mv_package

curl — HTTP client for MultiValue BASIC, via libcurl

Provides HTTPGET(url) and HTTPGETFILE(url, path) by calling libcurl from C. libcurl handles TLS, redirects and binary bodies — the things a raw-socket client and UniData's native HTTPS (createSecureRequest) do not: it will not reliably reach github, and a release URL 302s to the CDN.

provides: curl, so a dependency on curl resolves to this package — or to curl-cmd, which offers the same two functions by shelling out to the OS curl command and needs no compiler. Both satisfy the same dependency; this one needs libcurl.so.4 and a build, and in exchange never shells out.

| system | binding | built as | |---|---|---| | udt | UniData CallC (CURLGET/CURLGETFILE) | an object folded into libu2callc.so | | jbase | jBASE DEFC (JBCURLGET/JBCURLGETFILE) | a shared library, lib/libjbcurl.so | | mvx | built into the runtime | — (mvx needs no package) |

jBASE needs the library preloaded

This is jBASE's behaviour for DEFC generally, not something this package does: a CATALOGed subroutine cannot resolve a DEFC function unless the library is forced into the process. LD_LIBRARY_PATH is not enough — the symbol resolves at load time against the cataloged object, and you get

jBASE: /home/you/lib/lib0.so.NNN: undefined symbol: JBCURLGETFILE

which names the other function, because the loader resolves them all at once. So a session that calls HTTPGET must have:

LD_PRELOAD=<account>/lib/libjbcurl.so

Reproduced with five lines of C and no package at all — see mv_git#114, which documents the same constraint for the git engine.

The jBASE binding returns the status

DEFC declares a function, and an argument VAR written by the C side is visible to the caller — so the body comes back through an argument and the return value carries the HTTP status:

DEFC VAR JBCURLGET(VAR, VAR)
ST = JBCURLGET(URL, RESP)      ;* ST = 200, RESP = the body

UniData's CallC cannot do that: it marshals a char * and nothing else, so CURLGET has to answer the body itself and the status is lost — a 404 and an empty 200 are the same empty string there. Both arms agree on the contract the BASIC wrappers present (HTTPGET -> body on 2xx else ""), but jBASE keeps the status underneath it.