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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 
     29 #ifndef _INCLUDE_SYS_SYSTEM_PROPERTIES_H
     30 #define _INCLUDE_SYS_SYSTEM_PROPERTIES_H
     31 
     32 #include <sys/cdefs.h>
     33 
     34 __BEGIN_DECLS
     35 
     36 typedef struct prop_info prop_info;
     37 
     38 #define PROP_NAME_MAX   32
     39 #define PROP_VALUE_MAX  92
     40 
     41 /* Look up a system property by name, copying its value and a
     42 ** \0 terminator to the provided pointer.  The total bytes
     43 ** copied will be no greater than PROP_VALUE_MAX.  Returns
     44 ** the string length of the value.  A property that is not
     45 ** defined is identical to a property with a length 0 value.
     46 */
     47 int __system_property_get(const char *name, char *value);
     48 
     49 /* Set a system property by name.
     50 **/
     51 int __system_property_set(const char *key, const char *value);
     52 
     53 /* Return a pointer to the system property named name, if it
     54 ** exists, or NULL if there is no such property.  Use
     55 ** __system_property_read() to obtain the string value from
     56 ** the returned prop_info pointer.
     57 **
     58 ** It is safe to cache the prop_info pointer to avoid future
     59 ** lookups.  These returned pointers will remain valid for
     60 ** the lifetime of the system.
     61 */
     62 const prop_info *__system_property_find(const char *name);
     63 
     64 /* Read the value of a system property.  Returns the length
     65 ** of the value.  Copies the value and \0 terminator into
     66 ** the provided value pointer.  Total length (including
     67 ** terminator) will be no greater that PROP_VALUE_MAX.
     68 **
     69 ** If name is nonzero, up to PROP_NAME_MAX bytes will be
     70 ** copied into the provided name pointer.  The name will
     71 ** be \0 terminated.
     72 */
     73 int __system_property_read(const prop_info *pi, char *name, char *value);
     74 
     75 /* Return a prop_info for the nth system property, or NULL if
     76 ** there is no nth property.  Use __system_property_read() to
     77 ** read the value of this property.
     78 **
     79 ** Please do not call this method.  It only exists to provide
     80 ** backwards compatibility to NDK apps.  Its implementation
     81 ** is inefficient and order of results may change from call
     82 ** to call.
     83 */
     84 const prop_info *__system_property_find_nth(unsigned n);
     85 
     86 /* Pass a prop_info for each system property to the provided
     87 ** callback.  Use __system_property_read() to read the value
     88 ** of this property.
     89 **
     90 ** This method is for inspecting and debugging the property
     91 ** system.  Please use __system_property_find() instead.
     92 **
     93 ** Order of results may change from call to call.  This is
     94 ** not a bug.
     95 */
     96 int __system_property_foreach(
     97         void (*propfn)(const prop_info *pi, void *cookie),
     98         void *cookie);
     99 
    100 __END_DECLS
    101 
    102 #endif
    103