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use crate::{read_u64, safe_write, write_u64, Address, GrowFailed, Memory};
#[cfg(test)]
mod tests;
pub const INDEX_MAGIC: &[u8; 3] = b"GLI";
pub const DATA_MAGIC: &[u8; 3] = b"GLD";
const LAYOUT_VERSION: u8 = 1;
const HEADER_V1_SIZE: u64 = 4;
const RESERVED_HEADER_SIZE: u64 = 28;
const HEADER_OFFSET: u64 = HEADER_V1_SIZE + RESERVED_HEADER_SIZE;
struct HeaderV1 {
magic: [u8; 3],
version: u8,
}
#[derive(Debug, PartialEq, Eq)]
pub enum InitError {
IncompatibleDataVersion {
last_supported_version: u8,
decoded_version: u8,
},
IncompatibleIndexVersion {
last_supported_version: u8,
decoded_version: u8,
},
InvalidIndex,
}
#[derive(Debug, PartialEq, Eq)]
pub enum WriteError {
IndexFull { max_entries: u32 },
GrowFailed { current_size: u64, delta: u64 },
}
impl From<GrowFailed> for WriteError {
fn from(
GrowFailed {
current_size,
delta,
}: GrowFailed,
) -> Self {
Self::GrowFailed {
current_size,
delta,
}
}
}
#[derive(Debug, PartialEq, Eq)]
pub struct NoSuchEntry;
pub struct Log<INDEX: Memory, DATA: Memory> {
index_memory: INDEX,
data_memory: DATA,
}
impl<INDEX: Memory, DATA: Memory> Log<INDEX, DATA> {
pub fn new(index_memory: INDEX, data_memory: DATA) -> Self {
let log = Self {
index_memory,
data_memory,
};
Self::write_header(
&log.index_memory,
&HeaderV1 {
magic: *INDEX_MAGIC,
version: LAYOUT_VERSION,
},
);
Self::write_header(
&log.data_memory,
&HeaderV1 {
magic: *DATA_MAGIC,
version: LAYOUT_VERSION,
},
);
write_u64(&log.index_memory, Address::from(HEADER_OFFSET), 0);
log
}
pub fn init(index_memory: INDEX, data_memory: DATA) -> Result<Self, InitError> {
if data_memory.size() == 0 {
return Ok(Self::new(index_memory, data_memory));
}
let data_header = Self::read_header(&data_memory);
if &data_header.magic != DATA_MAGIC {
return Ok(Self::new(index_memory, data_memory));
}
if data_header.version != LAYOUT_VERSION {
return Err(InitError::IncompatibleDataVersion {
last_supported_version: LAYOUT_VERSION,
decoded_version: data_header.version,
});
}
let index_header = Self::read_header(&index_memory);
if &index_header.magic != INDEX_MAGIC {
return Err(InitError::InvalidIndex);
}
if index_header.version != LAYOUT_VERSION {
return Err(InitError::IncompatibleIndexVersion {
last_supported_version: LAYOUT_VERSION,
decoded_version: index_header.version,
});
}
#[cfg(debug_assertions)]
{
assert_eq!(Ok(()), Self::validate_v1_index(&index_memory));
}
Ok(Self {
index_memory,
data_memory,
})
}
fn write_header(memory: &impl Memory, header: &HeaderV1) {
if memory.size() < 1 {
assert!(
memory.grow(1) != -1,
"failed to allocate the first memory page"
);
}
memory.write(0, &header.magic);
memory.write(3, &[header.version]);
}
fn read_header(memory: &impl Memory) -> HeaderV1 {
let mut magic = [0u8; 3];
let mut version = [0u8; 1];
memory.read(0, &mut magic);
memory.read(3, &mut version);
HeaderV1 {
magic,
version: version[0],
}
}
#[cfg(debug_assertions)]
fn validate_v1_index(memory: &INDEX) -> Result<(), String> {
let num_entries = read_u64(memory, Address::from(HEADER_OFFSET));
if num_entries == 0 {
return Ok(());
}
let mut prev_entry = read_u64(memory, Address::from(HEADER_OFFSET + 8));
for i in 1..(num_entries as u64) {
let entry = read_u64(memory, Address::from(HEADER_OFFSET + 8 + i * 8));
if entry < prev_entry {
return Err(format!(
"invalid entry I[{}]: {} < {}",
i, entry, prev_entry
));
}
prev_entry = entry;
}
Ok(())
}
pub fn forget(self) -> (INDEX, DATA) {
(self.index_memory, self.data_memory)
}
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn index_size_bytes(&self) -> usize {
let num_entries = read_u64(&self.index_memory, Address::from(HEADER_OFFSET));
self.index_entry_offset(num_entries).get() as usize
}
pub fn data_size_bytes(&self) -> usize {
self.log_size_bytes() + HEADER_OFFSET as usize
}
pub fn log_size_bytes(&self) -> usize {
let num_entries = self.len();
if num_entries == 0 {
0
} else {
read_u64(
&self.index_memory,
self.index_entry_offset((num_entries - 1) as u64),
) as usize
}
}
pub fn len(&self) -> usize {
read_u64(&self.index_memory, Address::from(HEADER_OFFSET)) as usize
}
pub fn get(&self, idx: usize) -> Option<Vec<u8>> {
let mut buf = vec![];
self.read_entry(idx, &mut buf).ok().map(|_| buf)
}
pub fn read_entry(&self, idx: usize, buf: &mut Vec<u8>) -> Result<(), NoSuchEntry> {
let (offset, len) = self.entry_meta(idx).ok_or(NoSuchEntry)?;
buf.resize(len, 0);
self.data_memory.read((HEADER_OFFSET + offset) as u64, buf);
Ok(())
}
pub fn append(&self, bytes: &[u8]) -> Result<usize, WriteError> {
let idx = self.len() as u64;
let data_offset = if idx == 0 {
0
} else {
read_u64(&self.index_memory, self.index_entry_offset(idx - 1))
};
let new_offset = data_offset
.checked_add(bytes.len() as u64)
.expect("address overflow");
let entry_offset = HEADER_OFFSET
.checked_add(data_offset)
.expect("address overflow");
debug_assert!(new_offset >= data_offset);
safe_write(&self.data_memory, entry_offset, bytes)?;
safe_write(
&self.index_memory,
self.index_entry_offset(idx).get(),
&new_offset.to_le_bytes(),
)?;
write_u64(
&self.index_memory,
Address::from(HEADER_OFFSET),
idx as u64 + 1,
);
debug_assert_eq!(self.get(idx as usize), Some(bytes.to_vec()));
Ok(idx as usize)
}
fn entry_meta(&self, idx: usize) -> Option<(u64, usize)> {
if self.len() <= idx {
return None;
}
let idx = idx as u64;
if idx == 0 {
Some((
0,
read_u64(&self.index_memory, self.index_entry_offset(0)) as usize,
))
} else {
let offset = read_u64(&self.index_memory, self.index_entry_offset(idx - 1));
let next = read_u64(&self.index_memory, self.index_entry_offset(idx));
debug_assert!(offset <= next);
Some((offset, (next - offset) as usize))
}
}
fn index_entry_offset(&self, idx: u64) -> Address {
Address::from(
HEADER_OFFSET + std::mem::size_of::<u64>() as u64 + idx * (std::mem::size_of::<u64>() as u64), )
}
}