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The Android Open Source Project
2008-10-21 07:00:00 -07:00
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libc/include/sys/_system_properties.h Normal file
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/*
* 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_area prop_area;
typedef struct prop_msg prop_msg;
#define PROP_AREA_MAGIC 0x504f5250
#define PROP_AREA_VERSION 0x45434f76
#define PROP_SERVICE_NAME "property_service"
/* #define PROP_MAX_ENTRIES 247 */
/* 247 -> 32620 bytes (<32768) */
#define TOC_NAME_LEN(toc) ((toc) >> 24)
#define TOC_TO_INFO(area, toc) ((prop_info*) (((char*) area) + ((toc) & 0xFFFFFF)))
struct prop_area {
unsigned volatile count;
unsigned volatile serial;
unsigned magic;
unsigned version;
unsigned reserved[4];
unsigned toc[1];
};
#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
#define SERIAL_DIRTY(serial) ((serial) & 1)
struct prop_info {
unsigned char name[PROP_NAME_MAX];
unsigned volatile serial;
unsigned char value[PROP_VALUE_MAX];
};
struct prop_msg
{
unsigned cmd;
unsigned char name[PROP_NAME_MAX];
unsigned 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)
**
** Improvements:
** - maintain the toc sorted by pi->name to allow lookup
** by binary search
**
*/
#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"
#endif
#endif