init simple project that reads a file, generates a random lowercase character and writes counts so far to a file

src/main.rs

@@ -0,0 +1,47 @@
+use std::fs;
+use rand::rngs::OsRng;
+use rand::Rng;
+
+fn random_lower_char(rng: &mut OsRng) -> u8 {
+    rng.gen_range(0..25)
+}
+
+fn serialize_data(data: &[u32]) -> String {
+    println!("serializing...");
+    let mut serialization = String::new();
+    for (i, count) in data.iter().enumerate() {
+        let c = (i as u8 + 97) as char;
+        let s = format!("{} {}\n", c, count.to_string());
+        serialization.push_str(&s) 
+    }
+    // only stack object (ptr, len, capacity) is copied on the way out
+    serialization 
+}
+
+fn main() {
+    // considered using mutable static array for data
+    // but that requires unsafe, so we just use non-static memory
+    let mut data : [u32; 26] = [0; 26];
+
+    // deserialize file contents into data structure
+    if let Ok(contents) = fs::read_to_string("state.txt") {
+        println!("deserializing...");
+        for line in contents.split('\n') {
+            if let Some((letter, val)) = line.split_once(' ') {
+                let index = (letter.chars().next().unwrap() as u32) - 97; // todo: handle failure
+                let count = val.parse::<u32>().unwrap(); // todo: handle failure
+                data[index as usize] = count;
+            }
+        }
+    } 
+
+    // generate random char and give to data structure
+    let mut rng = OsRng;
+    let index = random_lower_char(&mut rng) as usize;
+    data[index] += 1;
+
+    // write data structure to file
+    let s_data = serialize_data(&data);
+    fs::write("state.txt", s_data).expect("Should be able to write to `state.txt`");
+    println!("done")
+}