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FTracker Identifiers

ftracker-identifiers is a Rust crate of small, validated value types for the identifiers used across financial and regulatory data.

Every type in this crate follows the same philosophy:

  • Parse, don’t validate. If you’re holding a value of the type, it is guaranteed correct. There is no “unchecked” variant floating around your codebase that might secretly be malformed.
  • Zero-cost. Types are small, Copy, and allocation-free. Validating and formatting an identifier should not require a heap allocation.
  • no_std-friendly. The crate builds without std by default consumers who need it, falling back to alloc only where unavoidable (see each identifier’s own chapter for specifics).
  • Additive feature flags. Integrations with serde, schemars, arbitrary, and proptest are opt-in and never change an identifier’s validation rules. Enabling a feature only adds capabilities, it never loosens or tightens what counts as “valid.”

What’s covered today

  • CNPJ — Brazil’s national registry identifier for legal entities, supporting both the legacy numeric-only format and the 2026 alphanumeric format.
  • ISIN — the ISO 6166 identifier for a fungible financial security, validated with the ISO 6166 Luhn check digit.

What’s planned

The Identifiers section of this book is organized so each identifier gets its own chapter, following the same shape: structure, parsing & validation, formatting, error handling, feature flags, and examples. CFI is next on the roadmap; see Adding a New Identifier if you’d like to help build it out.

Installation

Add the crate to your Cargo.toml, enabling only the feature flags you need:

[dependencies]
ftracker-identifiers = "0.0.1"

# Optional integrations — see each identifier's "Feature Flags" chapter for details.
# ftracker-identifiers = { version = "0.0.1", features = ["serde", "schemars"] }

Minimum supported Rust version

This crate targets the Rust version pinned in rust-toolchain.toml at the repository root. Check that file for the exact version this documentation was written against.