system_properties.h revision 1dc9e472e19acfe6dc7f41e429236e7eef7ceda1 
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
32typedef struct prop_info prop_info;
33
34#define PROP_NAME_MAX   32
35#define PROP_VALUE_MAX  92
36
37/* Look up a system property by name, copying its value and a
38** \0 terminator to the provided pointer.  The total bytes
39** copied will be no greater than PROP_VALUE_MAX.  Returns
40** the string length of the value.  A property that is not
41** defined is identical to a property with a length 0 value.
42*/
43int __system_property_get(const char *name, char *value);
44
45/* Return a pointer to the system property named name, if it
46** exists, or NULL if there is no such property.  Use
47** __system_property_read() to obtain the string value from
48** the returned prop_info pointer.
49**
50** It is safe to cache the prop_info pointer to avoid future
51** lookups.  These returned pointers will remain valid for
52** the lifetime of the system.
53*/
54const prop_info *__system_property_find(const char *name);
55
56/* Read the value of a system property.  Returns the length
57** of the value.  Copies the value and \0 terminator into
58** the provided value pointer.  Total length (including
59** terminator) will be no greater that PROP_VALUE_MAX.
60**
61** If name is nonzero, up to PROP_NAME_MAX bytes will be
62** copied into the provided name pointer.  The name will
63** be \0 terminated.
64*/
65int __system_property_read(const prop_info *pi, char *name, char *value);
66
67/* Return a prop_info for the nth system property, or NULL if
68** there is no nth property.  Use __system_property_read() to
69** read the value of this property.
70**
71** This method is for inspecting and debugging the property
72** system.  Please use __system_property_find() instead.
73**
74** Order of results may change from call to call.  This is
75** not a bug.
76*/
77const prop_info *__system_property_find_nth(unsigned n);
78
79#endif
80