b64

src/disc_id.rs

@@ -0,0 +1,69 @@
+use std::{convert, ops::Index};
+
+const B64TABLE: &str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._";
+
+fn b64(data: &[u8]) -> String {
+    let binary: Vec<u8> = data
+        .iter()
+        .flat_map(|b| (0..8).rev().map(move |i| (b >> i) & 1))
+        .collect();
+    let mut chunks: Vec<Vec<u8>> = binary.chunks(6).map(|s| s.to_vec()).collect();
+    let last = chunks.last_mut().unwrap();
+    if last.len() < 6 {
+        for _ in last.len()..6 {
+            last.push(0);
+        }
+    }
+    let decimal: Vec<u8> = chunks
+        .iter()
+        .map(|bits| bits.iter().fold(0, |acc, &bit| (acc << 1) | bit))
+        .collect();
+    let mut converted: Vec<String> = Vec::new();
+
+    for dec in decimal {
+        converted.push(B64TABLE.chars().nth(dec as usize).unwrap().to_string());
+    }
+    match data.len() % 3 {
+        1 => {
+            converted.push("--".to_string());
+        }
+        2 => {
+            converted.push("-".to_string());
+        }
+        _ => {}
+    }
+    converted.join("")
+}
+pub fn compute_disc_id(first_track: u8, last_track: u8, leadout: u32, offsets: &[u32]) -> String {
+    let mut toc = String::new();
+    toc.push_str(&format!("{first_track:02X}{last_track:02X}{leadout:08X}"));
+    for i in 0..99 {
+        let offset = offsets.get(i).copied().unwrap_or(0);
+        toc.push_str(&format!("{:08X}", offset));
+    }
+    toc
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn known_example() {
+        let first_track = 1;
+        let last_track = 12;
+        let leadout = 224556;
+        let offsets = [
+            150, 9078, 13528, 34182, 53768, 70987, 96424, 118425, 136793, 159514, 179777, 198006,
+        ];
+        assert_eq!(
+            compute_disc_id(first_track, last_track, leadout, &offsets),
+            "T_prJXQSrqbnH8OE.dgOKsHm5Uw-"
+        );
+    }
+    #[test]
+    fn base64() {
+        assert_eq!(b64("Man".as_bytes()), "TWFu".to_string());
+        assert_eq!(b64("M".as_bytes()), "TQ--".to_string());
+        assert_eq!(b64("Ma".as_bytes()), "TWE-".to_string());
+    }
+}