135 lines
3.4 KiB
C++
135 lines
3.4 KiB
C++
/** @defgroup Utilities
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*
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* @brief Miscellaneous utilities.
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*
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* @{
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*/
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/** @file environ.hh
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*
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* @brief A portable environment variable interface.
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*
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* Provides utility functions to portably get, set and unset environment
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* variables.
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*
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* @copyright See COPYING.md in the project tree for further information.
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*/
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#ifndef OSTD_ENVIRON_HH
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#define OSTD_ENVIRON_HH
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#include "ostd/platform.hh"
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#include "ostd/internal/win32.hh"
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#include <cstdlib>
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#include <cstring>
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#include <vector>
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#include <optional>
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#include "ostd/string.hh"
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namespace ostd {
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/** @addtogroup Utilities
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* @{
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*/
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/** @brief Gets an environment variable.
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*
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* @returns std::nullopt when the variable doesn't exist, and an std::string
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* containing the environment variable's value if it does.
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*
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* This function is thread-safe as long as the environment is not modified
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* within the program. Calling to lower level functions to set environment
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* vars as well as env_set() or env_unset() at the same time would introduce
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* potential data races.
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*
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* @see env_set(), env_unset()
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*/
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inline std::optional<std::string> env_get(string_range name) {
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char buf[256];
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auto tbuf = to_temp_cstr(name, buf, sizeof(buf));
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char const *ret = std::getenv(tbuf.get());
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if (!ret) {
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return std::nullopt;
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}
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return std::string{ret};
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}
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/** @brief Sets an environment variable.
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*
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* If `update` is false, the environment variable will not be overwritten
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* if it already exists. Keep in mind that true is still returned if the
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* variable already exists and it's not being updated.
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*
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* This function is not thread safe. Do not call it from multiple threads
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* and do not call it if a call to env_get() might be done from another
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* thread at the time.
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*
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* @returns true on success, false on failure.
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*
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* @see env_get(), env_unset()
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*/
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inline bool env_set(
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string_range name, string_range value, bool update = true
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) {
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char sbuf[2048];
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char *buf = sbuf;
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bool alloc = (name.size() + value.size() + 2) > sizeof(sbuf);
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if (alloc) {
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buf = new char[name.size() + value.size() + 2];
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}
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memcpy(buf, name.data(), name.size());
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buf[name.size()] = '\0';
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memcpy(&buf[name.size() + 1], value.data(), value.size());
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buf[name.size() + value.size() + 1] = '\0';
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#ifndef OSTD_PLATFORM_WIN32
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bool ret = !setenv(buf, &buf[name.size() + 1], update);
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#else
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if (!update && GetEnvironmentVariable(buf, nullptr, 0)) {
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return true;
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}
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bool ret = !!SetEnvironmentVariable(buf, &buf[name.size() + 1]);
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#endif
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if (alloc) {
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delete[] buf;
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}
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return ret;
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}
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/** @brief Unsets an environment varible.
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*
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* This function is not thread safe. Do not call it from multiple threads
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* and do not call it if a call to env_get() might be done from another
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* thread at the time.
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*
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* @returns true on success, false on failure.
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*
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* @see env_get(), env_set()
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*/
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inline bool env_unset(string_range name) {
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char buf[256];
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if (name.size() < sizeof(buf)) {
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memcpy(buf, name.data(), name.size());
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buf[name.size()] = '\0';
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#ifndef OSTD_PLATFORM_WIN32
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return !unsetenv(buf);
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#else
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return !!SetEnvironmentVariable(buf, nullptr);
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#endif
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}
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#ifndef OSTD_PLATFORM_WIN32
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return !unsetenv(std::string{name}.data());
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#else
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return !!SetEnvironmentVariable(std::string{name}.data(), nullptr);
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#endif
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}
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/** @} */
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} /* namespace ostd */
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#endif
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/** @} */
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