Shift X2 status from legacy to archived
[khatus.git] / x5 / khatus.c
index c7660b4..5407acd 100644 (file)
-/*
-
-- [ ] Switch from regular files to named pipes
-       - [ ] poll with select
-
-*/
+#include <sys/select.h>
+#include <sys/stat.h>
 
 #include <assert.h>
 #include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-
-#include <fcntl.h>
+#include <time.h>
 #include <unistd.h>
 
-#define debug(args...) {fprintf(stderr, "[debug] " args);}
-#define info( args...) {fprintf(stderr, "[info] "  args);}
-#define error(args...) {fprintf(stderr, "[error] " args);}
-#define fatal(args...) {fprintf(stderr, "[fatal] " args); exit(EXIT_FAILURE);}
-#define usage(args...) {print_usage(); fatal("[usage] " args);}
-
-char *argv0;
-
-typedef struct File File;
-struct File {
-       char   *name;
-       int     fd;
-       int     width;
-       int     last_read;
-       int     ttl;
-       int     pos;  /* Position on the output buffer. */
-       File   *next;
+#include <X11/Xlib.h>
+
+#include "bsdtimespec.h"
+#include "khlib_log.h"
+#include "khlib_time.h"
+
+#define usage(...) { \
+       print_usage(); \
+       fprintf(stderr, "Error:\n    " __VA_ARGS__); \
+       exit(EXIT_FAILURE); \
+}
+#define ERRMSG "ERROR"
+
+
+static const char errmsg[] = ERRMSG;
+static const int  errlen   = sizeof(ERRMSG) - 1;
+
+char *argv0 = NULL;
+int running = 1;
+
+/* TODO: Convert slot list to slot array. */
+typedef struct Slot Slot;
+struct Slot {
+       char            *in_fifo;
+       int              in_fd;
+       struct timespec  in_last_read;
+       struct timespec  out_ttl;
+       int              out_width;
+       int              out_pos_lo;   /* Lowest  position on the output buffer. */
+       int              out_pos_cur;  /* Current position on the output buffer. */
+       int              out_pos_hi;   /* Highest position on the output buffer. */
+       Slot            *next;
 };
 
 typedef struct Config Config;
 struct Config {
-       int    interval;
+       double interval;
        char * separator;
-       char * timefmt;
-       File * files;
-       int    file_count;
-       int    total_width;
-} defaults = {
-       .interval    = 1,
-       .separator   = "|",
-       .timefmt     = "%Y-%m-%d %H:%M:%S",
-       .files       = NULL,
-       .file_count  = 0,
-       .total_width = 0,
+       char   expiry_character;
+       Slot * slots;
+       int    slot_count;
+       int    buf_width;
+       int    to_x_root;
+};
+
+enum read_status {
+       END_OF_FILE,
+       END_OF_MESSAGE,
+       RETRY,
+       FAILURE
 };
 
+char *
+buf_create(Config *cfg)
+{
+       int seplen;
+       char *buf;
+       Slot *s;
+
+       buf = calloc(1, cfg->buf_width + 1);
+       if (buf == NULL)
+               khlib_fatal(
+                   "[memory] Failed to allocate buffer of %d bytes",
+                   cfg->buf_width
+               );
+       memset(buf, ' ', cfg->buf_width);
+       buf[cfg->buf_width] = '\0';
+       seplen = strlen(cfg->separator);
+       /* Set the separators */
+       for (s = cfg->slots; s; s = s->next) {
+               /* Skip the first, left-most */
+               if (s->out_pos_lo) {
+                       /* Copying only seplen ensures we omit the '\0' byte. */
+                       strncpy(
+                           buf + (s->out_pos_lo - seplen),
+                           cfg->separator,
+                           seplen
+                       );
+               }
+       }
+       return buf;
+}
+
+Slot *
+slots_rev(Slot *old)
+{
+       Slot *tmp = NULL;
+       Slot *new = NULL;
+
+       while (old) {
+               tmp       = old->next;
+               old->next = new;
+               new       = old;
+               old       = tmp;
+       }
+       return new;
+}
+
+void
+slot_log(Slot *s)
+{
+       khlib_info("Slot "
+           "{"
+           " in_fifo = %s,"
+           " in_fd = %d,"
+           " out_width = %d,"
+           " in_last_read = {tv_sec = %ld, tv_nsec = %ld}"
+           " out_ttl = {tv_sec = %ld, tv_nsec = %ld},"
+           " out_pos_lo = %d,"
+           " out_pos_cur = %d,"
+           " out_pos_hi = %d,"
+           " next = %p,"
+           " }\n",
+           s->in_fifo,
+           s->in_fd,
+           s->out_width,
+           s->in_last_read.tv_sec,
+           s->in_last_read.tv_nsec,
+           s->out_ttl.tv_sec,
+           s->out_ttl.tv_nsec,
+           s->out_pos_lo,
+           s->out_pos_cur,
+           s->out_pos_hi,
+           s->next
+       );
+}
+
+void
+slots_log(Slot *head)
+{
+       Slot *s = head;
+
+       for (; s; s = s->next) {
+               slot_log(s);
+       }
+}
+
+void
+slots_assert_fifos_exist(Slot *s)
+{
+       struct stat st;
+       int errors = 0;
+
+       for (; s; s = s->next) {
+               if (lstat(s->in_fifo, &st) < 0) {
+                       khlib_error(
+                           "Cannot stat \"%s\". Error: %s\n",
+                           s->in_fifo,
+                           strerror(errno)
+                       );
+                       errors++;
+                       continue;
+               }
+               if (!(st.st_mode & S_IFIFO)) {
+                       khlib_error("\"%s\" is not a FIFO\n", s->in_fifo);
+                       errors++;
+                       continue;
+               }
+       }
+       if (errors)
+               khlib_fatal(
+                   "Encountered errors with given file paths. See log.\n"
+               );
+}
+
+void
+slot_close(Slot *s)
+{
+       close(s->in_fd);
+       s->in_fd        = -1;
+       s->out_pos_cur  = s->out_pos_lo;
+}
+
+void
+slots_close(Slot *s)
+{
+       for (; s; s = s->next)
+               if (s->in_fd > -1)
+                       slot_close(s);
+}
+
+
+void
+slot_expire(Slot *s, struct timespec t, char expiry_character, char *buf)
+{
+       struct timespec td;
+
+       timespecsub(&t, &(s->in_last_read), &td);
+       if (timespeccmp(&td, &(s->out_ttl), >=)) {
+               memset(
+                   buf + s->out_pos_lo,
+                   expiry_character,
+                   s->out_width
+               );
+               khlib_warn("Slot expired: \"%s\"\n", s->in_fifo);
+       }
+}
+
+void
+slot_set_error(Slot *s, char *buf)
+{
+       char *b;
+       int i;
+
+       s->in_fd = -1;
+       b = buf + s->out_pos_lo;
+       /* Copy as much of the error message as possible.
+        * EXCLUDING the terminating \0. */
+       for (i = 0; i < errlen && i < s->out_width; i++)
+               b[i] = errmsg[i];
+       /* Any remaining positions: */
+       memset(b + i, '_', s->out_width - i);
+}
+
+enum read_status
+slot_read(Slot *s, char *buf)
+{
+       char c;  /* Character read. */
+       int  r;  /* Remaining unused positions in buffer range. */
+
+       for (;;) {
+               switch (read(s->in_fd, &c, 1)) {
+               case -1:
+                       khlib_error(
+                           "Failed to read: \"%s\". errno: %d, msg: %s\n",
+                           s->in_fifo,
+                           errno,
+                           strerror(errno)
+                       );
+                       switch (errno) {
+                       case EINTR:
+                       case EAGAIN:
+                               return RETRY;
+                       default:
+                               return FAILURE;
+                       }
+               case  0:
+                       khlib_debug("%s: End of FILE\n", s->in_fifo);
+                       s->out_pos_cur = s->out_pos_lo;
+                       return END_OF_FILE;
+               case  1:
+                       /* TODO: Consider making msg term char a CLI option */
+                       if (c == '\n' || c == '\0') {
+                               r = (s->out_pos_hi - s->out_pos_cur) + 1;
+                               if (r > 0)
+                                       memset(buf + s->out_pos_cur, ' ', r);
+                               return END_OF_MESSAGE;
+                       } else {
+                               if (s->out_pos_cur <= s->out_pos_hi)
+                                       buf[s->out_pos_cur++] = c;
+                               else
+                                       /*
+                                        * Force EOM beyond available range.
+                                        * To ensure that a rogue large message
+                                        * doesn't trap us here needlessly
+                                        * long.
+                                        */
+                                       return END_OF_MESSAGE;
+                       }
+                       break;
+               default:
+                       assert(0);
+               }
+       }
+}
+
+void
+slots_read(Config *cfg, struct timespec *ti, char *buf)
+{
+       fd_set fds;
+       int maxfd = -1;
+       int ready = 0;
+       struct stat st;
+       struct timespec t;
+       Slot *s;
+
+       FD_ZERO(&fds);
+       for (s = cfg->slots; s; s = s->next) {
+               /* TODO: Create the FIFO if it doesn't already exist. */
+               if (lstat(s->in_fifo, &st) < 0) {
+                       khlib_error(
+                           "Cannot stat \"%s\". Error: %s\n",
+                           s->in_fifo,
+                           strerror(errno)
+                       );
+                       slot_set_error(s, buf);
+                       continue;
+               }
+               if (!(st.st_mode & S_IFIFO)) {
+                       khlib_error("\"%s\" is not a FIFO\n", s->in_fifo);
+                       slot_set_error(s, buf);
+                       continue;
+               }
+               if (s->in_fd < 0) {
+                       khlib_debug(
+                           "%s: closed. opening. in_fd: %d\n",
+                           s->in_fifo,
+                           s->in_fd
+                       );
+                       s->in_fd = open(s->in_fifo, O_RDONLY | O_NONBLOCK);
+               } else {
+                       khlib_debug(
+                           "%s: already openned. in_fd: %d\n",
+                           s->in_fifo,
+                           s->in_fd
+                       );
+               }
+               if (s->in_fd == -1) {
+                       /* TODO Consider backing off retries for failed slots */
+                       khlib_error("Failed to open \"%s\"\n", s->in_fifo);
+                       slot_set_error(s, buf);
+                       continue;
+               }
+               khlib_debug("%s: open. in_fd: %d\n", s->in_fifo, s->in_fd);
+               if (s->in_fd > maxfd)
+                       maxfd = s->in_fd;
+               FD_SET(s->in_fd, &fds);
+       }
+       khlib_debug("selecting...\n");
+       ready = pselect(maxfd + 1, &fds, NULL, NULL, ti, NULL);
+       khlib_debug("ready: %d\n", ready);
+       clock_gettime(CLOCK_MONOTONIC, &t);
+       if (ready == -1) {
+               switch (errno) {
+               case EINTR:
+                       khlib_error(
+                           "pselect interrupted: %d, errno: %d, msg: %s\n",
+                           ready,
+                           errno,
+                           strerror(errno)
+                       );
+                       /* TODO: Reconsider what to do here. */
+                       return;
+               default:
+                       khlib_fatal(
+                           "pselect failed: %d, errno: %d, msg: %s\n",
+                           ready,
+                           errno,
+                           strerror(errno)
+                       );
+               }
+       }
+       /* At-least-once ensures that expiries are still checked on timeouts. */
+       do {
+               for (s = cfg->slots; s; s = s->next) {
+                       if (s->in_fd < 0)
+                               continue;
+                       if (FD_ISSET(s->in_fd, &fds)) {
+                               khlib_debug("reading: %s\n", s->in_fifo);
+                               switch (slot_read(s, buf)) {
+                               /*
+                                * ### MESSAGE LOSS ###
+                                * is introduced by closing at EOM in addition
+                                * to EOF, since there may be unread messages
+                                * remaining in the pipe. However,
+                                *
+                                * ### INTER-MESSAGE PUSHBACK ###
+                                * is also gained, since pipes block at the
+                                * "open" call.
+                                *
+                                * This is an acceptable trade-off because we
+                                * are a stateless reporter of a _most-recent_
+                                * status, not a stateful accumulator.
+                                *
+                                * ### LOSSLESS ALTERNATIVES ###
+                                * - Read each pipe until EOF before reading
+                                *   another.
+                                *   PROBLEM: a fast writer can trap us in the
+                                *   read loop.
+                                *
+                                * - Read each pipe until EOM, but close only
+                                *   at EOF.
+                                *   PROBLEM: a fast writer can fill the pipe
+                                *   faster than we can read it and we end-up
+                                *   displaying stale data.
+                                *
+                                */
+                               case END_OF_MESSAGE:
+                               case END_OF_FILE:
+                               case FAILURE:
+                                       slot_close(s);
+                                       s->in_last_read = t;
+                                       ready--;
+                                       break;
+                               case RETRY:
+                                       break;
+                               default:
+                                       assert(0);
+                               }
+                       } else {
+                               slot_expire(s, t, cfg->expiry_character, buf);
+                       }
+               }
+       } while (ready);
+       assert(ready == 0);
+}
+
+void
+config_log(Config *cfg)
+{
+       khlib_info(
+           "Config "
+           "{"
+           " interval = %f,"
+           " separator = %s,"
+           " slot_count = %d,"
+           " buf_width = %d,"
+           " slots = ..."
+           " }\n",
+           cfg->interval,
+           cfg->separator,
+           cfg->slot_count,
+           cfg->buf_width
+       );
+       slots_log(cfg->slots);
+}
+
+void
+config_stretch_for_separators(Config *cfg)
+{
+       int seplen = strlen(cfg->separator);
+       int prefix = 0;
+       int nslots = 0;
+       Slot *s    = cfg->slots;
+
+       while (s) {
+               s->out_pos_lo  += prefix;
+               s->out_pos_hi  += prefix;
+               s->out_pos_cur  = s->out_pos_lo;
+               prefix         += seplen;
+               nslots++;
+               s = s->next;
+       }
+       cfg->buf_width += (seplen * (nslots - 1));
+}
 
 int
-is_pos_num(char *s)
+is_pos_num(char *str)
 {
-       while (*s != '\0')
-               if (!isdigit(*(s++)))
+       while (*str != '\0')
+               if (!isdigit(*(str++)))
                        return 0;
        return 1;
 }
 
+int
+is_decimal(char *str)
+{
+       char c;
+       int seen = 0;
+
+       while ((c = *(str++)) != '\0')
+               if (!isdigit(c)) {
+                       if (c == '.' && !seen++)
+                               continue;
+                       else
+                               return 0;
+               }
+       return 1;
+}
+
 void
 print_usage()
 {
        assert(argv0);
        fprintf(
-               stderr,
-               "\n"
-               "Usage: %s [OPTION ...] SPEC [SPEC ...]\n"
-               "\n"
-               "  SPEC       = FILE_PATH DATA_WIDTH DATA_TTL\n"
-               "  FILE_PATH  = string\n"
-               "  DATA_WIDTH = int  (* (positive) number of characters *)\n"
-               "  DATA_TTL   = int  (* (positive) number of seconds *)\n"
-               "  OPTION     = -i INTERVAL\n"
-               "             | -s SEPARATOR\n"
-               "  SEPARATOR  = string\n"
-               "  INTERVAL   = int  (* (positive) number of seconds *)\n"
-               "\n",
-               argv0
+           stderr,
+           "\n"
+           "Usage: %s [OPTION ...] SPEC [SPEC ...]\n"
+           "\n"
+           "  SPEC       = FILE_PATH DATA_WIDTH DATA_TTL\n"
+           "  FILE_PATH  = string\n"
+           "  DATA_WIDTH = int  (* (positive) number of characters *)\n"
+           "  DATA_TTL   = float  (* (positive) number of seconds *)\n"
+           "  OPTION     = -i INTERVAL\n"
+           "             | -s SEPARATOR\n"
+           "             | -x (* Output to X root window *)\n"
+           "             | -l LOG_LEVEL\n"
+           "             | -e EXPIRY_CHARACTER\n"
+           "  SEPARATOR  = string\n"
+           "  INTERVAL   = float  (* (positive) number of seconds *)\n"
+           "  LOG_LEVEL  = int  (* %d through %d *)\n"
+           "  EXPIRY_CHARACTER = string  "
+           "(* Character with which to fill the slot upon expiration. *)\n"
+           "\n",
+           argv0,
+           Nothing,
+           Debug
        );
        fprintf(
-               stderr,
-               "Example: %s -i 1 /dev/shm/khatus/khatus_sensor_x 4 10\n"
-               "\n",
-               argv0
+           stderr,
+           "Example: %s -i 1 /dev/shm/khatus/khatus_sensor_x 4 10\n"
+           "\n",
+           argv0
        );
 }
 
-void opts_parse_any(Config *, int, char *[], int);  /* For mutually-recursive calls. */
+/* For mutually-recursive calls. */
+void opts_parse_any(Config *, int, char *[], int);
 
 void
 parse_opts_opt_i(Config *cfg, int argc, char *argv[], int i)
 {
-       if (i < argc) {
-               char *param = argv[i++];
+       char *param;
 
-               if (is_pos_num(param)) {
-                       cfg->interval = atoi(param);
-                       opts_parse_any(cfg, argc, argv, i);
-               } else {
-                       usage("Option -i parameter is invalid: \"%s\"\n", param);
-               }
-       } else {
+       if (i >= argc)
                usage("Option -i parameter is missing.\n");
-       }
+       param = argv[i++];
+       if (!is_decimal(param))
+               usage("Option -i parameter is invalid: \"%s\"\n", param);
+       cfg->interval = atof(param);
+       opts_parse_any(cfg, argc, argv, i);
 }
 
 void
 parse_opts_opt_s(Config *cfg, int argc, char *argv[], int i)
 {
-       if (i < argc) {
-               cfg->separator = malloc((strlen(argv[i]) + 1) * sizeof(char));
-               strcpy(cfg->separator, argv[i]);
-               opts_parse_any(cfg, argc, argv, ++i);
-       } else {
+       if (i >= argc)
                usage("Option -s parameter is missing.\n");
-       }
+       cfg->separator = calloc((strlen(argv[i]) + 1), sizeof(char));
+       strcpy(cfg->separator, argv[i]);
+       opts_parse_any(cfg, argc, argv, ++i);
 }
 
 void
-parse_opts_opt_t(Config *cfg, int argc, char *argv[], int i)
+parse_opts_opt_l(Config *cfg, int argc, char *argv[], int i)
 {
-       if (i < argc) {
-               cfg->timefmt = malloc((strlen(argv[i]) + 1) * sizeof(char));
-               strcpy(cfg->timefmt, argv[i]);
-               opts_parse_any(cfg, argc, argv, ++i);
-       } else {
-               usage("Option -t parameter is missing.\n");
-       }
+       char *param;
+       int log_level;
+
+       if (i >= argc)
+               usage("Option -l parameter is missing.\n");
+       param = argv[i++];
+       if (!is_pos_num(param))
+               usage("Option -l parameter is invalid: \"%s\"\n", param);
+       log_level = atoi(param);
+       if (log_level > Debug)
+               usage(
+                   "Option -l value (%d) exceeds maximum (%d)\n",
+                   log_level,
+                   Debug
+               );
+       _khlib_log_level = log_level;
+       opts_parse_any(cfg, argc, argv, i);
+}
+
+void
+parse_opts_opt_e(Config *cfg, int argc, char *argv[], int i)
+{
+       if (i >= argc)
+               usage("Option -e parameter is missing.\n");
+       cfg->expiry_character = argv[i++][0];
+       opts_parse_any(cfg, argc, argv, i);
 }
 
 void
 parse_opts_opt(Config *cfg, int argc, char *argv[], int i)
 {
        switch (argv[i][1]) {
-               case 'i': parse_opts_opt_i(cfg, argc, argv, ++i); break;  /* TODO: Generic set_int */
-               case 's': parse_opts_opt_s(cfg, argc, argv, ++i); break;  /* TODO: Generic set_str */
-               case 't': parse_opts_opt_t(cfg, argc, argv, ++i); break;  /* TODO: Generic set_str */
-               default : usage("Option \"%s\" is invalid\n", argv[i]);
+       case 'i':
+               /* TODO: Generic set_int */
+               parse_opts_opt_i(cfg, argc, argv, ++i);
+               break;
+       case 's':
+               /* TODO: Generic set_str */
+               parse_opts_opt_s(cfg, argc, argv, ++i);
+               break;
+       case 'x':
+               cfg->to_x_root = 1;
+               opts_parse_any(cfg, argc, argv, ++i);
+               break;
+       case 'l':
+               /* TODO: Generic set_int */
+               parse_opts_opt_l(cfg, argc, argv, ++i);
+               break;
+       case 'e':
+               /* TODO: Generic set_str */
+               parse_opts_opt_e(cfg, argc, argv, ++i);
+               break;
+       default :
+               usage("Option \"%s\" is invalid\n", argv[i]);
        }
 }
 
 void
 parse_opts_spec(Config *cfg, int argc, char *argv[], int i)
 {
+       char *n;
+       char *w;
+       char *t;
+       struct timespec in_last_read;
+       Slot *s;
+
        if ((i + 3) > argc)
-               usage("[spec] Parameter(s) missing for file \"%s\".\n", argv[i]);
+               usage(
+                   "[spec] Parameter(s) missing for fifo \"%s\".\n",
+                   argv[i]
+               );
 
-       char *n = argv[i++];
-       char *w = argv[i++];
-       char *t = argv[i++];
+       n = argv[i++];
+       w = argv[i++];
+       t = argv[i++];
 
        if (!is_pos_num(w))
-               usage("[spec] Invalid width: \"%s\", for file \"%s\"\n", w, n);
-       if (!is_pos_num(t))
-               usage("[spec] Invalid TTL: \"%s\", for file \"%s\"\n", t, n);
-       File *f = malloc(sizeof(struct File));
-       if (f) {
-               f->name      = n;
-               f->fd        = -1;
-               f->width     = atoi(w);
-               f->ttl       = atoi(t);
-               f->last_read = 0;
-               f->pos       = cfg->total_width;
-               f->next      = cfg->files;
-
-               cfg->files        = f;
-               cfg->total_width += f->width;
-               cfg->file_count++;
+               usage("[spec] Invalid width: \"%s\", for fifo \"%s\"\n", w, n);
+       if (!is_decimal(t))
+               usage("[spec] Invalid TTL: \"%s\", for fifo \"%s\"\n", t, n);
+
+       in_last_read.tv_sec  = 0;
+       in_last_read.tv_nsec = 0;
+       s = calloc(1, sizeof(struct Slot));
+
+       if (s) {
+               s->in_fifo      = n;
+               s->in_fd        = -1;
+               s->out_width    = atoi(w);
+               s->out_ttl      = khlib_timespec_of_float(atof(t));
+               s->in_last_read = in_last_read;
+               s->out_pos_lo   = cfg->buf_width;
+               s->out_pos_cur  = s->out_pos_lo;
+               s->out_pos_hi   = s->out_pos_lo + s->out_width - 1;
+               s->next         = cfg->slots;
+
+               cfg->slots        = s;
+               cfg->buf_width += s->out_width;
+               cfg->slot_count++;
        } else {
-               fatal("[memory] Allocation failure.");
+               khlib_fatal("[memory] Allocation failure.");
        }
        opts_parse_any(cfg, argc, argv, i);
 }
@@ -180,112 +649,102 @@ opts_parse_any(Config *cfg, int argc, char *argv[], int i)
 {
        if (i < argc) {
                switch (argv[i][0]) {
-                       case '-': parse_opts_opt(cfg, argc, argv, i); break;
-                       default : parse_opts_spec(cfg, argc, argv, i);
+               case '-':
+                       parse_opts_opt(cfg, argc, argv, i);
+                       break;
+               default :
+                       parse_opts_spec(cfg, argc, argv, i);
                }
        }
 }
 
 void
-opts_parse(Config *cfg, int argc, char *argv[], int i)
+opts_parse(Config *cfg, int argc, char *argv[])
 {
        opts_parse_any(cfg, argc, argv, 1);
-
-       File *last = cfg->files;
-       cfg->files = NULL;
-       for (File *f = last; f; ) {
-               File *next = f->next;
-               f->next = cfg->files;
-               cfg->files = f;
-               f = next;
-       }
+       cfg->slots = slots_rev(cfg->slots);
+       config_log(cfg);
+       if (cfg->slots == NULL)
+               usage("No slot specs were given!\n");
 }
 
 void
-read_all(Config *cfg, char *buf)
+loop(Config *cfg, char *buf, Display *d)
 {
-       /* TODO: stat then check TTL */
-       for (File *f = cfg->files; f; f = f->next) {
-               if (f->fd < 0)
-                       f->fd = open(f->name, O_RDONLY);
-               if (f->fd == -1) {
-                       /* TODO: Consider backing off retries for failed files. */
-                       fatal("Failed to open \"%s\"\n", f->name);
+       struct timespec
+               t0,  /* time stamp. before reading slots */
+               t1,  /* time stamp. after  reading slots */
+               ti,  /* time interval desired    (t1 - t0) */
+               td,  /* time interval measured   (t1 - t0) */
+               tc;  /* time interval correction (ti - td) when td < ti */
+
+       ti = khlib_timespec_of_float(cfg->interval);
+       while (running) {
+               clock_gettime(CLOCK_MONOTONIC, &t0); // FIXME: check errors
+               slots_read(cfg, &ti, buf);
+               if (cfg->to_x_root) {
+                       if (XStoreName(d, DefaultRootWindow(d), buf) < 0)
+                               khlib_fatal("XStoreName failed.\n");
+                       XFlush(d);
                } else {
-                       lseek(f->fd, 0, 0);
-                       ssize_t n = read(f->fd, buf + f->pos, f->width);
-                       int lasti = n + f->pos - 1;
-                       char lastc = buf[lasti];
-                       if (lastc == '\n')
-                               buf[lasti] = ' ';
+                       puts(buf);
+                       fflush(stdout);
+               }
+               clock_gettime(CLOCK_MONOTONIC, &t1); // FIXME: check errors
+               timespecsub(&t1, &t0, &td);
+               khlib_debug(
+                   "td {tv_sec = %ld, tv_nsec = %ld}\n",
+                   td.tv_sec,
+                   td.tv_nsec
+               );
+               if (timespeccmp(&td, &ti, <)) {
+                       /*
+                        * Pushback on data producers by refusing to read the
+                        * pipe more frequently than the interval.
+                        */
+                       timespecsub(&ti, &td, &tc);
+                       khlib_sleep(&tc);
                }
        }
 }
 
+void
+terminate(int s)
+{
+       khlib_debug("terminating due to signal %d\n", s);
+       running = 0;
+}
+
 int
 main(int argc, char *argv[])
 {
-       int width;
-       int nfiles = 0;
-       int seplen;
-       int prefix = 0;
-       char *buf;
-       Config *cfg = &defaults;
-
        argv0 = argv[0];
 
-       opts_parse(cfg, argc, argv, 1);
-       debug("argv0 = %s\n", argv0);
-       debug("[config] interval    = %d\n", cfg->interval);
-       debug("[config] separator   = %s\n", cfg->separator);
-       debug("[config] file_count  = %d\n", cfg->file_count);
-       debug("[config] total_width = %d\n", cfg->total_width);
-       if (cfg->files == NULL)
-               usage("No file specs were given!\n");
-       for (File *f = cfg->files; f; f = f->next) {
-               debug(
-                       "[config] file = "
-                       "{"
-                               " name = %s,"
-                               " pos = %d,"
-                               " width = %d,"
-                               " ttl = %d,"
-                               " last_read = %d,"
-                       " }\n",
-                       f->name,
-                       f->pos,
-                       f->width,
-                       f->ttl,
-                       f->last_read
-               );
-       }
-
-       width  = cfg->total_width;
-       seplen = strlen(cfg->separator);
+       Config cfg = {
+               .interval    = 1.0,
+               .separator   = "|",
+               .expiry_character = '_',
+               .slots       = NULL,
+               .slot_count  = 0,
+               .buf_width   = 0,
+               .to_x_root   = 0,
+       };
+       char *buf;
+       Display *d = NULL;
+       struct sigaction sa;
 
-       /* 1st pass to make space for separators */
-       for (File *f = cfg->files; f; f = f->next) {
-               f->pos += prefix;
-               prefix += seplen;
-               nfiles++;
-       }
-       width += (seplen * (nfiles - 1));
-       buf = malloc(width + 1);
-       if (buf == NULL)
-               fatal("[memory] Failed to allocate buffer of %d bytes", width);
-       memset(buf, ' ', width);
-       buf[width] = '\0';
-       /* 2nd pass to set the separators */
-       for (File *f = cfg->files; f; f = f->next) {
-               if (f->pos) {  /* Skip the first, left-most */
-                       strcpy(buf + (f->pos - seplen), cfg->separator);
-               }
-       }
+       memset(&sa, 0, sizeof(sa));
+       sa.sa_handler = terminate;
+       sigaction(SIGTERM, &sa, NULL);
+       sigaction(SIGINT , &sa, NULL);
 
-       /* TODO: nanosleep and nano time diff */
-       for (;;) {
-               read_all(cfg, buf);
-               printf("%s\n", buf);
-               sleep(cfg->interval);
-       }
+       opts_parse(&cfg, argc, argv);
+       slots_assert_fifos_exist(cfg.slots);
+       config_stretch_for_separators(&cfg);
+       buf = buf_create(&cfg);
+       if (cfg.to_x_root && !(d = XOpenDisplay(NULL)))
+               khlib_fatal("XOpenDisplay failed with: %p\n", d);
+       loop(&cfg, buf, d);
+       slots_close(cfg.slots);
+       return EXIT_SUCCESS;
 }
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