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/**
 * @file datatop_cpu_stats_poll.c
 * @brief Calls dtop_value_only_init for necessary cpu datapoints.
 *
 * File contains methods for determing number of cpu's online and calling
 * correct initialization function to gather scaling_cur_freq data point
 * for each cpu along with each cpu's online status.
 */

#include <unistd.h>
#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ctype.h>
#include "datatop_interface.h"
#include "datatop_fileops.h"
#include "datatop_str.h"
#include "datatop_polling.h"

#define DTOP_GEN_SIZE 8192
#define DTOP_GEN_LINE (DTOP_GEN_SIZE>>2)
#define NO_CPUS_ONLINE -1

/**
 * @brief Searches /sys/devices/system/cpu/ directory to get find number of CPUs.
 *
 * @return Number of CPUs found in directory.
 */
static int dtop_cpu_search(void)
{
	DIR *dp;
	struct dirent *entry;
	struct stat s;
	int cpu_amt;
	char cwd[1024];

	if (!getcwd(cwd, sizeof(cwd))) {
		fprintf(stderr, "Failed to get current working dir\n");
		return -1;
	}

	dp = opendir("/sys/devices/system/cpu/");
	if (dp == NULL) {
		fprintf(stderr, "err=%d: %s\n", errno, strerror(errno));
		fprintf(stderr, "Cannot open directory: %s\n",
					"/sys/devices/system/cpu/");
		return NO_CPUS_ONLINE;
	}

	chdir("/sys/devices/system/cpu/");
	cpu_amt = 0;
	while ((entry = readdir(dp))) {
		if (stat(entry->d_name, &s)) {
			printf("stat err=%d: %s\n", errno, strerror(errno));
			return NO_CPUS_ONLINE;
		}

		if (entry->d_name[0] == 'c' &&
			entry->d_name[1] == 'p' &&
			entry->d_name[2] == 'u' &&
			(isdigit(entry->d_name[3]))) {

			cpu_amt++;
		}
	}

	closedir(dp);
	chdir(cwd);
	return cpu_amt;
}

/**
 * @brief Creates a dpg designed for CPU online and CPU scaling_cur_freq stats.
 *
 * @param name Name of file dpg represents.
 */
static void construct_cpu_stat_dpg(char *name)
{
	char *file = malloc(strlen(name) + 1);
	struct dtop_data_point *dp =
			malloc(sizeof(struct dtop_data_point));
	struct dtop_data_point_gatherer *dpg = malloc
		(sizeof(struct dtop_data_point_gatherer));

	strlcpy(file, name, strlen(name) + 1);

	dp[0].type = DTOP_ULONG;
	dp[0].name = malloc(5);
	strlcpy(dp[0].name, "", 5);
	dp[0].prefix = NULL;
	dp[0].data.d_ulong = 0;
	dp[0].initial_data.d_ulong = 0;
	dp[0].skip = DO_NOT_SKIP;
	dp[0].initial_data_populated = NOT_POPULATED;

	dpg->prefix = file;
	dpg->file = file;
	dpg->poll = dtop_value_only_poll;
	dpg->data_points = dp;
	dpg->data_points_len = 1;
	dpg->deconstruct = dtop_value_only_dpg_deconstructor;

	dtop_register(dpg);
}

/**
 * @brief Calls dpg constructor for necessary CPU stat files.
 *
 * Creates file names based on number of CPUs found and calls the
 * dpg constructor for them.
 *
 * @param file Directory where the CPUs are found.
 * @param add String which is concatenated onto file and represents
 * the path after a CPU directory is entered.
 * @param cpu_amt Amount of CPUs found on device.
 */
static void cpu_poll_helper(char *file, char *add, int cpu_amt)
{
	int i;
	for (i = 0; i < cpu_amt; i++) {
		char *cpu_num = malloc(5);
		char *newfile;
		int nf_len;
		snprintf(cpu_num, 5, "%d", i);
		nf_len = strlen(file) + strlen(add) + strlen(cpu_num) + 2;
		newfile = malloc(nf_len);
		strlcpy(newfile, file, nf_len);
		strlcat(newfile, cpu_num, nf_len);
		strlcat(newfile, add, nf_len);
		free(cpu_num);
		construct_cpu_stat_dpg(newfile);
		free(newfile);
	}
}

/**
 * @brief Calls necessary functions for CPU stat dpgs.
 */
void dtop_cpu_stats_init(void)
{
	int cpu_amt;
	char *file = "/sys/devices/system/cpu/cpu";
	char *add = "/cpufreq/scaling_cur_freq";

	cpu_amt = dtop_cpu_search();
	cpu_poll_helper(file, add, cpu_amt);
	add = "/online";
	cpu_poll_helper(file, add, cpu_amt);
}