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Moved baud into git

This commit is contained in:
Neale Pickett 2023-09-25 12:42:53 -06:00
parent e1dabd53d3
commit fd0b6021b9
2 changed files with 0 additions and 132 deletions
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80
content/misc/baud/baud.c
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/*
* Pretend to be a modem by throttling output.
*
* 2023-09-12
* Neale Pickett <neale@woozle.org>
*
* To the extent possible under law,
* I waive all copyright and related or neighboring rights to this software.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <sysexits.h>
#include <unistd.h>
const int MICROSECOND = 1;
const int MILLISECOND = 1000 * MICROSECOND;
const int SECOND = 1000 * MILLISECOND;
const int NOISINESS_DENOMINATOR = 36000;
const int NOISELEN_DEFAULT = 16;
int
usage(char *me, char *error) {
if (error) {
fprintf(stderr, "ERROR: %s\n", error);
}
fprintf(stderr, "Usage: %s BAUD [NOISINESS] [NOISELEN]\n", me);
fprintf(stderr, "\n");
fprintf(stderr, "Reads stdin, and writes it back to stdout at BAUD bits per second.\n");
fprintf(stderr, "\n");
fprintf(stderr, "NOISINESS\tEvery bit can begin line noise, with probability NOISINESS/%d\n", NOISINESS_DENOMINATOR);
fprintf(stderr, "NOISELEN\tUp to this many bits of noise happens per burst (default: %d)\n", NOISELEN_DEFAULT);
return EX_USAGE;
}
int
main(int argc, char *argv[]) {
if (argc < 2) {
return usage(argv[0], NULL);
}
int baud = atoi(argv[1]);
if (baud < 1) {
return usage(argv[0], "Invalid baud rate");
}
int noisiness = 0;
if (argc > 2) {
noisiness = atoi(argv[2]);
}
int noiselen = NOISELEN_DEFAULT;
if (argc > 3) {
noiselen = atoi(argv[3]);
}
int cps = baud / 10; // 8N1 has 10 bits per octet: 8 data, 1 start, 1 parity
int delay = SECOND / cps;
int noisybits = 0;
int c;
while ((c = getchar()) != EOF) {
usleep(delay);
for (int bit = 0; bit < 8; bit++) {
int r = rand() % NOISINESS_DENOMINATOR;
if (r < noisiness) {
noisybits = rand() % noiselen;
}
if (noisybits) {
c ^= (rand() & 1) << bit;
noisybits -= 1;
}
}
putchar(c);
fflush(stdout);
}
return EX_OK;
}

52
content/misc/baud/index.md
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---
title: baud.c
---
[baud.c](baud.c) is a program to simulate going through a modem.
It reads stdin, and prints it to stdout at the provided baud rate (bits per second).
Building
--------
Download [baud.c](baud.c). Change to that directory, and type
make baud
That will generate a file named `baud` in whatever directory you're in.
If you like,
you can put it in `~/bin` or `~/.local/bin` or `/usr/games/bin` or
wherever you prefer.
Running
-------
If you'd like to see what life was like when I got my first modem, try
cat file | ./baud 110 40
Run that for a few hours, then try
cat file | ./baud 1200 20
And you will understand how mind-blowingly fast 1200 baud modems were at the time.
frotz zork1.zip | ./baud 4800
Gives Zork a retro vibe,
without being so slow that it's aggravating.
I don't think more than a dozen or so people every played Zork over a modem link,
but whatever.
Why
---
Every 10 years or so, somebody asks me for this program.
I don't know why.
The other day it happened again, and I couldn't find it soon enough,
so I just wrote it again from scratch.
I'm putting it on my web site so I don't have to write it again.