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common: Implement a ring buffer
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4 changed files with 243 additions and 0 deletions
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@ -71,6 +71,7 @@ add_library(common STATIC
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param_package.cpp
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param_package.h
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quaternion.h
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ring_buffer.h
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scm_rev.cpp
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scm_rev.h
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scope_exit.h
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111
src/common/ring_buffer.h
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111
src/common/ring_buffer.h
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@ -0,0 +1,111 @@
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// Copyright 2018 yuzu emulator team
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#pragma once
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#include <algorithm>
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#include <array>
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#include <atomic>
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#include <cstddef>
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#include <cstring>
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#include <type_traits>
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#include <vector>
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#include "common/common_types.h"
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namespace Common {
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/// SPSC ring buffer
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/// @tparam T Element type
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/// @tparam capacity Number of slots in ring buffer
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/// @tparam granularity Slot size in terms of number of elements
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template <typename T, size_t capacity, size_t granularity = 1>
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class RingBuffer {
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/// A "slot" is made of `granularity` elements of `T`.
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static constexpr size_t slot_size = granularity * sizeof(T);
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// T must be safely memcpy-able and have a trivial default constructor.
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static_assert(std::is_trivial_v<T>);
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// Ensure capacity is sensible.
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static_assert(capacity < std::numeric_limits<size_t>::max() / 2 / granularity);
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static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two");
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// Ensure lock-free.
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static_assert(std::atomic<size_t>::is_always_lock_free);
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public:
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/// Pushes slots into the ring buffer
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/// @param new_slots Pointer to the slots to push
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/// @param slot_count Number of slots to push
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/// @returns The number of slots actually pushed
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size_t Push(const void* new_slots, size_t slot_count) {
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const size_t write_index = m_write_index.load();
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const size_t slots_free = capacity + m_read_index.load() - write_index;
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const size_t push_count = std::min(slot_count, slots_free);
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const size_t pos = write_index % capacity;
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const size_t first_copy = std::min(capacity - pos, push_count);
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const size_t second_copy = push_count - first_copy;
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const char* in = static_cast<const char*>(new_slots);
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std::memcpy(m_data.data() + pos * granularity, in, first_copy * slot_size);
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in += first_copy * slot_size;
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std::memcpy(m_data.data(), in, second_copy * slot_size);
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m_write_index.store(write_index + push_count);
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return push_count;
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}
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size_t Push(const std::vector<T>& input) {
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return Push(input.data(), input.size());
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}
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/// Pops slots from the ring buffer
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/// @param output Where to store the popped slots
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/// @param max_slots Maximum number of slots to pop
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/// @returns The number of slots actually popped
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size_t Pop(void* output, size_t max_slots = ~size_t(0)) {
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const size_t read_index = m_read_index.load();
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const size_t slots_filled = m_write_index.load() - read_index;
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const size_t pop_count = std::min(slots_filled, max_slots);
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const size_t pos = read_index % capacity;
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const size_t first_copy = std::min(capacity - pos, pop_count);
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const size_t second_copy = pop_count - first_copy;
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char* out = static_cast<char*>(output);
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std::memcpy(out, m_data.data() + pos * granularity, first_copy * slot_size);
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out += first_copy * slot_size;
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std::memcpy(out, m_data.data(), second_copy * slot_size);
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m_read_index.store(read_index + pop_count);
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return pop_count;
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}
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std::vector<T> Pop(size_t max_slots = ~size_t(0)) {
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std::vector<T> out(std::min(max_slots, capacity) * granularity);
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const size_t count = Pop(out.data(), out.size() / granularity);
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out.resize(count * granularity);
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return out;
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}
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/// @returns Number of slots used
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size_t Size() const {
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return m_write_index.load() - m_read_index.load();
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}
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/// @returns Maximum size of ring buffer
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constexpr size_t Capacity() const {
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return capacity;
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}
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private:
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// It is important to align the below variables for performance reasons:
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// Having them on the same cache-line would result in false-sharing between them.
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alignas(128) std::atomic<size_t> m_read_index{0};
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alignas(128) std::atomic<size_t> m_write_index{0};
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std::array<T, granularity * capacity> m_data;
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};
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} // namespace Common
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@ -1,5 +1,6 @@
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add_executable(tests
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common/param_package.cpp
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common/ring_buffer.cpp
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core/arm/arm_test_common.cpp
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core/arm/arm_test_common.h
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core/core_timing.cpp
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130
src/tests/common/ring_buffer.cpp
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130
src/tests/common/ring_buffer.cpp
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// Copyright 2018 yuzu emulator team
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#include <algorithm>
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#include <array>
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#include <cstddef>
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#include <numeric>
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#include <thread>
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#include <vector>
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#include <catch2/catch.hpp>
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#include "common/ring_buffer.h"
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namespace Common {
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TEST_CASE("RingBuffer: Basic Tests", "[common]") {
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RingBuffer<char, 4, 1> buf;
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// Pushing values into a ring buffer with space should succeed.
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for (size_t i = 0; i < 4; i++) {
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const char elem = static_cast<char>(i);
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const size_t count = buf.Push(&elem, 1);
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REQUIRE(count == 1);
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}
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REQUIRE(buf.Size() == 4);
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// Pushing values into a full ring buffer should fail.
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{
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const char elem = static_cast<char>(42);
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const size_t count = buf.Push(&elem, 1);
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REQUIRE(count == 0);
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}
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REQUIRE(buf.Size() == 4);
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// Popping multiple values from a ring buffer with values should succeed.
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{
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const std::vector<char> popped = buf.Pop(2);
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REQUIRE(popped.size() == 2);
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REQUIRE(popped[0] == 0);
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REQUIRE(popped[1] == 1);
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}
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REQUIRE(buf.Size() == 2);
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// Popping a single value from a ring buffer with values should succeed.
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{
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const std::vector<char> popped = buf.Pop(1);
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REQUIRE(popped.size() == 1);
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REQUIRE(popped[0] == 2);
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}
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REQUIRE(buf.Size() == 1);
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// Pushing more values than space available should partially suceed.
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{
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std::vector<char> to_push(6);
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std::iota(to_push.begin(), to_push.end(), 88);
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const size_t count = buf.Push(to_push);
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REQUIRE(count == 3);
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}
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REQUIRE(buf.Size() == 4);
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// Doing an unlimited pop should pop all values.
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{
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const std::vector<char> popped = buf.Pop();
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REQUIRE(popped.size() == 4);
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REQUIRE(popped[0] == 3);
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REQUIRE(popped[1] == 88);
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REQUIRE(popped[2] == 89);
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REQUIRE(popped[3] == 90);
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}
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REQUIRE(buf.Size() == 0);
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}
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TEST_CASE("RingBuffer: Threaded Test", "[common]") {
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RingBuffer<char, 4, 2> buf;
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const char seed = 42;
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const size_t count = 1000000;
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size_t full = 0;
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size_t empty = 0;
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const auto next_value = [](std::array<char, 2>& value) {
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value[0] += 1;
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value[1] += 2;
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};
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std::thread producer{[&] {
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std::array<char, 2> value = {seed, seed};
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size_t i = 0;
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while (i < count) {
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if (const size_t c = buf.Push(&value[0], 1); c > 0) {
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REQUIRE(c == 1);
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i++;
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next_value(value);
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} else {
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full++;
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std::this_thread::yield();
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}
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}
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}};
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std::thread consumer{[&] {
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std::array<char, 2> value = {seed, seed};
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size_t i = 0;
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while (i < count) {
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if (const std::vector<char> v = buf.Pop(1); v.size() > 0) {
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REQUIRE(v.size() == 2);
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REQUIRE(v[0] == value[0]);
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REQUIRE(v[1] == value[1]);
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i++;
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next_value(value);
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} else {
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empty++;
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std::this_thread::yield();
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}
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}
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}};
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producer.join();
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consumer.join();
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REQUIRE(buf.Size() == 0);
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printf("RingBuffer: Threaded Test: full: %zu, empty: %zu\n", full, empty);
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}
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} // namespace Common
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