C++ (Cpp) __system_property_read_compat Examples

Example #1

File: system_properties.cpp Project: Acidburn0zzz/platform_bionic

int __system_property_read(const prop_info *pi, char *name, char *value)
{
    if (__predict_false(compat_mode)) {
        return __system_property_read_compat(pi, name, value);
    }

    while (true) {
        uint32_t serial = __system_property_serial(pi); // acquire semantics
        size_t len = SERIAL_VALUE_LEN(serial);
        memcpy(value, pi->value, len + 1);
        // TODO: Fix the synchronization scheme here.
        // There is no fully supported way to implement this kind
        // of synchronization in C++11, since the memcpy races with
        // updates to pi, and the data being accessed is not atomic.
        // The following fence is unintuitive, but would be the
        // correct one if memcpy used memory_order_relaxed atomic accesses.
        // In practice it seems unlikely that the generated code would
        // would be any different, so this should be OK.
        atomic_thread_fence(memory_order_acquire);
        if (serial ==
                load_const_atomic(&(pi->serial), memory_order_relaxed)) {
            if (name != 0) {
                strcpy(name, pi->name);
            }
            return len;
        }
    }
}

Example #2

File: system_properties.cpp Project: binzhang/platform_bionic

int __system_property_read(const prop_info *pi, char *name, char *value)
{
    unsigned serial, len;

    if (__predict_false(compat_mode)) {
        return __system_property_read_compat(pi, name, value);
    }

    for(;;) {
        serial = pi->serial;
        while(SERIAL_DIRTY(serial)) {
            __futex_wait((volatile void *)&pi->serial, serial, NULL);
            serial = pi->serial;
        }
        len = SERIAL_VALUE_LEN(serial);
        memcpy(value, pi->value, len + 1);
        ANDROID_MEMBAR_FULL();
        if(serial == pi->serial) {
            if(name != 0) {
                strcpy(name, pi->name);
            }
            return len;
        }
    }
}