/* vi: set sw=4 ts=4: */
/*
 * A tiny 'top' utility.
 *
 * This is written specifically for the linux /proc/<PID>/stat(m)
 * files format.

 * This reads the PIDs of all processes and their status and shows
 * the status of processes (first ones that fit to screen) at given
 * intervals.
 *
 * NOTES:
 * - At startup this changes to /proc, all the reads are then
 *   relative to that.
 *
 * (C) Eero Tamminen <oak at welho dot com>
 *
 * Rewritten by Vladimir Oleynik (C) 2002 <dzo@simtreas.ru>
 *
 * Sept 2008: Vineet Gupta <vineet.gupta@arc.com>
 * Added Support for reporting SMP Information
 * - CPU where Process was last seen running
 *   (to see effect of sched_setaffinity() etc)
 * - CPU Time Split (idle/IO/wait etc) PER CPU
 */

/* Original code Copyrights */
/*
 * Copyright (c) 1992 Branko Lankester
 * Copyright (c) 1992 Roger Binns
 * Copyright (C) 1994-1996 Charles L. Blake.
 * Copyright (C) 1992-1998 Michael K. Johnson
 * May be distributed under the conditions of the
 * GNU Library General Public License
 */

#include "libbb.h"


typedef struct top_status_t {
        unsigned long vsz;
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
        unsigned long ticks;
        unsigned pcpu; /* delta of ticks */
#endif
        unsigned pid, ppid;
        unsigned uid;
        char state[4];
        char comm[COMM_LEN];
#if ENABLE_FEATURE_TOP_SMP_PROCESS
        int last_seen_on_cpu;
#endif
} top_status_t;

typedef struct jiffy_counts_t {
        unsigned long long usr,nic,sys,idle,iowait,irq,softirq,steal;
        unsigned long long total;
        unsigned long long busy;
} jiffy_counts_t;

/* This structure stores some critical information from one frame to
   the next. Used for finding deltas. */
typedef struct save_hist {
        unsigned long ticks;
        pid_t pid;
} save_hist;

typedef int (*cmp_funcp)(top_status_t *P, top_status_t *Q);


enum { SORT_DEPTH = 3 };


struct globals {
        top_status_t *top;
        int ntop;
#if ENABLE_FEATURE_TOPMEM
        smallint sort_field;
        smallint inverted;
#endif
#if ENABLE_FEATURE_TOP_SMP_CPU
        smallint smp_cpu_info; /* one/many cpu info lines? */
#endif
#if ENABLE_FEATURE_USE_TERMIOS
        struct termios initial_settings;
#endif
#if !ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
        cmp_funcp sort_function[1];
#else
        cmp_funcp sort_function[SORT_DEPTH];
        struct save_hist *prev_hist;
        int prev_hist_count;
        jiffy_counts_t cur_jif, prev_jif;
        /* int hist_iterations; */
        unsigned total_pcpu;
        /* unsigned long total_vsz; */
#endif
#if ENABLE_FEATURE_TOP_SMP_CPU
        /* Per CPU samples: current and last */
        jiffy_counts_t *cpu_jif, *cpu_prev_jif;
        int num_cpus;
#endif
        char line_buf[80];
};

enum { LINE_BUF_SIZE = COMMON_BUFSIZE - offsetof(struct globals, line_buf) };

#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
        struct G_sizecheck { \
                char G_sizecheck[sizeof(G) > COMMON_BUFSIZE ? -1 : 1]; \
        }; \
} while (0)
#define top              (G.top               )
#define ntop             (G.ntop              )
#define sort_field       (G.sort_field        )
#define inverted         (G.inverted          )
#define smp_cpu_info     (G.smp_cpu_info      )
#define initial_settings (G.initial_settings  )
#define sort_function    (G.sort_function     )
#define prev_hist        (G.prev_hist         )
#define prev_hist_count  (G.prev_hist_count   )
#define cur_jif          (G.cur_jif           )
#define prev_jif         (G.prev_jif          )
#define cpu_jif          (G.cpu_jif           )
#define cpu_prev_jif     (G.cpu_prev_jif      )
#define num_cpus         (G.num_cpus          )
#define total_pcpu       (G.total_pcpu        )
#define line_buf         (G.line_buf          )

enum {
        OPT_d = (1 << 0),
        OPT_n = (1 << 1),
        OPT_b = (1 << 2),
        OPT_EOF = (1 << 3), /* pseudo: "we saw EOF in stdin" */
};
#define OPT_BATCH_MODE (option_mask32 & OPT_b)


#if ENABLE_FEATURE_USE_TERMIOS
static int pid_sort(top_status_t *P, top_status_t *Q)
{
        /* Buggy wrt pids with high bit set */
        /* (linux pids are in [1..2^15-1]) */
        return (Q->pid - P->pid);
}
#endif

static int mem_sort(top_status_t *P, top_status_t *Q)
{
        /* We want to avoid unsigned->signed and truncation errors */
        if (Q->vsz < P->vsz) return -1;
        return Q->vsz != P->vsz; /* 0 if ==, 1 if > */
}


#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE

static int pcpu_sort(top_status_t *P, top_status_t *Q)
{
        /* Buggy wrt ticks with high bit set */
        /* Affects only processes for which ticks overflow */
        return (int)Q->pcpu - (int)P->pcpu;
}

static int time_sort(top_status_t *P, top_status_t *Q)
{
        /* We want to avoid unsigned->signed and truncation errors */
        if (Q->ticks < P->ticks) return -1;
        return Q->ticks != P->ticks; /* 0 if ==, 1 if > */
}

static int mult_lvl_cmp(void* a, void* b)
{
        int i, cmp_val;

        for (i = 0; i < SORT_DEPTH; i++) {
                cmp_val = (*sort_function[i])(a, b);
                if (cmp_val != 0)
                        return cmp_val;
        }
        return 0;
}

/* NOINLINE so that complier doesn't unfold the call
 * causing multiple copies of the arithmatic instrns
 */
static NOINLINE int read_cpu_jiffy(FILE *fp, jiffy_counts_t *p_jif)
{
#if !ENABLE_FEATURE_TOP_SMP_CPU
        static const char fmt[] = "cpu %lld %lld %lld %lld %lld %lld %lld %lld";
#else
        static const char fmt[] = "cp%*s %lld %lld %lld %lld %lld %lld %lld %lld";
#endif
        int ret;

        if (!fgets(line_buf, LINE_BUF_SIZE, fp) || line_buf[0] != 'c' /* not "cpu" */)
                return 0;
        ret = sscanf(line_buf, fmt,
                        &p_jif->usr, &p_jif->nic, &p_jif->sys, &p_jif->idle,
                        &p_jif->iowait, &p_jif->irq, &p_jif->softirq,
                        &p_jif->steal);
        if (ret >= 4) {
                p_jif->total = p_jif->usr + p_jif->nic + p_jif->sys + p_jif->idle
                        + p_jif->iowait + p_jif->irq + p_jif->softirq + p_jif->steal;
                /* procps 2.x does not count iowait as busy time */
                p_jif->busy = p_jif->total - p_jif->idle - p_jif->iowait;
        }

        return ret;
}

static void get_jiffy_counts(void)
{
        FILE* fp = xfopen_for_read("stat");

        /* We need to parse cumulative counts even if SMP CPU display is on,
         * they are used to calculate per process CPU% */
        prev_jif = cur_jif;
        if (read_cpu_jiffy(fp, &cur_jif) < 4)
                bb_error_msg_and_die("can't read /proc/stat");

#if !ENABLE_FEATURE_TOP_SMP_CPU
        fclose(fp);
        return;
#else
        if (!smp_cpu_info) {
                fclose(fp);
                return;
        }

        if (!num_cpus) {
                /* First time here. How many CPUs?
                 * There will be at least 1 /proc/stat line with cpu%d
                 */
                while (1) {
                        cpu_jif = xrealloc_vector(cpu_jif, 1, num_cpus);
                        if (read_cpu_jiffy(fp, &cpu_jif[num_cpus]) <= 4)
                                break;
                        num_cpus++;
                }
                if (num_cpus == 0) /* /proc/stat with only "cpu ..." line?! */
                        smp_cpu_info = 0;

                cpu_prev_jif = xzalloc(sizeof(cpu_prev_jif[0]) * num_cpus);

                /* Otherwise the first per cpu display shows all 100% idles */
                usleep(50000);
        } else { /* Non first time invocation */
                jiffy_counts_t *tmp;
                int i;

                /* First switch the sample pointers: no need to copy */
                tmp = cpu_prev_jif;
                cpu_prev_jif = cpu_jif;
                cpu_jif = tmp;

                /* Get the new samples */
                for (i = 0; i < num_cpus; i++)
                        read_cpu_jiffy(fp, &cpu_jif[i]);
        }
#endif
        fclose(fp);
}

static void do_stats(void)
{
        top_status_t *cur;
        pid_t pid;
        int i, last_i, n;
        struct save_hist *new_hist;

        get_jiffy_counts();
        total_pcpu = 0;
        /* total_vsz = 0; */
        new_hist = xmalloc(sizeof(new_hist[0]) * ntop);
        /*
         * Make a pass through the data to get stats.
         */
        /* hist_iterations = 0; */
        i = 0;
        for (n = 0; n < ntop; n++) {
                cur = top + n;

                /*
                 * Calculate time in cur process.  Time is sum of user time
                 * and system time
                 */
                pid = cur->pid;
                new_hist[n].ticks = cur->ticks;
                new_hist[n].pid = pid;

                /* find matching entry from previous pass */
                cur->pcpu = 0;
                /* do not start at index 0, continue at last used one
                 * (brought hist_iterations from ~14000 down to 172) */
                last_i = i;
                if (prev_hist_count) do {
                        if (prev_hist[i].pid == pid) {
                                cur->pcpu = cur->ticks - prev_hist[i].ticks;
                                total_pcpu += cur->pcpu;
                                break;
                        }
                        i = (i+1) % prev_hist_count;
                        /* hist_iterations++; */
                } while (i != last_i);
                /* total_vsz += cur->vsz; */
        }

        /*
         * Save cur frame's information.
         */
        free(prev_hist);
        prev_hist = new_hist;
        prev_hist_count = ntop;
}

#endif /* FEATURE_TOP_CPU_USAGE_PERCENTAGE */

#if ENABLE_FEATURE_TOP_CPU_GLOBAL_PERCENTS && ENABLE_FEATURE_TOP_DECIMALS
/* formats 7 char string (8 with terminating NUL) */
static char *fmt_100percent_8(char pbuf[8], unsigned value, unsigned total)
{
        unsigned t;
        if (value >= total) { /* 100% ? */
                strcpy(pbuf, "  100% ");
                return pbuf;
        }
        /* else generate " [N/space]N.N% " string */
        value = 1000 * value / total;
        t = value / 100;
        value = value % 100;
        pbuf[0] = ' ';
        pbuf[1] = t ? t + '0' : ' ';
        pbuf[2] = '0' + (value / 10);
        pbuf[3] = '.';
        pbuf[4] = '0' + (value % 10);
        pbuf[5] = '%';
        pbuf[6] = ' ';
        pbuf[7] = '\0';
        return pbuf;
}
#endif

#if ENABLE_FEATURE_TOP_CPU_GLOBAL_PERCENTS
static void display_cpus(int scr_width, char *scrbuf, int *lines_rem_p)
{
        /*
         * xxx% = (cur_jif.xxx - prev_jif.xxx) / (cur_jif.total - prev_jif.total) * 100%
         */
        unsigned total_diff;
        jiffy_counts_t *p_jif, *p_prev_jif;
        int i;

#if ENABLE_FEATURE_TOP_SMP_CPU
        int n_cpu_lines;
#endif

        /* using (unsigned) casts to make operations cheaper */
#define  CALC_TOT_DIFF  ((unsigned)(p_jif->total - p_prev_jif->total) ? : 1)

#if ENABLE_FEATURE_TOP_DECIMALS
#define CALC_STAT(xxx) char xxx[8]
#define SHOW_STAT(xxx) fmt_100percent_8(xxx, (unsigned)(p_jif->xxx - p_prev_jif->xxx), total_diff)
#define FMT "%s"
#else
#define CALC_STAT(xxx) unsigned xxx = 100 * (unsigned)(p_jif->xxx - p_prev_jif->xxx) / total_diff
#define SHOW_STAT(xxx) xxx
#define FMT "%4u%% "
#endif

#if !ENABLE_FEATURE_TOP_SMP_CPU
        {
                i = 1;
                p_jif = &cur_jif;
                p_prev_jif = &prev_jif;
#else
        /* Loop thru CPU(s) */
        n_cpu_lines = smp_cpu_info ? num_cpus : 1;
        if (n_cpu_lines > *lines_rem_p)
                n_cpu_lines = *lines_rem_p;

        for (i = 0; i < n_cpu_lines; i++) {
                p_jif = &cpu_jif[i];
                p_prev_jif = &cpu_prev_jif[i];
#endif
                total_diff = CALC_TOT_DIFF;

                { /* Need a block: CALC_STAT are declarations */
                        CALC_STAT(usr);
                        CALC_STAT(sys);
                        CALC_STAT(nic);
                        CALC_STAT(idle);
                        CALC_STAT(iowait);
                        CALC_STAT(irq);
                        CALC_STAT(softirq);
                        /*CALC_STAT(steal);*/

                        snprintf(scrbuf, scr_width,
                                /* Barely fits in 79 chars when in "decimals" mode. */
#if ENABLE_FEATURE_TOP_SMP_CPU
                                "CPU%s:"FMT"usr"FMT"sys"FMT"nic"FMT"idle"FMT"io"FMT"irq"FMT"sirq",
                                (smp_cpu_info ? utoa(i) : ""),
#else
                                "CPU:"FMT"usr"FMT"sys"FMT"nic"FMT"idle"FMT"io"FMT"irq"FMT"sirq",
#endif
                                SHOW_STAT(usr), SHOW_STAT(sys), SHOW_STAT(nic), SHOW_STAT(idle),
                                SHOW_STAT(iowait), SHOW_STAT(irq), SHOW_STAT(softirq)
                                /*, SHOW_STAT(steal) - what is this 'steal' thing? */
                                /* I doubt anyone wants to know it */
                        );
                        puts(scrbuf);
                }
        }
#undef SHOW_STAT
#undef CALC_STAT
#undef FMT
        *lines_rem_p -= i;
}
#else  /* !ENABLE_FEATURE_TOP_CPU_GLOBAL_PERCENTS */
#define display_cpus(scr_width, scrbuf, lines_rem) ((void)0)
#endif

static unsigned long display_header(int scr_width, int *lines_rem_p)
{
        FILE *fp;
        char buf[80];
        char scrbuf[80];
        unsigned long total, used, mfree, shared, buffers, cached;

        /* read memory info */
        fp = xfopen_for_read("meminfo");

        /*
         * Old kernels (such as 2.4.x) had a nice summary of memory info that
         * we could parse, however this is gone entirely in 2.6. Try parsing
         * the old way first, and if that fails, parse each field manually.
         *
         * First, we read in the first line. Old kernels will have bogus
         * strings we don't care about, whereas new kernels will start right
         * out with MemTotal:
         *                              -- PFM.
         */
        if (fscanf(fp, "MemTotal: %lu %s\n", &total, buf) != 2) {
                fgets(buf, sizeof(buf), fp);    /* skip first line */

                fscanf(fp, "Mem: %lu %lu %lu %lu %lu %lu",
                        &total, &used, &mfree, &shared, &buffers, &cached);
                /* convert to kilobytes */
                used /= 1024;
                mfree /= 1024;
                shared /= 1024;
                buffers /= 1024;
                cached /= 1024;
                total /= 1024;
        } else {
                /*
                 * Revert to manual parsing, which incidentally already has the
                 * sizes in kilobytes. This should be safe for both 2.4 and
                 * 2.6.
                 */
                fscanf(fp, "MemFree: %lu %s\n", &mfree, buf);

                /*
                 * MemShared: is no longer present in 2.6. Report this as 0,
                 * to maintain consistent behavior with normal procps.
                 */
                if (fscanf(fp, "MemShared: %lu %s\n", &shared, buf) != 2)
                        shared = 0;

                fscanf(fp, "Buffers: %lu %s\n", &buffers, buf);
                fscanf(fp, "Cached: %lu %s\n", &cached, buf);

                used = total - mfree;
        }
        fclose(fp);

        /* output memory info */
        if (scr_width > (int)sizeof(scrbuf))
                scr_width = sizeof(scrbuf);
        snprintf(scrbuf, scr_width,
                "Mem: %luK used, %luK free, %luK shrd, %luK buff, %luK cached",
                used, mfree, shared, buffers, cached);
        /* clear screen & go to top */
        printf(OPT_BATCH_MODE ? "%s\n" : "\e[H\e[J%s\n", scrbuf);
        (*lines_rem_p)--;

        /* Display CPU time split as percentage of total time
         * This displays either a cumulative line or one line per CPU
         */
        display_cpus(scr_width, scrbuf, lines_rem_p);

        /* read load average as a string */
        buf[0] = '\0';
        open_read_close("loadavg", buf, sizeof(buf) - 1);
        buf[sizeof(buf) - 1] = '\n';
        *strchr(buf, '\n') = '\0';
        snprintf(scrbuf, scr_width, "Load average: %s", buf);
        puts(scrbuf);
        (*lines_rem_p)--;

        return total;
}

static NOINLINE void display_process_list(int lines_rem, int scr_width)
{
        enum {
                BITS_PER_INT = sizeof(int) * 8
        };

        top_status_t *s;
        char vsz_str_buf[8];
        unsigned long total_memory = display_header(scr_width, &lines_rem); /* or use total_vsz? */
        /* xxx_shift and xxx_scale variables allow us to replace
         * expensive divides with multiply and shift */
        unsigned pmem_shift, pmem_scale, pmem_half;
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
        unsigned pcpu_shift, pcpu_scale, pcpu_half;
        unsigned busy_jifs;
#endif

        /* what info of the processes is shown */
        printf(OPT_BATCH_MODE ? "%.*s" : "\e[7m%.*s\e[0m", scr_width,
                "  PID  PPID USER     STAT   VSZ %MEM"
#if ENABLE_FEATURE_TOP_SMP_PROCESS
                " CPU"
#endif
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                " %CPU"
#endif
                " COMMAND");
        lines_rem--;

#if ENABLE_FEATURE_TOP_DECIMALS
#define UPSCALE 1000
#define CALC_STAT(name, val) div_t name = div((val), 10)
#define SHOW_STAT(name) name.quot, '0'+name.rem
#define FMT "%3u.%c"
#else
#define UPSCALE 100
#define CALC_STAT(name, val) unsigned name = (val)
#define SHOW_STAT(name) name
#define FMT "%4u%%"
#endif
        /*
         * MEM% = s->vsz/MemTotal
         */
        pmem_shift = BITS_PER_INT-11;
        pmem_scale = UPSCALE*(1U<<(BITS_PER_INT-11)) / total_memory;
        /* s->vsz is in kb. we want (s->vsz * pmem_scale) to never overflow */
        while (pmem_scale >= 512) {
                pmem_scale /= 4;
                pmem_shift -= 2;
        }
        pmem_half = (1U << pmem_shift) / (ENABLE_FEATURE_TOP_DECIMALS? 20 : 2);
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
        busy_jifs = cur_jif.busy - prev_jif.busy;
        /* This happens if there were lots of short-lived processes
         * between two top updates (e.g. compilation) */
        if (total_pcpu < busy_jifs) total_pcpu = busy_jifs;

        /*
         * CPU% = s->pcpu/sum(s->pcpu) * busy_cpu_ticks/total_cpu_ticks
         * (pcpu is delta of sys+user time between samples)
         */
        /* (cur_jif.xxx - prev_jif.xxx) and s->pcpu are
         * in 0..~64000 range (HZ*update_interval).
         * we assume that unsigned is at least 32-bit.
         */
        pcpu_shift = 6;
        pcpu_scale = (UPSCALE*64 * (uint16_t)busy_jifs ? : 1);
        while (pcpu_scale < (1U << (BITS_PER_INT-2))) {
                pcpu_scale *= 4;
                pcpu_shift += 2;
        }
        pcpu_scale /= ( (uint16_t)(cur_jif.total - prev_jif.total) * total_pcpu ? : 1);
        /* we want (s->pcpu * pcpu_scale) to never overflow */
        while (pcpu_scale >= 1024) {
                pcpu_scale /= 4;
                pcpu_shift -= 2;
        }
        pcpu_half = (1U << pcpu_shift) / (ENABLE_FEATURE_TOP_DECIMALS? 20 : 2);
        /* printf(" pmem_scale=%u pcpu_scale=%u ", pmem_scale, pcpu_scale); */
#endif

        /* Ok, all preliminary data is ready, go through the list */
        scr_width += 2; /* account for leading '\n' and trailing NUL */
        if (lines_rem > ntop)
                lines_rem = ntop;
        s = top;
        while (--lines_rem >= 0) {
                unsigned col;
                CALC_STAT(pmem, (s->vsz*pmem_scale + pmem_half) >> pmem_shift);
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                CALC_STAT(pcpu, (s->pcpu*pcpu_scale + pcpu_half) >> pcpu_shift);
#endif

                if (s->vsz >= 100000)
                        sprintf(vsz_str_buf, "%6ldm", s->vsz/1024);
                else
                        sprintf(vsz_str_buf, "%7ld", s->vsz);
                /* PID PPID USER STAT VSZ %MEM [%CPU] COMMAND */
                col = snprintf(line_buf, scr_width,
                                "\n" "%5u%6u %-8.8s %s%s" FMT
#if ENABLE_FEATURE_TOP_SMP_PROCESS
                                " %3d"
#endif
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                                FMT
#endif
                                " ",
                                s->pid, s->ppid, get_cached_username(s->uid),
                                s->state, vsz_str_buf,
                                SHOW_STAT(pmem)
#if ENABLE_FEATURE_TOP_SMP_PROCESS
                                , s->last_seen_on_cpu
#endif
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                                , SHOW_STAT(pcpu)
#endif
                );
                if ((int)(col + 1) < scr_width)
                        read_cmdline(line_buf + col, scr_width - col - 1, s->pid, s->comm);
                fputs(line_buf, stdout);
                /* printf(" %d/%d %lld/%lld", s->pcpu, total_pcpu,
                        cur_jif.busy - prev_jif.busy, cur_jif.total - prev_jif.total); */
                s++;
        }
        /* printf(" %d", hist_iterations); */
        bb_putchar(OPT_BATCH_MODE ? '\n' : '\r');
        fflush(stdout);
}
#undef UPSCALE
#undef SHOW_STAT
#undef CALC_STAT
#undef FMT

static void clearmems(void)
{
        clear_username_cache();
        free(top);
        top = NULL;
        ntop = 0;
}

#if ENABLE_FEATURE_USE_TERMIOS
#include <termios.h>
#include <signal.h>

static void reset_term(void)
{
        tcsetattr_stdin_TCSANOW(&initial_settings);
        if (ENABLE_FEATURE_CLEAN_UP) {
                clearmems();
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                free(prev_hist);
#endif
        }
}

static void sig_catcher(int sig UNUSED_PARAM)
{
        reset_term();
        exit(EXIT_FAILURE);
}
#endif /* FEATURE_USE_TERMIOS */

/*
 * TOPMEM support
 */

typedef unsigned long mem_t;

typedef struct topmem_status_t {
        unsigned pid;
        char comm[COMM_LEN];
        /* vsz doesn't count /dev/xxx mappings except /dev/zero */
        mem_t vsz     ;
        mem_t vszrw   ;
        mem_t rss     ;
        mem_t rss_sh  ;
        mem_t dirty   ;
        mem_t dirty_sh;
        mem_t stack   ;
} topmem_status_t;

enum { NUM_SORT_FIELD = 7 };

#define topmem ((topmem_status_t*)top)

#if ENABLE_FEATURE_TOPMEM

static int topmem_sort(char *a, char *b)
{
        int n;
        mem_t l, r;

        n = offsetof(topmem_status_t, vsz) + (sort_field * sizeof(mem_t));
        l = *(mem_t*)(a + n);
        r = *(mem_t*)(b + n);
//      if (l == r) {
//              l = a->mapped_rw;
//              r = b->mapped_rw;
//      }
        /* We want to avoid unsigned->signed and truncation errors */
        /* l>r: -1, l=r: 0, l<r: 1 */
        n = (l > r) ? -1 : (l != r);
        return inverted ? -n : n;
}

/* Cut "NNNN " out of "    NNNN kb" */
static char *grab_number(char *str, const char *match, unsigned sz)
{
        if (strncmp(str, match, sz) == 0) {
                str = skip_whitespace(str + sz);
                (skip_non_whitespace(str))[1] = '\0';
                return xstrdup(str);
        }
        return NULL;
}

/* display header info (meminfo / loadavg) */
static void display_topmem_header(int scr_width, int *lines_rem_p)
{
        char linebuf[128];
        unsigned i;
        FILE *fp;
        union {
                struct {
                        /*  1 */ char *total;
                        /*  2 */ char *mfree;
                        /*  3 */ char *buf;
                        /*  4 */ char *cache;
                        /*  5 */ char *swaptotal;
                        /*  6 */ char *swapfree;
                        /*  7 */ char *dirty;
                        /*  8 */ char *mwrite;
                        /*  9 */ char *anon;
                        /* 10 */ char *map;
                        /* 11 */ char *slab;
                } u;
                char *str[11];
        } Z;
#define total     Z.u.total
#define mfree     Z.u.mfree
#define buf       Z.u.buf
#define cache     Z.u.cache
#define swaptotal Z.u.swaptotal
#define swapfree  Z.u.swapfree
#define dirty     Z.u.dirty
#define mwrite    Z.u.mwrite
#define anon      Z.u.anon
#define map       Z.u.map
#define slab      Z.u.slab
#define str       Z.str

        memset(&Z, 0, sizeof(Z));

        /* read memory info */
        fp = xfopen_for_read("meminfo");
        while (fgets(linebuf, sizeof(linebuf), fp)) {
                char *p;

#define SCAN(match, name) \
                p = grab_number(linebuf, match, sizeof(match)-1); \
                if (p) { name = p; continue; }

                SCAN("MemTotal:", total);
                SCAN("MemFree:", mfree);
                SCAN("Buffers:", buf);
                SCAN("Cached:", cache);
                SCAN("SwapTotal:", swaptotal);
                SCAN("SwapFree:", swapfree);
                SCAN("Dirty:", dirty);
                SCAN("Writeback:", mwrite);
                SCAN("AnonPages:", anon);
                SCAN("Mapped:", map);
                SCAN("Slab:", slab);
#undef SCAN
        }
        fclose(fp);

#define S(s) (s ? s : "0 ")
        snprintf(linebuf, sizeof(linebuf),
                "Mem %stotal %sanon %smap %sfree",
                S(total), S(anon), S(map), S(mfree));
        printf(OPT_BATCH_MODE ? "%.*s\n" : "\e[H\e[J%.*s\n", scr_width, linebuf);

        snprintf(linebuf, sizeof(linebuf),
                " %sslab %sbuf %scache %sdirty %swrite",
                S(slab), S(buf), S(cache), S(dirty), S(mwrite));
        printf("%.*s\n", scr_width, linebuf);

        snprintf(linebuf, sizeof(linebuf),
                "Swap %stotal %sfree", // TODO: % used?
                S(swaptotal), S(swapfree));
        printf("%.*s\n", scr_width, linebuf);

        (*lines_rem_p) -= 3;
#undef S

        for (i = 0; i < ARRAY_SIZE(str); i++)
                free(str[i]);
#undef total
#undef free
#undef buf
#undef cache
#undef swaptotal
#undef swapfree
#undef dirty
#undef write
#undef anon
#undef map
#undef slab
#undef str
}

static void ulltoa6_and_space(unsigned long long ul, char buf[6])
{
        /* see http://en.wikipedia.org/wiki/Tera */
        smart_ulltoa5(ul, buf, " mgtpezy");
        buf[5] = ' ';
}

static NOINLINE void display_topmem_process_list(int lines_rem, int scr_width)
{
#define HDR_STR "  PID   VSZ VSZRW   RSS (SHR) DIRTY (SHR) STACK"
#define MIN_WIDTH sizeof(HDR_STR)
        const topmem_status_t *s = topmem;

        display_topmem_header(scr_width, &lines_rem);
        strcpy(line_buf, HDR_STR " COMMAND");
        line_buf[5 + sort_field * 6] = '*';
        printf(OPT_BATCH_MODE ? "%.*s" : "\e[7m%.*s\e[0m", scr_width, line_buf);
        lines_rem--;

        if (lines_rem > ntop)
                lines_rem = ntop;
        while (--lines_rem >= 0) {
                /* PID VSZ VSZRW RSS (SHR) DIRTY (SHR) COMMAND */
                ulltoa6_and_space(s->pid     , &line_buf[0*6]);
                ulltoa6_and_space(s->vsz     , &line_buf[1*6]);
                ulltoa6_and_space(s->vszrw   , &line_buf[2*6]);
                ulltoa6_and_space(s->rss     , &line_buf[3*6]);
                ulltoa6_and_space(s->rss_sh  , &line_buf[4*6]);
                ulltoa6_and_space(s->dirty   , &line_buf[5*6]);
                ulltoa6_and_space(s->dirty_sh, &line_buf[6*6]);
                ulltoa6_and_space(s->stack   , &line_buf[7*6]);
                line_buf[8*6] = '\0';
                if (scr_width > (int)MIN_WIDTH) {
                        read_cmdline(&line_buf[8*6], scr_width - MIN_WIDTH, s->pid, s->comm);
                }
                printf("\n""%.*s", scr_width, line_buf);
                s++;
        }
        bb_putchar(OPT_BATCH_MODE ? '\n' : '\r');
        fflush(stdout);
#undef HDR_STR
#undef MIN_WIDTH
}

#else
void display_topmem_process_list(int lines_rem, int scr_width);
int topmem_sort(char *a, char *b);
#endif /* TOPMEM */

/*
 * end TOPMEM support
 */

enum {
        TOP_MASK = 0
                | PSSCAN_PID
                | PSSCAN_PPID
                | PSSCAN_VSZ
                | PSSCAN_STIME
                | PSSCAN_UTIME
                | PSSCAN_STATE
                | PSSCAN_COMM
#if ENABLE_FEATURE_TOP_SMP_PROCESS
                | PSSCAN_CPU
#endif
                | PSSCAN_UIDGID,
        TOPMEM_MASK = 0
                | PSSCAN_PID
                | PSSCAN_SMAPS
                | PSSCAN_COMM,
};

int top_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int top_main(int argc UNUSED_PARAM, char **argv)
{
        int iterations;
        unsigned lines, col;
        int lines_rem;
        unsigned interval;
        char *str_interval, *str_iterations;
        SKIP_FEATURE_TOPMEM(const) unsigned scan_mask = TOP_MASK;
#if ENABLE_FEATURE_USE_TERMIOS
        struct termios new_settings;
        struct pollfd pfd[1];
        unsigned char c;

        pfd[0].fd = 0;
        pfd[0].events = POLLIN;
#endif /* FEATURE_USE_TERMIOS */

        INIT_G();

        interval = 5; /* default update interval is 5 seconds */
        iterations = 0; /* infinite */
#if ENABLE_FEATURE_TOP_SMP_CPU
        /*num_cpus = 0;*/
        /*smp_cpu_info = 0;*/  /* to start with show aggregate */
        cpu_jif = &cur_jif;
        cpu_prev_jif = &prev_jif;
#endif

        /* all args are options; -n NUM */
        opt_complementary = "-";
        col = getopt32(argv, "d:n:b", &str_interval, &str_iterations);
        if (col & OPT_d) {
                /* work around for "-d 1" -> "-d -1" done by getopt32 */
                if (str_interval[0] == '-')
                        str_interval++;
                /* Need to limit it to not overflow poll timeout */
                interval = xatou16(str_interval);
        }
        if (col & OPT_n) {
                if (str_iterations[0] == '-')
                        str_iterations++;
                iterations = xatou(str_iterations);
        }

        /* change to /proc */
        xchdir("/proc");
#if ENABLE_FEATURE_USE_TERMIOS
        tcgetattr(0, (void *) &initial_settings);
        memcpy(&new_settings, &initial_settings, sizeof(new_settings));
        /* unbuffered input, turn off echo */
        new_settings.c_lflag &= ~(ISIG | ICANON | ECHO | ECHONL);

        bb_signals(BB_FATAL_SIGS, sig_catcher);
        tcsetattr_stdin_TCSANOW(&new_settings);
#endif /* FEATURE_USE_TERMIOS */

#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
        sort_function[0] = pcpu_sort;
        sort_function[1] = mem_sort;
        sort_function[2] = time_sort;
#else
        sort_function[0] = mem_sort;
#endif /* FEATURE_TOP_CPU_USAGE_PERCENTAGE */

        while (1) {
                procps_status_t *p = NULL;

                lines = 24; /* default */
                col = 79;
#if ENABLE_FEATURE_USE_TERMIOS
                /* We output to stdout, we need size of stdout (not stdin)! */
                get_terminal_width_height(STDOUT_FILENO, &col, &lines);
                if (lines < 5 || col < 10) {
                        sleep(interval);
                        continue;
                }
#endif /* FEATURE_USE_TERMIOS */
                if (col > LINE_BUF_SIZE-2) /* +2 bytes for '\n', NUL, */
                        col = LINE_BUF_SIZE-2;

                /* read process IDs & status for all the processes */
                while ((p = procps_scan(p, scan_mask)) != NULL) {
                        int n;
                        if (scan_mask == TOP_MASK) {
                                n = ntop;
                                top = xrealloc_vector(top, 6, ntop++);
                                top[n].pid = p->pid;
                                top[n].ppid = p->ppid;
                                top[n].vsz = p->vsz;
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                                top[n].ticks = p->stime + p->utime;
#endif
                                top[n].uid = p->uid;
                                strcpy(top[n].state, p->state);
                                strcpy(top[n].comm, p->comm);
#if ENABLE_FEATURE_TOP_SMP_PROCESS
                                top[n].last_seen_on_cpu = p->last_seen_on_cpu;
#endif
                        } else { /* TOPMEM */
#if ENABLE_FEATURE_TOPMEM
                                if (!(p->mapped_ro | p->mapped_rw))
                                        continue; /* kernel threads are ignored */
                                n = ntop;
                                /* No bug here - top and topmem are the same */
                                top = xrealloc_vector(topmem, 6, ntop++);
                                strcpy(topmem[n].comm, p->comm);
                                topmem[n].pid      = p->pid;
                                topmem[n].vsz      = p->mapped_rw + p->mapped_ro;
                                topmem[n].vszrw    = p->mapped_rw;
                                topmem[n].rss_sh   = p->shared_clean + p->shared_dirty;

                                topmem[n].rss      = p->private_clean + p->private_dirty + topmem[n].rss_sh;
                                topmem[n].dirty    = p->private_dirty + p->shared_dirty;
                                topmem[n].dirty_sh = p->shared_dirty;
                                topmem[n].stack    = p->stack;
#endif
                        }
                } /* end of "while we read /proc" */
                if (ntop == 0) {
                        bb_error_msg("no process info in /proc");
                        break;
                }

                if (scan_mask == TOP_MASK) {
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                        if (!prev_hist_count) {
                                do_stats();
                                usleep(100000);
                                clearmems();
                                continue;
                        }
                        do_stats();
                        /* TODO: we don't need to sort all 10000 processes, we need to find top 24! */
                        qsort(top, ntop, sizeof(top_status_t), (void*)mult_lvl_cmp);
#else
                        qsort(top, ntop, sizeof(top_status_t), (void*)(sort_function[0]));
#endif /* FEATURE_TOP_CPU_USAGE_PERCENTAGE */
                }
#if ENABLE_FEATURE_TOPMEM
                else { /* TOPMEM */
                        qsort(topmem, ntop, sizeof(topmem_status_t), (void*)topmem_sort);
                }
#endif
                lines_rem = lines;
                if (OPT_BATCH_MODE) {
                        lines_rem = INT_MAX;
                }
                if (scan_mask == TOP_MASK)
                        display_process_list(lines_rem, col);
#if ENABLE_FEATURE_TOPMEM
                else
                        display_topmem_process_list(lines_rem, col);
#endif
                clearmems();
                if (iterations >= 0 && !--iterations)
                        break;
#if !ENABLE_FEATURE_USE_TERMIOS
                sleep(interval);
#else
                if (option_mask32 & (OPT_b|OPT_EOF))
                         /* batch mode, or EOF on stdin ("top </dev/null") */
                        sleep(interval);
                else if (safe_poll(pfd, 1, interval * 1000) > 0) {
                        if (safe_read(STDIN_FILENO, &c, 1) != 1) { /* error/EOF? */
                                option_mask32 |= OPT_EOF;
                                continue;
                        }
                        if (c == initial_settings.c_cc[VINTR])
                                break;
                        c |= 0x20; /* lowercase */
                        if (c == 'q')
                                break;
                        if (c == 'n') {
                                USE_FEATURE_TOPMEM(scan_mask = TOP_MASK;)
                                sort_function[0] = pid_sort;
                        }
                        if (c == 'm') {
                                USE_FEATURE_TOPMEM(scan_mask = TOP_MASK;)
                                sort_function[0] = mem_sort;
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                                sort_function[1] = pcpu_sort;
                                sort_function[2] = time_sort;
#endif
                        }
#if ENABLE_FEATURE_TOP_CPU_USAGE_PERCENTAGE
                        if (c == 'p') {
                                USE_FEATURE_TOPMEM(scan_mask = TOP_MASK;)
                                sort_function[0] = pcpu_sort;
                                sort_function[1] = mem_sort;
                                sort_function[2] = time_sort;
                        }
                        if (c == 't') {
                                USE_FEATURE_TOPMEM(scan_mask = TOP_MASK;)
                                sort_function[0] = time_sort;
                                sort_function[1] = mem_sort;
                                sort_function[2] = pcpu_sort;
                        }
#if ENABLE_FEATURE_TOPMEM
                        if (c == 's') {
                                scan_mask = TOPMEM_MASK;
                                free(prev_hist);
                                prev_hist = NULL;
                                prev_hist_count = 0;
                                sort_field = (sort_field + 1) % NUM_SORT_FIELD;
                        }
                        if (c == 'r')
                                inverted ^= 1;
#endif
#if ENABLE_FEATURE_TOP_SMP_CPU
                        /* procps-2.0.18 uses 'C', 3.2.7 uses '1' */
                        if (c == 'c' || c == '1') {
                                /* User wants to toggle per cpu <> aggregate */
                                if (smp_cpu_info) {
                                        free(cpu_prev_jif);
                                        free(cpu_jif);
                                        cpu_jif = &cur_jif;
                                        cpu_prev_jif = &prev_jif;
                                } else {
                                        /* Prepare for xrealloc() */
                                        cpu_jif = cpu_prev_jif = NULL;
                                }
                                num_cpus = 0;
                                smp_cpu_info = !smp_cpu_info;
                                get_jiffy_counts();
                        }
#endif
#endif
                }
#endif /* FEATURE_USE_TERMIOS */
        } /* end of "while (1)" */

        bb_putchar('\n');
#if ENABLE_FEATURE_USE_TERMIOS
        reset_term();
#endif
        return EXIT_SUCCESS;
}