/* vi: set sw=4 ts=4: */
/*
 * Mini free implementation for busybox
 *
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
//config:config FREE
//config:	bool "free (3.1 kb)"
//config:	default y
//config:	help
//config:	free displays the total amount of free and used physical and swap
//config:	memory in the system, as well as the buffers used by the kernel.
//config:	The shared memory column should be ignored; it is obsolete.

//applet:IF_FREE(APPLET_NOFORK(free, free, BB_DIR_USR_BIN, BB_SUID_DROP, free))

//kbuild:lib-$(CONFIG_FREE) += free.o

//usage:#define free_trivial_usage
//usage:       "" IF_DESKTOP("[-b/k/m/g]")
//usage:#define free_full_usage "\n\n"
//usage:       "Display the amount of free and used system memory"
//usage:
//usage:#define free_example_usage
//usage:       "$ free\n"
//usage:       "              total         used         free       shared      buffers\n"
//usage:       "  Mem:       257628       248724         8904        59644        93124\n"
//usage:       " Swap:       128516         8404       120112\n"
//usage:       "Total:       386144       257128       129016\n"

#include "libbb.h"
#ifdef __linux__
# include <sys/sysinfo.h>
#endif

struct globals {
	unsigned mem_unit;
#if ENABLE_DESKTOP
	uint8_t unit_steps;
# define G_unit_steps g->unit_steps
#else
# define G_unit_steps 10
#endif
	unsigned long cached_kb, available_kb, reclaimable_kb;
};
/* Because of NOFORK, "globals" are not in global data */

static unsigned long long scale(struct globals *g, unsigned long d)
{
	return ((unsigned long long)d * g->mem_unit) >> G_unit_steps;
}

/* NOINLINE reduces main() stack usage, which makes code smaller (on x86 at least) */
static NOINLINE unsigned int parse_meminfo(struct globals *g)
{
	char buf[60]; /* actual lines we expect are ~30 chars or less */
	FILE *fp;
	int seen_cached_and_available_and_reclaimable;

	fp = xfopen_for_read("/proc/meminfo");
	g->cached_kb = g->available_kb = g->reclaimable_kb = 0;
	seen_cached_and_available_and_reclaimable = 3;
	while (fgets(buf, sizeof(buf), fp)) {
		if (sscanf(buf, "Cached: %lu %*s\n", &g->cached_kb) == 1)
			if (--seen_cached_and_available_and_reclaimable == 0)
				break;
		if (sscanf(buf, "MemAvailable: %lu %*s\n", &g->available_kb) == 1)
			if (--seen_cached_and_available_and_reclaimable == 0)
				break;
		if (sscanf(buf, "SReclaimable: %lu %*s\n", &g->reclaimable_kb) == 1)
			if (--seen_cached_and_available_and_reclaimable == 0)
				break;
	}
	/* Have to close because of NOFORK */
	fclose(fp);

	return seen_cached_and_available_and_reclaimable == 0;
}

int free_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int free_main(int argc UNUSED_PARAM, char **argv IF_NOT_DESKTOP(UNUSED_PARAM))
{
	struct globals G;
	struct sysinfo info;
	unsigned long long cached, cached_plus_free, available;
	int seen_available;

#if ENABLE_DESKTOP
	G.unit_steps = 10;
	if (argv[1] && argv[1][0] == '-') {
		switch (argv[1][1]) {
		case 'b':
			G.unit_steps = 0;
			break;
		case 'k': /* 2^10 */
			/* G.unit_steps = 10; - already is */
			break;
		case 'm': /* 2^20 */
			G.unit_steps = 20;
			break;
		case 'g': /* 2^30 */
			G.unit_steps = 30;
			break;
		default:
			bb_show_usage();
		}
	}
#endif
	printf("       %12s%12s%12s%12s%12s%12s\n"
	"Mem:   ",
		"total",
		"used",
		"free",
		"shared", "buff/cache", "available" /* swap and total don't have these columns */
	);

	sysinfo(&info);
	/* Extract cached and memavailable from /proc/meminfo and convert to mem_units */
	seen_available = parse_meminfo(&G);
	G.mem_unit = (info.mem_unit ? info.mem_unit : 1); /* kernels < 2.4.x return mem_unit==0, so cope */
	available = ((unsigned long long) G.available_kb * 1024) / G.mem_unit;
	cached = ((unsigned long long) G.cached_kb * 1024) / G.mem_unit;
	cached += info.bufferram;
	cached += ((unsigned long long) G.reclaimable_kb * 1024) / G.mem_unit;
	cached_plus_free = cached + info.freeram;

/* In case (long long * G.mem_unit) can overflow, this can be used to reduce the chances */
#if 0 //ENABLE_DESKTOP
	while (!(G.mem_unit & 1) && G.unit_steps != 0) {
		G.mem_unit >>= 1;
		G.unit_steps--;
		//bb_error_msg("mem_unit:%d unit_steps:%d", G.mem_unit, G.unit_steps);
	}
#endif

#define FIELDS_6 "%12llu %11llu %11llu %11llu %11llu %11llu\n"
#define FIELDS_3 (FIELDS_6 + 6 + 7 + 7)
#define FIELDS_2 (FIELDS_6 + 6 + 7 + 7 + 7)

	printf(FIELDS_6,
		scale(&G, info.totalram),                //total
		scale(&G, info.totalram - cached_plus_free), //used
		scale(&G, info.freeram),                 //free
		scale(&G, info.sharedram),               //shared
		scale(&G, cached),                       //buff/cache
		scale(&G, available)                     //available
	);
	/* On kernels < 3.14, MemAvailable is not provided.
	 * Show alternate, more meaningful busy/free numbers by counting
	 * buffer cache as free memory. */
	if (!seen_available) {
		printf("-/+ buffers/cache: ");
		printf(FIELDS_2,
			scale(&G, info.totalram - cached_plus_free), //used
			scale(&G, cached_plus_free)                  //free
		);
	}
#if BB_MMU
	printf("Swap:  ");
	printf(FIELDS_3,
		scale(&G, info.totalswap),                 //total
		scale(&G, info.totalswap - info.freeswap), //used
		scale(&G, info.freeswap)                   //free
	);
#endif
	return EXIT_SUCCESS;
}