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// 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.
#define PW_LOG_MODULE_NAME "KVS"
#define PW_LOG_LEVEL PW_KVS_LOG_LEVEL
#include "pw_kvs/internal/entry.h"
#include <cinttypes>
#include <cstring>
#include "pw_kvs_private/config.h"
#include "pw_log/log.h"
#include "pw_status/try.h"
namespace pw::kvs::internal {
static_assert(
kMaxFlashAlignment >= Entry::kMinAlignmentBytes,
"Flash alignment is required to be at least Entry::kMinAlignmentBytes");
constexpr size_t kWriteBufferSize =
std::max(kMaxFlashAlignment, 4 * Entry::kMinAlignmentBytes);
using std::byte;
Status Entry::Read(FlashPartition& partition,
Address address,
const internal::EntryFormats& formats,
Entry* entry) {
EntryHeader header;
PW_TRY(partition.Read(address, sizeof(header), &header));
if (partition.AppearsErased(as_bytes(span(&header.magic, 1)))) {
return Status::NotFound();
}
if (header.key_length_bytes > kMaxKeyLength) {
return Status::DataLoss();
}
const EntryFormat* format = formats.Find(header.magic);
if (format == nullptr) {
PW_LOG_ERROR("Found corrupt magic: %" PRIx32 " at address %u",
header.magic,
unsigned(address));
return Status::DataLoss();
}
*entry = Entry(&partition, address, *format, header);
return OkStatus();
}
Status Entry::ReadKey(FlashPartition& partition,
Address address,
size_t key_length,
char* key) {
if (key_length == 0u || key_length > kMaxKeyLength) {
return Status::DataLoss();
}
return partition.Read(address + sizeof(EntryHeader), key_length, key)
.status();
}
Entry::Entry(FlashPartition& partition,
Address address,
const EntryFormat& format,
Key key,
span<const byte> value,
uint16_t value_size_bytes,
uint32_t transaction_id)
: Entry(&partition,
address,
format,
{.magic = format.magic,
.checksum = 0,
.alignment_units =
alignment_bytes_to_units(partition.alignment_bytes()),
.key_length_bytes = static_cast<uint8_t>(key.size()),
.value_size_bytes = value_size_bytes,
.transaction_id = transaction_id}) {
if (checksum_algo_ != nullptr) {
span<const byte> checksum = CalculateChecksum(key, value);
std::memcpy(&header_.checksum,
checksum.data(),
std::min(checksum.size(), sizeof(header_.checksum)));
}
}
StatusWithSize Entry::Write(Key key, span<const byte> value) const {
FlashPartition::Output flash(partition(), address_);
return AlignedWrite<kWriteBufferSize>(
flash,
alignment_bytes(),
{as_bytes(span(&header_, 1)), as_bytes(span(key)), value});
}
Status Entry::Update(const EntryFormat& new_format,
uint32_t new_transaction_id) {
checksum_algo_ = new_format.checksum;
header_.magic = new_format.magic;
header_.alignment_units =
alignment_bytes_to_units(partition_->alignment_bytes());
header_.transaction_id = new_transaction_id;
// If we could write the header last, we could avoid reading the entry twice
// when moving an entry. However, to support alignments greater than the
// header size, we first read the entire value to calculate the new checksum,
// then write the full entry in WriteFrom.
return CalculateChecksumFromFlash();
}
StatusWithSize Entry::Copy(Address new_address) const {
PW_LOG_DEBUG("Copying entry from %u to %u as ID %" PRIu32,
unsigned(address()),
unsigned(new_address),
transaction_id());
FlashPartition::Output output(partition(), new_address);
AlignedWriterBuffer<kWriteBufferSize> writer(alignment_bytes(), output);
// Use this object's header rather than the header in flash of flash, since
// this Entry may have been updated.
PW_TRY_WITH_SIZE(writer.Write(&header_, sizeof(header_)));
// Write only the key and value from the original entry.
FlashPartition::Input input(partition(), address() + sizeof(EntryHeader));
PW_TRY_WITH_SIZE(writer.Write(input, key_length() + value_size()));
return writer.Flush();
}
StatusWithSize Entry::ReadValue(span<byte> buffer, size_t offset_bytes) const {
if (offset_bytes > value_size()) {
return StatusWithSize::OutOfRange();
}
const size_t remaining_bytes = value_size() - offset_bytes;
const size_t read_size = std::min(buffer.size(), remaining_bytes);
StatusWithSize result = partition().Read(
address_ + sizeof(EntryHeader) + key_length() + offset_bytes,
buffer.subspan(0, read_size));
PW_TRY_WITH_SIZE(result);
if (read_size != remaining_bytes) {
return StatusWithSize::ResourceExhausted(read_size);
}
return StatusWithSize(read_size);
}
Status Entry::ValueMatches(span<const std::byte> value) const {
if (value_size() != value.size_bytes()) {
return Status::NotFound();
}
Address address = address_ + sizeof(EntryHeader) + key_length();
Address end = address + value_size();
const std::byte* value_ptr = value.data();
std::array<std::byte, 2 * kMinAlignmentBytes> buffer;
while (address < end) {
const size_t read_size = std::min(size_t(end - address), buffer.size());
PW_TRY(partition_->Read(address, span(buffer).first(read_size)));
if (std::memcmp(buffer.data(), value_ptr, read_size) != 0) {
return Status::NotFound();
}
address += read_size;
value_ptr += read_size;
}
return OkStatus();
}
Status Entry::VerifyChecksum(Key key, span<const byte> value) const {
if (checksum_algo_ == nullptr) {
return header_.checksum == 0 ? OkStatus() : Status::DataLoss();
}
CalculateChecksum(key, value);
return checksum_algo_->Verify(checksum_bytes());
}
Status Entry::VerifyChecksumInFlash() const {
// Read the entire entry piece-by-piece into a small buffer. If the entry is
// 32 B or less, only one read is required.
union {
EntryHeader header_to_verify;
byte buffer[sizeof(EntryHeader) * 2];
};
size_t bytes_to_read = size();
size_t read_size = std::min(sizeof(buffer), bytes_to_read);
Address read_address = address_;
// Read the first chunk, which includes the header, and compare the checksum.
PW_TRY(partition().Read(read_address, read_size, buffer));
if (header_to_verify.checksum != header_.checksum) {
PW_LOG_ERROR("Expected checksum 0x%08" PRIx32 ", found 0x%08" PRIx32,
header_.checksum,
header_to_verify.checksum);
return Status::DataLoss();
}
if (checksum_algo_ == nullptr) {
return header_.checksum == 0 ? OkStatus() : Status::DataLoss();
}
// The checksum is calculated as if the header's checksum field were 0.
header_to_verify.checksum = 0;
checksum_algo_->Reset();
while (true) {
// Add the chunk in the buffer to the checksum.
checksum_algo_->Update(buffer, read_size);
bytes_to_read -= read_size;
if (bytes_to_read == 0u) {
break;
}
// Read the next chunk into the buffer.
read_address += read_size;
read_size = std::min(sizeof(buffer), bytes_to_read);
PW_TRY(partition().Read(read_address, read_size, buffer));
}
checksum_algo_->Finish();
return checksum_algo_->Verify(checksum_bytes());
}
void Entry::DebugLog() const {
PW_LOG_DEBUG("Entry [%s]: ", deleted() ? "tombstone" : "present");
PW_LOG_DEBUG(" Address = 0x%x", unsigned(address_));
PW_LOG_DEBUG(" Transaction = %u", unsigned(transaction_id()));
PW_LOG_DEBUG(" Magic = 0x%x", unsigned(magic()));
PW_LOG_DEBUG(" Checksum = 0x%x", unsigned(header_.checksum));
PW_LOG_DEBUG(" Key length = 0x%x", unsigned(key_length()));
PW_LOG_DEBUG(" Value length = 0x%x", unsigned(value_size()));
PW_LOG_DEBUG(" Entry size = 0x%x", unsigned(size()));
PW_LOG_DEBUG(" Alignment = 0x%x", unsigned(alignment_bytes()));
}
span<const byte> Entry::CalculateChecksum(const Key key,
span<const byte> value) const {
checksum_algo_->Reset();
{
EntryHeader header_for_checksum = header_;
header_for_checksum.checksum = 0;
checksum_algo_->Update(&header_for_checksum, sizeof(header_for_checksum));
checksum_algo_->Update(as_bytes(span(key)));
checksum_algo_->Update(value);
}
AddPaddingBytesToChecksum();
return checksum_algo_->Finish();
}
Status Entry::CalculateChecksumFromFlash() {
header_.checksum = 0;
if (checksum_algo_ == nullptr) {
return OkStatus();
}
checksum_algo_->Reset();
checksum_algo_->Update(&header_, sizeof(header_));
Address address = address_ + sizeof(EntryHeader);
// To handle alignment changes, do not read the padding. The padding is added
// after checksumming the key and value from flash.
const Address end = address_ + content_size();
std::array<std::byte, 2 * kMinAlignmentBytes> buffer;
while (address < end) {
const size_t read_size = std::min(size_t(end - address), buffer.size());
PW_TRY(partition_->Read(address, span(buffer).first(read_size)));
checksum_algo_->Update(buffer.data(), read_size);
address += read_size;
}
AddPaddingBytesToChecksum();
span checksum = checksum_algo_->Finish();
std::memcpy(&header_.checksum,
checksum.data(),
std::min(checksum.size(), sizeof(header_.checksum)));
return OkStatus();
}
void Entry::AddPaddingBytesToChecksum() const {
constexpr byte padding[kMinAlignmentBytes - 1] = {};
size_t padding_to_add = Padding(content_size(), alignment_bytes());
while (padding_to_add != 0u) {
const size_t chunk_size = std::min(padding_to_add, sizeof(padding));
checksum_algo_->Update(padding, chunk_size);
padding_to_add -= chunk_size;
}
}
} // namespace pw::kvs::internal