| // 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. |
| #pragma once |
| |
| #include <array> |
| #include <cstddef> |
| #include <cstdint> |
| #include <span> |
| #include <string_view> |
| #include <type_traits> |
| |
| #include "pw_containers/vector.h" |
| #include "pw_kvs/checksum.h" |
| #include "pw_kvs/flash_memory.h" |
| #include "pw_kvs/format.h" |
| #include "pw_kvs/internal/entry.h" |
| #include "pw_kvs/internal/entry_cache.h" |
| #include "pw_kvs/internal/key_descriptor.h" |
| #include "pw_kvs/internal/sectors.h" |
| #include "pw_kvs/internal/span_traits.h" |
| #include "pw_status/status.h" |
| #include "pw_status/status_with_size.h" |
| |
| namespace pw::kvs { |
| |
| enum class GargbageCollectOnWrite { |
| // Disable all automatic garbage collection on write. |
| kDisabled, |
| |
| // Allow up to a single sector, if needed, to be garbage collected on write. |
| kOneSector, |
| |
| // Allow as many sectors as needed be garbage collected on write. |
| kAsManySectorsNeeded, |
| }; |
| |
| enum class ErrorRecovery { |
| // Immediately do full recovery of any errors that are detected. |
| kImmediate, |
| |
| // Recover from errors, but delay time consuming recovery steps until later |
| // as part of other time consuming operations. Such as waiting to garbage |
| // collect sectors with corrupt entries until the next garbage collection. |
| kLazy, |
| |
| // Only recover from errors when manually triggered as part of maintenance |
| // operations. This is not recommended for normal use, only for test or |
| // read-only use. |
| kManual, |
| }; |
| |
| struct Options { |
| // Perform garbage collection if necessary when writing. If not kDisabled, |
| // garbage collection is attempted if space for an entry cannot be found. This |
| // is a relatively lengthy operation. If kDisabled, Put calls that would |
| // require garbage collection fail with RESOURCE_EXHAUSTED. |
| GargbageCollectOnWrite gc_on_write = GargbageCollectOnWrite::kOneSector; |
| |
| // When the KVS handles errors that are discovered, such as corrupt entries, |
| // not enough redundant copys of an entry, etc. |
| ErrorRecovery recovery = ErrorRecovery::kLazy; |
| |
| // Verify an entry's checksum after reading it from flash. |
| bool verify_on_read = true; |
| |
| // Verify an in-flash entry's checksum after writing it. |
| bool verify_on_write = true; |
| }; |
| |
| class KeyValueStore { |
| public: |
| // KeyValueStores are declared as instances of |
| // KeyValueStoreBuffer<MAX_ENTRIES, MAX_SECTORS>, which allocates buffers for |
| // tracking entries and flash sectors. |
| |
| // Initializes the key-value store. Must be called before calling other |
| // functions. |
| // |
| // Return values: |
| // |
| // OK: KVS successfully initialized. |
| // DATA_LOSS: KVS initialized and is usable, but contains corrupt data. |
| // UNKNOWN: Unknown error. KVS is not initialized. |
| // |
| Status Init(); |
| |
| bool initialized() const { |
| return initialized_ == InitializationState::kReady; |
| } |
| |
| // Reads the value of an entry in the KVS. The value is read into the provided |
| // buffer and the number of bytes read is returned. If desired, the read can |
| // be started at an offset. |
| // |
| // If the output buffer is too small for the value, Get returns |
| // RESOURCE_EXHAUSTED with the number of bytes read. The remainder of the |
| // value can be read by calling get with an offset. |
| // |
| // OK: the entry was successfully read |
| // NOT_FOUND: the key is not present in the KVS |
| // DATA_LOSS: found the entry, but the data was corrupted |
| // RESOURCE_EXHAUSTED: the buffer could not fit the entire value, but as |
| // many bytes as possible were written to it |
| // FAILED_PRECONDITION: the KVS is not initialized |
| // INVALID_ARGUMENT: key is empty or too long or value is too large |
| // |
| StatusWithSize Get(std::string_view key, |
| std::span<std::byte> value, |
| size_t offset_bytes = 0) const; |
| |
| // This overload of Get accepts a pointer to a trivially copyable object. |
| // If the value is an array, call Get with |
| // std::as_writable_bytes(std::span(array)), or pass a pointer to the array |
| // instead of the array itself. |
| template <typename Pointer, |
| typename = std::enable_if_t<std::is_pointer_v<Pointer>>> |
| Status Get(const std::string_view& key, const Pointer& pointer) const { |
| using T = std::remove_reference_t<std::remove_pointer_t<Pointer>>; |
| CheckThatObjectCanBePutOrGet<T>(); |
| return FixedSizeGet(key, pointer, sizeof(T)); |
| } |
| |
| // Adds a key-value entry to the KVS. If the key was already present, its |
| // value is overwritten. |
| // |
| // The value may be a std::span of bytes or a trivially copyable object. |
| // |
| // In the current implementation, all keys in the KVS must have a unique hash. |
| // If Put is called with a key whose hash matches an existing key, nothing |
| // is added and ALREADY_EXISTS is returned. |
| // |
| // OK: the entry was successfully added or updated |
| // DATA_LOSS: checksum validation failed after writing the data |
| // RESOURCE_EXHAUSTED: there is not enough space to add the entry |
| // ALREADY_EXISTS: the entry could not be added because a different key |
| // with the same hash is already in the KVS |
| // FAILED_PRECONDITION: the KVS is not initialized |
| // INVALID_ARGUMENT: key is empty or too long or value is too large |
| // |
| template <typename T> |
| Status Put(const std::string_view& key, const T& value) { |
| if constexpr (ConvertsToSpan<T>::value) { |
| return PutBytes(key, std::as_bytes(std::span(value))); |
| } else { |
| CheckThatObjectCanBePutOrGet<T>(); |
| return PutBytes(key, std::as_bytes(std::span(&value, 1))); |
| } |
| } |
| |
| // Removes a key-value entry from the KVS. |
| // |
| // OK: the entry was successfully added or updated |
| // NOT_FOUND: the key is not present in the KVS |
| // DATA_LOSS: checksum validation failed after recording the erase |
| // RESOURCE_EXHAUSTED: insufficient space to mark the entry as deleted |
| // FAILED_PRECONDITION: the KVS is not initialized |
| // INVALID_ARGUMENT: key is empty or too long |
| // |
| Status Delete(std::string_view key); |
| |
| // Returns the size of the value corresponding to the key. |
| // |
| // OK: the size was returned successfully |
| // NOT_FOUND: the key is not present in the KVS |
| // DATA_LOSS: checksum validation failed after reading the entry |
| // FAILED_PRECONDITION: the KVS is not initialized |
| // INVALID_ARGUMENT: key is empty or too long |
| // |
| StatusWithSize ValueSize(std::string_view key) const; |
| |
| // Perform all maintenance possible, including all neeeded repairing of |
| // corruption and garbage collection of all reclaimable space in the KVS. When |
| // configured for manual recovery, this is the only way KVS repair is |
| // triggered. |
| Status FullMaintenance(); |
| |
| // Perform a portion of KVS maintenance. If configured for at least lazy |
| // recovery, will do any needed repairing of corruption. Does garbage |
| // collection of part of the KVS, typically a single sector or similar unit |
| // that makes sense for the KVS implementation. |
| Status PartialMaintenance(); |
| |
| void LogDebugInfo() const; |
| |
| // Classes and functions to support STL-style iteration. |
| class iterator; |
| |
| class Item { |
| public: |
| // The key as a null-terminated string. |
| const char* key() const { return key_buffer_.data(); } |
| |
| // Gets the value referred to by this iterator. Equivalent to |
| // KeyValueStore::Get. |
| StatusWithSize Get(std::span<std::byte> value_buffer, |
| size_t offset_bytes = 0) const { |
| return kvs_.Get(key(), *iterator_, value_buffer, offset_bytes); |
| } |
| |
| template <typename Pointer, |
| typename = std::enable_if_t<std::is_pointer_v<Pointer>>> |
| Status Get(const Pointer& pointer) const { |
| using T = std::remove_reference_t<std::remove_pointer_t<Pointer>>; |
| CheckThatObjectCanBePutOrGet<T>(); |
| return kvs_.FixedSizeGet(key(), *iterator_, pointer, sizeof(T)); |
| } |
| |
| // Reads the size of the value referred to by this iterator. Equivalent to |
| // KeyValueStore::ValueSize. |
| StatusWithSize ValueSize() const { return kvs_.ValueSize(*iterator_); } |
| |
| private: |
| friend class iterator; |
| |
| constexpr Item(const KeyValueStore& kvs, |
| const internal::EntryCache::const_iterator& item_iterator) |
| : kvs_(kvs), iterator_(item_iterator), key_buffer_{} {} |
| |
| void ReadKey(); |
| |
| const KeyValueStore& kvs_; |
| internal::EntryCache::const_iterator iterator_; |
| |
| // Buffer large enough for a null-terminated version of any valid key. |
| std::array<char, internal::Entry::kMaxKeyLength + 1> key_buffer_; |
| }; |
| |
| class iterator { |
| public: |
| iterator& operator++(); |
| |
| iterator& operator++(int) { return operator++(); } |
| |
| // Reads the entry's key from flash. |
| const Item& operator*() { |
| item_.ReadKey(); |
| return item_; |
| } |
| |
| const Item* operator->() { |
| return &operator*(); // Read the key into the Item object. |
| } |
| |
| constexpr bool operator==(const iterator& rhs) const { |
| return item_.iterator_ == rhs.item_.iterator_; |
| } |
| |
| constexpr bool operator!=(const iterator& rhs) const { |
| return item_.iterator_ != rhs.item_.iterator_; |
| } |
| |
| private: |
| friend class KeyValueStore; |
| |
| constexpr iterator( |
| const KeyValueStore& kvs, |
| const internal::EntryCache::const_iterator& item_iterator) |
| : item_(kvs, item_iterator) {} |
| |
| Item item_; |
| }; |
| |
| using const_iterator = iterator; // Standard alias for iterable types. |
| |
| iterator begin() const; |
| iterator end() const { return iterator(*this, entry_cache_.end()); } |
| |
| // Returns the number of valid entries in the KeyValueStore. |
| size_t size() const { return entry_cache_.present_entries(); } |
| |
| size_t max_size() const { return entry_cache_.max_entries(); } |
| |
| size_t empty() const { return size() == 0u; } |
| |
| // Returns the number of transactions that have occurred since the KVS was |
| // first used. This value is retained across initializations, but is reset if |
| // the underlying flash is erased. |
| uint32_t transaction_count() const { return last_transaction_id_; } |
| |
| struct StorageStats { |
| size_t writable_bytes; |
| size_t in_use_bytes; |
| size_t reclaimable_bytes; |
| size_t corrupt_sectors_recovered; |
| size_t missing_redundant_entries_recovered; |
| }; |
| |
| StorageStats GetStorageStats() const; |
| |
| // Level of redundancy to use for writing entries. |
| size_t redundancy() const { return entry_cache_.redundancy(); } |
| |
| bool error_detected() const { return error_detected_; } |
| |
| // Check KVS for any error conditions. Primarily intended for test and |
| // internal use. |
| bool CheckForErrors(); |
| |
| protected: |
| using Address = FlashPartition::Address; |
| using Entry = internal::Entry; |
| using KeyDescriptor = internal::KeyDescriptor; |
| using SectorDescriptor = internal::SectorDescriptor; |
| |
| // In the future, will be able to provide additional EntryFormats for |
| // backwards compatibility. |
| KeyValueStore(FlashPartition* partition, |
| std::span<const EntryFormat> formats, |
| const Options& options, |
| size_t redundancy, |
| Vector<SectorDescriptor>& sector_descriptor_list, |
| const SectorDescriptor** temp_sectors_to_skip, |
| Vector<KeyDescriptor>& key_descriptor_list, |
| Address* addresses); |
| |
| private: |
| using EntryMetadata = internal::EntryMetadata; |
| using EntryState = internal::EntryState; |
| |
| template <typename T> |
| static constexpr void CheckThatObjectCanBePutOrGet() { |
| static_assert( |
| std::is_trivially_copyable_v<T> && !std::is_pointer_v<T>, |
| "Only trivially copyable, non-pointer objects may be Put and Get by " |
| "value. Any value may be stored by converting it to a byte std::span " |
| "with std::as_bytes(std::span(&value, 1)) or " |
| "std::as_writable_bytes(std::span(&value, 1))."); |
| } |
| |
| Status InitializeMetadata(); |
| Status LoadEntry(Address entry_address, Address* next_entry_address); |
| Status ScanForEntry(const SectorDescriptor& sector, |
| Address start_address, |
| Address* next_entry_address); |
| |
| Status PutBytes(std::string_view key, std::span<const std::byte> value); |
| |
| StatusWithSize ValueSize(const EntryMetadata& metadata) const; |
| |
| Status ReadEntry(const EntryMetadata& metadata, Entry& entry) const; |
| |
| // Finds the metadata for an entry matching a particular key. Searches for a |
| // KeyDescriptor that matches this key and sets *metadata to point to it if |
| // one is found. |
| // |
| // OK: there is a matching descriptor and *metadata is set |
| // NOT_FOUND: there is no descriptor that matches this key, but this key |
| // has a unique hash (and could potentially be added to the |
| // KVS) |
| // ALREADY_EXISTS: there is no descriptor that matches this key, but the |
| // key's hash collides with the hash for an existing |
| // descriptor |
| // |
| Status FindEntry(std::string_view key, EntryMetadata* metadata) const; |
| |
| // Searches for a KeyDescriptor that matches this key and sets *metadata to |
| // point to it if one is found. |
| // |
| // OK: there is a matching descriptor and *metadata is set |
| // NOT_FOUND: there is no descriptor that matches this key |
| // |
| Status FindExisting(std::string_view key, EntryMetadata* metadata) const; |
| |
| StatusWithSize Get(std::string_view key, |
| const EntryMetadata& metadata, |
| std::span<std::byte> value_buffer, |
| size_t offset_bytes) const; |
| |
| Status FixedSizeGet(std::string_view key, |
| void* value, |
| size_t size_bytes) const; |
| |
| Status FixedSizeGet(std::string_view key, |
| const EntryMetadata& descriptor, |
| void* value, |
| size_t size_bytes) const; |
| |
| Status CheckWriteOperation(std::string_view key) const; |
| Status CheckReadOperation(std::string_view key) const; |
| |
| Status WriteEntryForExistingKey(EntryMetadata& metadata, |
| EntryState new_state, |
| std::string_view key, |
| std::span<const std::byte> value); |
| |
| Status WriteEntryForNewKey(std::string_view key, |
| std::span<const std::byte> value); |
| |
| Status WriteEntry(std::string_view key, |
| std::span<const std::byte> value, |
| EntryState new_state, |
| EntryMetadata* prior_metadata = nullptr, |
| const internal::Entry* prior_entry = nullptr); |
| |
| EntryMetadata CreateOrUpdateKeyDescriptor(const Entry& new_entry, |
| std::string_view key, |
| EntryMetadata* prior_metadata, |
| size_t prior_size); |
| |
| EntryMetadata UpdateKeyDescriptor(const Entry& entry, |
| Address new_address, |
| EntryMetadata* prior_metadata, |
| size_t prior_size); |
| |
| Status GetAddressesForWrite(Address* write_addresses, size_t write_size); |
| |
| Status GetSectorForWrite(SectorDescriptor** sector, |
| size_t entry_size, |
| std::span<const Address> addresses_to_skip); |
| |
| Status MarkSectorCorruptIfNotOk(Status status, SectorDescriptor* sector); |
| |
| Status AppendEntry(const Entry& entry, |
| std::string_view key, |
| std::span<const std::byte> value); |
| |
| StatusWithSize CopyEntryToSector(Entry& entry, |
| SectorDescriptor* new_sector, |
| Address new_address); |
| |
| Status RelocateEntry(const EntryMetadata& metadata, |
| KeyValueStore::Address& address, |
| std::span<const Address> addresses_to_skip); |
| |
| // Find and garbage collect a singe sector that does not include an address to |
| // skip. |
| Status GarbageCollect(std::span<const Address> addresses_to_skip); |
| |
| Status RelocateKeyAddressesInSector( |
| SectorDescriptor& sector_to_gc, |
| const EntryMetadata& descriptor, |
| std::span<const Address> addresses_to_skip); |
| |
| Status GarbageCollectSector(SectorDescriptor& sector_to_gc, |
| std::span<const Address> addresses_to_skip); |
| |
| // Ensure that all entries are on the primary (first) format. Entries that are |
| // not on the primary format are rewritten. |
| // |
| // Return: status + number of entries updated. |
| StatusWithSize UpdateEntriesToPrimaryFormat(); |
| |
| Status AddRedundantEntries(EntryMetadata& metadata); |
| |
| Status RepairCorruptSectors(); |
| |
| Status EnsureFreeSectorExists(); |
| |
| Status EnsureEntryRedundancy(); |
| |
| Status FixErrors(); |
| |
| Status Repair(); |
| |
| internal::Entry CreateEntry(Address address, |
| std::string_view key, |
| std::span<const std::byte> value, |
| EntryState state); |
| |
| void LogSectors() const; |
| void LogKeyDescriptor() const; |
| |
| FlashPartition& partition_; |
| const internal::EntryFormats formats_; |
| |
| // List of sectors used by this KVS. |
| internal::Sectors sectors_; |
| |
| // Unordered list of KeyDescriptors. Finding a key requires scanning and |
| // verifying a match by reading the actual entry. |
| internal::EntryCache entry_cache_; |
| |
| Options options_; |
| |
| // Threshold value for when to garbage collect all stale data. Above the |
| // threshold, GC all reclaimable bytes regardless of if valid data is in |
| // sector. Below the threshold, only GC sectors with reclaimable bytes and no |
| // valid bytes. The threshold is based on the portion of KVS capacity used by |
| // valid bytes. |
| static constexpr size_t kGcUsageThresholdPercentage = 70; |
| |
| enum class InitializationState { |
| // KVS Init() has not been called and KVS is not usable. |
| kNotInitialized, |
| |
| // KVS Init() run but not all the needed invariants are met for an operating |
| // KVS. KVS is not writable, but read operaions are possible. |
| kNeedsMaintenance, |
| |
| // KVS is fully ready for use. |
| kReady, |
| }; |
| InitializationState initialized_; |
| |
| // error_detected_ needs to be set from const KVS methods (such as Get), so |
| // make it mutable. |
| mutable bool error_detected_; |
| |
| struct ErrorStats { |
| size_t corrupt_sectors_recovered; |
| size_t missing_redundant_entries_recovered; |
| }; |
| ErrorStats error_stats_; |
| |
| uint32_t last_transaction_id_; |
| }; |
| |
| template <size_t kMaxEntries, |
| size_t kMaxUsableSectors, |
| size_t kRedundancy = 1, |
| size_t kEntryFormats = 1> |
| class KeyValueStoreBuffer : public KeyValueStore { |
| public: |
| // Constructs a KeyValueStore on the partition, with support for one |
| // EntryFormat (kEntryFormats must be 1). |
| KeyValueStoreBuffer(FlashPartition* partition, |
| const EntryFormat& format, |
| const Options& options = {}) |
| : KeyValueStoreBuffer( |
| partition, |
| std::span(reinterpret_cast<const EntryFormat (&)[1]>(format)), |
| options) { |
| static_assert(kEntryFormats == 1, |
| "kEntryFormats EntryFormats must be specified"); |
| } |
| |
| // Constructs a KeyValueStore on the partition. Supports multiple entry |
| // formats. The first EntryFormat is used for new entries. |
| KeyValueStoreBuffer(FlashPartition* partition, |
| std::span<const EntryFormat, kEntryFormats> formats, |
| const Options& options = {}) |
| : KeyValueStore(partition, |
| formats_, |
| options, |
| kRedundancy, |
| sectors_, |
| temp_sectors_to_skip_, |
| key_descriptors_, |
| addresses_) { |
| std::copy(formats.begin(), formats.end(), formats_.begin()); |
| } |
| |
| private: |
| static_assert(kMaxEntries > 0u); |
| static_assert(kMaxUsableSectors > 0u); |
| static_assert(kRedundancy > 0u); |
| static_assert(kEntryFormats > 0u); |
| |
| Vector<SectorDescriptor, kMaxUsableSectors> sectors_; |
| |
| // Allocate space for an list of SectorDescriptors to avoid while searching |
| // for space to write entries. This is used to avoid changing sectors that are |
| // reserved for a new entry or marked as having other redundant copies of an |
| // entry. Up to kRedundancy sectors are reserved for a new entry, and up to |
| // kRedundancy - 1 sectors can have redundant copies of an entry, giving a |
| // maximum of 2 * kRedundancy - 1 sectors to avoid. |
| const SectorDescriptor* temp_sectors_to_skip_[2 * kRedundancy - 1]; |
| |
| // KeyDescriptors for use by the KVS's EntryCache. |
| Vector<KeyDescriptor, kMaxEntries> key_descriptors_; |
| |
| // An array of addresses associated with the KeyDescriptors for use with the |
| // EntryCache. To support having KeyValueStores with different redundancies, |
| // the addresses are stored in a parallel array instead of inside |
| // KeyDescriptors. |
| internal::EntryCache::AddressList<kRedundancy, kMaxEntries> addresses_; |
| |
| // EntryFormats that can be read by this KeyValueStore. |
| std::array<EntryFormat, kEntryFormats> formats_; |
| }; |
| |
| } // namespace pw::kvs |