libc/bionic/sysprop_helpers.h

/*
 * Copyright (C) 2021 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#pragma once

#include <stdint.h>
#include <sys/cdefs.h>

// Get the presiding config string, in the following order of priority:
//   1. Environment variables.
//   2. System properties, in the order they're specified in sys_prop_names.
// If neither of these options are specified (or they're both an empty string),
// this function returns false. Otherwise, it returns true, and the presiding
// options string is written to the `options` buffer of size `size`. It will
// store a pointer to either env_var_name, or into the relevant entry of
// sys_prop_names into choicen_source, indiciating which value was used. If
// this function returns true, `options` is guaranteed to be null-terminated.
// `options_size` should be at least PROP_VALUE_MAX.
__LIBC_HIDDEN__ bool get_config_from_env_or_sysprops(const char* env_var_name,
                                                     const char* const* sys_prop_names,
                                                     size_t sys_prop_names_size, char* options,
                                                     size_t options_size,
                                                     const char** chosen_source);