Finish challenge 16 and problem set 2.

src/bytes.rs

@@ -1,6 +1,6 @@
 #![allow(dead_code)]
 use rand::Rng;
-use std::fmt::Write; // need to import this trait
+use std::fmt::Write;
 
 #[derive(PartialEq, PartialOrd, Debug)]
 pub struct Bytes(pub Vec<u8>);
@@ -117,6 +117,23 @@ impl Bytes {
         return true;
     }
 
+    pub fn remove_pkcs7(&mut self, block_size: usize) -> () {
+        if !self.has_valid_pkcs7(block_size) {
+            return;
+        }
+        let Bytes(v) = self;
+        let pad_byte_count = v[v.len() - 1];
+        for _ in 0..(pad_byte_count as usize) {
+            v.pop();
+        }
+    }
+
+    pub fn flip_bit(&mut self, byte_index: usize, bit_index: usize) -> () {
+        let Bytes(v) = self;
+        let flip_mask: u8 = 0b1 << bit_index;
+        v[byte_index] ^= flip_mask;
+    }
+
     pub fn xor(Bytes(a): &Bytes, Bytes(b): &Bytes) -> Bytes {
         Bytes(
             Iterator::zip(a.iter(), b.iter())