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      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 #include <stdio.h>
     29 #include <stdlib.h>
     30 #include <unistd.h>
     31 #include <stddef.h>
     32 #include <errno.h>
     33 
     34 #include <sys/mman.h>
     35 
     36 #include <sys/socket.h>
     37 #include <sys/un.h>
     38 #include <sys/select.h>
     39 #include <sys/types.h>
     40 #include <netinet/in.h>
     41 
     42 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
     43 #include <sys/_system_properties.h>
     44 
     45 #include <sys/atomics.h>
     46 
     47 static const char property_service_name[] = PROP_SERVICE_NAME;
     48 
     49 static unsigned dummy_props = 0;
     50 
     51 prop_area *__system_property_area__ = (void*) &dummy_props;
     52 
     53 int __system_properties_init(void)
     54 {
     55     prop_area *pa;
     56     int s, fd;
     57     unsigned sz;
     58     char *env;
     59 
     60     if(__system_property_area__ != ((void*) &dummy_props)) {
     61         return 0;
     62     }
     63 
     64     env = getenv("ANDROID_PROPERTY_WORKSPACE");
     65     if (!env) {
     66         return -1;
     67     }
     68     fd = atoi(env);
     69     env = strchr(env, ',');
     70     if (!env) {
     71         return -1;
     72     }
     73     sz = atoi(env + 1);
     74 
     75     pa = mmap(0, sz, PROT_READ, MAP_SHARED, fd, 0);
     76 
     77     if(pa == MAP_FAILED) {
     78         return -1;
     79     }
     80 
     81     if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
     82         munmap(pa, sz);
     83         return -1;
     84     }
     85 
     86     __system_property_area__ = pa;
     87     return 0;
     88 }
     89 
     90 const prop_info *__system_property_find_nth(unsigned n)
     91 {
     92     prop_area *pa = __system_property_area__;
     93 
     94     if(n >= pa->count) {
     95         return 0;
     96     } else {
     97         return TOC_TO_INFO(pa, pa->toc[n]);
     98     }
     99 }
    100 
    101 const prop_info *__system_property_find(const char *name)
    102 {
    103     prop_area *pa = __system_property_area__;
    104     unsigned count = pa->count;
    105     unsigned *toc = pa->toc;
    106     unsigned len = strlen(name);
    107     prop_info *pi;
    108 
    109     while(count--) {
    110         unsigned entry = *toc++;
    111         if(TOC_NAME_LEN(entry) != len) continue;
    112 
    113         pi = TOC_TO_INFO(pa, entry);
    114         if(memcmp(name, pi->name, len)) continue;
    115 
    116         return pi;
    117     }
    118 
    119     return 0;
    120 }
    121 
    122 int __system_property_read(const prop_info *pi, char *name, char *value)
    123 {
    124     unsigned serial, len;
    125 
    126     for(;;) {
    127         serial = pi->serial;
    128         while(SERIAL_DIRTY(serial)) {
    129             __futex_wait((volatile void *)&pi->serial, serial, 0);
    130             serial = pi->serial;
    131         }
    132         len = SERIAL_VALUE_LEN(serial);
    133         memcpy(value, pi->value, len + 1);
    134         if(serial == pi->serial) {
    135             if(name != 0) {
    136                 strcpy(name, pi->name);
    137             }
    138             return len;
    139         }
    140     }
    141 }
    142 
    143 int __system_property_get(const char *name, char *value)
    144 {
    145     const prop_info *pi = __system_property_find(name);
    146 
    147     if(pi != 0) {
    148         return __system_property_read(pi, 0, value);
    149     } else {
    150         value[0] = 0;
    151         return 0;
    152     }
    153 }
    154 
    155 int __system_property_wait(const prop_info *pi)
    156 {
    157     unsigned n;
    158     if(pi == 0) {
    159         prop_area *pa = __system_property_area__;
    160         n = pa->serial;
    161         do {
    162             __futex_wait(&pa->serial, n, 0);
    163         } while(n == pa->serial);
    164     } else {
    165         n = pi->serial;
    166         do {
    167             __futex_wait((volatile void *)&pi->serial, n, 0);
    168         } while(n == pi->serial);
    169     }
    170     return 0;
    171 }
    172