base122-fast

Base122 is a binary-to-text encoding scheme designed to be significantly more space-efficient than Base64. It incurs only ~14% overhead (compared to Base64's 33%) while remaining valid UTF-8.

base122-fast is a high-performance implementation optimized for modern CPUs, featuring no_std support.

Key Features

High Throughput: Optimized for Gbps-level processing.
no_std: Suitable for embedded systems and WASM (requires alloc).
SIMD Within A Register: Uses SWAR techniques to process multiple bytes in 64-bit registers.
Safety: While leveraging unsafe for performance, it is rigorously tested for round-trip integrity.

Performance

The following throughput was measured on high-entropy binary data using an AMD Ryzen 5 5600 (single core).

Data Size	Encode (Throughput)	Decode (Throughput)
16 B	301.9 MiB/s	335.9 MiB/s
64 B	883.6 MiB/s	834.2 MiB/s
1 KiB	2.15 GiB/s	1.63 GiB/s
64 KiB	2.40 GiB/s	1.64 GiB/s
1 MiB	814.6 MiB/s	678.9 MiB/s

For large payloads (≥1 MiB), the implementation sustains approximately 6.5 Gbps encoding and 5.4 Gbps decoding.

Note: Run cargo bench to reproduce these results. The benchmarks evaluate encoding, decoding, and round-trip integrity on random byte streams.

Quick Start

Add to Cargo.toml:

[dependencies]

base122-fast = "0.1"

Usage

use base122_fast::{encode, decode};

// Encoding
let data = b"hello world";
let encoded_str = encode(data);

// Decoding
let decoded_vec = decode(&encoded_str).expect("Invalid Base122");
assert_eq!(data, decoded_vec.as_slice());

Implementation Details

Base122 maps binary data to a UTF-8 safe subset of 122 non-control bytes. Six ASCII codes (\x00, \x0A, \x0D, \x22, \x26, \x5C) are considered illegal and are handled via an escape mechanism.

Optimization Strategy

High throughput is achieved by processing 64-bit chunks. When a chunk contains no illegal bytes, a branchless fast-path is taken. By utilizing unsafe pointer arithmetic and pre-calculating output capacities, the hot loop avoids bounds checking and reallocations.

License

MIT License.

base122-fast 0.1.2