Struct Config 

#[non_exhaustive]
pub struct Config {
    pub max_alloc: usize,
}

Configuration for a decode session.

At construction time the codec validates the configuration; an invalid config (currently: max_alloc == 0) is rejected before any bytes are read. Validation happens once, in Decoder::with_config / crate::IoDecoder::with_config, not on every operation.

Config is #[non_exhaustive] so the project can add knobs in a MINOR release without breaking downstream code. Build instances with Config::new / Config::with_max_alloc or via Default.

Examples

use pack_io::{Config, Decoder};

// Refuse to allocate more than 16 KiB for any single length-prefixed
// value (a `String`, a `Vec<u8>`, a collection element count, …).
// Hostile producers that send multi-gigabyte length prefixes fail fast.
let cfg = Config::new().with_max_alloc(16 * 1024);
let dec = Decoder::with_config(&[], cfg).expect("non-zero cap");
drop(dec);

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

max_alloc: usize

Maximum number of bytes the decoder may allocate for any single length-prefixed value (a String, a Vec<u8>, a collection element count, …).

The default is 1 GiB, which is enough that well-formed inputs are never rejected on size, while still defending against the obvious hostile-length-prefix DoS. Tighten this in any context that accepts untrusted input from a low-budget producer.

Implementations

impl Config

pub const fn new() -> Self

Default configuration: max_alloc = 1 GiB.

1 GiB is large enough to be irrelevant for well-formed inputs and small enough to refuse the obvious length = u64::MAX attack before allocating a single byte.

Examples

let cfg = pack_io::Config::new();
assert_eq!(cfg.max_alloc, 1 << 30);

pub const fn with_max_alloc(self, max_alloc: usize) -> Self

Replace max_alloc and return the updated config.

Examples

let cfg = pack_io::Config::new().with_max_alloc(4096);
assert_eq!(cfg.max_alloc, 4096);

Trait Implementations

impl Clone for Config

fn clone(&self) -> Config

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Config

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Config

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for Config

fn eq(&self, other: &Config) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Config

impl Eq for Config

impl StructuralPartialEq for Config