Function: readDelimiters()

readDelimiters(headerRecord): Delimiters | undefined

Read the four delimiters from a header record's raw text (a single H record, its terminator already stripped).

Returns undefined when the record cannot declare all four delimiters - it is shorter than H + a field separator + a 3-char delimiter definition, or the field separator it names also appears among the other three.

What the caller does with that depends on which header it is. On the first header it is the ASTM_RECORD_UNDECLARED_DELIMITERS fatal, because there is no earlier set to fall back to. On any later header - a stream may carry several messages, each declaring its own set - the delimiters already in force are kept and an ASTM_RECORD_UNREADABLE_REDECLARATION warning is raised instead; a set is never guessed and no record is dropped.

This function does not throw: delimiter resolution and the escalation decision are kept separate so the reader stays pure and testable.

Parameters

headerRecord

string

The raw H record text (no trailing CR/LF).

Returns

Delimiters | undefined

The resolved delimiters, or a declared failure.

Example

import { readDelimiters } from "@cosyte/astm";
const d = readDelimiters("H|\\^&|||sender");
d.field; // "|"