Crate hl7kit 

A small, dependency-free HL7 v2.x parser.

The parser splits a message into segments, fields, repetitions, components and subcomponents and keeps the byte span of every node, so a caller can point back into the original text (for highlighting, diffing or error reporting) without searching for the value again.

Design constraints:

• No dependencies, no unsafe, no panics on malformed input. Malformed messages are the normal case in integration work; every failure is a value.
• Tolerant of what real interfaces produce: \r, \r\n and bare \n segment terminators, MLLP framing bytes, a UTF-8 BOM, a malformed MSH-2.
• MSH numbering is handled correctly: MSH-1 is the field separator and MSH-2 the encoding characters, so MSH-9 is the message type in this crate exactly as it is in the standard.
• Encoding characters come from MSH-2, never hardcoded. Escape sequences (\F\, \S\, \T\, \R\, \E\, \Xdd..\, \.br\) decode on demand.
• Host-target only code: no web-sys, no I/O. It compiles for wasm32-unknown-unknown unchanged.

use hl7kit::Message;

let text = "MSH|^~\\&|RIS|HOSP|PACS|HOSP|20260905120000||ORM^O01|42|P|2.5.1\r\
            PID|1||4MR1^^^HOSP^MR||Doe^Jane||19700101|F\r\
            OBR|1|A1001||MR1^MRI HEAD|||20260905|||||||||||A1001|RP-77\r\
            ZDS|1.3.6.1.4.1.5962.1.2.4.20040826185059.5457^^Application^DICOM\r";

let msg = Message::parse(text).unwrap();
assert_eq!(msg.get("MSH-9.1"), Some("ORM"));
assert_eq!(msg.get("PID-3.1"), Some("4MR1"));
assert_eq!(msg.get("OBR-18"), Some("A1001"));
assert_eq!(msg.get("ZDS-1.1"), Some("1.3.6.1.4.1.5962.1.2.4.20040826185059.5457"));

// Every value knows where it came from.
let span = msg.get_span("PID-3.1").unwrap();
assert_eq!(&text[span.range()], "4MR1");

The order module builds on the parser to extract the four identifiers an imaging order carries (patient ID, accession number, requested procedure ID and study instance UID) as defined by the IHE Radiology Technical Framework.

The builder module writes messages: values are set structurally and delimiter characters inside them are escaped, so what you build parses back to what you set.

Modules

builder

Building messages.

order

Imaging-order identifiers as carried by ORM^O01, OMI^O23 and ORU^R01 messages.

Structs

Component

A component view.

Encoding

The five delimiter characters of an HL7 v2 message.

Field

A field view.

Message

A parsed HL7 v2 message.

MessageType

MSH-9, the message type.

Path

A parsed query path.

Repetition

A repetition view.

Segment

A segment view.

Span

A byte range into Message::raw.

Subcomponent

A subcomponent view.

Enums

ParseError

Why a message could not be parsed.

PathError

Why a query path such as PID-3.1 could not be parsed.

Warning

Something the parser tolerated but a reviewer may want to know about.

Functions

unescape

Decode HL7 escape sequences in text using the message’s encoding characters.