Parsing & Validation

Constructors

Cfi::new is a plain alias for Cfi::parse; FromStr and TryFrom<&str> both delegate to it too, so "...".parse::<Cfi>() and Cfi::try_from("...") behave identically to calling Cfi::parse directly.

Cfi::from_bytes is the lower-level constructor: it skips whitespace-trimming and case-folding and expects an already-normalized [u8; 6]. It still runs every validation rule below. PreferCfi::parse unless you’re constructing bytes programmatically (for example, in a generator or migration script).

What Cfi::parse accepts

• The canonical 6-character form.
• Lowercase letters — they’re folded to uppercase automatically.
• Leading and trailing whitespace — it’s trimmed before validation.

Interior separators are not stripped: a CFI has no conventional internal punctuation, so a character in the middle of the string that isn’t a letter is reported as invalid rather than silently removed.

use ftracker_identifiers::Cfi;

assert!(Cfi::parse("ESVUFR").is_ok());
assert!(Cfi::parse("esvufr").is_ok());    // lowercase is folded
assert!(Cfi::parse("  ESVUFR ").is_ok()); // surrounding whitespace is trimmed
assert!(Cfi::parse("EZVUFR").is_err());   // 'Z' is not a group of category 'E'

Validation rules

The string-based constructors run the following rules, in this order:

1. Length — after surrounding whitespace is trimmed, the input must contain exactly 6 characters. (Cfi::parse rejects an empty string up front.)
2. Character class — every position must be an uppercase ASCII letter (A–Z).
3. Category — position 1 must be a category defined by ISO 10962.
4. Group — position 2 must be a group defined for that category.
5. Attributes — each of positions 3–6 must be a code the standard permits for the resolved category and group at that attribute position.

Rules 3–5 are checked against the embedded taxonomy table with a couple of allocation-free binary searches and bitmask tests — no heap, no runtime initialization. Each rule maps to exactly one CfiError variant; see Error Handling for the full list and how to match on it.

What it doesn’t do

Cfi::parse validates shape and taxonomy, not meaning or existence. It cannot tell you what a code classifies in human-readable terms (the descriptive names are not embedded; see Structure & Formats), nor whether a particular instrument has been assigned that classification by an issuer or numbering agency.