| // 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_kvs/internal/entry_cache.h" |
| |
| #include <cinttypes> |
| |
| #include "pw_kvs/flash_memory.h" |
| #include "pw_kvs/internal/entry.h" |
| #include "pw_kvs/internal/hash.h" |
| #include "pw_kvs_private/macros.h" |
| #include "pw_log/log.h" |
| |
| namespace pw::kvs::internal { |
| namespace { |
| |
| using std::string_view; |
| |
| constexpr FlashPartition::Address kNoAddress = FlashPartition::Address(-1); |
| |
| } // namespace |
| |
| void EntryMetadata::RemoveAddress(Address address_to_remove) { |
| // Find the index of the address to remove. |
| for (Address& address : addresses_) { |
| if (address == address_to_remove) { |
| // Move the address at the back of the list to the slot of the address |
| // being removed. Do this unconditionally, even if the address to remove |
| // is the last slot since the logic still works. |
| address = addresses_.back(); |
| |
| // Remove the back entry of the address list. |
| addresses_.back() = kNoAddress; |
| addresses_ = span(addresses_.begin(), addresses_.size() - 1); |
| break; |
| } |
| } |
| } |
| |
| void EntryMetadata::Reset(const KeyDescriptor& descriptor, Address address) { |
| *descriptor_ = descriptor; |
| |
| addresses_[0] = address; |
| for (size_t i = 1; i < addresses_.size(); ++i) { |
| addresses_[i] = kNoAddress; |
| } |
| addresses_ = addresses_.first(1); |
| } |
| |
| StatusWithSize EntryCache::Find(FlashPartition& partition, |
| const Sectors& sectors, |
| const EntryFormats& formats, |
| string_view key, |
| EntryMetadata* metadata) const { |
| const uint32_t hash = internal::Hash(key); |
| Entry::KeyBuffer key_buffer; |
| bool error_detected = false; |
| |
| for (size_t i = 0; i < descriptors_.size(); ++i) { |
| if (descriptors_[i].key_hash == hash) { |
| bool key_found = false; |
| string_view read_key; |
| |
| for (Address address : addresses(i)) { |
| Status read_result = |
| Entry::ReadKey(partition, address, key.size(), key_buffer.data()); |
| |
| read_key = string_view(key_buffer.data(), key.size()); |
| |
| if (read_result.ok() && hash == internal::Hash(read_key)) { |
| key_found = true; |
| break; |
| } else { |
| // A hash mismatch can be caused by reading invalid data or a key hash |
| // collision of keys with differing size. To verify the data read from |
| // flash is good, validate the entry. |
| Entry entry; |
| read_result = Entry::Read(partition, address, formats, &entry); |
| if (read_result.ok() && entry.VerifyChecksumInFlash().ok()) { |
| key_found = true; |
| break; |
| } |
| |
| PW_LOG_WARN( |
| " Found corrupt entry, invalidating this copy of the key"); |
| error_detected = true; |
| sectors.FromAddress(address).mark_corrupt(); |
| } |
| } |
| size_t error_val = error_detected ? 1 : 0; |
| |
| if (!key_found) { |
| PW_LOG_ERROR("No valid entries for key. Data has been lost!"); |
| return StatusWithSize(Status::DATA_LOSS, error_val); |
| } else if (key == read_key) { |
| PW_LOG_DEBUG("Found match for key hash 0x%08" PRIx32, hash); |
| *metadata = EntryMetadata(descriptors_[i], addresses(i)); |
| return StatusWithSize(Status::OK, error_val); |
| } else { |
| PW_LOG_WARN("Found key hash collision for 0x%08" PRIx32, hash); |
| return StatusWithSize(Status::ALREADY_EXISTS, error_val); |
| } |
| } |
| } |
| return StatusWithSize::NOT_FOUND; |
| } |
| |
| EntryMetadata EntryCache::AddNew(const KeyDescriptor& descriptor, |
| Address entry_address) const { |
| // TODO(hepler): DCHECK(!full()); |
| Address* first_address = ResetAddresses(descriptors_.size(), entry_address); |
| descriptors_.push_back(descriptor); |
| return EntryMetadata(descriptors_.back(), span(first_address, 1)); |
| } |
| |
| // TODO: This method is the trigger of the O(valid_entries * all_entries) time |
| // complexity for reading. At some cost to memory, this could be optimized by |
| // using a hash table instead of scanning, but in practice this should be fine |
| // for a small number of keys |
| Status EntryCache::AddNewOrUpdateExisting(const KeyDescriptor& descriptor, |
| Address address, |
| size_t sector_size_bytes) const { |
| // With the new key descriptor, either add it to the descriptor table or |
| // overwrite an existing entry with an older version of the key. |
| const int index = FindIndex(descriptor.key_hash); |
| |
| // Write a new entry if there is room. |
| if (index == -1) { |
| if (full()) { |
| return Status::RESOURCE_EXHAUSTED; |
| } |
| AddNew(descriptor, address); |
| return Status::OK; |
| } |
| |
| // Existing entry is old; replace the existing entry with the new one. |
| if (descriptor.transaction_id > descriptors_[index].transaction_id) { |
| descriptors_[index] = descriptor; |
| ResetAddresses(index, address); |
| return Status::OK; |
| } |
| |
| // If the entries have a duplicate transaction ID, add the new (redundant) |
| // entry to the existing descriptor. |
| if (descriptors_[index].transaction_id == descriptor.transaction_id) { |
| if (descriptors_[index].key_hash != descriptor.key_hash) { |
| PW_LOG_ERROR("Duplicate entry for key 0x%08" PRIx32 |
| " with transaction ID %" PRIu32 " has non-matching hash", |
| descriptor.key_hash, |
| descriptor.transaction_id); |
| return Status::DATA_LOSS; |
| } |
| |
| // Verify that this entry is not in the same sector as an existing copy of |
| // this same key. |
| for (Address existing_address : addresses(index)) { |
| if (existing_address / sector_size_bytes == address / sector_size_bytes) { |
| PW_LOG_DEBUG("Multiple Redundant entries in same sector %u", |
| unsigned(address / sector_size_bytes)); |
| return Status::DATA_LOSS; |
| } |
| } |
| |
| AddAddressIfRoom(index, address); |
| } else { |
| PW_LOG_DEBUG("Found stale entry when appending; ignoring"); |
| } |
| return Status::OK; |
| } |
| |
| size_t EntryCache::present_entries() const { |
| size_t present_entries = 0; |
| |
| for (const KeyDescriptor& descriptor : descriptors_) { |
| if (descriptor.state != EntryState::kDeleted) { |
| present_entries += 1; |
| } |
| } |
| |
| return present_entries; |
| } |
| |
| int EntryCache::FindIndex(uint32_t key_hash) const { |
| for (size_t i = 0; i < descriptors_.size(); ++i) { |
| if (descriptors_[i].key_hash == key_hash) { |
| return i; |
| } |
| } |
| return -1; |
| } |
| |
| void EntryCache::AddAddressIfRoom(size_t descriptor_index, |
| Address address) const { |
| Address* const existing = first_address(descriptor_index); |
| |
| for (size_t i = 0; i < redundancy(); ++i) { |
| if (existing[i] == kNoAddress) { |
| existing[i] = address; |
| return; |
| } |
| } |
| } |
| |
| span<EntryCache::Address> EntryCache::addresses(size_t descriptor_index) const { |
| Address* const addresses = first_address(descriptor_index); |
| |
| size_t size = 0; |
| while (size < redundancy() && addresses[size] != kNoAddress) { |
| size += 1; |
| } |
| |
| return span(addresses, size); |
| } |
| |
| EntryCache::Address* EntryCache::ResetAddresses(size_t descriptor_index, |
| Address address) const { |
| Address* first = first_address(descriptor_index); |
| *first = address; |
| |
| // Clear the additional addresses, if any. |
| for (size_t i = 1; i < redundancy_; ++i) { |
| first[i] = kNoAddress; |
| } |
| |
| return first; |
| } |
| |
| } // namespace pw::kvs::internal |