Merge "Move RingBuffer from SF utils into libui" into main

3 files changed, 151 insertions, 0 deletions

diff --git a/libs/ui/include/ui/RingBuffer.h b/libs/ui/include/ui/RingBuffer.h
new file mode 100644
index 0000000000..31d5a950ef
--- /dev/null
+++ b/libs/ui/include/ui/RingBuffer.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <array>
+
+namespace android::ui {
+
+template <class T, size_t SIZE>
+class RingBuffer {
+    RingBuffer(const RingBuffer&) = delete;
+    void operator=(const RingBuffer&) = delete;
+
+public:
+    RingBuffer() = default;
+    ~RingBuffer() = default;
+
+    constexpr size_t capacity() const { return SIZE; }
+    size_t size() const { return mCount; }
+    bool isFull() const { return size() == capacity(); }
+
+    T& next() {
+        mHead = static_cast<size_t>(mHead + 1) % SIZE;
+        if (mCount < SIZE) {
+            mCount++;
+        }
+        return mBuffer[static_cast<size_t>(mHead)];
+    }
+
+    T& front() { return (*this)[0]; }
+    const T& front() const { return (*this)[0]; }
+
+    T& back() { return (*this)[size() - 1]; }
+    const T& back() const { return (*this)[size() - 1]; }
+
+    T& operator[](size_t index) {
+        return mBuffer[(static_cast<size_t>(mHead + 1) + index) % mCount];
+    }
+
+    const T& operator[](size_t index) const {
+        return mBuffer[(static_cast<size_t>(mHead + 1) + index) % mCount];
+    }
+
+    void clear() {
+        mCount = 0;
+        mHead = -1;
+    }
+
+private:
+    std::array<T, SIZE> mBuffer;
+    int mHead = -1;
+    size_t mCount = 0;
+};
+
+} // namespace android::ui
diff --git a/libs/ui/tests/Android.bp b/libs/ui/tests/Android.bp
index 2d8a1e326c..2b11786df3 100644
--- a/libs/ui/tests/Android.bp
+++ b/libs/ui/tests/Android.bp
@@ -144,6 +144,17 @@ cc_test {
 }
 
 cc_test {
+    name: "RingBuffer_test",
+    test_suites: ["device-tests"],
+    shared_libs: ["libui"],
+    srcs: ["RingBuffer_test.cpp"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+}
+
+cc_test {
     name: "Size_test",
     test_suites: ["device-tests"],
     shared_libs: ["libui"],
diff --git a/libs/ui/tests/RingBuffer_test.cpp b/libs/ui/tests/RingBuffer_test.cpp
new file mode 100644
index 0000000000..9839492b9f
--- /dev/null
+++ b/libs/ui/tests/RingBuffer_test.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+#include <ui/RingBuffer.h>
+
+namespace android::ui {
+
+TEST(RingBuffer, basic) {
+    RingBuffer<int, 5> rb;
+
+    rb.next() = 1;
+    ASSERT_EQ(1, rb.size());
+    ASSERT_EQ(1, rb.back());
+    ASSERT_EQ(1, rb.front());
+
+    rb.next() = 2;
+    ASSERT_EQ(2, rb.size());
+    ASSERT_EQ(2, rb.back());
+    ASSERT_EQ(1, rb.front());
+    ASSERT_EQ(1, rb[-1]);
+
+    rb.next() = 3;
+    ASSERT_EQ(3, rb.size());
+    ASSERT_EQ(3, rb.back());
+    ASSERT_EQ(1, rb.front());
+    ASSERT_EQ(2, rb[-1]);
+    ASSERT_EQ(1, rb[-2]);
+
+    rb.next() = 4;
+    ASSERT_EQ(4, rb.size());
+    ASSERT_EQ(4, rb.back());
+    ASSERT_EQ(1, rb.front());
+    ASSERT_EQ(3, rb[-1]);
+    ASSERT_EQ(2, rb[-2]);
+    ASSERT_EQ(1, rb[-3]);
+
+    rb.next() = 5;
+    ASSERT_EQ(5, rb.size());
+    ASSERT_EQ(5, rb.back());
+    ASSERT_EQ(1, rb.front());
+    ASSERT_EQ(4, rb[-1]);
+    ASSERT_EQ(3, rb[-2]);
+    ASSERT_EQ(2, rb[-3]);
+    ASSERT_EQ(1, rb[-4]);
+
+    rb.next() = 6;
+    ASSERT_EQ(5, rb.size());
+    ASSERT_EQ(6, rb.back());
+    ASSERT_EQ(2, rb.front());
+    ASSERT_EQ(5, rb[-1]);
+    ASSERT_EQ(4, rb[-2]);
+    ASSERT_EQ(3, rb[-3]);
+    ASSERT_EQ(2, rb[-4]);
+}
+
+} // namespace android::ui
\ No newline at end of file