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// This source code is released into the public domain.
module;
#include <cerrno>
#include <stdlib.h> // NOLINT: getenv_r
#include "nihil.hh"
export module nihil.posix:getenv;
import nihil.std;
import nihil.error;
import nihil.util;
namespace nihil {
// Find a variable by the given name in the environment by calling getenv_r() if available,
// or getenv() if not. In either case the value is copied, so will not be affected by
// future calls to setenv().
export [[nodiscard]] auto getenv(std::string_view varname) -> std::expected<std::string, error>
{
auto errno_guard = save_errno();
auto cvarname = std::string(varname);
#if NIHIL_HAVE_GETENV_R == 1
// Start with a buffer of this size, and double it every iteration.
constexpr auto bufinc = std::size_t{1024};
auto buf = std::vector<char>(bufinc);
for (;;) {
auto const ret = ::getenv_r(cvarname.c_str(), buf.data(), buf.size());
if (ret == 0)
return {std::string(buf.data())};
if (ret == -1 && errno == ERANGE) {
buf.resize(buf.size() * 2);
continue;
}
return std::unexpected(error(std::errc(errno)));
}
#else // NIHIL_HAVE_GETENV_R
// getenv() may not set errno on failure, so initialise it to a reasonable value.
errno = ENOENT;
auto const *v = ::getenv(cvarname.c_str()); // NOLINT
if (v != nullptr)
return {std::string(v)};
return error(sys_error());
#endif // NIHIL_HAVE_GETENV_R
}
} // namespace nihil
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