[bencode] Implement sha1 hash

Cargo.toml

@@ -5,3 +5,7 @@ edition = "2021"
 
 [dependencies]
 anyhow = "1.0.86"
+sha1 = "0.10.6"
+
+[dev-dependencies]
+hex-literal = "0.4.1"

src/bencode.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::fmt::{Display, Formatter};
 
 use anyhow::{anyhow, ensure, Result};
+use sha1::{Digest, Sha1};
 
 /*struct FileInfo {
     length: i64,
@@ -116,6 +117,14 @@ impl Bencode {
         Ok(result)
     }
 
+    pub fn sha1(input: &Self) -> [u8; 20] {
+        let mut hasher = Sha1::new();
+
+        hasher.update(Self::encode(input));
+
+        hasher.finalize().into()
+    }
+
     fn decode_type(input: &[u8]) -> Result<(Bencode, usize)>{
         if input.len() == 0 {
             return Err(anyhow!("Empty string is not valid bencode"))
@@ -228,8 +237,15 @@ impl Bencode {
 
 #[cfg(test)]
 mod tests {
+    use hex_literal::hex;
     use super::*;
 
+    #[test]
+    fn test_sha1() {
+        assert_eq!(Bencode::sha1(&Bencode::Integer(42)), hex!("3ce69356df4222111c27b41cccf2164e6cced799"));
+        assert_eq!(Bencode::sha1(&Bencode::Bytes(ByteString::from_str("foo"))), hex!("a8f4559a9623f25c4d5f1155f31a2604c55e1334"));
+    }
+
     #[test]
     fn test_encode_int() {
         assert_eq!(Bencode::encode(&Bencode::Integer(42)), "i42e".as_bytes());