From 1e84f2cb58ac06f3851b3c95adf55c32f9e6c163 Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Sat, 26 Mar 2022 19:14:38 -0400
Subject: [PATCH] Implement conversion from base64 into bytes.

---
 src/bytes_base64.rs | 59 +++++++++++++++++++++++++++++----------------
 src/main.rs         | 10 ++++----
 src/set1.rs         | 21 ++++++++++------
 3 files changed, 57 insertions(+), 33 deletions(-)

diff --git a/src/bytes_base64.rs b/src/bytes_base64.rs
index c535294..e3b93ac 100644
--- a/src/bytes_base64.rs
+++ b/src/bytes_base64.rs
@@ -12,30 +12,47 @@ impl std::fmt::Display for BytesBase64 {
 
 impl BytesBase64 {
     pub fn from_bytes(Bytes(bytes): Bytes) -> BytesBase64 {
-        fn chunk_to_base64(c: &[u8]) -> Vec<u8> {
-            let (value, iterations) = match c.len() {
-                0 => return vec![],
-                1 => ((c[0] as u32) << 16, 2),
-                2 => ((c[0] as u32) << 16 | (c[1] as u32) << 8, 3),
-                3 => ((c[0] as u32) << 16 | (c[1] as u32) << 8 | (c[2] as u32), 4),
-                _ => panic!("Unexpected number of chunks {}.", c.len()),
-            };
-
-            (0..iterations)
-                .map(|i| (value.rotate_right((3 - i) * 6) & 0b111111) as u8)
-                .collect()
+        fn to_base64(c: &[u8]) -> Vec<u8> {
+            let mut v = c.to_vec();
+            // pad with bytes for conversion
+            while v.len() < 3 {
+                v.push(0);
+            }
+            let mut result = vec![
+                (v[0] & 0b11111100) >> 2,
+                (v[0] & 0b00000011) << 4 | (v[1] & 0b11110000) >> 4,
+                (v[1] & 0b00001111) << 2 | (v[2] & 0b11000000) >> 6,
+                (v[2] & 0b00111111) << 0,
+            ];
+            // removed padded bytes
+            for _ in c.len()..3 {
+                result.pop();
+            }
+            result
         }
-        BytesBase64(
-            bytes
-                .chunks(3)
-                .map(|c| chunk_to_base64(c))
-                .flatten()
-                .collect(),
-        )
+        BytesBase64(bytes.chunks(3).map(|c| to_base64(c)).flatten().collect())
     }
 
     pub fn to_bytes(&self) -> Bytes {
-        Bytes(vec![])
+        let BytesBase64(v) = self;
+        fn chunk_to_bytes(c: &[u8]) -> Vec<u8> {
+            let mut v = c.to_vec();
+            // pad with bytes for conversion
+            while v.len() < 4 {
+                v.push(0);
+            }
+            let mut result: Vec<u8> = vec![
+                ((v[0] & 0b00111111) << 2) | ((v[1] & 0b00110000) >> 4),
+                ((v[1] & 0b00001111) << 4) | ((v[2] & 0b00111100) >> 2),
+                ((v[2] & 0b00000011) << 6) | ((v[3] & 0b00111111) >> 0),
+            ];
+            // removed padded bytes
+            for _ in c.len()..4 {
+                result.pop();
+            }
+            result
+        }
+        Bytes(v.chunks(4).map(|c| chunk_to_bytes(c)).flatten().collect())
     }
 
     pub fn from_base64(s: &str) -> BytesBase64 {
@@ -75,7 +92,7 @@ impl BytesBase64 {
                 r.push(pad);
             }
             3 => r.push(pad),
-            _ => (),
+            _ => panic!("Unexpected lenght for padding '{}'", r.len()),
         }
         str::from_utf8(r.as_slice()).unwrap().to_string()
     }
diff --git a/src/main.rs b/src/main.rs
index 8b7aef6..1539d9e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,10 +3,10 @@ mod bytes_base64;
 mod set1;
 
 fn main() {
-    // set1::challenge1();
-    // set1::challenge2();
-    // set1::challenge3();
-    // set1::challenge4();
-    // set1::challenge5();
+    set1::challenge1();
+    set1::challenge2();
+    set1::challenge3();
+    set1::challenge4();
+    set1::challenge5();
     set1::challenge6();
 }
diff --git a/src/set1.rs b/src/set1.rs
index 23cf0f5..20c0cac 100644
--- a/src/set1.rs
+++ b/src/set1.rs
@@ -72,12 +72,12 @@ pub fn challenge5() {
 }
 
 pub fn challenge6() {
-    fn read(path: &str) -> BytesBase64 {
+    fn read(path: &str) -> Bytes {
         let s = std::fs::read_to_string(path).unwrap();
-        BytesBase64::from_base64(&s)
+        BytesBase64::from_base64(&s).to_bytes()
     }
 
-    fn write(path: &str, bytes_base64: &BytesBase64) {
+    fn _write(path: &str, bytes_base64: &BytesBase64) {
         let width = 60;
         let bytes = bytes_base64.to_string();
         let mut output_vec = vec![];
@@ -88,12 +88,19 @@ pub fn challenge6() {
             }
             output_vec.push(*e.0);
         }
-
+        output_vec.push('\n' as u8);
         let mut f = std::fs::File::create(path).unwrap();
         f.write(&output_vec).unwrap();
     }
 
-    let bytes_base64 = read("data/6.txt");
-    write("data/6_out.txt", &bytes_base64);
-    println!("[open] Challenge 6");
+    fn _test_roundtrip() {
+        // Test that conversion from to bytes and back works
+        let bytes = read("data/6.txt");
+        let bytes_base64 = BytesBase64::from_bytes(bytes);
+        _write("data/6.txt", &bytes_base64);
+    }
+
+    _test_roundtrip();
+    let _bytes = read("data/6.txt");
+    println!("[open] Challenge 6: {}", 0);
 }