6ac8e6a46d
See the comments for an explanation of how properties are stored. The trie structure is designed to scale better than the previous array-based implementation. Searching an array with n properties required average O(n) string compares of the entire key; searching the trie requires average O(log n) string compares of each token (substrings between '.' characters). Change-Id: I491305bc7aca59609abcd871a5f33d97f89ce714 Signed-off-by: Greg Hackmann <ghackmann@google.com>
140 lines
4.8 KiB
C
140 lines
4.8 KiB
C
/*
|
|
* Copyright (C) 2008 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.
|
|
*/
|
|
|
|
#ifndef _INCLUDE_SYS__SYSTEM_PROPERTIES_H
|
|
#define _INCLUDE_SYS__SYSTEM_PROPERTIES_H
|
|
|
|
#ifndef _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
|
|
#error you should #include <sys/system_properties.h> instead
|
|
#else
|
|
#include <sys/system_properties.h>
|
|
|
|
typedef struct prop_msg prop_msg;
|
|
|
|
#define PROP_AREA_MAGIC 0x504f5250
|
|
#define PROP_AREA_VERSION 0xfc6ed0ab
|
|
|
|
#define PROP_SERVICE_NAME "property_service"
|
|
#define PROP_FILENAME "/dev/__properties__"
|
|
|
|
/* (4 header words + 28 toc words) = 128 bytes */
|
|
/* 128 bytes header and toc + 28 prop_infos @ 128 bytes = 3712 bytes */
|
|
|
|
#define PA_REGION_COUNT 128
|
|
#define PA_SIZE 4096
|
|
|
|
#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
|
|
#define SERIAL_DIRTY(serial) ((serial) & 1)
|
|
|
|
__BEGIN_DECLS
|
|
|
|
struct prop_msg
|
|
{
|
|
unsigned cmd;
|
|
char name[PROP_NAME_MAX];
|
|
char value[PROP_VALUE_MAX];
|
|
};
|
|
|
|
#define PROP_MSG_SETPROP 1
|
|
|
|
/*
|
|
** Rules:
|
|
**
|
|
** - there is only one writer, but many readers
|
|
** - prop_area.count will never decrease in value
|
|
** - once allocated, a prop_info's name will not change
|
|
** - once allocated, a prop_info's offset will not change
|
|
** - reading a value requires the following steps
|
|
** 1. serial = pi->serial
|
|
** 2. if SERIAL_DIRTY(serial), wait*, then goto 1
|
|
** 3. memcpy(local, pi->value, SERIAL_VALUE_LEN(serial) + 1)
|
|
** 4. if pi->serial != serial, goto 2
|
|
**
|
|
** - writing a value requires the following steps
|
|
** 1. pi->serial = pi->serial | 1
|
|
** 2. memcpy(pi->value, local_value, value_len)
|
|
** 3. pi->serial = (value_len << 24) | ((pi->serial + 1) & 0xffffff)
|
|
*/
|
|
|
|
#define PROP_PATH_RAMDISK_DEFAULT "/default.prop"
|
|
#define PROP_PATH_SYSTEM_BUILD "/system/build.prop"
|
|
#define PROP_PATH_SYSTEM_DEFAULT "/system/default.prop"
|
|
#define PROP_PATH_LOCAL_OVERRIDE "/data/local.prop"
|
|
#define PROP_PATH_FACTORY "/factory/factory.prop"
|
|
|
|
/*
|
|
** Map the property area from the specified filename. This
|
|
** method is for testing only.
|
|
*/
|
|
int __system_property_set_filename(const char *filename);
|
|
|
|
/*
|
|
** Initialize the area to be used to store properties. Can
|
|
** only be done by a single process that has write access to
|
|
** the property area.
|
|
*/
|
|
int __system_property_area_init();
|
|
|
|
/* Add a new system property. Can only be done by a single
|
|
** process that has write access to the property area, and
|
|
** that process must handle sequencing to ensure the property
|
|
** does not already exist and that only one property is added
|
|
** or updated at a time.
|
|
**
|
|
** Returns 0 on success, -1 if the property area is full.
|
|
*/
|
|
int __system_property_add(const char *name, unsigned int namelen,
|
|
const char *value, unsigned int valuelen);
|
|
|
|
/* Update the value of a system property returned by
|
|
** __system_property_find. Can only be done by a single process
|
|
** that has write access to the property area, and that process
|
|
** 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 *pi, const char *value, unsigned int len);
|
|
|
|
/* Read the serial number of a system property returned by
|
|
** __system_property_find.
|
|
**
|
|
** Returns the serial number on success, -1 on error.
|
|
*/
|
|
unsigned int __system_property_serial(const prop_info *pi);
|
|
|
|
/* Wait for any system property to be updated. Caller must pass
|
|
** in 0 the first time, and the previous return value on each
|
|
** successive call. */
|
|
unsigned int __system_property_wait_any(unsigned int serial);
|
|
|
|
__END_DECLS
|
|
|
|
#endif
|
|
#endif
|