/*
 * Copyright 2018 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 "Thread.h"

#include <sched.h>
#include <unistd.h>

namespace swappy {

int32_t getNumCpus() {
    static int32_t sNumCpus = []() {
        pid_t pid = gettid();
        cpu_set_t cpuSet;
        CPU_ZERO(&cpuSet);
        sched_getaffinity(pid, sizeof(cpuSet), &cpuSet);

        int32_t numCpus = 0;
        while (CPU_ISSET(numCpus, &cpuSet)) {
            ++numCpus;
        }

        return numCpus;
    }();

    return sNumCpus;
}

void setAffinity(int32_t cpu) {
    cpu_set_t cpuSet;
    CPU_ZERO(&cpuSet);
    CPU_SET(cpu, &cpuSet);
    sched_setaffinity(gettid(), sizeof(cpuSet), &cpuSet);
}

void setAffinity(Affinity affinity) {
    const int32_t numCpus = getNumCpus();

    cpu_set_t cpuSet;
    CPU_ZERO(&cpuSet);
    for (int32_t cpu = 0; cpu < numCpus; ++cpu) {
        switch (affinity) {
            case Affinity::None:
                CPU_SET(cpu, &cpuSet);
                break;
            case Affinity::Even:
                if (cpu % 2 == 0) CPU_SET(cpu, &cpuSet);
                break;
            case Affinity::Odd:
                if (cpu % 2 == 1) CPU_SET(cpu, &cpuSet);
                break;
        }
    }

    sched_setaffinity(gettid(), sizeof(cpuSet), &cpuSet);
}

} // namespace swappy