logistics.sscc

def build_sscc(extension_digit: int, company_prefix: str, serial_reference: int) -> str

from fune.logistics.sscc import build_sscc  # logistics.sscc@^1

import re

from .validation_gs1_check_digit import gs1_check_digit  ← from validation.gs1-check-digit ^1.0.0 · built alongside by fune

_PREFIX = re.compile(r"^[0-9]{4,12}$")


def _whole(value: object) -> bool:
    return isinstance(value, int) and not isinstance(value, bool)


def build_sscc(extension_digit: int, company_prefix: str, serial_reference: int) -> str:
    """Build an 18-digit SSCC: extension digit, GS1 company prefix, zero-padded
    serial reference and GS1 mod-10 check digit."""
    if not _whole(extension_digit) or extension_digit < 0 or extension_digit > 9:
        raise ValueError("extensionDigit must be 0 to 9, received %r" % (extension_digit,))
    # fullmatch, not match: "$" in re also matches before a trailing newline.
    if not isinstance(company_prefix, str) or not _PREFIX.fullmatch(company_prefix):
        raise ValueError('companyPrefix must be 4 to 12 digits, received "%s"' % (company_prefix,))
    if not _whole(serial_reference):
        raise TypeError("serialReference must be an integer, received %r" % (serial_reference,))
    if serial_reference < 0:
        raise ValueError("serialReference must not be negative, received %d" % serial_reference)
    # Prefix and serial share 16 digits, so a longer prefix leaves less room.
    # Too large is an error: truncating would reuse another unit's number.
    room = 16 - len(company_prefix)
    serial = str(serial_reference)
    if len(serial) > room:
        raise ValueError(
            "serialReference must fit in %d digits after a %d-digit company prefix, received %d"
            % (room, len(company_prefix), serial_reference)
        )
    data = str(extension_digit) + company_prefix + serial.rjust(room, "0")
    return data + str(gs1_check_digit(data))

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the Python package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add logistics.sscc

The manifest, vectors and README with only the Python implementation. Install it without the registry with fune add ./logistics.sscc-1.1.0-python.fune, or fetch it from a terminal with fune pull logistics.sscc@1.1.0:python.

The whole function, every language, is one file too: logistics.sscc-1.1.0.fune, 10,910 bytes, sha256 aea2a0319e89e237e8778fea97ac8cd01600de11bd63409a4546fd35791a5e55. It installs into a project of any language.

# fune: before logistics.sscc

# fune: after logistics.sscc

# fune: replace validation.gs1-check-digit in logistics.sscc

# fune: step logistics.sscc after <n|label>

More from the author

So a 7-digit prefix leaves 9 digits of serial reference and a 10-digit prefix leaves 6. A serial reference too large for the room left is an error rather than being truncated, because a truncated serial silently re-uses another pallet's number.

## Check digit

The standard GS1 mod-10 over the 17 data digits, from `validation.gs1-check-digit` since 1.1.0 (1.0.0 repeated the arithmetic here, because `validation.gtin` only accepted GTIN lengths). The answers are the same. GS1's own example, `(00) 1 0614141 123456789 7`, is a vector, and so is the SSCC from GS1's check digit worked example, `376104250021234569`.

## What it does not do

- It returns the bare 18 digits. The label's human-readable line shows them after the application identifier as `(00) 106141411234567897`; the barcode (GS1-128) encodes `00` followed by the 18 digits. - It does not allocate serial references. GS1 asks that an SSCC is not re-used for at least a year after the unit was shipped; keeping the counter is the caller's job. - It cannot tell whether a prefix was really allocated to you.

## Source

GS1 General Specifications, the SSCC (logistic units) and check digit calculation sections, https://www.gs1.org/standards/barcodes-epcrfid-id-keys/gs1-general-specifications ; GS1 UK, "How do I create SSCCs and logistics labels?", https://www.gs1uk.org/knowledge-hub/barcodes/how-do-i-create-ssccs-and-logistics-labels

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