Zig client for the public CEP API http://git.cep.is/zig/atom?h=v0.2.0 2026-07-27T23:39:06Z 2026-07-27T23:39:06Z Murilo Ijanc murilo@ijanc.org 2026-07-27T23:39:06Z urn:sha1:497b1c1b01f6c9a584e5b40e02aff4763447529c A CEP that fails to resolve is rarely a random number. It is almost always someone who knows the city and guessed the digits, and the classic guess is the -000 that 957 municipalities never received. The API now says so: a 404 carries an optional faixa block naming the municipality the number would have belonged to, and answering "no such CEP in Areal/RJ, which has 118 of them" is a great deal more useful than "not found". It arrives through Diagnostics, which is where every other detail a Zig error tag cannot carry already travels, and it is read with diag.faixa(). Like message(), it lives in a fixed buffer inside the value and allocates nothing, so no caller has to learn a new deinit for it. The lookup still fails. faixa is context for the error, never an address, and cep_ini/cep_fim are the smallest and largest CEP that actually exist there rather than the bounds the Correios publish — for Areal the DNE's own start is 25845000, which is exactly the CEP that failed. The range is also sparse, 118 CEPs over ~4,900 numbers, so ceps is the count and the pair must never be presented as a list. The doc comments and the README say all three, because this field is easy to misread as a success. Parsing is deliberately inert: a faixa that is missing, null, not an object, nameless or oversized yields null, and an unreadable body is skipped. Nothing about this field may promote a clean not-found into a parse failure. 2026-07-26T15:48:43Z Murilo Ijanc murilo@ijanc.org 2026-07-26T15:48:43Z urn:sha1:87166a5299aa551517a86379a0c05eb2110b52b0