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Module: (curry codesets)

unreleased

SRFI-238 codesets: a unified interface for translating between numeric codes and symbolic mnemonics, plus human-readable messages, across errno, POSIX signals, and HTTP status codes. Pure system libc (<errno.h>, <signal.h>, strerror/strsignal); no external dependency, macOS/Linux portable. Built by default (-DBUILD_MODULE_CODESETS=ON).

A portable re-export under the SRFI's own naming convention is available as (srfi s238 codesets) — see srfi/s238.md.

Import

(import (curry codesets))

Codesets

Three codesets are known: 'errno, 'signal, 'http-status.

errno and signal symbol names and their numeric values come straight from this platform's own <errno.h>/<signal.h> macros at build time — the set of known codes and their spelling is fixed, but the actual number behind e.g. ENOTSUP can (and does) differ between macOS and Linux, exactly as it does in C. http-status is a static table of standard HTTP status codes (100–511) with no platform dependency, since it isn't a libc concept — its symbols are kebab-case ('not-found, 'internal-server-error), not the numeric-code style of the other two.

Procedures

(codeset? x) → boolean

#t if x is one of the known codeset symbols ('errno, 'signal, 'http-status).

(codeset-symbols codeset) → list of symbols

Every known symbol in codeset. Raises an error if codeset isn't recognized.

(codeset-symbol codeset code) → symbol | #f

Converts a numeric code to its symbolic name, or passes an already-valid symbol through. Returns #f for an unrecognized code.

(codeset-number codeset code) → exact integer | #f

Converts a symbolic code to its number, or passes an already-valid number through. Returns #f for an unrecognized code.

(codeset-message codeset code) → string | #f

A human-readable message for code (symbol or number) — strerror(3) for errno, strsignal(3) for signal, the standard reason phrase for http-status. Returns #f if code isn't recognized.

(import (curry codesets))

(codeset-symbol 'errno 2)              ; => ENOENT
(codeset-message 'errno 'ENOENT)       ; => "No such file or directory"

(codeset-symbol 'signal 9)             ; => SIGKILL
(codeset-message 'signal 'SIGSEGV)     ; => "Segmentation fault" (exact wording is platform-dependent)

(codeset-symbol 'http-status 404)      ; => not-found
(codeset-number 'http-status 'not-found) ; => 404
(codeset-message 'http-status 500)     ; => "Internal Server Error"

(codeset? 'errno)                      ; => #t
(codeset-symbol 'errno 999999)         ; => #f

Notes

  • errno/signal cover the POSIX.1-2008 base codes common to macOS and Linux, plus a handful of platform-conditional ones (ENODATA, ENOSR, ENOSTR, ETIME, EOPNOTSUPP, EWOULDBLOCK, SIGPOLL, SIGIO) included only when this platform's headers actually define them (and, for EWOULDBLOCK, only when it isn't just an alias of EAGAIN) — per the SRFI, codeset-symbols is expected to return "as many as are known," not necessarily every code that exists anywhere.
  • This complements (curry posix), whose errors already embed strerror() text but don't expose a structured errno symbol/number lookup on their own.