Struct agdb::FileStorage

pub struct FileStorage { /* private fields */ }

Single file based storage with write ahead log (WAL) for resiliency implementing StorageData. It uses the storage name as the file name (.{name} for WAL). It allows multiple readers from the file by opening additional temporary file handles if the single member file handle is being used (read). The StorageData::read() always returns owning buffer.

The StorageData::backup() is implemented so that it copes the file to the new name.

The StorageData::flush() merely clears the WAL. This implementation relies on the OS to flush the content to the disk. It is specifically not using manual calls to File::sync_data() / File::sync_all() because they result in extreme slowdown.

Trait Implementations

impl Drop for FileStorage

fn drop(&mut self)

Executes the destructor for this type.

impl StorageData for FileStorage

fn backup(&self, name: &str) -> Result<(), DbError>

Copy the underlying data storage to a new name. The default implementation does nothing. File implementations might need to copy the underlying file(s).

fn copy(&self, name: &str) -> Result<Self, DbError>

fn flush(&mut self) -> Result<(), DbError>

Flushes any buffers to the underlying storage (e.g. file). The default implementation does nothing.

fn len(&self) -> u64

Returns the length of the underlying storage in bytes.

fn name(&self) -> &str

Returns the name this storage was constructed with.

fn new(name: &str) -> Result<Self, DbError>

Constructs or loads the storage name. The name might be a file name or other identifier.

fn read(&self, pos: u64, value_len: u64) -> Result<StorageSlice<'_>, DbError>

Reads value_len bytes starting at pos. Returns StorageSlice (COW).

fn rename(&mut self, new_name: &str) -> Result<(), DbError>

Changes the name of the storage changing also the names of the files (if the storage is file based).

fn resize(&mut self, new_len: u64) -> Result<(), DbError>

Resizes the underlying storage to new_len. If the storage is enlarged as a result the new bytes should be initialized to 0_u8.

fn write(&mut self, pos: u64, bytes: &[u8]) -> Result<(), DbError>

Writes the bytes to the underlying storage at pos. The implementation must handle the case where the pos + bytes.len() exceeds the current len().

fn is_empty(&self) -> bool

Convenience method that returns len() == 0.