/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#include <stdio.h>

#include <stdint.h>

#include <stdarg.h>

#include <unistd.h>

#include <errno.h>

#include <string.h>

#include <sys/resource.h>

#include <sys/types.h>

#include <dirent.h>

#include <stdlib.h>

#include <dlfcn.h>

#include <pthread.h>

#include <inttypes.h>

struct ticks {

    uint64_t  used;

    uint64_t  usedKernel;

    uint64_t  total;

};

typedef struct ticks ticks;

typedef enum {

    CPU_LOAD_VM_ONLY,

    CPU_LOAD_GLOBAL,

} CpuLoadTarget;

static struct perfbuf {

    int   nProcs;

    ticks jvmTicks;

    ticks cpuTicks;

    ticks *cpus;

} counters;

#define DEC_64 "%"SCNd64

static void next_line(FILE *f) {

    while (fgetc(f) != '\n');

}

/**

 * Return the total number of ticks since the system was booted.

 * If the usedTicks parameter is not NULL, it will be filled with

 * the number of ticks spent on actual processes (user, system or

 * nice processes) since system boot. Note that this is the total number

 * of "executed" ticks on _all_ CPU:s, that is on a n-way system it is

 * n times the number of ticks that has passed in clock time.

 *

 * Returns a negative value if the reading of the ticks failed.

 */

static int get_totalticks(int which, ticks *pticks) {

    FILE         *fh;

    uint64_t        userTicks, niceTicks, systemTicks, idleTicks;

    int             n;

    if((fh = fopen("/proc/stat", "r")) == NULL) {

        return -1;

    }

    n = fscanf(fh, "cpu " DEC_64 " " DEC_64 " " DEC_64 " " DEC_64,

           &userTicks, &niceTicks, &systemTicks, &idleTicks);

    // Move to next line

    next_line(fh);

    //find the line for requested cpu faster to just iterate linefeeds?

    if (which != -1) {

        int i;

        for (i = 0; i < which; i++) {

            if (fscanf(fh, "cpu%*d " DEC_64 " " DEC_64 " " DEC_64 " " DEC_64, &userTicks, &niceTicks, &systemTicks, &idleTicks) != 4) {

                fclose(fh);

                return -2;

            }

            next_line(fh);

        }

        n = fscanf(fh, "cpu%*d " DEC_64 " " DEC_64 " " DEC_64 " " DEC_64 "\n",

           &userTicks, &niceTicks, &systemTicks, &idleTicks);

    }

    fclose(fh);

    if (n != 4) {

        return -2;

    }

    pticks->used       = userTicks + niceTicks;

    pticks->usedKernel = systemTicks;

    pticks->total      = userTicks + niceTicks + systemTicks + idleTicks;

    return 0;

}

static int vread_statdata(const char *procfile, const char *fmt, va_list args) {

    FILE    *f;

    int     n;

    char     buf[2048];

    if ((f = fopen(procfile, "r")) == NULL) {

        return -1;

    }

    if ((n = fread(buf, 1, sizeof(buf), f)) != -1) {

    char *tmp;

    buf[n-1] = '\0';

    /** skip through pid and exec name. the exec name _could be wacky_ (renamed) and

     *  make scanf go mupp.

     */

    if ((tmp = strrchr(buf, ')')) != NULL) {

        // skip the ')' and the following space but check that the buffer is long enough

        tmp += 2;

        if (tmp < buf + n) {

        n = vsscanf(tmp, fmt, args);

        }

    }

    }

    fclose(f);

    return n;

}

static int read_statdata(const char *procfile, const char *fmt, ...) {

    int       n;

    va_list args;

    va_start(args, fmt);

    n = vread_statdata(procfile, fmt, args);

    va_end(args);

    return n;

}

/** read user and system ticks from a named procfile, assumed to be in 'stat' format then. */

static int read_ticks(const char *procfile, uint64_t *userTicks, uint64_t *systemTicks) {

    return read_statdata(procfile, "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u "DEC_64" "DEC_64,

             userTicks, systemTicks

             );

}

/**

 * Return the number of ticks spent in any of the processes belonging

 * to the JVM on any CPU.

 */

static int get_jvmticks(ticks *pticks) {

    uint64_t userTicks;

    uint64_t systemTicks;

    if (read_ticks("/proc/self/stat", &userTicks, &systemTicks) < 0) {

        return -1;

    }

    // get the total

    if (get_totalticks(-1, pticks) < 0) {

        return -1;

    }

    pticks->used       = userTicks;

    pticks->usedKernel = systemTicks;

    return 0;

}

/**

 * This method must be called first, before any data can be gathererd.

 */

int perfInit() {

    static int initialized=1;

    if (!initialized) {

        int  i;

        int n = sysconf(_SC_NPROCESSORS_ONLN);

        if (n <= 0) {

            n = 1;

        }

        counters.cpus = calloc(n,sizeof(ticks));

        if (counters.cpus != NULL)  {

            // For the CPU load

            get_totalticks(-1, &counters.cpuTicks);

            for (i = 0; i < n; i++) {

                get_totalticks(i, &counters.cpus[i]);

            }

            // For JVM load

            get_jvmticks(&counters.jvmTicks);

            initialized = 1;

        }

    }

    return initialized ? 0 : -1;

}

#define MAX(a,b) (a>b?a:b)

#define MIN(a,b) (a<b?a:b)

static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

/**

 * Return the load of the CPU as a double. 1.0 means the CPU process uses all

 * available time for user or system processes, 0.0 means the CPU uses all time

 * being idle.

 *

 * Returns a negative value if there is a problem in determining the CPU load.

 */

static double get_cpuload_internal(int which, double *pkernelLoad, CpuLoadTarget target) {

    uint64_t udiff, kdiff, tdiff;

    ticks *pticks, tmp;

    double user_load = -1.0;

    int failed = 0;

    *pkernelLoad = 0.0;

    pthread_mutex_lock(&lock);

    if(perfInit() == 0) {

        if (target == CPU_LOAD_VM_ONLY) {

            pticks = &counters.jvmTicks;

        } else if (which == -1) {

            pticks = &counters.cpuTicks;

        } else {

            pticks = &counters.cpus[which];

        }

        tmp = *pticks;

        if (target == CPU_LOAD_VM_ONLY) {

            if (get_jvmticks(pticks) != 0) {

                failed = 1;

            }

        } else if (get_totalticks(which, pticks) < 0) {

            failed = 1;

        }

        if(!failed) {

            // seems like we sometimes end up with less kernel ticks when

            // reading /proc/self/stat a second time, timing issue between cpus?

            if (pticks->usedKernel < tmp.usedKernel) {

                kdiff = 0;

            } else {

                kdiff = pticks->usedKernel - tmp.usedKernel;

            }

            tdiff = pticks->total - tmp.total;

            udiff = pticks->used - tmp.used;

            if (tdiff == 0) {

                user_load = 0;

            } else {

                if (tdiff < (udiff + kdiff)) {

                    tdiff = udiff + kdiff;

                }

                *pkernelLoad = (kdiff / (double)tdiff);

                // BUG9044876, normalize return values to sane values

                *pkernelLoad = MAX(*pkernelLoad, 0.0);

                *pkernelLoad = MIN(*pkernelLoad, 1.0);

                user_load = (udiff / (double)tdiff);

                user_load = MAX(user_load, 0.0);

                user_load = MIN(user_load, 1.0);

            }

        }

    }

    pthread_mutex_unlock(&lock);

    return user_load;

}

double get_cpu_load(int which) {

    double u, s;

    u = get_cpuload_internal(which, &s, CPU_LOAD_GLOBAL);

    if (u < 0) {

        return -1.0;

    }

    // Cap total systemload to 1.0

    return MIN((u + s), 1.0);

}

double get_process_load() {

    double u, s;

    u = get_cpuload_internal(-1, &s, CPU_LOAD_VM_ONLY);

    if (u < 0) {

        return -1.0;

    }

    return u + s;

}

JNIEXPORT jdouble JNICALL

(JNIEnv *env, jobject dummy)

{

    if(perfInit() == 0) {

        return get_cpu_load(-1);

    } else {

        return -1.0;

    }

}

JNIEXPORT jdouble JNICALL

(JNIEnv *env, jobject dummy)

{

    if(perfInit() == 0) {

        return get_process_load();

    } else {

        return -1.0;

    }

}