libcutils/include/cutils/properties.h

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef __CUTILS_PROPERTIES_H
#define __CUTILS_PROPERTIES_H

#include <sys/cdefs.h>
#include <stddef.h>
#include <sys/system_properties.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/* System properties are *small* name value pairs managed by the
** property service.  If your data doesn't fit in the provided
** space it is not appropriate for a system property.
**
** WARNING: system/bionic/include/sys/system_properties.h also defines
**          these, but with different names.  (TODO: fix that)
*/
#define PROPERTY_KEY_MAX   PROP_NAME_MAX
#define PROPERTY_VALUE_MAX  PROP_VALUE_MAX

/* property_get: returns the length of the value which will never be
** greater than PROPERTY_VALUE_MAX - 1 and will always be zero terminated.
** (the length does not include the terminating zero).
**
** If the property read fails or returns an empty value, the default
** value is used (if nonnull).
*/
int property_get(const char *key, char *value, const char *default_value)
/* Sometimes we use not-Bionic with this, so we need this check. */
#if defined(__BIONIC_FORTIFY)
        __overloadable __RENAME_CLANG(property_get)
#endif
        ;

/* property_get_bool: returns the value of key coerced into a
** boolean. If the property is not set, then the default value is returned.
**
* The following is considered to be true (1):
**   "1", "true", "y", "yes", "on"
**
** The following is considered to be false (0):
**   "0", "false", "n", "no", "off"
**
** The conversion is whitespace-sensitive (e.g. " off" will not be false).
**
** If no property with this key is set (or the key is NULL) or the boolean
** conversion fails, the default value is returned.
**/
int8_t property_get_bool(const char *key, int8_t default_value);

/* property_get_int64: returns the value of key truncated and coerced into a
** int64_t. If the property is not set, then the default value is used.
**
** The numeric conversion is identical to strtoimax with the base inferred:
** - All digits up to the first non-digit characters are read
** - The longest consecutive prefix of digits is converted to a long
**
** Valid strings of digits are:
** - An optional sign character + or -
** - An optional prefix indicating the base (otherwise base 10 is assumed)
**   -- 0 prefix is octal
**   -- 0x / 0X prefix is hex
**
** Leading/trailing whitespace is ignored. Overflow/underflow will cause
** numeric conversion to fail.
**
** If no property with this key is set (or the key is NULL) or the numeric
** conversion fails, the default value is returned.
**/
int64_t property_get_int64(const char *key, int64_t default_value);

/* property_get_int32: returns the value of key truncated and coerced into an
** int32_t. If the property is not set, then the default value is used.
**
** The numeric conversion is identical to strtoimax with the base inferred:
** - All digits up to the first non-digit characters are read
** - The longest consecutive prefix of digits is converted to a long
**
** Valid strings of digits are:
** - An optional sign character + or -
** - An optional prefix indicating the base (otherwise base 10 is assumed)
**   -- 0 prefix is octal
**   -- 0x / 0X prefix is hex
**
** Leading/trailing whitespace is ignored. Overflow/underflow will cause
** numeric conversion to fail.
**
** If no property with this key is set (or the key is NULL) or the numeric
** conversion fails, the default value is returned.
**/
int32_t property_get_int32(const char *key, int32_t default_value);

/* property_set: returns 0 on success, < 0 on failure
*/
int property_set(const char *key, const char *value);

int property_list(void (*propfn)(const char *key, const char *value, void *cookie), void *cookie);

#if defined(__BIONIC_FORTIFY)
#define __property_get_err_str "property_get() called with too small of a buffer"

#if defined(__clang__)

/* Some projects use -Weverything; enable_if is clang-specific.
** FIXME: This is marked used because we'll otherwise get complaints about an
** unused static function. This is more robust than marking it unused, since
** -Wused-but-marked-unused is a thing that will complain if this function is
** actually used, thus making FORTIFY noisier when an error happens. It's going
** to go away anyway during our FORTIFY cleanup.
**/
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgcc-compat"
__BIONIC_ERROR_FUNCTION_VISIBILITY
int property_get(const char *key, char *value, const char *default_value)
        __overloadable
        __enable_if(__bos(value) != __BIONIC_FORTIFY_UNKNOWN_SIZE &&
                    __bos(value) < PROPERTY_VALUE_MAX, __property_get_err_str)
        __errorattr(__property_get_err_str)
        __attribute__((used));
#pragma clang diagnostic pop

/* No object size? No FORTIFY.
*/

#else /* defined(__clang__) */

extern int __property_get_real(const char *, char *, const char *)
    __asm__(__USER_LABEL_PREFIX__ "property_get");
__errordecl(__property_get_too_small_error, __property_get_err_str);

__BIONIC_FORTIFY_INLINE
int property_get(const char *key, char *value, const char *default_value) {
    size_t bos = __bos(value);
    if (bos < PROPERTY_VALUE_MAX) {
        __property_get_too_small_error();
    }
    return __property_get_real(key, value, default_value);
}

#endif /* defined(__clang__) */

#undef __property_get_err_str
#endif /* defined(__BIONIC_FORTIFY) */

#ifdef __cplusplus
}
#endif

#endif