Merge <sys/system_properties.h> and <sys/_system_properties.h>.
You could argue that some of this stuff (such as the constants used for communication between init and libc that _aren't_ passed on to callers) should be moved to a new <platform/system_properties.h> instead, but in the sense of "exposed to the NDK" rather than "useful to NDK users", all of this is already technically public API.
We can worry about how to make the platform-only implementation details less visible in documentation if/when we ever actually have the bionic docs generated and published on the web...
Change-Id: I1a6456cf7d301753ec8f541a2046538cd59ed58a
diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index ae94db5..e8b6e34 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -110,11 +110,136 @@
*/
#define PROP_NAME_MAX 32
+/** Deprecated. Use __system_property_foreach() instead. */
+const prop_info* _Nullable __system_property_find_nth(unsigned __n);
/** Deprecated. Use __system_property_read_callback() instead. */
int __system_property_read(const prop_info* _Nonnull __pi, char* _Nullable __name, char* _Nonnull __value);
/** Deprecated. Use __system_property_read_callback() instead. */
int __system_property_get(const char* _Nonnull __name, char* _Nonnull __value);
-/** Deprecated. Use __system_property_foreach() instead. */
-const prop_info* _Nullable __system_property_find_nth(unsigned __n);
+/** Deprecated: use __system_property_wait() instead. */
+uint32_t __system_property_wait_any(uint32_t __old_serial);
+
+/**
+ * Reads the global serial number of the system properties _area_.
+ *
+ * Called to predict if a series of cached __system_property_find()
+ * objects will have seen __system_property_serial() values change.
+ * Also aids the converse, as changes in the global serial can
+ * also be used to predict if a failed __system_property_find()
+ * could in turn now find a new object; thus preventing the
+ * cycles of effort to poll __system_property_find().
+ *
+ * Typically called at beginning of a cache cycle to signal if _any_ possible
+ * changes have occurred since last. If there is, one may check each individual
+ * __system_property_serial() to confirm dirty, or __system_property_find()
+ * to check if the property now exists. If a call to __system_property_add()
+ * or __system_property_update() has completed between two calls to
+ * __system_property_area_serial() then the second call will return a larger
+ * value than the first call. Beware of race conditions as changes to the
+ * properties are not atomic, the main value of this call is to determine
+ * whether the expensive __system_property_find() is worth retrying to see if
+ * a property now exists.
+ *
+ * Returns the serial number on success, -1 on error.
+ */
+uint32_t __system_property_area_serial(void);
+
+/**
+ * Reads the serial number of a specific system property previously returned by
+ * __system_property_find(). This is a cheap way to check whether a system
+ * property has changed or not.
+ *
+ * Returns the serial number on success, -1 on error.
+ */
+uint32_t __system_property_serial(const prop_info* _Nonnull __pi);
+
+//
+// libc implementation detail.
+//
+
+/**
+ * Initializes the system properties area in read-only mode.
+ *
+ * This is called automatically during libc initialization,
+ * so user code should never need to call this.
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int __system_properties_init(void);
+
+//
+// init implementation details.
+//
+
+#define PROP_SERVICE_NAME "property_service"
+#define PROP_SERVICE_FOR_SYSTEM_NAME "property_service_for_system"
+#define PROP_DIRNAME "/dev/__properties__"
+
+// Messages sent to init.
+#define PROP_MSG_SETPROP 1
+#define PROP_MSG_SETPROP2 0x00020001
+
+// Status codes returned by init (but not passed from libc to the caller).
+#define PROP_SUCCESS 0
+#define PROP_ERROR_READ_CMD 0x0004
+#define PROP_ERROR_READ_DATA 0x0008
+#define PROP_ERROR_READ_ONLY_PROPERTY 0x000B
+#define PROP_ERROR_INVALID_NAME 0x0010
+#define PROP_ERROR_INVALID_VALUE 0x0014
+#define PROP_ERROR_PERMISSION_DENIED 0x0018
+#define PROP_ERROR_INVALID_CMD 0x001B
+#define PROP_ERROR_HANDLE_CONTROL_MESSAGE 0x0020
+#define PROP_ERROR_SET_FAILED 0x0024
+
+/**
+ * Initializes the area to be used to store properties.
+ *
+ * Can only be done by the process that has write access to the property area,
+ * typically init.
+ *
+ * See __system_properties_init() for the equivalent for all other processes.
+ */
+int __system_property_area_init(void);
+
+/**
+ * Adds a new system property.
+ * Can only be done by the process that has write access to the property area --
+ * typically init -- which must handle sequencing to ensure that only one property is
+ * updated at a time.
+ *
+ * Returns 0 on success, -1 if the property area is full.
+ */
+int __system_property_add(const char* _Nonnull __name, unsigned int __name_length, const char* _Nonnull __value, unsigned int __value_length);
+
+/**
+ * Updates the value of a system property returned by __system_property_find().
+ * Can only be done by the process that has write access to the property area --
+ * typically init -- which must handle sequencing to ensure that only one property is
+ * updated at a time.
+ *
+ * Returns 0 on success, -1 if the parameters are incorrect.
+ */
+int __system_property_update(prop_info* _Nonnull __pi, const char* _Nonnull __value, unsigned int __value_length);
+
+/**
+ * Reloads the system properties from disk.
+ * Not intended for use by any apps except the Zygote.
+ * Should only be called from the main thread.
+ *
+ * Pointers received from functions such as __system_property_find()
+ * may be invalidated by calls to this function.
+ *
+ * Returns 0 on success, -1 otherwise.
+ *
+ * Available since API level 35.
+ */
+int __system_properties_zygote_reload(void) __INTRODUCED_IN(35);
+
+/**
+ * Deprecated: previously for testing, but now that SystemProperties is its own
+ * testable class, there is never a reason to call this function and its
+ * implementation simply returns -1.
+ */
+int __system_property_set_filename(const char* _Nullable __unused __filename);
__END_DECLS