pw_ring_buffer/prefixed_entry_ring_buffer_test.cc - 3p/google/pigweed - Git at Google

 // Copyright 2020 The Pigweed Authors
 //
 // 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
 //
 //     https://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 "pw_ring_buffer/prefixed_entry_ring_buffer.h"

 #include <cstddef>
 #include <cstdint>

 #include "pw_containers/vector.h"
 #include "pw_unit_test/framework.h"

 using std::byte;

 namespace pw {
 namespace ring_buffer {
 namespace {

 TEST(PrefixedEntryRingBuffer, NoBuffer) {
   PrefixedEntryRingBuffer ring(false);

   byte buf[32];
   size_t count;

   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.SetBuffer(span<byte>(nullptr, 10u)), Status::INVALID_ARGUMENT);
   EXPECT_EQ(ring.SetBuffer(span(buf, 0u)), Status::INVALID_ARGUMENT);
   EXPECT_EQ(ring.FrontEntryDataSizeBytes(), 0u);

   EXPECT_EQ(ring.PushBack(buf), Status::FAILED_PRECONDITION);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PeekFront(buf, &count), Status::FAILED_PRECONDITION);
   EXPECT_EQ(count, 0u);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PeekFrontWithPreamble(buf, &count),
             Status::FAILED_PRECONDITION);
   EXPECT_EQ(count, 0u);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PopFront(), Status::FAILED_PRECONDITION);
   EXPECT_EQ(ring.EntryCount(), 0u);
 }

 // Single entry to write/read/pop over and over again.
 constexpr byte single_entry_data[] = {byte(1),
                                       byte(2),
                                       byte(3),
                                       byte(4),
                                       byte(5),
                                       byte(6),
                                       byte(7),
                                       byte(8),
                                       byte(9)};
 constexpr size_t single_entry_total_size = sizeof(single_entry_data) + 1;
 constexpr size_t single_entry_test_buffer_size =
     (single_entry_total_size * 7) / 2;

 // Make sure the single_entry_size is even so single_entry_buffer_Size gets the
 // proper wrap/even behavior when getting to the end of the buffer.
 static_assert((single_entry_total_size % 2) == 0u);
 constexpr size_t kSingleEntryCycles = 300u;

 // Repeatedly write the same data, read it, and pop it, done over and over
 // again.
 void SingleEntryWriteReadTest(bool user_data) {
   PrefixedEntryRingBuffer ring(user_data);
   byte test_buffer[single_entry_test_buffer_size];

   byte read_buffer[single_entry_total_size];

   // Set read_size to an unexpected value to make sure result checks don't luck
   // out and happen to see a previous value.
   size_t read_size = 500U;

   EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PopFront(), Status::OUT_OF_RANGE);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PushBack(span(single_entry_data, 0u)),
             Status::INVALID_ARGUMENT);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PushBack(span(single_entry_data, sizeof(test_buffer) + 5)),
             Status::OUT_OF_RANGE);
   EXPECT_EQ(ring.EntryCount(), 0u);
   EXPECT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OUT_OF_RANGE);
   EXPECT_EQ(read_size, 0u);
   read_size = 500U;
   EXPECT_EQ(ring.PeekFrontWithPreamble(read_buffer, &read_size),
             Status::OUT_OF_RANGE);
   EXPECT_EQ(read_size, 0u);

   size_t user_preamble_bytes = (user_data ? 1 : 0);
   size_t data_size = sizeof(single_entry_data) - user_preamble_bytes;
   size_t data_offset = single_entry_total_size - data_size;

   byte expect_buffer[single_entry_total_size] = {};
   expect_buffer[user_preamble_bytes] = byte(data_size);
   memcpy(expect_buffer + data_offset, single_entry_data, data_size);

   for (size_t i = 0; i < kSingleEntryCycles; i++) {
     ASSERT_EQ(ring.FrontEntryDataSizeBytes(), 0u);
     ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), 0u);

     ASSERT_EQ(ring.PushBack(span(single_entry_data, data_size), byte(i)),
               Status::OK);
     ASSERT_EQ(ring.FrontEntryDataSizeBytes(), data_size);
     ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), single_entry_total_size);

     read_size = 500U;
     ASSERT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OK);
     ASSERT_EQ(read_size, data_size);

     // ASSERT_THAT(span(expect_buffer).last(data_size),
     //            testing::ElementsAreArray(span(read_buffer, data_size)));
     ASSERT_EQ(
         memcmp(
             span(expect_buffer).last(data_size).data(), read_buffer, data_size),
         0);

     read_size = 500U;
     ASSERT_EQ(ring.PeekFrontWithPreamble(read_buffer, &read_size), Status::OK);
     ASSERT_EQ(read_size, single_entry_total_size);
     ASSERT_EQ(ring.PopFront(), Status::OK);

     if (user_data) {
       expect_buffer[0] = byte(i);
     }

     // ASSERT_THAT(span(expect_buffer),
     //            testing::ElementsAreArray(span(read_buffer)));
     ASSERT_EQ(memcmp(expect_buffer, read_buffer, single_entry_total_size), 0);
   }
 }

 TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadNoUserData) {
   SingleEntryWriteReadTest(false);
 }

 TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadYesUserData) {
   SingleEntryWriteReadTest(true);
 }

 constexpr size_t kOuterCycles = 5000u;
 constexpr size_t kCountingUpMaxExpectedEntries =
     single_entry_test_buffer_size / single_entry_total_size;

 // Write data that is filled with a byte value that increments each write. Write
 // many times without read/pop and then check to make sure correct contents are
 // in the ring buffer.
 template <bool user_data>
 void CountingUpWriteReadTest() {
   PrefixedEntryRingBuffer ring(user_data);
   byte test_buffer[single_entry_test_buffer_size];

   EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);
   EXPECT_EQ(ring.EntryCount(), 0u);

   constexpr size_t data_size = sizeof(single_entry_data) - (user_data ? 1 : 0);

   for (size_t i = 0; i < kOuterCycles; i++) {
     size_t seed = i;

     byte write_buffer[data_size];

     size_t j;
     for (j = 0; j < kSingleEntryCycles; j++) {
       memset(write_buffer, j + seed, sizeof(write_buffer));

       ASSERT_EQ(ring.PushBack(write_buffer), Status::OK);

       size_t expected_count = (j < kCountingUpMaxExpectedEntries)
                                   ? j + 1
                                   : kCountingUpMaxExpectedEntries;
       ASSERT_EQ(ring.EntryCount(), expected_count);
     }
     size_t final_write_j = j;
     size_t fill_val = seed + final_write_j - kCountingUpMaxExpectedEntries;

     for (j = 0; j < kCountingUpMaxExpectedEntries; j++) {
       byte read_buffer[sizeof(write_buffer)];
       size_t read_size;
       memset(write_buffer, fill_val + j, sizeof(write_buffer));
       ASSERT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OK);

       ASSERT_EQ(memcmp(write_buffer, read_buffer, data_size), 0);

       ASSERT_EQ(ring.PopFront(), Status::OK);
     }
   }
 }

 TEST(PrefixedEntryRingBuffer, CountingUpWriteReadNoUserData) {
   CountingUpWriteReadTest<false>();
 }

 TEST(PrefixedEntryRingBuffer, CountingUpWriteReadYesUserData) {
   CountingUpWriteReadTest<true>();
 }

 // Create statically to prevent allocating a capture in the lambda below.
 static pw::Vector<byte, single_entry_total_size> read_buffer;

 // Repeatedly write the same data, read it, and pop it, done over and over
 // again.
 void SingleEntryWriteReadWithSectionWriterTest(bool user_data) {
   PrefixedEntryRingBuffer ring(user_data);
   byte test_buffer[single_entry_test_buffer_size];

   EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

   auto output = [](span<const byte> src) -> Status {
     for (byte b : src) {
       read_buffer.push_back(b);
     }
     return Status::OK;
   };

   size_t user_preamble_bytes = (user_data ? 1 : 0);
   size_t data_size = sizeof(single_entry_data) - user_preamble_bytes;
   size_t data_offset = single_entry_total_size - data_size;

   byte expect_buffer[single_entry_total_size] = {};
   expect_buffer[user_preamble_bytes] = byte(data_size);
   memcpy(expect_buffer + data_offset, single_entry_data, data_size);

   for (size_t i = 0; i < kSingleEntryCycles; i++) {
     ASSERT_EQ(ring.FrontEntryDataSizeBytes(), 0u);
     ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), 0u);

     ASSERT_EQ(ring.PushBack(span(single_entry_data, data_size), byte(i)),
               Status::OK);
     ASSERT_EQ(ring.FrontEntryDataSizeBytes(), data_size);
     ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), single_entry_total_size);

     read_buffer.clear();
     ASSERT_EQ(ring.PeekFront(output), Status::OK);
     ASSERT_EQ(read_buffer.size(), data_size);

     ASSERT_EQ(memcmp(span(expect_buffer).last(data_size).data(),
                      read_buffer.data(),
                      data_size),
               0);

     read_buffer.clear();
     ASSERT_EQ(ring.PeekFrontWithPreamble(output), Status::OK);
     ASSERT_EQ(read_buffer.size(), single_entry_total_size);
     ASSERT_EQ(ring.PopFront(), Status::OK);

     if (user_data) {
       expect_buffer[0] = byte(i);
     }

     ASSERT_EQ(
         memcmp(expect_buffer, read_buffer.data(), single_entry_total_size), 0);
   }
 }

 TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadWithSectionWriterNoUserData) {
   SingleEntryWriteReadWithSectionWriterTest(false);
 }

 TEST(PrefixedEntryRingBuffer,
      SingleEntryWriteReadWithSectionWriterYesUserData) {
   SingleEntryWriteReadWithSectionWriterTest(true);
 }

 constexpr size_t kEntrySizeBytes = 8u;
 constexpr size_t kTotalEntryCount = 20u;
 constexpr size_t kBufferExtraBytes = 5u;
 constexpr size_t kTestBufferSize =
     (kEntrySizeBytes * kTotalEntryCount) + kBufferExtraBytes;

 // Create statically to prevent allocating a capture in the lambda below.
 static pw::Vector<byte, kTestBufferSize> actual_result;

 void DeringTest(bool preload) {
   PrefixedEntryRingBuffer ring;

   byte test_buffer[kTestBufferSize];
   EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

   // Entry data is entry size - preamble (single byte in this case).
   byte single_entry_buffer[kEntrySizeBytes - 1u];
   auto entry_data = span(single_entry_buffer);
   size_t i;

   size_t loop_goal = preload ? 500 : 1;

   for (size_t main_loop_count = 0; main_loop_count < loop_goal;
        main_loop_count++) {
     if (preload) {
       // Prime the ringbuffer with some junk data to get the buffer
       // wrapped.
       for (i = 0; i < (kTotalEntryCount * (main_loop_count % 64u)); i++) {
         memset(single_entry_buffer, i, sizeof(single_entry_buffer));
         ring.PushBack(single_entry_buffer);
       }
     }

     // Build up the expected buffer and fill the ring buffer with the test data.
     pw::Vector<byte, kTestBufferSize> expected_result;
     for (i = 0; i < kTotalEntryCount; i++) {
       // First component of the entry: the varint size.
       static_assert(sizeof(single_entry_buffer) < 127);
       expected_result.push_back(byte(sizeof(single_entry_buffer)));

       // Second component of the entry: the raw data.
       memset(single_entry_buffer, 'a' + i, sizeof(single_entry_buffer));
       for (byte b : entry_data) {
         expected_result.push_back(b);
       }

       // The ring buffer internally pushes the varint size byte.
       ring.PushBack(single_entry_buffer);
     }

     // Check values before doing the dering.
     EXPECT_EQ(ring.EntryCount(), kTotalEntryCount);
     EXPECT_EQ(expected_result.size(), ring.TotalUsedBytes());

     ASSERT_EQ(ring.Dering(), Status::OK);

     // Check values after doing the dering.
     EXPECT_EQ(ring.EntryCount(), kTotalEntryCount);
     EXPECT_EQ(expected_result.size(), ring.TotalUsedBytes());

     // Read out the entries of the ring buffer.
     actual_result.clear();
     auto output = [](span<const byte> src) -> Status {
       for (byte b : src) {
         actual_result.push_back(b);
       }
       return Status::OK;
     };
     while (ring.EntryCount()) {
       ASSERT_EQ(ring.PeekFrontWithPreamble(output), Status::OK);
       ASSERT_EQ(ring.PopFront(), Status::OK);
     }

     // Ensure the actual result out of the ring buffer matches our manually
     // computed result.
     EXPECT_EQ(expected_result.size(), actual_result.size());
     ASSERT_EQ(memcmp(test_buffer, actual_result.data(), actual_result.size()),
               0);
     ASSERT_EQ(
         memcmp(
             expected_result.data(), actual_result.data(), actual_result.size()),
         0);
   }
 }

 TEST(PrefixedEntryRingBuffer, Dering) { DeringTest(true); }
 TEST(PrefixedEntryRingBuffer, DeringNoPreload) { DeringTest(false); }

 }  // namespace
 }  // namespace ring_buffer
 }  // namespace pw
	// Copyright 2020 The Pigweed Authors
	//
	// 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
	//
	// https://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 "pw_ring_buffer/prefixed_entry_ring_buffer.h"

	#include <cstddef>
	#include <cstdint>

	#include "pw_containers/vector.h"
	#include "pw_unit_test/framework.h"

	using std::byte;

	namespace pw {
	namespace ring_buffer {
	namespace {

	TEST(PrefixedEntryRingBuffer, NoBuffer) {
	PrefixedEntryRingBuffer ring(false);

	byte buf[32];
	size_t count;

	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.SetBuffer(span<byte>(nullptr, 10u)), Status::INVALID_ARGUMENT);
	EXPECT_EQ(ring.SetBuffer(span(buf, 0u)), Status::INVALID_ARGUMENT);
	EXPECT_EQ(ring.FrontEntryDataSizeBytes(), 0u);

	EXPECT_EQ(ring.PushBack(buf), Status::FAILED_PRECONDITION);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PeekFront(buf, &count), Status::FAILED_PRECONDITION);
	EXPECT_EQ(count, 0u);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PeekFrontWithPreamble(buf, &count),
	Status::FAILED_PRECONDITION);
	EXPECT_EQ(count, 0u);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PopFront(), Status::FAILED_PRECONDITION);
	EXPECT_EQ(ring.EntryCount(), 0u);
	}

	// Single entry to write/read/pop over and over again.
	constexpr byte single_entry_data[] = {byte(1),
	byte(2),
	byte(3),
	byte(4),
	byte(5),
	byte(6),
	byte(7),
	byte(8),
	byte(9)};
	constexpr size_t single_entry_total_size = sizeof(single_entry_data) + 1;
	constexpr size_t single_entry_test_buffer_size =
	(single_entry_total_size * 7) / 2;

	// Make sure the single_entry_size is even so single_entry_buffer_Size gets the
	// proper wrap/even behavior when getting to the end of the buffer.
	static_assert((single_entry_total_size % 2) == 0u);
	constexpr size_t kSingleEntryCycles = 300u;

	// Repeatedly write the same data, read it, and pop it, done over and over
	// again.
	void SingleEntryWriteReadTest(bool user_data) {
	PrefixedEntryRingBuffer ring(user_data);
	byte test_buffer[single_entry_test_buffer_size];

	byte read_buffer[single_entry_total_size];

	// Set read_size to an unexpected value to make sure result checks don't luck
	// out and happen to see a previous value.
	size_t read_size = 500U;

	EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PopFront(), Status::OUT_OF_RANGE);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PushBack(span(single_entry_data, 0u)),
	Status::INVALID_ARGUMENT);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PushBack(span(single_entry_data, sizeof(test_buffer) + 5)),
	Status::OUT_OF_RANGE);
	EXPECT_EQ(ring.EntryCount(), 0u);
	EXPECT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OUT_OF_RANGE);
	EXPECT_EQ(read_size, 0u);
	read_size = 500U;
	EXPECT_EQ(ring.PeekFrontWithPreamble(read_buffer, &read_size),
	Status::OUT_OF_RANGE);
	EXPECT_EQ(read_size, 0u);

	size_t user_preamble_bytes = (user_data ? 1 : 0);
	size_t data_size = sizeof(single_entry_data) - user_preamble_bytes;
	size_t data_offset = single_entry_total_size - data_size;

	byte expect_buffer[single_entry_total_size] = {};
	expect_buffer[user_preamble_bytes] = byte(data_size);
	memcpy(expect_buffer + data_offset, single_entry_data, data_size);

	for (size_t i = 0; i < kSingleEntryCycles; i++) {
	ASSERT_EQ(ring.FrontEntryDataSizeBytes(), 0u);
	ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), 0u);

	ASSERT_EQ(ring.PushBack(span(single_entry_data, data_size), byte(i)),
	Status::OK);
	ASSERT_EQ(ring.FrontEntryDataSizeBytes(), data_size);
	ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), single_entry_total_size);

	read_size = 500U;
	ASSERT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OK);
	ASSERT_EQ(read_size, data_size);

	// ASSERT_THAT(span(expect_buffer).last(data_size),
	// testing::ElementsAreArray(span(read_buffer, data_size)));
	ASSERT_EQ(
	memcmp(
	span(expect_buffer).last(data_size).data(), read_buffer, data_size),
	0);

	read_size = 500U;
	ASSERT_EQ(ring.PeekFrontWithPreamble(read_buffer, &read_size), Status::OK);
	ASSERT_EQ(read_size, single_entry_total_size);
	ASSERT_EQ(ring.PopFront(), Status::OK);

	if (user_data) {
	expect_buffer[0] = byte(i);
	}

	// ASSERT_THAT(span(expect_buffer),
	// testing::ElementsAreArray(span(read_buffer)));
	ASSERT_EQ(memcmp(expect_buffer, read_buffer, single_entry_total_size), 0);
	}
	}

	TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadNoUserData) {
	SingleEntryWriteReadTest(false);
	}

	TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadYesUserData) {
	SingleEntryWriteReadTest(true);
	}

	constexpr size_t kOuterCycles = 5000u;
	constexpr size_t kCountingUpMaxExpectedEntries =
	single_entry_test_buffer_size / single_entry_total_size;

	// Write data that is filled with a byte value that increments each write. Write
	// many times without read/pop and then check to make sure correct contents are
	// in the ring buffer.
	template <bool user_data>
	void CountingUpWriteReadTest() {
	PrefixedEntryRingBuffer ring(user_data);
	byte test_buffer[single_entry_test_buffer_size];

	EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);
	EXPECT_EQ(ring.EntryCount(), 0u);

	constexpr size_t data_size = sizeof(single_entry_data) - (user_data ? 1 : 0);

	for (size_t i = 0; i < kOuterCycles; i++) {
	size_t seed = i;

	byte write_buffer[data_size];

	size_t j;
	for (j = 0; j < kSingleEntryCycles; j++) {
	memset(write_buffer, j + seed, sizeof(write_buffer));

	ASSERT_EQ(ring.PushBack(write_buffer), Status::OK);

	size_t expected_count = (j < kCountingUpMaxExpectedEntries)
	? j + 1
	: kCountingUpMaxExpectedEntries;
	ASSERT_EQ(ring.EntryCount(), expected_count);
	}
	size_t final_write_j = j;
	size_t fill_val = seed + final_write_j - kCountingUpMaxExpectedEntries;

	for (j = 0; j < kCountingUpMaxExpectedEntries; j++) {
	byte read_buffer[sizeof(write_buffer)];
	size_t read_size;
	memset(write_buffer, fill_val + j, sizeof(write_buffer));
	ASSERT_EQ(ring.PeekFront(read_buffer, &read_size), Status::OK);

	ASSERT_EQ(memcmp(write_buffer, read_buffer, data_size), 0);

	ASSERT_EQ(ring.PopFront(), Status::OK);
	}
	}
	}

	TEST(PrefixedEntryRingBuffer, CountingUpWriteReadNoUserData) {
	CountingUpWriteReadTest<false>();
	}

	TEST(PrefixedEntryRingBuffer, CountingUpWriteReadYesUserData) {
	CountingUpWriteReadTest<true>();
	}

	// Create statically to prevent allocating a capture in the lambda below.
	static pw::Vector<byte, single_entry_total_size> read_buffer;

	// Repeatedly write the same data, read it, and pop it, done over and over
	// again.
	void SingleEntryWriteReadWithSectionWriterTest(bool user_data) {
	PrefixedEntryRingBuffer ring(user_data);
	byte test_buffer[single_entry_test_buffer_size];

	EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

	auto output = [](span<const byte> src) -> Status {
	for (byte b : src) {
	read_buffer.push_back(b);
	}
	return Status::OK;
	};

	size_t user_preamble_bytes = (user_data ? 1 : 0);
	size_t data_size = sizeof(single_entry_data) - user_preamble_bytes;
	size_t data_offset = single_entry_total_size - data_size;

	byte expect_buffer[single_entry_total_size] = {};
	expect_buffer[user_preamble_bytes] = byte(data_size);
	memcpy(expect_buffer + data_offset, single_entry_data, data_size);

	for (size_t i = 0; i < kSingleEntryCycles; i++) {
	ASSERT_EQ(ring.FrontEntryDataSizeBytes(), 0u);
	ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), 0u);

	ASSERT_EQ(ring.PushBack(span(single_entry_data, data_size), byte(i)),
	Status::OK);
	ASSERT_EQ(ring.FrontEntryDataSizeBytes(), data_size);
	ASSERT_EQ(ring.FrontEntryTotalSizeBytes(), single_entry_total_size);

	read_buffer.clear();
	ASSERT_EQ(ring.PeekFront(output), Status::OK);
	ASSERT_EQ(read_buffer.size(), data_size);

	ASSERT_EQ(memcmp(span(expect_buffer).last(data_size).data(),
	read_buffer.data(),
	data_size),
	0);

	read_buffer.clear();
	ASSERT_EQ(ring.PeekFrontWithPreamble(output), Status::OK);
	ASSERT_EQ(read_buffer.size(), single_entry_total_size);
	ASSERT_EQ(ring.PopFront(), Status::OK);

	if (user_data) {
	expect_buffer[0] = byte(i);
	}

	ASSERT_EQ(
	memcmp(expect_buffer, read_buffer.data(), single_entry_total_size), 0);
	}
	}

	TEST(PrefixedEntryRingBuffer, SingleEntryWriteReadWithSectionWriterNoUserData) {
	SingleEntryWriteReadWithSectionWriterTest(false);
	}

	TEST(PrefixedEntryRingBuffer,
	SingleEntryWriteReadWithSectionWriterYesUserData) {
	SingleEntryWriteReadWithSectionWriterTest(true);
	}

	constexpr size_t kEntrySizeBytes = 8u;
	constexpr size_t kTotalEntryCount = 20u;
	constexpr size_t kBufferExtraBytes = 5u;
	constexpr size_t kTestBufferSize =
	(kEntrySizeBytes * kTotalEntryCount) + kBufferExtraBytes;

	// Create statically to prevent allocating a capture in the lambda below.
	static pw::Vector<byte, kTestBufferSize> actual_result;

	void DeringTest(bool preload) {
	PrefixedEntryRingBuffer ring;

	byte test_buffer[kTestBufferSize];
	EXPECT_EQ(ring.SetBuffer(test_buffer), Status::OK);

	// Entry data is entry size - preamble (single byte in this case).
	byte single_entry_buffer[kEntrySizeBytes - 1u];
	auto entry_data = span(single_entry_buffer);
	size_t i;

	size_t loop_goal = preload ? 500 : 1;

	for (size_t main_loop_count = 0; main_loop_count < loop_goal;
	main_loop_count++) {
	if (preload) {
	// Prime the ringbuffer with some junk data to get the buffer
	// wrapped.
	for (i = 0; i < (kTotalEntryCount * (main_loop_count % 64u)); i++) {
	memset(single_entry_buffer, i, sizeof(single_entry_buffer));
	ring.PushBack(single_entry_buffer);
	}
	}

	// Build up the expected buffer and fill the ring buffer with the test data.
	pw::Vector<byte, kTestBufferSize> expected_result;
	for (i = 0; i < kTotalEntryCount; i++) {
	// First component of the entry: the varint size.
	static_assert(sizeof(single_entry_buffer) < 127);
	expected_result.push_back(byte(sizeof(single_entry_buffer)));

	// Second component of the entry: the raw data.
	memset(single_entry_buffer, 'a' + i, sizeof(single_entry_buffer));
	for (byte b : entry_data) {
	expected_result.push_back(b);
	}

	// The ring buffer internally pushes the varint size byte.
	ring.PushBack(single_entry_buffer);
	}

	// Check values before doing the dering.
	EXPECT_EQ(ring.EntryCount(), kTotalEntryCount);
	EXPECT_EQ(expected_result.size(), ring.TotalUsedBytes());

	ASSERT_EQ(ring.Dering(), Status::OK);

	// Check values after doing the dering.
	EXPECT_EQ(ring.EntryCount(), kTotalEntryCount);
	EXPECT_EQ(expected_result.size(), ring.TotalUsedBytes());

	// Read out the entries of the ring buffer.
	actual_result.clear();
	auto output = [](span<const byte> src) -> Status {
	for (byte b : src) {
	actual_result.push_back(b);
	}
	return Status::OK;
	};
	while (ring.EntryCount()) {
	ASSERT_EQ(ring.PeekFrontWithPreamble(output), Status::OK);
	ASSERT_EQ(ring.PopFront(), Status::OK);
	}

	// Ensure the actual result out of the ring buffer matches our manually
	// computed result.
	EXPECT_EQ(expected_result.size(), actual_result.size());
	ASSERT_EQ(memcmp(test_buffer, actual_result.data(), actual_result.size()),
	0);
	ASSERT_EQ(
	memcmp(
	expected_result.data(), actual_result.data(), actual_result.size()),
	0);
	}
	}

	TEST(PrefixedEntryRingBuffer, Dering) { DeringTest(true); }
	TEST(PrefixedEntryRingBuffer, DeringNoPreload) { DeringTest(false); }

	} // namespace
	} // namespace ring_buffer
	} // namespace pw