libcutils/cpu_info.c

/*
** Copyright 2007, 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.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <cutils/cpu_info.h>

// we cache the serial number here.
// this is also used as a fgets() line buffer when we are reading /proc/cpuinfo
static char serial_number[100] = { 0 };

extern const char* get_cpu_serial_number(void)
{
    if (serial_number[0] == 0)
    {
        FILE* file;
        char* chp, *end;
        char* whitespace;
        
        // read serial number from /proc/cpuinfo
        file = fopen("proc/cpuinfo", "r");
        if (! file)
            return NULL;
        
        while ((chp = fgets(serial_number, sizeof(serial_number), file)) != NULL)
        {
            // look for something like "Serial          : 999206122a03591c"

            if (strncmp(chp, "Serial", 6) != 0)
                continue;
            
            chp = strchr(chp, ':');
            if (!chp)
                continue;
                
             // skip colon and whitespace
            while ( *(++chp) == ' ') {}
            
            // truncate trailing whitespace
            end = chp;
            while (*end && *end != ' ' && *end != '\t' && *end != '\n' && *end != '\r')
                ++end;
            *end = 0; 
            
            whitespace = strchr(chp, ' ');
            if (whitespace)
                *whitespace = 0;
            whitespace = strchr(chp, '\t');
            if (whitespace)
                *whitespace = 0;
            whitespace = strchr(chp, '\r');
            if (whitespace)
                *whitespace = 0;
            whitespace = strchr(chp, '\n');
            if (whitespace)
                *whitespace = 0;

            // shift serial number to beginning of the buffer
            memmove(serial_number, chp, strlen(chp) + 1);
            break;
        }
        
        fclose(file);
    }

    return (serial_number[0] ? serial_number : NULL);
}