grain.c

/*
 * A terminal character rain toy just like the famous *matrix*
 * make sure your terminal supports 256 color
 */

#include <math.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <time.h>
#include <unistd.h>

// length of "\e[38;5NmX" is no more than 13
#define STR_UNIT 16
#define min(x, y)                                                              \
  ({                                                                           \
    typeof(x) _x = (x);                                                        \
    typeof(y) _y = (y);                                                        \
    (_x < _y) ? _x : _y;                                                       \
  })
#define dye(r, g, b) ((r)*36 + (g)*6 + (b) + 16)

struct rgb_t {
  short r : 4;
  short g : 4;
  short b : 4;
  short a : 4;
};

void alloc_scene(char ****pscene, struct winsize *pwsz) {
  *pscene = (char ***)malloc(sizeof(char **) * (pwsz->ws_row + 1));
  int i, j;
  for (i = 0; i < pwsz->ws_row + 1; i++) {
    (*pscene)[i] = (char **)malloc(sizeof(char *) * pwsz->ws_col);
    if (!(*pscene)[i]) {
      perror("memory allocation failure.\n");
      abort();
    }
    for (j = 0; j < pwsz->ws_col; j++) {
      (*pscene)[i][j] = (char *)calloc(STR_UNIT, sizeof(char));
      if (!(*pscene)[i][j]) {
        perror("memory allocation failure.\n");
        abort();
      }
    }
  }
  return;
}

void free_scene(char ***scene, struct winsize *pwsz) {
  int i, j;
  for (i = 0; i < pwsz->ws_row + 1; i++) {
    for (j = 0; j < pwsz->ws_col; j++) {
      free(scene[i][j]);
    }
    free(scene[i]);
  }
  free(scene);
  return;
}

void copy_scene(char ***dst, char ***src, int ws_row, int ws_col) {
  for (int i = 0; i < ws_row + 1; i++) {
    for (int j = 0; j < ws_col; j++) {
      strcpy(dst[i][j], src[i][j]);
    }
  }
}

void init_scene(char ***scene, struct winsize *pwsz, struct rgb_t c) {
  int i, j;
  for (j = 0; j < pwsz->ws_col; j++) {
    scene[0][j][14] = rand() % 8; // str[14]: color depth
    scene[0][j][15] = 1;          // str[15]: speed factor
    sprintf(scene[0][j],
            "\e[38;5;%dm"
            "%c",
            dye(c.r, c.g, c.b),            // just green
            (char)(0x20 + rand() % 0x5f)); // all visible ascii
  }
  for (i = 1; i < pwsz->ws_row; i++) {
    for (j = 0; j < pwsz->ws_col; j++) {
      scene[i][j][0] = ' '; // fill it with space
    }
  }
}

void dump_scene(char ***scene, struct winsize *pwsz, struct rgb_t c) {
  int i, j;
  for (j = 0; j < pwsz->ws_col; j++) {
    if (scene[0][j][14] == 6) {
      scene[0][j][14] = 2 + (rand() + j) % 4;
    } else if (rand() % (1 + scene[0][j][14]) == 0) {
      scene[0][j][14] = (scene[0][j][14] + 6) % 7;
    }
    sprintf(scene[0][j],
            "\e[38;5;%dm"
            "%c",
            dye(c.r * scene[0][j][14] / 6, c.g * scene[0][j][14] / 6,
                c.b * scene[0][j][14] / 6),
            (char)(0x20 + rand() % 0x5f));
  }
  for (i = pwsz->ws_row; i > 0; i--) {
    for (j = 0; j < pwsz->ws_col; j++) {
      if (scene[i - 1][j][15] == 0) {
        scene[i - 1][j][15] =
            rand() % (2 + 2 * (pwsz->ws_row - i) / pwsz->ws_row);
        strcpy(scene[i][j], scene[i - 1][j]);
      } else {
        scene[i - 1][j][15]--;
      }
    }
  }
  return;
}

void print_sence(char ***scene, struct winsize *pwsz) {
  int i, j;
  printf("\e[1;1H"); // set cursor to (1,1)
  for (i = 1; i <= pwsz->ws_row; i++) {
    for (j = 0; j < pwsz->ws_col; j++) {
      printf("%s", scene[i][j]);
    }
  }
  fflush(stdout);
  return;
}

int pflag = 1; // set it to 0 for pause

void hquit() {
  // pop & show cursor, recover style, clear screen
  puts("\e[u"
       "\e[?25h"
       "\e[0m"
       "\e[2J");
  exit(0);
}

void hpause() { pflag = !pflag; }

int main(int argc, char *argv[]) {
  if (argc > 1) {
    puts("please run this program without argument");
    puts("Usage:");
    puts("\tCtrl+z for pause");
    puts("\tCtrl+c for quit");
    return 0;
  }

  char ***scene;
  struct winsize wsz;
  struct rgb_t color = {0, 5, 0, 0};
  // get terminal size(in characters)
  ioctl(fileno(stdout), TIOCGWINSZ, (char *)&wsz);
  alloc_scene(&scene, &wsz);
  srand(time(0));
  init_scene(scene, &wsz, color);
  // register INT handlers, optional
  signal(SIGINT, hquit);
  signal(SIGTSTP, hpause);

  char ***tscene;
  struct winsize twsz;
  int cnt = 0;
  int rainbowcnt = 0;
  // push & hide cursor
  puts("\e[s"
       "\e[25?l");
  while (1) { // add more interactive features here
    if (cnt++ == 5) {
      cnt = 0;
      ioctl(fileno(stdout), TIOCGWINSZ, (char *)&twsz);
      if (twsz.ws_col != wsz.ws_col || twsz.ws_row != wsz.ws_row) {
        alloc_scene(&tscene, &twsz);
        init_scene(tscene, &twsz, color);
        copy_scene(tscene, scene, min(wsz.ws_row, twsz.ws_row),
                   min(wsz.ws_col, twsz.ws_col));
        free_scene(scene, &wsz);
        scene = tscene;
        wsz = twsz;
      }
    }
    if (pflag) {
      dump_scene(scene, &wsz, color);
      print_sence(scene, &wsz);
    } else {
      fflush(stdout);
      while (!pflag)
        ;
    }
    usleep(40000); // fps = 1,000,000 / 40,000 = 25hz
    rainbowcnt++;
    if (rainbowcnt == 20) { // rainbow!
      color.r = rand() % 6;
      color.g = rand() % 6;
      color.b = rand() % 6;
      rainbowcnt = 0;
    }
  }
  return 0;
}