AK: Add CircularDuplexStream class.

AK/Tests/TestCircularDuplexStream.cpp

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+/*
+ * Copyright (c) 2020, the SerenityOS developers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/TestSuite.h>
+
+#include <AK/CircularDuplexStream.h>
+
+TEST_CASE(works_like_a_queue)
+{
+    constexpr size_t capacity = 32;
+
+    CircularQueue<u8, capacity> queue;
+    CircularDuplexStream<capacity> stream;
+
+    for (size_t idx = 0; idx < capacity; ++idx) {
+        queue.enqueue(static_cast<u8>(idx % 256));
+        stream << static_cast<u8>(idx % 256);
+    }
+
+    for (size_t idx = 0; idx < capacity; ++idx) {
+        u8 byte;
+        stream >> byte;
+
+        EXPECT_EQ(queue.dequeue(), byte);
+    }
+
+    EXPECT(stream.eof());
+}
+
+TEST_CASE(overwritting_is_well_defined)
+{
+    constexpr size_t half_capacity = 16;
+    constexpr size_t capacity = 2 * half_capacity;
+
+    CircularDuplexStream<capacity> stream;
+
+    for (size_t idx = 0; idx < capacity; ++idx)
+        stream << static_cast<u8>(idx % 256);
+
+    u8 bytes[half_capacity];
+
+    stream >> Bytes { bytes, sizeof(bytes) };
+
+    for (size_t idx = 0; idx < half_capacity; ++idx) {
+        EXPECT_EQ(bytes[idx], idx % 256);
+    }
+
+    for (size_t idx = 0; idx < half_capacity; ++idx)
+        stream << static_cast<u8>(idx % 256);
+
+    for (size_t idx = 0; idx < capacity; ++idx) {
+        u8 byte;
+        stream >> byte;
+
+        if (idx < half_capacity)
+            EXPECT_EQ(byte, half_capacity + idx % 256);
+        else
+            EXPECT_EQ(byte, idx % 256 - half_capacity);
+    }
+
+    EXPECT(stream.eof());
+}
+
+TEST_MAIN(CircularDuplexStream)