Recreate py util for generating random markdown file.

*It's more than 10x faster*

Author: 1Git2Clone

utils/generate_markdown/Cargo.lock

@@ -0,0 +1,10 @@
+[package]
+name = "generate_markdown"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+# `char::from`: be743d53d3404c9b13486c266b3b982fdd6c38ed | ~0.81s
+# unsafe `String` as mut vec extend: 4148dc7b01bb7d5b62817c660d64620652242c91 | ~0.61s
+# Branchless jump (using `char::from`): 4148dc7b01bb7d5b62817c660d64620652242c91 | ~0.81s
+rand = { git = "https://github.com/1Git2Clone/rand", rev = "4148dc7b01bb7d5b62817c660d64620652242c91" }

utils/generate_markdown/Cargo.toml

@@ -0,0 +1,57 @@
+/*!
+Mainly made for benchmarking `taboc`.
+
+The performance (Ryzen 5 3600X):
+
+```sh
+time taboc output.md --allow-dirty
+# taboc output.md --allow-dirty  0.89s user 0.40s system 97% cpu 1.321 total
+```
+*/
+
+use rand::{
+    distr::{Alphabetic, SampleString},
+    prelude::*,
+};
+use std::{
+    fs::OpenOptions,
+    io::{BufWriter, Write},
+};
+
+const RAND_CHAR_COUNT: usize = 128;
+const LINE_COUNT: usize = 1_000_000;
+
+fn generate_heading_level(rng: &mut ThreadRng) -> u32 {
+    rng.next_u32() % 6
+}
+
+fn generate_heading(rng: &mut ThreadRng) -> String {
+    Alphabetic.sample_string(rng, RAND_CHAR_COUNT)
+}
+
+fn main() -> std::io::Result<()> {
+    let file = OpenOptions::new()
+        .create(true)
+        .truncate(true)
+        .write(true)
+        .read(true)
+        .open("output.md")?;
+    let mut writer = BufWriter::new(file);
+    let mut rng = rand::rng();
+
+    // Taboc requires the first two headings to be proper markdown headings.
+    // (Otherwise it'd just insert itself in a wrong section).
+    writer.write_all(format!("# {}\n\n", generate_heading(&mut rng)).as_bytes())?;
+    writer.write_all(format!("## {}\n\n", generate_heading(&mut rng)).as_bytes())?;
+
+    for _ in 3..=LINE_COUNT {
+        let line = format!(
+            "{} {}\n\n",
+            "#".repeat(generate_heading_level(&mut rng) as usize + 1),
+            generate_heading(&mut rng)
+        );
+        writer.write_all(line.as_bytes())?;
+    }
+
+    Ok(())
+}