/*
 * Copyright (C) 2014 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/sysinfo.h>

#include <dirent.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

#include "private/ScopedReaddir.h"

static bool __matches_cpuN(const char* s) {
  // The %c trick is to ensure that we have the anchored match "^cpu[0-9]+$".
  unsigned cpu;
  char dummy;
  return (sscanf(s, "cpu%u%c", &cpu, &dummy) == 1);
}

int get_nprocs_conf() {
  // On x86 kernels you can use /proc/cpuinfo for this, but on ARM kernels offline CPUs disappear
  // from there. This method works on both.
  ScopedReaddir reader("/sys/devices/system/cpu");
  if (reader.IsBad()) {
    return 1;
  }

  int result = 0;
  dirent* entry;
  while ((entry = reader.ReadEntry()) != NULL) {
    if (entry->d_type == DT_DIR && __matches_cpuN(entry->d_name)) {
      ++result;
    }
  }
  return result;
}

int get_nprocs() {
  FILE* fp = fopen("/proc/stat", "re");
  if (fp == NULL) {
    return 1;
  }

  int result = 0;
  char buf[256];
  while (fgets(buf, sizeof(buf), fp) != NULL) {
    // Extract just the first word from the line.
    // 'cpu0 7976751 1364388 3116842 469770388 8629405 0 49047 0 0 0'
    char* p = strchr(buf, ' ');
    if (p != NULL) {
      *p = 0;
    }
    if (__matches_cpuN(buf)) {
      ++result;
    }
  }
  fclose(fp);
  return result;
}

static int __get_meminfo_page_count(const char* pattern) {
  FILE* fp = fopen("/proc/meminfo", "re");
  if (fp == NULL) {
    return -1;
  }

  int page_count = -1;
  char buf[256];
  while (fgets(buf, sizeof(buf), fp) != NULL) {
    long total;
    if (sscanf(buf, pattern, &total) == 1) {
      page_count = static_cast<int>(total / (PAGE_SIZE / 1024));
      break;
    }
  }
  fclose(fp);
  return page_count;
}

long get_phys_pages() {
  return __get_meminfo_page_count("MemTotal: %ld kB");
}

long get_avphys_pages() {
  return __get_meminfo_page_count("MemFree: %ld kB");
}