Data commit

Task/Base64-decode-data/Rust/base64-decode-data.rust

@@ -0,0 +1,38 @@
+use std::str;
+
+const INPUT: &str = "VG8gZXJyIGlzIGh1bWFuLCBidXQgdG8gcmVhbGx5IGZvdWwgdGhpbmdzIHVwIHlvdSBuZWVkIGEgY29tcHV0ZXIuCiAgICAtLVBhdWwgUi5FaHJsaWNo";
+const UPPERCASE_OFFSET: i8 = -65;
+const LOWERCASE_OFFSET: i8 = 26 - 97;
+const NUM_OFFSET: i8 = 52 - 48;
+
+fn main() {
+    println!("Input: {}", INPUT);
+
+    let result = INPUT.chars()
+        .filter(|&ch| ch != '=')                                //Filter '=' chars
+        .map(|ch| {                                             //Map char values using Base64 Characters Table
+            let ascii = ch as i8;
+            let convert = match ch {
+                '0' ... '9' => ascii + NUM_OFFSET,
+                'a' ... 'z' => ascii + LOWERCASE_OFFSET,
+                'A' ... 'Z' => ascii + UPPERCASE_OFFSET,
+                '+' => 62,
+                '/' => 63,
+                _ => panic!("Not a valid base64 encoded string")
+            };
+            format!("{:#08b}", convert)[2..].to_string()        //convert indices to binary format and remove the two first digits
+        })
+        .collect::<String>()                                    //concatenate the resulting binary values
+        .chars()
+        .collect::<Vec<char>>()
+        .chunks(8)                                              //split into 8 character chunks
+        .map(|chunk| {
+            let num_str = chunk.iter().collect::<String>();
+            usize::from_str_radix(&num_str, 2).unwrap() as u8   //convert the binary string into its u8 value
+        })
+        .collect::<Vec<_>>();
+
+    let result = str::from_utf8(&result).unwrap();              //convert into UTF-8 string
+
+    println!("Output: {}", result);
+}