Transpose the encoding matrix
Stripe together the encodings from each of the 16 codewords, so that
if a 512-byte DRAM line is knocked out, it affects 256 bits from each
codeword rather than 4096 bits from a single encoded codeword.
Rather than using std::bitset, we directly set and read bits in
the std::vector<uint8_t>, because the striping means that copying it
will now cost not4k in allocation but 64k.
Decode directly to a word, without using list decoding. It seems
we don't need list decoding for the error rates that matter here,
and we never completed the implementation of it anyway.
Declare and test only the full interface, now that it doesn't decompose
quite so neatly.
Bug: 63928581
Test: atest HadamardTest
Change-Id: If022d3f4a8d6fccdf68119d4666f83ce5005bccb
diff --git a/rebootescrow/aidl/default/HadamardUtilsTest.cpp b/rebootescrow/aidl/default/HadamardUtilsTest.cpp
index e397e76..1c9a2fb 100644
--- a/rebootescrow/aidl/default/HadamardUtilsTest.cpp
+++ b/rebootescrow/aidl/default/HadamardUtilsTest.cpp
@@ -17,110 +17,35 @@
#include <stdint.h>
#include <random>
-#include <bitset>
-#include <utility>
-#include <vector>
-
#include <gtest/gtest.h>
#include <HadamardUtils.h>
using namespace aidl::android::hardware::rebootescrow::hadamard;
-class HadamardTest : public testing::Test {
- protected:
- void SetUp() override {
- auto ones = std::bitset<ENCODE_LENGTH>{}.set();
- // Expects 0x4000 to encode as top half as ones, and lower half as zeros. i.e.
- // [1, 1 .. 1, 0, 0 .. 0]
- expected_half_size_ = ones << half_size_;
+class HadamardTest : public testing::Test {};
- // Expects 0x1 to encode as interleaved 1 and 0s i.e. [1, 0, 1, 0 ..]
- expected_one_ = ones;
- for (uint32_t i = ENCODE_LENGTH / 2; i >= 1; i /= 2) {
- expected_one_ ^= (expected_one_ >> i);
+static void AddError(std::vector<uint8_t>* data) {
+ for (size_t i = 0; i < data->size(); i++) {
+ for (size_t j = 0; j < BYTE_LENGTH; j++) {
+ if (random() % 100 < 47) {
+ (*data)[i] ^= (1 << j);
+ }
}
}
-
- uint16_t half_size_ = ENCODE_LENGTH / 2;
- std::bitset<ENCODE_LENGTH> expected_one_;
- std::bitset<ENCODE_LENGTH> expected_half_size_;
-};
-
-static void AddError(std::bitset<ENCODE_LENGTH>* corrupted_bits) {
- // The hadamard code has a hamming distance of ENCODE_LENGTH/2. So we should always be able to
- // correct the data if less than a quarter of the encoded bits are corrupted.
- auto corrupted_max = 0.24f * corrupted_bits->size();
- auto corrupted_num = 0;
- for (size_t i = 0; i < corrupted_bits->size() && corrupted_num < corrupted_max; i++) {
- if (random() % 2 == 0) {
- (*corrupted_bits)[i] = !(*corrupted_bits)[i];
- corrupted_num += 1;
- }
- }
-}
-
-static void EncodeAndDecodeKeys(const std::vector<uint8_t>& key) {
- auto encoded = EncodeKey(key);
- ASSERT_EQ(64 * 1024, encoded.size());
- auto decoded = DecodeKey(encoded);
- ASSERT_EQ(key, std::vector<uint8_t>(decoded.begin(), decoded.begin() + key.size()));
-}
-
-TEST_F(HadamardTest, Encode_smoke) {
- ASSERT_EQ(expected_half_size_, EncodeWord(half_size_));
- ASSERT_EQ(expected_one_, EncodeWord(1));
- // Check the complement of 1.
- ASSERT_EQ(~expected_one_, EncodeWord(1u << CODE_K | 1u));
-}
-
-TEST_F(HadamardTest, Decode_smoke) {
- auto candidate = DecodeWord(expected_half_size_);
- auto expected = std::pair<int32_t, uint16_t>{ENCODE_LENGTH, half_size_};
- ASSERT_EQ(expected, candidate.top());
-
- candidate = DecodeWord(expected_one_);
- expected = std::pair<int32_t, uint16_t>{ENCODE_LENGTH, 1};
- ASSERT_EQ(expected, candidate.top());
}
TEST_F(HadamardTest, Decode_error_correction) {
constexpr auto iteration = 10;
for (int i = 0; i < iteration; i++) {
- uint16_t word = random() % (ENCODE_LENGTH * 2);
- auto corrupted_bits = EncodeWord(word);
- AddError(&corrupted_bits);
-
- auto candidate = DecodeWord(corrupted_bits);
- ASSERT_EQ(word, candidate.top().second);
+ std::vector<uint8_t> key;
+ for (int j = 0; j < KEY_SIZE_IN_BYTES; j++) {
+ key.emplace_back(random() & 0xff);
+ }
+ auto encoded = EncodeKey(key);
+ ASSERT_EQ(64 * 1024, encoded.size());
+ AddError(&encoded);
+ auto decoded = DecodeKey(encoded);
+ ASSERT_EQ(key, std::vector<uint8_t>(decoded.begin(), decoded.begin() + key.size()));
}
}
-
-TEST_F(HadamardTest, BytesToBitset_smoke) {
- auto bytes = BitsetToBytes(expected_one_);
-
- auto read_back = BytesToBitset(bytes);
- ASSERT_EQ(expected_one_, read_back);
-}
-
-TEST_F(HadamardTest, EncodeAndDecodeKey) {
- std::vector<uint8_t> KEY_1{
- 0xA5, 0x00, 0xFF, 0x01, 0xA5, 0x5a, 0xAA, 0x55, 0x00, 0xD3, 0x2A,
- 0x8C, 0x2E, 0x83, 0x0E, 0x65, 0x9E, 0x8D, 0xC6, 0xAC, 0x1E, 0x83,
- 0x21, 0xB3, 0x95, 0x02, 0x89, 0x64, 0x64, 0x92, 0x12, 0x1F,
- };
- std::vector<uint8_t> KEY_2{
- 0xFF, 0x00, 0x00, 0xAA, 0x5A, 0x19, 0x20, 0x71, 0x9F, 0xFB, 0xDA,
- 0xB6, 0x2D, 0x06, 0xD5, 0x49, 0x7E, 0xEF, 0x63, 0xAC, 0x18, 0xFF,
- 0x5A, 0xA3, 0x40, 0xBB, 0x64, 0xFA, 0x67, 0xC1, 0x10, 0x18,
- };
-
- EncodeAndDecodeKeys(KEY_1);
- EncodeAndDecodeKeys(KEY_2);
-
- std::vector<uint8_t> key;
- for (uint8_t i = 0; i < KEY_SIZE_IN_BYTES; i++) {
- key.push_back(i);
- };
- EncodeAndDecodeKeys(key);
-}