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ring_buffer: Remove granularity template argument

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Non-obvious bug in RingBuffer::Push(std::vector<T>&) when granularity != 1

Just remove it altogether because we do not have a use for granularity != 1
This commit is contained in:
MerryMage 2021-02-06 19:13:03 +00:00
parent 821fc4a7b6
commit 8d00265998
2 changed files with 15 additions and 16 deletions
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21
src/common/ring_buffer.h
View file

@ -19,15 +19,14 @@ namespace Common {
/// SPSC ring buffer
/// @tparam T Element type
/// @tparam capacity Number of slots in ring buffer
/// @tparam granularity Slot size in terms of number of elements
template <typename T, std::size_t capacity, std::size_t granularity = 1>
template <typename T, std::size_t capacity>
class RingBuffer {
/// A "slot" is made of `granularity` elements of `T`.
static constexpr std::size_t slot_size = granularity * sizeof(T);
/// A "slot" is made of a single `T`.
static constexpr std::size_t slot_size = sizeof(T);
// T must be safely memcpy-able and have a trivial default constructor.
static_assert(std::is_trivial_v<T>);
// Ensure capacity is sensible.
static_assert(capacity < std::numeric_limits<std::size_t>::max() / 2 / granularity);
static_assert(capacity < std::numeric_limits<std::size_t>::max() / 2);
static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two");
// Ensure lock-free.
static_assert(std::atomic_size_t::is_always_lock_free);
@ -47,7 +46,7 @@ public:
const std::size_t second_copy = push_count - first_copy;
const char* in = static_cast<const char*>(new_slots);
std::memcpy(m_data.data() + pos * granularity, in, first_copy * slot_size);
std::memcpy(m_data.data() + pos, in, first_copy * slot_size);
in += first_copy * slot_size;
std::memcpy(m_data.data(), in, second_copy * slot_size);
@ -74,7 +73,7 @@ public:
const std::size_t second_copy = pop_count - first_copy;
char* out = static_cast<char*>(output);
std::memcpy(out, m_data.data() + pos * granularity, first_copy * slot_size);
std::memcpy(out, m_data.data() + pos, first_copy * slot_size);
out += first_copy * slot_size;
std::memcpy(out, m_data.data(), second_copy * slot_size);
@ -84,9 +83,9 @@ public:
}
std::vector<T> Pop(std::size_t max_slots = ~std::size_t(0)) {
std::vector<T> out(std::min(max_slots, capacity) * granularity);
const std::size_t count = Pop(out.data(), out.size() / granularity);
out.resize(count * granularity);
std::vector<T> out(std::min(max_slots, capacity));
const std::size_t count = Pop(out.data(), out.size());
out.resize(count);
return out;
}
@ -113,7 +112,7 @@ private:
alignas(128) std::atomic_size_t m_write_index{0};
#endif
std::array<T, granularity * capacity> m_data;
std::array<T, capacity> m_data;
};
} // namespace Common

10
src/tests/common/ring_buffer.cpp
View file

@ -14,7 +14,7 @@
namespace Common {
TEST_CASE("RingBuffer: Basic Tests", "[common]") {
RingBuffer<char, 4, 1> buf;
RingBuffer<char, 4> buf;
// Pushing values into a ring buffer with space should succeed.
for (std::size_t i = 0; i < 4; i++) {
@ -77,7 +77,7 @@ TEST_CASE("RingBuffer: Basic Tests", "[common]") {
}
TEST_CASE("RingBuffer: Threaded Test", "[common]") {
RingBuffer<char, 4, 2> buf;
RingBuffer<char, 8> buf;
const char seed = 42;
const std::size_t count = 1000000;
std::size_t full = 0;
@ -92,8 +92,8 @@ TEST_CASE("RingBuffer: Threaded Test", "[common]") {
std::array<char, 2> value = {seed, seed};
std::size_t i = 0;
while (i < count) {
if (const std::size_t c = buf.Push(&value[0], 1); c > 0) {
REQUIRE(c == 1U);
if (const std::size_t c = buf.Push(&value[0], 2); c > 0) {
REQUIRE(c == 2U);
i++;
next_value(value);
} else {
@ -107,7 +107,7 @@ TEST_CASE("RingBuffer: Threaded Test", "[common]") {
std::array<char, 2> value = {seed, seed};
std::size_t i = 0;
while (i < count) {
if (const std::vector<char> v = buf.Pop(1); v.size() > 0) {
if (const std::vector<char> v = buf.Pop(2); v.size() > 0) {
REQUIRE(v.size() == 2U);
REQUIRE(v[0] == value[0]);
REQUIRE(v[1] == value[1]);