diff --git a/src/bbp.rs b/src/bbp.rs
new file mode 100644
index 0000000..52efa68
--- /dev/null
+++ b/src/bbp.rs
@@ -0,0 +1,93 @@
+pub fn get_byte(id: i32) -> u8 {
+    let pid : f64 = 4.0 * series(1, id) - 2.0 * series(4, id) - series(5, id) - series(6, id);
+
+    let mut y : f64 = (pid - (pid as i32) as f64 + 1.0).abs(); // TODO use .trunc() instead
+
+    y = 16.0 * (y - y.floor()); // TODO use .trunc() instead of floor?
+
+    let first : u8 = y as u8;
+
+    y = 16.0 * (y - y.floor()); // TODO use .trunc() instead of floor?
+
+    let second : u8 = y as u8;
+
+    (first << 4) | second
+}
+
+fn series(m: i32, id: i32) -> f64 {
+    const EPS : f64 = 1e-17;
+
+    let mut ak : f64;
+    let mut t : f64;
+    let mut s : f64 = 0.0;
+
+    for k in 0..id {
+      ak = (8 * k + m) as f64;
+      t = expm((id - k) as f64, ak);
+
+      s += t / ak;
+      s -= (s as i32) as f64; // TODO: use .truc() instead.
+    }
+
+    for k in id..id + 101 {
+      ak = (8 * k + m) as f64;
+      t = 16f64.powi(id - k) / ak;
+
+      if t < EPS {
+          break;
+      }
+
+      s += t;
+      s -= (s as i32) as f64; // TODO: use .truc() instead.
+    }
+
+    s
+}
+
+fn expm(p: f64, ak: f64) -> f64 {
+    if ak == 1.0 {
+        return 0.0;
+    }
+
+    const NTP : usize = 25;
+
+    lazy_static! {
+        static ref TP : Vec<f64> = {
+            let mut v = vec![1f64; NTP];
+
+            for i in 1..NTP {
+                v[i] = 2.0 * v[i - 1];
+            }
+
+            v
+        };
+    }
+
+    let mut i : usize = 0;
+
+    while TP[i] <= p {
+        i += 1;
+    }
+
+    let mut pt = TP[i - 1];
+    let mut p1 : f64 = p; // TODO: use p instead of p1?
+    let mut r : f64 = 1.0;
+
+    for _ in 1..i + 1 {
+      if p1 >= pt {
+        r = 16.0 * r;
+        r = r - ((r / ak) as i32) as f64 * ak; // TODO: use .truc() instead.
+
+        p1 -= pt;
+      }
+
+      pt = 0.5 * pt;
+
+      if pt >= 1.0 {
+        r *= r;
+        r -= ((r / ak) as i32) as f64 * ak; // TODO: use .truc() instead.
+      }
+    }
+
+    r
+}
diff --git a/src/main.rs b/src/main.rs
index 5ba0ea9..9db8e74 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
 extern crate getopts;
 extern crate byteorder;
 extern crate pbr;
+
 #[macro_use]
 extern crate lazy_static;
 
@@ -15,6 +16,8 @@ use getopts::Options;
 use byteorder::{ReadBytesExt, WriteBytesExt, LittleEndian};
 use pbr::{ProgressBar, Units};
 
+mod bbp;
+
 
 fn main() {
     let args: Vec<String> = env::args().collect();
@@ -68,7 +71,7 @@ fn compress(input: &String, output: &String) {
         let b = b.unwrap();
 
         for n in 0..i32::MAX {
-            if b == get_byte(n) {
+            if b == bbp::get_byte(n) {
                 i = n;
                 break;
             }
@@ -105,102 +108,8 @@ fn extract(input: &String, output: &String) {
         let mut c = Cursor::new(&buf);
         let index = c.read_i32::<LittleEndian>().unwrap();
 
-        output_file.write_all(&[get_byte(index)]).unwrap();
+        output_file.write_all(&[bbp::get_byte(index)]).unwrap();
 
         pb.add(size as u64);
     }
 }
-
-fn get_byte(id: i32) -> u8 {
-    let pid : f64 = 4.0 * series(1, id) - 2.0 * series(4, id) - series(5, id) - series(6, id);
-
-    let mut y : f64 = (pid - (pid as i32) as f64 + 1.0).abs();
-
-    y = 16.0 * (y - y.floor());
-
-    let first : u8 = y as u8;
-
-    y = 16.0 * (y - y.floor());
-
-    let second : u8 = y as u8;
-
-    (first << 4) | second
-}
-
-fn series(m: i32, id: i32) -> f64 {
-    const EPS : f64 = 1e-17;
-
-    let mut ak : f64;
-    let mut t : f64;
-    let mut s : f64 = 0.0;
-
-    for k in 0..id {
-      ak = (8 * k + m) as f64;
-      t = expm((id - k) as f64, ak);
-
-      s += t / ak;
-      s -= (s as i32) as f64;
-    }
-
-    for k in id..id + 101 {
-      ak = (8 * k + m) as f64;
-      t = 16f64.powi(id - k) / ak;
-
-      if t < EPS {
-          break;
-      }
-
-      s += t;
-      s -= (s as i32) as f64;
-    }
-
-    s
-}
-
-fn expm(p: f64, ak: f64) -> f64 {
-    if ak == 1.0 {
-        return 0.0;
-    }
-
-    const NTP : usize = 25;
-
-    lazy_static! {
-        static ref TP : Vec<f64> = {
-            let mut v = vec![1f64; NTP];
-
-            for i in 1..NTP {
-                v[i] = 2.0 * v[i - 1];
-            }
-
-            v
-        };
-    }
-
-    let mut i : usize = 0;
-
-    while TP[i] <= p {
-        i += 1;
-    }
-
-    let mut pt = TP[i - 1];
-    let mut p1 : f64 = p;
-    let mut r : f64 = 1.0;
-
-    for _ in 1..i + 1 {
-      if p1 >= pt {
-        r = 16.0 * r;
-        r = r - ((r / ak) as i32) as f64 * ak;
-
-        p1 -= pt;
-      }
-
-      pt = 0.5 * pt;
-
-      if pt >= 1.0 {
-        r *= r;
-        r -= ((r / ak) as i32) as f64 * ak;
-      }
-    }
-
-    r
-}