1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #pragma once 30 31 /** 32 * @file system_properties.h 33 * @brief System properties. 34 */ 35 36 #include <sys/cdefs.h> 37 #include <stdbool.h> 38 #include <stddef.h> 39 #include <stdint.h> 40 41 __BEGIN_DECLS 42 43 /** An opaque structure representing a system property. */ 44 typedef struct prop_info prop_info; 45 46 /** 47 * The limit on the length of a property value. 48 * (See PROP_NAME_MAX for property names.) 49 */ 50 #define PROP_VALUE_MAX 92 51 52 /** 53 * Sets system property `name` to `value`, creating the system property if it doesn't already exist. 54 * 55 * Returns 0 on success, or -1 on failure. 56 */ 57 int __system_property_set(const char* _Nonnull __name, const char* _Nonnull __value); 58 59 /** 60 * Returns a `prop_info` corresponding system property `name`, or nullptr if it doesn't exist. 61 * Use __system_property_read_callback() to query the current value. 62 * 63 * Property lookup is expensive, so it can be useful to cache the result of this 64 * function rather than using __system_property_get(). 65 */ 66 const prop_info* _Nullable __system_property_find(const char* _Nonnull __name); 67 68 /** 69 * Calls `callback` with a consistent trio of name, value, and serial number 70 * for property `pi`. 71 * 72 * Available since API level 26. 73 */ 74 void __system_property_read_callback(const prop_info* _Nonnull __pi, 75 void (* _Nonnull __callback)(void* _Nullable __cookie, const char* _Nonnull __name, const char* _Nonnull __value, uint32_t __serial), 76 void* _Nullable __cookie) __INTRODUCED_IN(26); 77 78 /** 79 * Passes a `prop_info` for each system property to the provided 80 * callback. Use __system_property_read_callback() to read the value of 81 * any of the properties. 82 * 83 * This method is for inspecting and debugging the property system, and not generally useful. 84 * 85 * Returns 0 on success, or -1 on failure. 86 */ 87 int __system_property_foreach(void (* _Nonnull __callback)(const prop_info* _Nonnull __pi, void* _Nullable __cookie), void* _Nullable __cookie); 88 89 /** 90 * Waits for the specific system property identified by `pi` to be updated 91 * past `old_serial`. Waits no longer than `relative_timeout`, or forever 92 * if `relative_timeout` is null. 93 * 94 * If `pi` is null, waits for the global serial number instead. 95 * 96 * If you don't know the current serial, use 0. 97 * 98 * Returns true and updates `*new_serial_ptr` on success, or false if the call 99 * timed out. 100 * 101 * Available since API level 26. 102 */ 103 struct timespec; 104 bool __system_property_wait(const prop_info* _Nullable __pi, uint32_t __old_serial, uint32_t* _Nonnull __new_serial_ptr, const struct timespec* _Nullable __relative_timeout) 105 __INTRODUCED_IN(26); 106 107 /** 108 * Deprecated: there's no limit on the length of a property name since 109 * API level 26, though the limit on property values (PROP_VALUE_MAX) remains. 110 */ 111 #define PROP_NAME_MAX 32 112 113 /** Deprecated. Use __system_property_read_callback() instead. */ 114 int __system_property_read(const prop_info* _Nonnull __pi, char* _Nullable __name, char* _Nonnull __value); 115 /** Deprecated. Use __system_property_read_callback() instead. */ 116 int __system_property_get(const char* _Nonnull __name, char* _Nonnull __value); 117 /** Deprecated. Use __system_property_foreach() instead. */ 118 const prop_info* _Nullable __system_property_find_nth(unsigned __n); 119 120 __END_DECLS 121