text: /*
   * 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_LEGACY_PROPERTIES_H
  #define _INCLUDE_LEGACY_PROPERTIES_H
  
  #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 {
      char name[PROP_NAME_MAX];
      unsigned volatile serial;
      char value[PROP_VALUE_MAX];
  };
  
  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)
  **
  ** 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
  