tickv/tickv.rs
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//! The TicKV implementation.
use crate::crc32;
use crate::error_codes::ErrorCode;
use crate::flash_controller::FlashController;
use crate::success_codes::SuccessCode;
use core::cell::Cell;
/// The current version of TicKV
pub const VERSION: u8 = 1;
#[derive(Clone, Copy, PartialEq)]
pub(crate) enum InitState {
/// Trying to read the key from a region
GetKeyReadRegion(usize),
/// Trying to erase a region
EraseRegion(usize),
/// Finished erasing regions
EraseComplete,
/// Trying to read a region while appending a key
AppendKeyReadRegion(usize),
}
#[derive(Clone, Copy, PartialEq)]
pub(crate) enum KeyState {
/// Trying to read the key from a region
ReadRegion(usize),
}
#[derive(Clone, Copy, PartialEq)]
pub(crate) enum RubbishState {
ReadRegion(usize),
EraseRegion(usize),
}
#[derive(Clone, Copy, PartialEq)]
/// The current state machine when trying to complete a previous operation.
/// This is used when returning from a complete async `FlashController` call.
pub(crate) enum State {
/// No previous state
None,
/// Init Operation
Init(InitState),
/// Appending a key
AppendKey(KeyState),
/// Getting a key
GetKey(KeyState),
/// Invalidating a key
InvalidateKey(KeyState),
/// Running garbage collection
GarbageCollect(RubbishState),
}
/// The struct storing all of the TicKV information.
pub struct TicKV<'a, C: FlashController<S>, const S: usize> {
/// The controller used for flash commands
pub controller: C,
flash_size: usize,
pub(crate) read_buffer: Cell<Option<&'a mut [u8; S]>>,
pub(crate) state: Cell<State>,
}
/// This is the current object header used for TicKV objects
struct ObjectHeader {
version: u8,
// In reality this is a u4.
flags: u8,
// In reality this is a u12.
len: u16,
hashed_key: u64,
}
pub(crate) const FLAGS_VALID: u8 = 8;
impl ObjectHeader {
fn new(hashed_key: u64, len: u16) -> Self {
assert!(len < 0xFFF);
Self {
version: VERSION,
flags: FLAGS_VALID,
len,
hashed_key,
}
}
}
// A list of offsets into the ObjectHeader
pub(crate) const VERSION_OFFSET: usize = 0;
pub(crate) const LEN_OFFSET: usize = 1;
pub(crate) const HASH_OFFSET: usize = 3;
pub(crate) const HEADER_LENGTH: usize = HASH_OFFSET + 8;
pub(crate) const CHECK_SUM_LEN: usize = 4;
/// The main key. A hashed version of this should be passed to
/// `initialise()`.
pub const MAIN_KEY: &[u8; 15] = b"tickv-super-key";
/// This is the main TicKV struct.
impl<'a, C: FlashController<S>, const S: usize> TicKV<'a, C, S> {
/// Create a new struct
///
/// `C`: An implementation of the `FlashController` trait
///
/// `controller`: An new struct implementing `FlashController`
/// `flash_size`: The total size of the flash used for TicKV
pub fn new(controller: C, read_buffer: &'a mut [u8; S], flash_size: usize) -> Self {
Self {
controller,
flash_size,
read_buffer: Cell::new(Some(read_buffer)),
state: Cell::new(State::None),
}
}
/// This function setups the flash region to be used as a key-value store.
/// If the region is already initialised this won't make any changes.
///
/// `hashed_main_key`: The u64 hash of the const string `MAIN_KEY`.
///
/// If the specified region has not already been setup for TicKV
/// the entire region will be erased.
///
/// On success nothing will be returned.
/// On error a `ErrorCode` will be returned.
pub fn initialise(&self, hashed_main_key: u64) -> Result<SuccessCode, ErrorCode> {
let mut buf: [u8; 0] = [0; 0];
let key_ret = match self.state.get() {
State::None => self.get_key(hashed_main_key, &mut buf),
State::Init(state) => match state {
InitState::GetKeyReadRegion(_) => self.get_key(hashed_main_key, &mut buf),
_ => Err(ErrorCode::EraseNotReady(0)),
},
_ => unreachable!(),
};
match key_ret {
Ok(ret) => Ok(ret),
Err(e) => {
match e {
ErrorCode::ReadNotReady(reg) => {
self.state
.set(State::Init(InitState::GetKeyReadRegion(reg)));
Err(ErrorCode::ReadNotReady(reg))
}
_ => {
match self.state.get() {
State::None
| State::Init(InitState::GetKeyReadRegion(_))
| State::Init(InitState::EraseRegion(_)) => {
// Erase all regions
let mut start = 0;
if let State::Init(InitState::EraseRegion(reg)) = self.state.get() {
// We already erased region reg, so move to the next one
start = reg + 1;
}
if start < (self.flash_size / S) {
for r in start..(self.flash_size / S) {
match self.controller.erase_region(r) {
Ok(()) => {}
Err(e) => {
self.state
.set(State::Init(InitState::EraseRegion(r)));
return Err(e);
}
}
}
}
self.state.set(State::Init(InitState::EraseComplete));
}
_ => {}
}
// Save the main key
match self.append_key(hashed_main_key, &buf) {
Ok(ret) => {
self.state.set(State::None);
Ok(ret)
}
Err(e) => match e {
ErrorCode::ReadNotReady(reg) => {
self.state
.set(State::Init(InitState::AppendKeyReadRegion(reg)));
Err(e)
}
ErrorCode::WriteNotReady(_) => {
self.state.set(State::None);
Ok(SuccessCode::Queued)
}
_ => Err(e),
},
}
}
}
}
}
}
/// Get region number from a hashed key
fn get_region(&self, hash: u64) -> usize {
assert_ne!(hash, 0xFFFF_FFFF_FFFF_FFFF);
assert_ne!(hash, 0);
// Determine the number of regions
let num_region = self.flash_size / S;
// Determine the block where the data should be
(hash as usize & 0xFFFF) % num_region
}
// Determine the new region offset to try.
// Returns None if there aren't any more in range.
fn increment_region_offset(&self, region_offset: isize) -> Option<isize> {
let mut too_big = false;
let mut too_small = false;
// Loop until we find a region we can use
while !too_big && !too_small {
let new_offset = match region_offset {
0 => 1,
region_offset if region_offset > 0 => -region_offset,
region_offset if region_offset < 0 => -region_offset + 1,
_ => unreachable!(),
};
// Make sure our new offset is valid
if new_offset as usize > ((self.flash_size / S) - 1) {
too_big = true;
continue;
}
if new_offset < 0 {
too_small = true;
continue;
}
return Some(new_offset);
}
None
}
/// Find a key in some loaded region data.
///
/// On success return the offset in the region_data where the key is and the
/// total length of the key.
/// On failure return a bool indicating if the caller should keep looking in
/// neighboring regions and the error code.
fn find_key_offset(
&self,
hash: u64,
region_data: &[u8],
) -> Result<(usize, u16), (bool, ErrorCode)> {
// Determine the total size of our payload
// Split the hash
let hash = hash.to_ne_bytes();
let mut offset: usize = 0;
let mut empty: bool = true;
loop {
if offset + HEADER_LENGTH >= S {
// We have reached the end of the region
return Err((false, ErrorCode::KeyNotFound));
}
// Check to see if we have data
if region_data[offset + VERSION_OFFSET] != 0xFF {
// Mark that this region isn't empty
empty = false;
// We found a version, check that we support it
if region_data[offset + VERSION_OFFSET] != VERSION {
return Err((false, ErrorCode::UnsupportedVersion));
}
// Find this entries length
let total_length = ((region_data[offset + LEN_OFFSET] as u16) & !0xF0) << 8
| region_data[offset + LEN_OFFSET + 1] as u16;
// Check to see if all fields are just 0
if total_length == 0 {
// We found something invalid here
return Err((false, ErrorCode::KeyNotFound));
}
// Check to see if the entry has been deleted
if region_data[offset + LEN_OFFSET] & 0x80 != 0x80 {
// Increment our offset by the length and repeat the loop
offset += total_length as usize;
continue;
}
// We have found a valid entry, see if it is ours.
if region_data[offset + HASH_OFFSET] != hash[7]
|| region_data[offset + HASH_OFFSET + 1] != hash[6]
|| region_data[offset + HASH_OFFSET + 2] != hash[5]
|| region_data[offset + HASH_OFFSET + 3] != hash[4]
|| region_data[offset + HASH_OFFSET + 4] != hash[3]
|| region_data[offset + HASH_OFFSET + 5] != hash[2]
|| region_data[offset + HASH_OFFSET + 6] != hash[1]
|| region_data[offset + HASH_OFFSET + 7] != hash[0]
{
// Increment our offset by the length and repeat the loop
offset += total_length as usize;
continue;
}
// If we get here we have found out value (assuming no collisions)
return Ok((offset, total_length));
} else {
// We hit the end.
return Err((!empty, ErrorCode::KeyNotFound));
}
}
}
/// Appends the key/value pair to flash storage.
///
/// `hash`: A hashed key. This key will be used in future to retrieve
/// or remove the `value`.
/// `value`: A buffer containing the data to be stored to flash.
///
/// On success nothing will be returned.
/// On error a `ErrorCode` will be returned.
pub fn append_key(&self, hash: u64, value: &[u8]) -> Result<SuccessCode, ErrorCode> {
let region = self.get_region(hash);
let crc = crc32::Crc::new();
let mut check_sum = crc.digest();
// Length not including check sum
let package_length = HEADER_LENGTH + value.len();
let object_length = HEADER_LENGTH + value.len() + CHECK_SUM_LEN;
if object_length > 0xFFF {
return Err(ErrorCode::ObjectTooLarge);
}
// Create the header:
let header = ObjectHeader::new(hash, object_length as u16);
let mut region_offset: isize = 0;
loop {
let new_region = match self.state.get() {
State::None => region as isize + region_offset,
State::Init(state) => {
match state {
InitState::AppendKeyReadRegion(reg) => reg as isize,
_ => {
// Get the data from that region
region as isize + region_offset
}
}
}
State::AppendKey(key_state) => match key_state {
KeyState::ReadRegion(reg) => reg as isize,
},
State::GarbageCollect(RubbishState::ReadRegion(reg)) => reg as isize,
_ => unreachable!(),
};
let mut region_data = self.read_buffer.take().unwrap();
if self.state.get() != State::AppendKey(KeyState::ReadRegion(new_region as usize))
&& self.state.get()
!= State::Init(InitState::AppendKeyReadRegion(new_region as usize))
{
match self
.controller
.read_region(new_region as usize, 0, &mut region_data)
{
Ok(()) => {}
Err(e) => {
self.read_buffer.replace(Some(region_data));
if let ErrorCode::ReadNotReady(reg) = e {
self.state.set(State::AppendKey(KeyState::ReadRegion(reg)));
}
return Err(e);
}
};
}
if self.find_key_offset(hash, region_data).is_ok() {
// Check to make sure we don't already have this key
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::KeyAlreadyExists);
}
let mut offset: usize = 0;
loop {
if offset + package_length >= S {
// We have reached the end of the region
// We will need to try the next region
// Replace the buffer
self.read_buffer.replace(Some(region_data));
match self.increment_region_offset(new_region) {
Some(o) => {
region_offset = o;
}
None => {
return Err(ErrorCode::FlashFull);
}
}
break;
}
// Check to see if we have data
if region_data[offset + VERSION_OFFSET] != 0xFF {
// We found a version, check that we support it
if region_data[offset + VERSION_OFFSET] != VERSION {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::UnsupportedVersion);
}
// Find this entries length
let total_length = ((region_data[offset + LEN_OFFSET] as u16) & !0xF0) << 8
| region_data[offset + LEN_OFFSET + 1] as u16;
// Increment our offset by the length and repeat the loop
offset += total_length as usize;
continue;
}
// If we get here we have found an empty spot
// Double check that there is no valid hash
// Check to see if the entire header is 0xFFFF_FFFF_FFFF_FFFF
// To avoid operating on 64-bit values check every 8 bytes at a time
if region_data[offset + HASH_OFFSET] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 1] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 2] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 3] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 4] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 5] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 6] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
if region_data[offset + HASH_OFFSET + 7] != 0xFF {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::CorruptData);
}
// If we get here we have found an empty spot
// Copy in new header
// This is a little painful, but avoids any unsafe Rust
region_data[offset + VERSION_OFFSET] = header.version;
region_data[offset + LEN_OFFSET] =
(header.len >> 8) as u8 & 0x0F | (header.flags << 4) & 0xF0;
region_data[offset + LEN_OFFSET + 1] = (header.len & 0xFF) as u8;
region_data[offset + HASH_OFFSET] = (header.hashed_key >> 56) as u8;
region_data[offset + HASH_OFFSET + 1] = (header.hashed_key >> 48) as u8;
region_data[offset + HASH_OFFSET + 2] = (header.hashed_key >> 40) as u8;
region_data[offset + HASH_OFFSET + 3] = (header.hashed_key >> 32) as u8;
region_data[offset + HASH_OFFSET + 4] = (header.hashed_key >> 24) as u8;
region_data[offset + HASH_OFFSET + 5] = (header.hashed_key >> 16) as u8;
region_data[offset + HASH_OFFSET + 6] = (header.hashed_key >> 8) as u8;
region_data[offset + HASH_OFFSET + 7] = (header.hashed_key) as u8;
// Hash the new header data
check_sum.update(®ion_data[offset + VERSION_OFFSET..=offset + HASH_OFFSET + 7]);
// Copy the value
let slice = &mut region_data[(offset + HEADER_LENGTH)..(offset + package_length)];
slice.copy_from_slice(value);
// Include the value in the hash
check_sum.update(value);
// Append a Check Hash
let check_sum = check_sum.finalise();
let slice = &mut region_data
[(offset + package_length)..(offset + package_length + CHECK_SUM_LEN)];
slice.copy_from_slice(&check_sum.to_ne_bytes());
// Write the data back to the region
if let Err(e) = self.controller.write(
S * new_region as usize + offset,
®ion_data[offset..(offset + package_length + CHECK_SUM_LEN)],
) {
self.read_buffer.replace(Some(region_data));
match e {
ErrorCode::WriteNotReady(_) => return Ok(SuccessCode::Queued),
_ => return Err(e),
}
}
self.read_buffer.replace(Some(region_data));
return Ok(SuccessCode::Written);
}
}
}
/// Retrieves the value from flash storage.
///
/// `hash`: A hashed key.
/// `buf`: A buffer to store the value to.
///
/// On success nothing will be returned.
/// On error a `ErrorCode` will be returned.
///
/// If a power loss occurs before success is returned the data is
/// assumed to be lost.
pub fn get_key(&self, hash: u64, buf: &mut [u8]) -> Result<SuccessCode, ErrorCode> {
let region = self.get_region(hash);
let mut region_offset: isize = 0;
loop {
let crc = crc32::Crc::new();
let mut check_sum = crc.digest();
let new_region = match self.state.get() {
State::None => region as isize + region_offset,
State::Init(state) => {
match state {
InitState::GetKeyReadRegion(reg) => reg as isize,
_ => {
// Get the data from that region
region as isize + region_offset
}
}
}
State::GetKey(key_state) => match key_state {
KeyState::ReadRegion(reg) => reg as isize,
},
_ => unreachable!(),
};
// Get the data from that region
let mut region_data = self.read_buffer.take().unwrap();
if self.state.get() != State::GetKey(KeyState::ReadRegion(new_region as usize))
&& self.state.get() != State::Init(InitState::GetKeyReadRegion(new_region as usize))
{
match self
.controller
.read_region(new_region as usize, 0, &mut region_data)
{
Ok(()) => {}
Err(e) => {
self.read_buffer.replace(Some(region_data));
if let ErrorCode::ReadNotReady(reg) = e {
self.state.set(State::GetKey(KeyState::ReadRegion(reg)));
}
return Err(e);
}
};
}
match self.find_key_offset(hash, region_data) {
Ok((offset, total_length)) => {
// Add the header data to the check hash
check_sum.update(®ion_data[offset..(HEADER_LENGTH + offset)]);
// Make sure if will fit in the buffer
if buf.len() < (total_length as usize - HEADER_LENGTH - CHECK_SUM_LEN) {
// The entire value is not going to fit,
// Let's still copy in what we can and return an error
for i in 0..buf.len() {
buf[i] = region_data[offset + HEADER_LENGTH + i];
}
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::BufferTooSmall(
total_length as usize - HEADER_LENGTH - CHECK_SUM_LEN,
));
}
// Copy in the value
for i in 0..(total_length as usize - HEADER_LENGTH - CHECK_SUM_LEN) {
buf[i] = region_data[offset + HEADER_LENGTH + i];
check_sum.update(&[buf[i]])
}
// Check the hash
let check_sum = check_sum.finalise();
let check_sum = check_sum.to_ne_bytes();
if check_sum[3] != region_data[offset + total_length as usize - 1]
|| check_sum[2] != region_data[offset + total_length as usize - 2]
|| check_sum[1] != region_data[offset + total_length as usize - 3]
|| check_sum[0] != region_data[offset + total_length as usize - 4]
{
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::InvalidCheckSum);
}
self.read_buffer.replace(Some(region_data));
return Ok(SuccessCode::Complete);
}
Err((cont, e)) => {
self.read_buffer.replace(Some(region_data));
if cont {
match self.increment_region_offset(new_region) {
Some(o) => {
region_offset = o;
}
None => {
return Err(e);
}
}
} else {
return Err(e);
}
}
}
}
}
/// Invalidates the key in flash storage
///
/// `hash`: A hashed key.
///
/// On success nothing will be returned.
/// On error a `ErrorCode` will be returned.
///
/// If a power loss occurs before success is returned the data is
/// assumed to be lost.
pub fn invalidate_key(&self, hash: u64) -> Result<SuccessCode, ErrorCode> {
let region = self.get_region(hash);
let mut region_offset: isize = 0;
loop {
// Get the data from that region
let new_region = match self.state.get() {
State::None => region as isize + region_offset,
State::InvalidateKey(key_state) => match key_state {
KeyState::ReadRegion(reg) => reg as isize,
},
_ => unreachable!(),
};
// Get the data from that region
let mut region_data = self.read_buffer.take().unwrap();
if self.state.get() != State::InvalidateKey(KeyState::ReadRegion(new_region as usize)) {
match self
.controller
.read_region(new_region as usize, 0, &mut region_data)
{
Ok(()) => {}
Err(e) => {
self.read_buffer.replace(Some(region_data));
if let ErrorCode::ReadNotReady(reg) = e {
self.state
.set(State::InvalidateKey(KeyState::ReadRegion(reg)));
}
return Err(e);
}
};
}
match self.find_key_offset(hash, region_data) {
Ok((offset, _data_len)) => {
// We found a key, let's delete it
region_data[offset + LEN_OFFSET] &= !0x80;
if let Err(e) = self.controller.write(
S * new_region as usize + offset + LEN_OFFSET,
®ion_data[offset + LEN_OFFSET..offset + LEN_OFFSET + 1],
) {
self.read_buffer.replace(Some(region_data));
match e {
ErrorCode::WriteNotReady(_) => return Ok(SuccessCode::Queued),
_ => return Err(e),
}
}
self.read_buffer.replace(Some(region_data));
return Ok(SuccessCode::Written);
}
Err((cont, e)) => {
self.read_buffer.replace(Some(region_data));
if cont {
match self.increment_region_offset(new_region) {
Some(o) => {
region_offset = o;
}
None => {
return Err(e);
}
}
} else {
return Err(e);
}
}
}
}
}
fn garbage_collect_region(&self, region: usize) -> Result<usize, ErrorCode> {
// Get the data from that region
let mut region_data = self.read_buffer.take().unwrap();
if self.state.get() != State::GarbageCollect(RubbishState::ReadRegion(region)) {
match self.controller.read_region(region, 0, &mut region_data) {
Ok(()) => {}
Err(e) => {
self.read_buffer.replace(Some(region_data));
if let ErrorCode::ReadNotReady(reg) = e {
self.state
.set(State::GarbageCollect(RubbishState::ReadRegion(reg)));
}
return Err(e);
}
};
}
let mut entry_found = false;
let mut offset: usize = 0;
loop {
if offset >= S {
// We have reached the end of the region without finding a
// valid object. All entries must be marked for deletion then.
break;
}
// Check to see if we have data
if region_data[offset + VERSION_OFFSET] != 0xFF {
// We found a version, check that we support it
if region_data[offset + VERSION_OFFSET] != VERSION {
self.read_buffer.replace(Some(region_data));
return Err(ErrorCode::UnsupportedVersion);
}
entry_found = true;
// Find this entries length
let total_length = ((region_data[offset + LEN_OFFSET] as u16) & !0xF0) << 8
| region_data[offset + LEN_OFFSET + 1] as u16;
// Check to see if the entry has been deleted
if region_data[offset + LEN_OFFSET] & 0x80 != 0x80 {
// The entry has been deleted, this region might be ready
// for erasure.
// Increment our offset by the length and repeat the loop
offset += total_length as usize;
continue;
}
// We have found a valid entry!
// Don't perform an erase!
self.read_buffer.replace(Some(region_data));
return Ok(0);
} else {
// We hit the end of valid data.
// The possible outcomes:
// * The region is empty, we don't need to do anything
// * The region has entries, all of which are marked for
// deletion
if !entry_found {
// We didn't find anything, don't bother erasing an empty region.
self.read_buffer.replace(Some(region_data));
return Ok(0);
}
break;
}
}
self.read_buffer.replace(Some(region_data));
// If we got down here, the region is ready to be erased.
if let Err(e) = self.controller.erase_region(region) {
if let ErrorCode::EraseNotReady(reg) = e {
self.state
.set(State::GarbageCollect(RubbishState::EraseRegion(reg)));
}
return Err(e);
}
Ok(S)
}
/// Perform a garbage collection on TicKV
///
/// On success the number of bytes freed will be returned.
/// On error a `ErrorCode` will be returned.
pub fn garbage_collect(&self) -> Result<usize, ErrorCode> {
let num_region = self.flash_size / S;
let mut flash_freed = 0;
let start = match self.state.get() {
State::None => 0,
State::GarbageCollect(state) => match state {
RubbishState::ReadRegion(reg) => reg,
// We already erased region reg, so move to the next one
RubbishState::EraseRegion(reg) => reg + 1,
},
_ => unreachable!(),
};
for i in start..num_region {
match self.garbage_collect_region(i) {
Ok(freed) => flash_freed += freed,
Err(e) => return Err(e),
}
}
Ok(flash_freed)
}
}