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https://github.com/NixOS/nix
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0fe3b54ee1
In these trivial cases the final vector size (or lower bound on the size) is known, so we can avoid some vector reallocations. This is not very important, but is just good practice and general hygiene.
98 lines
3.2 KiB
C++
98 lines
3.2 KiB
C++
#include "environment-variables.hh"
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#include "executable-path.hh"
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#include "strings-inline.hh"
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#include "util.hh"
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#include "file-path-impl.hh"
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namespace nix {
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namespace fs {
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using namespace std::filesystem;
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}
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constexpr static const OsStringView path_var_separator{
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&ExecutablePath::separator,
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1,
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};
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ExecutablePath ExecutablePath::load()
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{
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// "If PATH is unset or is set to null, the path search is
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// implementation-defined."
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// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
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return ExecutablePath::parse(getEnvOs(OS_STR("PATH")).value_or(OS_STR("")));
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}
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ExecutablePath ExecutablePath::parse(const OsString & path)
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{
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auto strings = path.empty() ? (std::list<OsString>{})
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: basicSplitString<std::list<OsString>, OsChar>(path, path_var_separator);
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std::vector<fs::path> ret;
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ret.reserve(strings.size());
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std::transform(
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std::make_move_iterator(strings.begin()),
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std::make_move_iterator(strings.end()),
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std::back_inserter(ret),
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[](auto && str) {
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return fs::path{
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str.empty()
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// "A zero-length prefix is a legacy feature that
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// indicates the current working directory. It
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// appears as two adjacent <colon> characters
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// ("::"), as an initial <colon> preceding the rest
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// of the list, or as a trailing <colon> following
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// the rest of the list."
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// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
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? OS_STR(".")
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: std::move(str),
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};
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});
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return {ret};
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}
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OsString ExecutablePath::render() const
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{
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std::vector<PathViewNG> path2;
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path2.reserve(directories.size());
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for (auto & p : directories)
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path2.push_back(p.native());
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return basicConcatStringsSep(path_var_separator, path2);
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}
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std::optional<fs::path>
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ExecutablePath::findName(const OsString & exe, std::function<bool(const fs::path &)> isExecutable) const
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{
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// "If the pathname being sought contains a <slash>, the search
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// through the path prefixes shall not be performed."
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// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
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assert(OsPathTrait<fs::path::value_type>::rfindPathSep(exe) == exe.npos);
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for (auto & dir : directories) {
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auto candidate = dir / exe;
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if (isExecutable(candidate))
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return std::filesystem::canonical(candidate);
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}
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return std::nullopt;
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}
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fs::path ExecutablePath::findPath(const fs::path & exe, std::function<bool(const fs::path &)> isExecutable) const
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{
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// "If the pathname being sought contains a <slash>, the search
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// through the path prefixes shall not be performed."
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// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
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if (exe.filename() == exe) {
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auto resOpt = findName(exe, isExecutable);
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if (resOpt)
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return *resOpt;
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else
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throw ExecutableLookupError("Could not find executable '%s'", exe.string());
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} else {
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return exe;
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}
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}
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} // namespace nix
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