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Introduce example program for viewing BBS art
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‎examples/art.c

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#if 0
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/*─────────────────────────────────────────────────────────────────╗
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│ To the extent possible under law, Justine Tunney has waived │
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│ all copyright and related or neighboring rights to this file, │
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│ as it is written in the following disclaimers: │
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│ • http://unlicense.org/ │
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│ • http://creativecommons.org/publicdomain/zero/1.0/ │
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╚─────────────────────────────────────────────────────────────────*/
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <getopt.h>
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#include <iconv.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <termios.h>
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#include <time.h>
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#include <unistd.h>
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/**
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* @fileoverview program for viewing bbs art files
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* @see http://www.textfiles.com/art/
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*/
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#define INBUFSZ 256
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#define OUBUFSZ (INBUFSZ * 6)
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#define SLIT(s) ((unsigned)s[3] << 24 | s[2] << 16 | s[1] << 8 | s[0])
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volatile sig_atomic_t got_signal;
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void on_signal(int sig) {
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got_signal = 1;
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}
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void process_file(const char *path, int fd, iconv_t cd, int baud_rate) {
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char input_buffer[INBUFSZ];
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char output_buffer[OUBUFSZ];
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size_t input_left, output_left;
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char *input_ptr, *output_ptr;
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struct timespec next = timespec_mono();
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for (;;) {
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// read from file
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ssize_t bytes_read = read(fd, input_buffer, INBUFSZ);
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if (bytes_read == -1) {
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perror(path);
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exit(1);
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}
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if (!bytes_read)
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break;
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// modernize character set
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input_ptr = input_buffer;
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input_left = bytes_read;
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output_ptr = output_buffer;
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output_left = OUBUFSZ;
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if (iconv(cd, &input_ptr, &input_left, &output_ptr, &output_left) ==
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(size_t)-1) {
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perror(path);
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exit(1);
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}
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// write to terminal
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for (char *p = output_buffer; p < output_ptr; p++) {
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if (got_signal)
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return;
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write(STDOUT_FILENO, p, 1);
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// allow arrow keys to change baud rate
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char key[4] = {0};
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if (read(STDIN_FILENO, key, sizeof(key)) > 0) {
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if (SLIT(key) == SLIT("\e[A") || // up
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SLIT(key) == SLIT("\e[C")) { // right
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baud_rate *= 1.4;
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} else if (SLIT(key) == SLIT("\e[B") || // down
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SLIT(key) == SLIT("\e[D")) { // left
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baud_rate *= 0.6;
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}
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}
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// insert artificial delay for one byte. we divide by 10 to convert
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// bits to bytes, because that is how many bits 8-N-1 encoding used
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next = timespec_add(next, timespec_fromnanos(1e9 / (baud_rate / 10.)));
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usleep(timespec_tomicros(timespec_subz(next, timespec_mono())));
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}
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}
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}
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int main(int argc, char *argv[]) {
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// "When new technology comes out, people don't all buy it right away.
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// If what they have works, some will wait until it doesn't. A few
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// people do get the latest though. In 1984 2400 baud modems became
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// available, so some people had them, but many didn't. A BBS list
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// from 1986 shows operators were mostly 300 and 1200, but some were
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// using 2400. The next 5 years were the hayday of the 2400."
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//
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// https://forum.vcfed.org/index.php?threads/the-2400-baud-modem.44241/
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int baud_rate = 2400; // -b 2400
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const char *from_charset = "CP437"; // -f CP437
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const char *to_charset = "UTF-8"; // -t UTF-8
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int opt;
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while ((opt = getopt(argc, argv, "hb:f:t:")) != -1) {
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switch (opt) {
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case 'b': {
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char *endptr;
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double rate = strtod(optarg, &endptr);
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if (*endptr == 'k') {
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rate *= 1e3;
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++endptr;
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} else if (*endptr == 'm') {
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rate *= 1e6;
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++endptr;
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}
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if (*endptr || baud_rate <= 0) {
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fprintf(stderr, "%s: invalid baud rate: %s\n", argv[0], optarg);
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exit(1);
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}
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baud_rate = rate;
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break;
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}
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case 'f':
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from_charset = optarg;
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break;
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case 't':
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to_charset = optarg;
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break;
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case 'h':
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fprintf(stderr, "\
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Usage:\n\
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%s [-b BAUD] [-f CP437] [-t UTF-8] FILE...\n\
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\n\
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Supported charsets:\n\
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utf8, wchart, ucs2be, ucs2le, utf16be, utf16le, ucs4be, ucs4le,\n\
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ascii, utf16, ucs4, ucs2, eucjp, shiftjis, iso2022jp, gb18030, gbk,\n\
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gb2312, big5, euckr, iso88591, latin1, iso88592, iso88593, iso88594,\n\
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iso88595, iso88596, iso88597, iso88598, iso88599, iso885910,\n\
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iso885911, iso885913, iso885914, iso885915, iso885916, cp1250,\n\
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windows1250, cp1251, windows1251, cp1252, windows1252, cp1253,\n\
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windows1253, cp1254, windows1254, cp1255, windows1255, cp1256,\n\
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windows1256, cp1257, windows1257, cp1258, windows1258, koi8r, koi8u,\n\
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cp437, cp850, cp866, ibm1047, cp1047.\n\
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\n\
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See also:\n\
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http://www.textfiles.com/art/\n\
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\n",
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argv[0]);
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exit(0);
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default:
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fprintf(stderr, "protip: pass the -h flag for help\n");
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exit(1);
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}
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}
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if (optind == argc) {
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fprintf(stderr, "%s: missing operand\n", argv[0]);
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exit(1);
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}
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iconv_t cd = iconv_open(to_charset, from_charset);
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if (cd == (iconv_t)-1) {
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fprintf(stderr, "error: conversion from %s to %s not supported\n",
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from_charset, to_charset);
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exit(1);
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}
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// catch ctrl-c
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signal(SIGINT, on_signal);
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// don't wait until newline to read() keystrokes
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struct termios t;
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if (!tcgetattr(STDIN_FILENO, &t)) {
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struct termios t2 = t;
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t2.c_lflag &= ~(ICANON | ECHO);
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tcsetattr(STDIN_FILENO, TCSANOW, &t2);
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}
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// make stdin nonblocking
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fcntl(STDIN_FILENO, F_SETFL, fcntl(STDIN_FILENO, F_GETFL) | O_NONBLOCK);
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// hide cursor
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write(STDOUT_FILENO, "\e[?25l", 6);
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// Process each file specified on the command line
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for (int i = optind; i < argc && !got_signal; i++) {
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int fd = open(argv[i], O_RDONLY);
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if (fd == -1) {
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perror(argv[i]);
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continue;
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}
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process_file(argv[i], fd, cd, baud_rate);
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close(fd);
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}
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// cleanup
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iconv_close(cd);
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// show cursor
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write(STDOUT_FILENO, "\e[?25h", 6);
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// restore terminal
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tcsetattr(STDIN_FILENO, TCSANOW, &t);
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}

‎libc/calls/usleep.c

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* @norestart
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*/
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int usleep(uint64_t micros) {
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errno_t err;
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struct timespec ts = timespec_frommicros(micros);
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err = clock_nanosleep(CLOCK_REALTIME, 0, &ts, 0);
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if (err)
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return errno = err, -1;
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// All OSes except OpenBSD return instantly on usleep(0). So we might
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// as well avoid system call overhead and helping OpenBSD work better
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if (micros) {
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errno_t err;
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struct timespec ts = timespec_frommicros(micros);
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err = clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, 0);
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if (err)
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return errno = err, -1;
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}
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return 0;
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}

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