# HL7v2
```
_ _ _ ___ ____
| | | | | |__ \__ _|___ \
| |_| | | ) \ \ / / __) |
| _ | |__ / / \ V / / __/
|_| |_|____|_/ \_/ |_____|
Pure Elixir HL7 v2.x Toolkit
Schema-driven parsing, building, and MLLP transport.
```
[](https://hex.pm/packages/hl7v2)
[](https://hexdocs.pm/hl7v2)
[](https://github.com/Balneario-de-Cofrentes/hl7v2/blob/main/LICENSE)
Pure Elixir HL7 v2.x toolkit — typed segment structs, programmatic message building,
structural validation, and integrated MLLP transport.
## What You Get
- **Typed segments** — every v2.5.1 segment is an Elixir struct with named fields,
not string maps with integer keys
- **Programmatic message building** — `Message.new/3` + `add_segment/2` with
auto-populated MSH
- **Structural validation** — positional order/group/cardinality checks for
supported message structures, opt-in HL7 table validation
- **Lossless raw mode** — canonical round-trip parsing that preserves everything,
including malformed input
- **Integrated MLLP** — Ranch 2.x listener, GenServer client, TLS/mTLS, telemetry
- **ACK/NAK builder** — `HL7v2.ack/2` with sender/receiver swap
- **Path access** — `get/2`, `fetch/2`, `~h` sigil with compile-time validation
```elixir
# Typed structs with named fields
{:ok, msg} = HL7v2.parse(text, mode: :typed)
pid = Enum.find(msg.segments, &is_struct(&1, HL7v2.Segment.PID))
pid.patient_name #=> [%XPN{family_name: %FN{surname: "Smith"}, given_name: "John"}]
# Build messages programmatically
msg = HL7v2.Message.new("ADT", "A01", sending_application: "PHAOS")
|> HL7v2.Message.add_segment(%HL7v2.Segment.PID{
patient_name: [%XPN{family_name: %FN{surname: "Smith"}, given_name: "John"}]
})
```
## Installation
```elixir
def deps do
[{:hl7v2, "~> 2.6"}]
end
```
## Quick Start
### Parse
```elixir
# Raw mode — canonical round-trip, zero allocation overhead
{:ok, raw} = HL7v2.parse(text)
raw.type #=> {"ADT", "A01"}
# Typed mode — segments become structs
{:ok, msg} = HL7v2.parse(text, mode: :typed)
# Access fields naturally
HL7v2.get(msg, "PID-5") #=> %XPN{family_name: %FN{surname: "Smith"}, ...}
HL7v2.get(msg, "PID-3") #=> %CX{id: "12345", identifier_type_code: "MR"}
HL7v2.get(msg, "PID-8") #=> "M"
HL7v2.get(msg, "PID-3[2]") #=> second identifier (repetition)
```
### Build
```elixir
msg =
HL7v2.Message.new("ADT", "A01",
sending_application: "PHAOS",
sending_facility: "HOSP"
)
|> HL7v2.Message.add_segment(%HL7v2.Segment.PID{
set_id: 1,
patient_identifier_list: [
%HL7v2.Type.CX{id: "MRN001", identifier_type_code: "MR"}
],
patient_name: [
%HL7v2.Type.XPN{
family_name: %HL7v2.Type.FN{surname: "Smith"},
given_name: "John"
}
],
administrative_sex: "M"
})
wire = HL7v2.encode(msg)
# => "MSH|^~\\&|PHAOS|HOSP|...\rPID|1||MRN001^^^^MR||Smith^John|||M\r"
```
### Validate
```elixir
{:ok, typed} = HL7v2.parse(text, mode: :typed)
case HL7v2.validate(typed) do
:ok ->
:good
{:error, errors} ->
# [%{level: :error, location: "PID", field: :patient_name,
# message: "Required field is missing"}]
Enum.each(errors, &IO.inspect/1)
end
```
### ACK/NAK
```elixir
# Accept
{ack_msh, msa} = HL7v2.Ack.accept(original_msh)
wire = HL7v2.Ack.encode({ack_msh, msa})
# Reject with error details
{ack_msh, msa, err} = HL7v2.Ack.reject(original_msh,
text: "Unknown patient",
error_code: "204"
)
```
### MLLP Transport
```elixir
# Server
defmodule MyHandler do
@behaviour HL7v2.MLLP.Handler
@impl true
def handle_message(message, _meta) do
{:ok, typed} = HL7v2.parse(message, mode: :typed)
msh = hd(typed.segments)
{ack_msh, msa} = HL7v2.Ack.accept(msh)
{:ok, HL7v2.Ack.encode({ack_msh, msa})}
end
end
{:ok, _} = HL7v2.MLLP.Listener.start_link(port: 2575, handler: MyHandler)
# Client
{:ok, client} = HL7v2.MLLP.Client.start_link(host: "hl7.hospital.local", port: 2575)
{:ok, ack} = HL7v2.MLLP.Client.send_message(client, wire)
# TLS / mTLS
{:ok, _} = HL7v2.MLLP.Listener.start_link(
port: 2576,
handler: MyHandler,
tls: HL7v2.MLLP.TLS.mutual_tls_options(certfile: "cert.pem", keyfile: "key.pem", cacertfile: "ca.pem")
)
```
## Coverage
```
Segments 152 standard + generic ZXX
152 of 152 v2.5.1 segments (100%) + generic Z-segment pass-through
149 fully typed, 3 with intentional raw holes (RDT, QPD, OBX)
Run `mix hl7v2.coverage` for the full list
Types 89 v2.5.1 data types + legacy TN (100% of official catalog)
Structures 190 message structure definitions covering all major v2.5.1 families
ADT, BAR, BPS/BRP/BRT/BTS, CRM, CSU, DFT, MDM, MFN/MFK/MFR,
OML/OMG/OMD/OMP/OMS/OMI/OMN/OMB, ORU/OUL/ORA, ORM/ORR/ORG/ORL/ORP/ORD/ORS/ORN/ORI/ORB,
RDE/RDS/RGV/RAS, RRE/RRD/RRG/RRA, REF/RRI, SIU/SRM/SRR,
PGL/PPG/PPP/PPR/PPT, QBP/QSB/QVR/RSP/RTB/RDY, PMU, PEX/SUR,
CCR/CCI/CCU/CCQ/CCF, EHC, RQI/RQA/RQC/RQP/RPA/RPI/RPL/RPR/RCI,
RER/RDR/RAR/ROR, VXU/VXQ/VXR/VXX, DOC, UDM, ACK + more
Transport MLLP framing, Ranch 2.x listener, GenServer client,
TLS/mTLS, telemetry instrumentation
Validation structural (order/groups/cardinality) + opt-in table checking
108 HL7 tables, 80 coded fields validated, conditional field rules
Speed <1s full suite
```
## Scope
**HL7 v2.5.1** schema with best-effort adjacent-version tolerance (v2.3 through v2.8.x
messages parse and round-trip; version-specific deltas are not semantically enforced).
- Every v2.5.1 segment and data type has a typed Elixir module
- Raw mode is lossless after successful MSH/separator detection
- Typed mode preserves values it cannot parse (invalid dates, malformed
numbers) in `original` fields for round-trip fidelity
- Extra fields beyond declared definitions are preserved in `extra_fields`
- Escape sequences are preserved literally in typed fields — call
`HL7v2.Escape.decode/2` when you need decoded text
Run `mix hl7v2.coverage` for detailed per-segment field completeness.
## Handling Unknown Segments
Real-world HL7 is messy. Messages arrive with vendor-specific Z-segments, obsolete
segments from older versions, and segments your system doesn't care about. The library
handles all of them without crashing or losing data:
```elixir
{:ok, msg} = HL7v2.parse(text, mode: :typed)
# Known segments → typed structs with named fields
%HL7v2.Segment.PID{patient_name: [%XPN{...}], ...}
# Z-segments → ZXX struct preserving segment ID and all raw fields
%HL7v2.Segment.ZXX{segment_id: "ZPD", raw_fields: ["custom", "data"]}
# Unknown segments from other versions → raw tuples, lossless
{"XYZ", ["1", "DATA001", ...]}
```
All three forms encode back to valid HL7 wire format. The typed API (`get/2`, `fetch/2`,
`~h` sigil) works across all forms — typed segments return struct fields with component
and repetition selection, raw tuples return whole fields by position (component/repetition
selectors are not applied to raw tuples).
This means you can parse any HL7 message from any source, work with the segments you
understand, and forward the rest unchanged. No schema registration required.
## Documentation
Full API docs: [hexdocs.pm/hl7v2](https://hexdocs.pm/hl7v2)
Getting started guide included.
## Part of the Balneario Healthcare Toolkit
Three pure-Elixir libraries covering the core protocol surface of healthcare IT. Zero NIFs. Built for production.
| Library | Domain | Standards | |
|---------|--------|-----------|---|
| **dicom** | Medical imaging data | PS3.5 / 6 / 10 / 15 / 16 / 18 | [Hex](https://hex.pm/packages/dicom) · [Docs](https://hexdocs.pm/dicom) · [GitHub](https://github.com/Balneario-de-Cofrentes/dicom) |
| **dimse** | DICOM networking | PS3.7 / 8 / 15 | [Hex](https://hex.pm/packages/dimse) · [Docs](https://hexdocs.pm/dimse) · [GitHub](https://github.com/Balneario-de-Cofrentes/dimse) |
| **hl7v2** | Clinical messaging | HL7 v2.5.1 | [Hex](https://hex.pm/packages/hl7v2) · [Docs](https://hexdocs.pm/hl7v2) · [GitHub](https://github.com/Balneario-de-Cofrentes/hl7v2) |
[`dicom`](https://github.com/Balneario-de-Cofrentes/dicom) parses and writes DICOM files. [`dimse`](https://github.com/Balneario-de-Cofrentes/dimse) moves them over the network via DIMSE-C/N services. `hl7v2` handles the clinical messages (ADT, ORM, ORU) that trigger and contextualize imaging workflows.
Together they give Elixir the same healthcare protocol coverage that Java has with dcm4che + HAPI, or C++ with DCMTK — on the BEAM.
## License
MIT — see [LICENSE](LICENSE).
