Append Only Log

Generic purpose append only log implementation. [

][Github-url] LoC

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][CI-url] [

][codecov-url] [

][doc-url] [

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][crates-url]

English | [简体中文][zh-cn-url]

## Introducation When developing infrastructure softwares, write-ahead log or append-only log plays an important role, and people re-implement same funcationalities multiple times, but actually, the core for append-only log is just atomic `append`, `append_batch`, `replay`, and `rewrite`. This crate provides generic purpose append-only log implementation based on `std::fs::File`. - `aol::fs::AppendLog`: Generic purpose append-only log implementation based on `std::fs::File`. - It is good for: - The encoded entry size is smaller than `64` bytes. - Manifest file. - Write is not too frequently. - Pros: - It is growable, do not require pre-allocated. - Support automatically rewrite. - No holes in the file. ### File Structure ```text +----------------------+--------------------------+-----------------------+ | magic text (4 bytes) | external magic (2 bytes) | magic (2 bytes) | +----------------------+--------------------------+-----------------------+-----------------------+-----------------------+ | op (1 bit) | custom flag (7 bits) | len (4 bytes) | data (N bytes) | checksum (8 bytes) | +----------------------+--------------------------+-----------------------+-----------------------+-----------------------+ | op (1 bit) | custom flag (7 bits) | len (4 bytes) | data (N bytes) | checksum (8 bytes) | +----------------------+--------------------------+-----------------------+-----------------------+-----------------------+ | ... | ... | ... | ... | ... | +----------------------+--------------------------+-----------------------+-----------------------+-----------------------+ ``` ## Installation ```toml [dependencies] aol = "0.3" ``` ## Example - [Manifest file for bitcask database](./examples/bitcask_manifest.rs) #### License `aol` is under the terms of both the MIT license and the Apache License (Version 2.0). See [LICENSE-APACHE](LICENSE-APACHE), [LICENSE-MIT](LICENSE-MIT) for details. Copyright (c) 2024 Al Liu. [Github-url]: https://github.com/al8n/aol/ [CI-url]: https://github.com/al8n/aol/actions/workflows/ci.yml [doc-url]: https://docs.rs/aol [crates-url]: https://crates.io/crates/aol [codecov-url]: https://app.codecov.io/gh/al8n/aol/ [zh-cn-url]: https://github.com/al8n/aol/tree/main/README-zh_CN.md