ansi-player.c

// SPDX-License-Identifier: 0BSD OR MIT-0 OR Unlicense OR CC0-1.0+
// Copyright © 2022 Ryan Castellucci, no rights reserved

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>

#define FRAME_DELAY 36496350ULL

int64_t get_nanoseconds(void) {
  int64_t r;
  struct timespec ts;
  r = clock_gettime(CLOCK_MONOTONIC, &ts);
  if (r < 0)
    return -1;
  r = ts.tv_nsec + ts.tv_sec * 1000000000;
  return r;
}

int main(int argc, char **argv) {
  int fd, frame_len, dropped = 0;
  struct stat statbuf;
  unsigned char *input, *frame, *frame_end;

  struct timespec ts_wait, ts_slept;

  int64_t ns_now, ns_then, ns_wait;

  if (argc != 2) {
    fprintf(stderr, "Usage: %s filename\n", argv[0]);
    return -1;
  }

  if ((fd = open(argv[1], O_RDONLY)) < 0) {
    fprintf(stderr, "failed to open input file");
    return 1;
  }

  if (fstat(fd, &statbuf) < 0) {
    fprintf(stderr, "failed to stat input file");
    return 1;
  }

  if ((input = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
    fprintf(stderr, "failed to mmap input file");
    return 1;
  }

  // move cursor and clear screen
  fwrite("\033[1;1H\033[2J", 10, 1, stdout);

  // initialize clocking
  ns_then = get_nanoseconds();

  frame = input;
  while (frame < input + statbuf.st_size) {
    if (!(frame_end = strstr(frame+1, "\033[H"))) {
      if (!(frame_end = strstr(frame+1, "\033[m"))) break;
    }
    frame_len = frame_end - frame;
    ns_now = get_nanoseconds();
    ns_wait = ns_then - ns_now;
    double delay = (double)ns_wait / 1000000000;
    fprintf(stdout, "\033[G\033[2K  next %7.4f (%u bytes, %u frames dropped)\033[G", delay, frame_len, dropped);
    fflush(stdout);
    if (ns_wait > 0) {
      ts_wait.tv_sec  = ns_wait / 1000000000;
      ts_wait.tv_nsec = ns_wait % 1000000000;
      nanosleep(&ts_wait, &ts_slept);
    } else if (ns_wait < -10000000000) {
      fprintf(stdout, "\033[2KYour connection is too slow to play this, sorry.\n");
      break;
    }
    // drop or display frame
    if (ns_wait > -100000000) {
      fwrite(frame, frame_len, 1, stdout);
      fwrite("\033[m", 3, 1, stdout);
      fflush(stdout);
    } else {
      dropped += 1;
    }

    frame += frame_len;
    ns_then += FRAME_DELAY;
  }

  // reset attributes
  fwrite("\033[G\033[2K\033[0m", 11, 1, stdout);
  fflush(stdout);

  return 0;
}

/* vim: set ts=2 sw=2 et ai si: */