70ecd6caa0
Transaction Science open standards monorepo. Each subdirectory is a self-contained reference protocol with its own README and licence. - openpay/ Apache-2.0 payment-acceptance stack (Rust, 26 crates) - smart-byte/ CC-BY-4.0 content-addressed value carrier (spec) - eoc/ CC-BY-4.0 energy-optimised compute (spec) The wire format and the right to fork are public. The optional hosted services are the offer; the protocols are not.
57 lines
2 KiB
Rust
57 lines
2 KiB
Rust
//! # `op-emv` — EMV BER-TLV codec
|
||
//!
|
||
//! Parses Tag-Length-Value bundles per **EMV Book 3, Annex B** (BER-TLV).
|
||
//! This is the binary format used everywhere in chip-card and Tap-to-Pay
|
||
//! payloads: the data returned by Apple's `ProximityReader` on iOS, the
|
||
//! Android `IsoDep` APDU responses, and what every EMVCo-certified
|
||
//! terminal kernel produces.
|
||
//!
|
||
//! ## Why a custom parser
|
||
//!
|
||
//! Generic ASN.1 BER libraries handle a superset of what EMV uses, are
|
||
//! `std`-heavy, and don't enforce EMV's restrictions:
|
||
//!
|
||
//! - **Tag**: 1 to 4 bytes. First byte's lower 5 bits = `0x1F` means
|
||
//! multi-byte tag; subsequent bytes' bit 8 = 1 means another follows.
|
||
//! EMV caps tags at 4 bytes; we enforce that.
|
||
//! - **Length**: short form (one byte, 0–127) or long form (`0x8N`
|
||
//! followed by N length bytes). EMV bans indefinite length (`0x80`
|
||
//! alone). We reject it.
|
||
//! - **Constructed vs primitive**: bit 6 of the first tag byte. A
|
||
//! constructed TLV's value is itself a sequence of TLVs.
|
||
//! - **Padding**: `0x00` bytes between TLVs are allowed and skipped.
|
||
//!
|
||
//! ## API shape
|
||
//!
|
||
//! Two layers:
|
||
//!
|
||
//! - [`stream`] — zero-alloc, no-std iterator. Each step yields a
|
||
//! borrowed [`TlvRef`] pointing into the input slice. This is what
|
||
//! the FFI layer hands to platform shells.
|
||
//! - [`tree`] — `std`-only builder that turns a flat stream into a
|
||
//! [`Tlv`] tree with owned values. Useful for diagnostics, caching,
|
||
//! and the AI-fraud pre-processor in `op-fraud`.
|
||
//!
|
||
//! ## Safety
|
||
//!
|
||
//! `#![forbid(unsafe_code)]`. All indexing is bounds-checked.
|
||
|
||
#![cfg_attr(not(feature = "std"), no_std)]
|
||
#![forbid(unsafe_code)]
|
||
#![warn(missing_docs)]
|
||
#![warn(clippy::pedantic)]
|
||
#![allow(clippy::module_name_repetitions)]
|
||
|
||
extern crate alloc;
|
||
|
||
pub mod error;
|
||
pub mod stream;
|
||
pub mod tag;
|
||
#[cfg(feature = "std")]
|
||
pub mod tree;
|
||
|
||
pub use error::{Error, Result};
|
||
pub use stream::{TlvIter, TlvRef};
|
||
pub use tag::{Tag, TagClass};
|
||
#[cfg(feature = "std")]
|
||
pub use tree::Tlv;
|