Decompression and limits

Decompressor owns reusable state. decompress returns a Vec, decompress_into appends atomically, and decompress_to_slice writes into caller storage. Sessions report consumed/produced counts; reader and writer adapt synchronous I/O.

Set limits for untrusted input

The default accepts one complete raw member and extended window declarations up to 62 bits. Numeric budgets are unlimited by default. Configure them for your application before decoding input you do not control:

use mbrotli::{DecodeLimits, DecoderConfig, Decompressor, WindowLimit};

fn decode_payload(input: &[u8]) -> Result<Vec<u8>, Box<dyn std::error::Error>> {
    let limits = DecodeLimits::default()
        .with_max_input_bytes(Some(1 << 20))
        .with_max_output_bytes(Some(8 << 20))
        .with_max_workspace_bytes(Some(32 << 20));
    let config = DecoderConfig::default()
        .with_window_limit(WindowLimit::standard(24)?)
        .with_limits(limits);
    let mut decoder = Decompressor::new(config)?;
    Ok(decoder.decompress(input)?)
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let payload = b"a payload from the network";
    let compressed = mbrotli::Compressor::new(Default::default())?.compress(payload)?;
    assert_eq!(decode_payload(&compressed)?, payload);
    Ok(())
}

The workspace budget excludes caller output and borrowed dictionaries; it is not a process-memory limit. Keep the decoder across calls when reuse matters.

Members, dictionaries and backends

MemberMode::Concatenated accepts successive raw members. DecodeDictionary prepares decoding data without encoder indexes; PreparedDictionary can also be borrowed. RAW dictionaries work in all profiles; serialized/custom dictionaries require experimental.

Vec appends are rolled back on failure. The decoder specializes its command loops and history copies for the selected CPU backend using safe fearless_simd abstractions.

See decoder mechanics and compatibility limits.

Where to go next