High-level Rust API for working with the kpathsea file-searching library for TeX
Two backends are provided:
- in-process — FFI calls into the system
libkpathsea(the fast path, microseconds per lookup). Selected automatically when the library was found at build time: pkg-config or theKPATHSEA_LIB_DIRoverride on Unix, TeX Live's own kpathsea DLL (found next tokpsewhich.exe) on Windows — seekpathsea_sys's build script.KPATHSEA_NO_LINK=1at build time forces the subprocess backend even when a library is available. - subprocess — delegates to the host TeX distribution's own
kpsewhichexecutable, fronted by a one-shot cache of the TeX tree'sls-Rdatabases. Selected automatically whenlibkpathseawas not found at build time (e.g. MacTeX/BasicTeX ship no library at all), or explicitly via [Kpaths::new_subprocess]. Because it asks the host's resolver binary, it stays in sync with the ambient distribution by construction — including MiKTeX, which reimplements kpathsea. (This mirrors how Perl LaTeXML has always resolved TeX files; seesrc/subprocess.rs.)
Latency profile (measured on a full TeX Live): in-process lookups are
tens of µs, hit or miss. Subprocess lookups are bimodal: sub-µs on an
ls-R cache hit — faster than the FFI path — but a cache miss costs a
kpsewhich spawn (tens to hundreds of ms, memoized process-wide per
executable so a repeated miss is only ever paid once, regardless of
which instance or thread asks).