position)
        {
            // The new implementation of Stream.CopyTo calculates the bytes left
            // in the Stream by calling Length - Position. This can overflow to a
            // negative number, so this tests that if that happens we don't send
            // in a negative bufferSize.

            var baseStream = new DelegateStream(
                canReadFunc: () => true,
                canSeekFunc: () => true,
                lengthFunc: () => length,
                positionGetFunc: () => position,
                readFunc: (buffer, offset, count) => 0);
            var trackingStream = new CallTrackingStream(baseStream);

            var dest = Stream.Null;

            trackingStream.CopyTo(dest);

            // CopyTo is not virtual, so we can't override it in
            // CallTrackingStream and record the arguments directly.
            // Instead, validate the arguments passed to Read.

            Assert.Equal(1, trackingStream.TimesCalled(nameof(trackingStream.Read)));

            byte[] outerBuffer = trackingStream.ReadBuffer;
            int    outerOffset = trackingStream.ReadOffset;
            int    outerCount  = trackingStream.ReadCount;

            Assert.NotNull(outerBuffer);
            Assert.InRange(outerOffset, 0, outerBuffer.Length - outerCount);
            Assert.InRange(outerCount, 1, int.MaxValue);
        }
        public void IfLengthIsLessThanOrEqualToPositionCopyToShouldStillBeCalledWithAPositiveBufferSize(long length, long position)
        {
            // Streams with their Lengths <= their Positions, e.g.
            // new MemoryStream { Position = 3 }.SetLength(1)
            // should still be called CopyTo{Async} on with a
            // bufferSize of at least 1.

            var baseStream = new DelegateStream(
                canReadFunc: () => true,
                canSeekFunc: () => true,
                lengthFunc: () => length,
                positionGetFunc: () => position,
                readFunc: (buffer, offset, count) => 0);
            var trackingStream = new CallTrackingStream(baseStream);

            var dest = Stream.Null;

            trackingStream.CopyTo(dest);

            // CopyTo is not virtual, so we can't override it in
            // CallTrackingStream and record the arguments directly.
            // Instead, validate the arguments passed to Read.

            Assert.Equal(1, trackingStream.TimesCalled(nameof(trackingStream.Read)));

            byte[] outerBuffer = trackingStream.ReadBuffer;
            int    outerOffset = trackingStream.ReadOffset;
            int    outerCount  = trackingStream.ReadCount;

            Assert.NotNull(outerBuffer);
            Assert.InRange(outerOffset, 0, outerBuffer.Length - outerCount);
            Assert.InRange(outerCount, 1, int.MaxValue);
        }
        public void IfCanSeekIsTrueLengthAndPositionShouldOnlyBeCalledOnce()
        {
            var baseStream = new DelegateStream(
                canReadFunc: () => true,
                canSeekFunc: () => true,
                readFunc: (buffer, offset, count) => 0,
                lengthFunc: () => 0L,
                positionGetFunc: () => 0L);
            var trackingStream = new CallTrackingStream(baseStream);

            var dest = Stream.Null;

            trackingStream.CopyTo(dest);

            Assert.InRange(trackingStream.TimesCalled(nameof(trackingStream.Length)), 0, 1);
            Assert.InRange(trackingStream.TimesCalled(nameof(trackingStream.Position)), 0, 1);
        }
        public void IfLengthIsGreaterThanPositionAndDoesNotOverflowEverythingShouldGoNormally(long length, long position)
        {
            const int ReadLimit = 7;

            // Lambda state
            byte[] outerBuffer = null;
            int?   outerOffset = null;
            int?   outerCount  = null;
            int    readsLeft   = ReadLimit;

            var srcBase = new DelegateStream(
                canReadFunc: () => true,
                canSeekFunc: () => true,
                lengthFunc: () => length,
                positionGetFunc: () => position,
                readFunc: (buffer, offset, count) =>
            {
                Assert.NotNull(buffer);
                Assert.InRange(offset, 0, buffer.Length - count);
                Assert.InRange(count, 1, int.MaxValue);

                // CopyTo should always pass in the same buffer/offset/count

                if (outerBuffer != null)
                {
                    Assert.Same(outerBuffer, buffer);
                }
                else
                {
                    outerBuffer = buffer;
                }

                if (outerOffset != null)
                {
                    Assert.Equal(outerOffset, offset);
                }
                else
                {
                    outerOffset = offset;
                }

                if (outerCount != null)
                {
                    Assert.Equal(outerCount, count);
                }
                else
                {
                    outerCount = count;
                }

                return(--readsLeft);    // CopyTo will call Read on this ReadLimit times before stopping
            });

            var src = new CallTrackingStream(srcBase);

            var destBase = new DelegateStream(
                canWriteFunc: () => true,
                writeFunc: (buffer, offset, count) =>
            {
                Assert.Same(outerBuffer, buffer);
                Assert.Equal(outerOffset, offset);
                Assert.Equal(readsLeft, count);
            });

            var dest = new CallTrackingStream(destBase);

            src.CopyTo(dest);

            Assert.Equal(ReadLimit, src.TimesCalled(nameof(src.Read)));
            Assert.Equal(ReadLimit - 1, dest.TimesCalled(nameof(dest.Write)));
        }