diff --git a/src/block.rs b/src/block.rs
index 96aa8b8..88475e2 100644
--- a/src/block.rs
+++ b/src/block.rs
@@ -4,39 +4,33 @@ use core::ops::{Add, Sub};
 use core::fmt::{self, Debug, Display, LowerHex};
 use core::iter::Step;
 
-pub trait Size {
-    // log_block_size = log_2(block_size) - 10
-    // i.e. block_size = 1024 << log_block_size
+pub trait Size: PartialOrd {
+    // log_block_size = log_2(block_size)
     const LOG_SIZE: u32;
-    const SIZE: usize = 1024 << Self::LOG_SIZE;
+    const SIZE: usize = 1 << Self::LOG_SIZE;
     const OFFSET_MASK: usize = Self::SIZE - 1;
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct Size1024;
-impl Size for Size1024 {
-    const LOG_SIZE: u32 = 0;
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct Size512;
+impl Size for Size512 {
+    const LOG_SIZE: u32 = 9;
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
 pub struct Size2048;
 impl Size for Size2048 {
-    const LOG_SIZE: u32 = 1;
+    const LOG_SIZE: u32 = 11;
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
 pub struct Size4096;
 impl Size for Size4096 {
-    const LOG_SIZE: u32 = 2;
+    const LOG_SIZE: u32 = 12;
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct Size8192;
-impl Size for Size8192 {
-    const LOG_SIZE: u32 = 3;
-}
-
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+/// Address in a physical sector
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
 pub struct Address<S: Size> {
     block: usize,
     offset: usize,
@@ -55,14 +49,30 @@ impl<S: Size> Address<S> {
     }
 
     pub fn new(block: usize, offset: isize) -> Address<S> {
-        let block = (block as isize + (offset >> (S::LOG_SIZE + 10))) as usize;
+        let block = (block as isize + (offset >> S::LOG_SIZE)) as usize;
         let offset = offset.abs() as usize & S::OFFSET_MASK;
         unsafe { Address::new_unchecked(block, offset) }
     }
 
+    pub fn with_block_size(
+        block: usize,
+        offset: usize,
+        log_block_size: u32,
+    ) -> Address<S> {
+        let log_diff = log_block_size as isize - S::LOG_SIZE as isize;
+        let top_offset = offset >> S::LOG_SIZE;
+        let offset = offset >> log_diff;
+        let block = block << log_diff | top_offset;
+        Address::new(block, offset as isize)
+    }
+
+    pub fn index64(&self) -> u64 {
+        ((self.block as u64) << S::LOG_SIZE) + self.offset as u64
+    }
+
     pub fn into_index(&self) -> Option<usize> {
         self.block
-            .checked_shl(S::LOG_SIZE + 10)
+            .checked_shl(S::LOG_SIZE)
             .and_then(|block| block.checked_add(self.offset))
     }
 
@@ -137,9 +147,17 @@ impl<S: Size> LowerHex for Address<S> {
     }
 }
 
+impl<S: Size> From<u64> for Address<S> {
+    fn from(idx: u64) -> Address<S> {
+        let block = idx >> S::LOG_SIZE;
+        let offset = idx & S::OFFSET_MASK as u64;
+        Address::new(block as usize, offset as isize)
+    }
+}
+
 impl<S: Size> From<usize> for Address<S> {
     fn from(idx: usize) -> Address<S> {
-        let block = idx >> (S::LOG_SIZE + 10);
+        let block = idx >> S::LOG_SIZE;
         let offset = idx & S::OFFSET_MASK;
         Address::new(block, offset as isize)
     }
@@ -172,13 +190,13 @@ mod tests {
     #[test]
     fn arithmetic() {
         assert_eq!(
-            Address::<Size1024>::new(0, 1024),
-            Address::<Size1024>::new(1, 0),
+            Address::<Size512>::new(0, 512),
+            Address::<Size512>::new(1, 0),
         );
 
         assert_eq!(
-            Address::<Size1024>::new(2, -512),
-            Address::<Size1024>::new(1, 512),
+            Address::<Size512>::new(2, -256),
+            Address::<Size512>::new(1, 256),
         );
 
         let a = Address::<Size2048>::new(0, 1024);
@@ -186,9 +204,9 @@ mod tests {
         assert_eq!(a + b, Address::<Size2048>::new(1, 0));
         assert_eq!((a + b).into_index(), Some(2048));
 
-        let a = Address::<Size1024>::new(0, 4096);
-        let b = Address::<Size1024>::new(0, 512);
-        assert_eq!(a - b, Address::<Size1024>::new(3, 512));
-        assert_eq!((a - b).into_index(), Some(3584));
+        let a = Address::<Size512>::new(0, 2048);
+        let b = Address::<Size512>::new(0, 256);
+        assert_eq!(a - b, Address::<Size512>::new(3, 256));
+        assert_eq!((a - b).into_index(), Some(1792));
     }
 }
diff --git a/src/buffer/mod.rs b/src/buffer/mod.rs
index 7b52be0..d3b5446 100644
--- a/src/buffer/mod.rs
+++ b/src/buffer/mod.rs
@@ -7,6 +7,7 @@ use alloc::boxed::Box;
 use alloc::borrow::{Cow, ToOwned};
 
 use error::Infallible;
+use block::{Address, Size};
 
 pub mod length;
 use self::length::Length;
@@ -21,14 +22,17 @@ where
     fn len(&self) -> Length<Idx>;
     fn commit(
         &mut self,
-        slice: Option<BufferCommit<T>>,
+        slice: Option<BufferCommit<T, Idx>>,
     ) -> Result<(), Self::Error>;
     unsafe fn slice_unchecked<'a>(
         &'a self,
         range: Range<Idx>,
-    ) -> BufferSlice<'a, T>;
+    ) -> BufferSlice<'a, T, Idx>;
 
-    fn slice<'a>(&'a self, range: Range<Idx>) -> Option<BufferSlice<'a, T>> {
+    fn slice<'a>(
+        &'a self,
+        range: Range<Idx>,
+    ) -> Option<BufferSlice<'a, T, Idx>> {
         if self.len() >= range.end && self.len() > range.start {
             unsafe { Some(self.slice_unchecked(range)) }
         } else {
@@ -37,29 +41,34 @@ where
     }
 }
 
-pub struct BufferSlice<'a, T: 'a>
+pub struct BufferSlice<'a, T: 'a, Idx>
 where
     [T]: ToOwned,
 {
     inner: Cow<'a, [T]>,
-    index: usize,
+    index: Idx,
 }
 
-impl<T> BufferSlice<'static, T>
+impl<T, Idx: Default> BufferSlice<'static, T, Idx>
 where
     [T]: ToOwned,
 {
-    pub fn with_static(inner: &'static [T]) -> BufferSlice<'static, T> {
+    pub fn with_static(inner: &'static [T]) -> BufferSlice<'static, T, Idx> {
         BufferSlice {
             inner: Cow::Borrowed(inner),
-            index: 0,
+            index: Idx::default(),
         }
     }
+}
 
+impl<T, Idx> BufferSlice<'static, T, Idx>
+where
+    [T]: ToOwned,
+{
     pub fn new_owned(
         inner: <[T] as ToOwned>::Owned,
-        index: usize,
-    ) -> BufferSlice<'static, T> {
+        index: Idx,
+    ) -> BufferSlice<'static, T, Idx> {
         BufferSlice {
             inner: Cow::Owned(inner),
             index,
@@ -67,11 +76,11 @@ where
     }
 }
 
-impl<'a, T> BufferSlice<'a, T>
+impl<'a, T, Idx> BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned,
 {
-    pub fn new(inner: &'a [T], index: usize) -> BufferSlice<'a, T> {
+    pub fn new(inner: &'a [T], index: Idx) -> BufferSlice<'a, T, Idx> {
         BufferSlice {
             inner: Cow::Borrowed(inner),
             index,
@@ -85,14 +94,13 @@ where
         }
     }
 
-    #[inline]
-    pub fn at_index(&self) -> usize {
-        self.index
+    pub fn at_index(&self) -> &Idx {
+        &self.index
     }
 }
 
-impl<'a> BufferSlice<'a, u8> {
-    pub unsafe fn dynamic_cast<T: Copy>(&self) -> (T, usize) {
+impl<'a, Idx: Copy> BufferSlice<'a, u8, Idx> {
+    pub unsafe fn dynamic_cast<T: Copy>(&self) -> (T, Idx) {
         assert!(self.inner.len() >= mem::size_of::<T>());
         let index = self.index;
         let cast = mem::transmute_copy(self.inner.as_ptr().as_ref().unwrap());
@@ -101,8 +109,8 @@ impl<'a> BufferSlice<'a, u8> {
 
     pub fn from_cast<T: Copy>(
         cast: &'a T,
-        index: usize,
-    ) -> BufferSlice<'a, u8> {
+        index: Idx,
+    ) -> BufferSlice<'a, u8, Idx> {
         let len = mem::size_of::<T>();
         let ptr = cast as *const T as *const u8;
         let slice = unsafe { slice::from_raw_parts(ptr, len) };
@@ -110,11 +118,11 @@ impl<'a> BufferSlice<'a, u8> {
     }
 }
 
-impl<'a, T> BufferSlice<'a, T>
+impl<'a, T, Idx> BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned<Owned = Vec<T>>,
 {
-    pub fn commit(self) -> Option<BufferCommit<T>> {
+    pub fn commit(self) -> Option<BufferCommit<T, Idx>> {
         if self.is_mutated() {
             Some(BufferCommit::new(self.inner.into_owned(), self.index))
         } else {
@@ -123,7 +131,7 @@ where
     }
 }
 
-impl<'a, T> AsRef<[T]> for BufferSlice<'a, T>
+impl<'a, T, Idx> AsRef<[T]> for BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned,
 {
@@ -132,7 +140,7 @@ where
     }
 }
 
-impl<'a, T> AsMut<[T]> for BufferSlice<'a, T>
+impl<'a, T, Idx> AsMut<[T]> for BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned,
     <[T] as ToOwned>::Owned: AsMut<[T]>,
@@ -142,7 +150,7 @@ where
     }
 }
 
-impl<'a, T> Deref for BufferSlice<'a, T>
+impl<'a, T, Idx> Deref for BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned,
 {
@@ -153,7 +161,7 @@ where
     }
 }
 
-impl<'a, T> DerefMut for BufferSlice<'a, T>
+impl<'a, T, Idx> DerefMut for BufferSlice<'a, T, Idx>
 where
     [T]: ToOwned,
     <[T] as ToOwned>::Owned: AsMut<[T]>,
@@ -163,17 +171,22 @@ where
     }
 }
 
-pub struct BufferCommit<T> {
+pub struct BufferCommit<T, Idx> {
     inner: Vec<T>,
-    index: usize,
+    index: Idx,
 }
 
-impl<T> BufferCommit<T> {
-    pub fn with_vec(inner: Vec<T>) -> BufferCommit<T> {
-        BufferCommit { inner, index: 0 }
+impl<T, Idx: Default> BufferCommit<T, Idx> {
+    pub fn with_vec(inner: Vec<T>) -> BufferCommit<T, Idx> {
+        BufferCommit {
+            inner,
+            index: Idx::default(),
+        }
     }
+}
 
-    pub fn new(inner: Vec<T>, index: usize) -> BufferCommit<T> {
+impl<T, Idx> BufferCommit<T, Idx> {
+    pub fn new(inner: Vec<T>, index: Idx) -> BufferCommit<T, Idx> {
         BufferCommit { inner, index }
     }
 
@@ -181,25 +194,24 @@ impl<T> BufferCommit<T> {
         self.inner
     }
 
-    #[inline]
-    pub fn at_index(&self) -> usize {
-        self.index
+    pub fn at_index(&self) -> &Idx {
+        &self.index
     }
 }
 
-impl<T> AsRef<[T]> for BufferCommit<T> {
+impl<T, Idx> AsRef<[T]> for BufferCommit<T, Idx> {
     fn as_ref(&self) -> &[T] {
         self.inner.as_ref()
     }
 }
 
-impl<T> AsMut<[T]> for BufferCommit<T> {
+impl<T, Idx> AsMut<[T]> for BufferCommit<T, Idx> {
     fn as_mut(&mut self) -> &mut [T] {
         self.inner.as_mut()
     }
 }
 
-impl<T> Deref for BufferCommit<T> {
+impl<T, Idx> Deref for BufferCommit<T, Idx> {
     type Target = [T];
 
     fn deref(&self) -> &Self::Target {
@@ -207,7 +219,7 @@ impl<T> Deref for BufferCommit<T> {
     }
 }
 
-impl<T> DerefMut for BufferCommit<T> {
+impl<T, Idx> DerefMut for BufferCommit<T, Idx> {
     fn deref_mut(&mut self) -> &mut Self::Target {
         self.as_mut()
     }
@@ -215,20 +227,20 @@ impl<T> DerefMut for BufferCommit<T> {
 
 macro_rules! impl_slice {
     (@inner $buffer:ty $( , $lt:lifetime )* ) => {
-        impl<$( $lt, )* T> Buffer<T, usize> for $buffer
+        impl<$( $lt, )* S: Size + PartialOrd + Copy, T> Buffer<T, Address<S>> for $buffer
         where
             T: Clone,
             [T]: ToOwned,
         {
             type Error = Infallible;
 
-            fn len(&self) -> Length<usize> {
-                Length::Bounded(<Self as AsRef<[T]>>::as_ref(self).len())
+            fn len(&self) -> Length<Address<S>> {
+                Length::Bounded(Address::from(<Self as AsRef<[T]>>::as_ref(self).len()))
             }
 
-            fn commit(&mut self, slice: Option<BufferCommit<T>>) -> Result<(), Infallible> {
+            fn commit(&mut self, slice: Option<BufferCommit<T, Address<S>>>) -> Result<(), Infallible> {
                 slice.map(|slice| {
-                    let index = slice.at_index();
+                    let index = slice.at_index().index64() as usize;
                     let end = index + slice.as_ref().len();
                     // XXX: it would be much better to drop the contents of dst
                     // and move the contents of slice instead of cloning
@@ -241,9 +253,10 @@ macro_rules! impl_slice {
 
             unsafe fn slice_unchecked<'a>(
                 &'a self,
-                range: Range<usize>,
-            ) -> BufferSlice<'a, T> {
+                range: Range<Address<S>>,
+            ) -> BufferSlice<'a, T, Address<S>> {
                 let index = range.start;
+                let range = range.start.index64() as usize..range.end.index64() as usize;
                 BufferSlice::new(
                     <Self as AsRef<[T]>>::as_ref(self).get_unchecked(range),
                     index,
@@ -270,33 +283,35 @@ mod file {
     use std::fs::File;
     use std::cell::RefCell;
 
+    use block::{Address, Size};
+
     use super::{Buffer, BufferCommit, BufferSlice};
     use super::length::Length;
 
-    impl Buffer<u8, usize> for RefCell<File> {
+    impl<S: Size + PartialOrd + Copy> Buffer<u8, Address<S>> for RefCell<File> {
         type Error = io::Error;
 
-        fn len(&self) -> Length<usize> {
+        fn len(&self) -> Length<Address<S>> {
             Length::Bounded(
                 self.borrow()
                     .metadata()
-                    .map(|data| data.len() as usize)
-                    .unwrap_or(0),
+                    .map(|data| Address::from(data.len()))
+                    .unwrap_or(Address::from(0_usize)),
             )
         }
 
         fn commit(
             &mut self,
-            slice: Option<BufferCommit<u8>>,
+            slice: Option<BufferCommit<u8, Address<S>>>,
         ) -> Result<(), Self::Error> {
             slice
                 .map(|slice| {
-                    let index = slice.at_index();
-                    let end = index + slice.as_ref().len();
+                    let index = *slice.at_index();
+                    let end = index + Address::from(slice.as_ref().len());
                     let mut refmut = self.borrow_mut();
                     refmut
-                        .seek(SeekFrom::Start(index as u64))
-                        .and_then(|_| refmut.write(&slice.as_ref()[index..end]))
+                        .seek(SeekFrom::Start(index.index64()))
+                        .and_then(|_| refmut.write(slice.as_ref()))
                         .map(|_| ())
                 })
                 .unwrap_or(Ok(()))
@@ -304,15 +319,15 @@ mod file {
 
         unsafe fn slice_unchecked<'a>(
             &'a self,
-            range: Range<usize>,
-        ) -> BufferSlice<'a, u8> {
+            range: Range<Address<S>>,
+        ) -> BufferSlice<'a, u8, Address<S>> {
             let index = range.start;
             let len = range.end - range.start;
-            let mut vec = Vec::with_capacity(len);
-            vec.set_len(len);
+            let mut vec = Vec::with_capacity(len.index64() as usize);
+            vec.set_len(len.index64() as usize);
             let mut refmut = self.borrow_mut();
             refmut
-                .seek(SeekFrom::Start(index as u64))
+                .seek(SeekFrom::Start(index.index64()))
                 .and_then(|_| refmut.read_exact(&mut vec[..]))
                 .unwrap_or_else(|err| {
                     panic!("could't read from File Buffer: {:?}", err)
@@ -322,14 +337,16 @@ mod file {
 
         fn slice<'a>(
             &'a self,
-            range: Range<usize>,
-        ) -> Option<BufferSlice<'a, u8>> {
+            range: Range<Address<S>>,
+        ) -> Option<BufferSlice<'a, u8, Address<S>>> {
             let index = range.start;
-            let mut vec = Vec::with_capacity(range.end - range.start);
+            let mut vec = Vec::with_capacity(
+                (range.end - range.start).index64() as usize,
+            );
             let mut refmut = self.borrow_mut();
             refmut
-                .seek(SeekFrom::Start(index as u64))
-                .and_then(|_| refmut.read_exact(&mut vec[range]))
+                .seek(SeekFrom::Start(index.index64()))
+                .and_then(|_| refmut.read_exact(&mut vec[..]))
                 .map(move |_| BufferSlice::new_owned(vec, index))
                 .ok()
         }
@@ -338,13 +355,19 @@ mod file {
 
 #[cfg(test)]
 mod tests {
+    use block::{Address, Size512};
     use super::*;
 
     #[test]
     fn buffer() {
         let mut buffer = vec![0; 1024];
         let commit = {
-            let mut slice = buffer.slice(256..512).unwrap();
+            let mut slice = buffer
+                .slice(
+                    Address::<Size512>::from(256_usize)
+                        ..Address::<Size512>::from(512_usize),
+                )
+                .unwrap();
             slice.iter_mut().for_each(|x| *x = 1);
             slice.commit()
         };
diff --git a/src/error.rs b/src/error.rs
index 83be4e2..7c3a8f9 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -6,6 +6,7 @@ use std::io;
 pub enum Error {
     BadMagic(u16),
     OutOfBounds(usize),
+    AddressOutOfBounds(usize, usize, usize),
     BadBlockGroupCount(u32, u32),
     #[cfg(any(test, not(feature = "no_std")))]
     Io(io::Error),
diff --git a/src/fs.rs b/src/fs.rs
index 2acc507..1c90de1 100644
--- a/src/fs.rs
+++ b/src/fs.rs
@@ -1,41 +1,45 @@
 use core::mem;
+use core::marker::PhantomData;
+
 use alloc::Vec;
 
 use error::Error;
-use block::Address; // TODO
+use block::{Address, Size};
 use buffer::{Buffer, BufferSlice};
 use sys::superblock::Superblock;
 use sys::block_group::BlockGroupDescriptor;
 use sys::inode::Inode;
 
-struct Struct<T> {
+struct Struct<T, S: Size> {
     pub inner: T,
-    pub offset: usize,
+    pub offset: Address<S>,
 }
 
-impl<T> From<(T, usize)> for Struct<T> {
+impl<T, S: Size> From<(T, Address<S>)> for Struct<T, S> {
     #[inline]
-    fn from((inner, offset): (T, usize)) -> Struct<T> {
+    fn from((inner, offset): (T, Address<S>)) -> Struct<T, S> {
         Struct { inner, offset }
     }
 }
 
 /// Safe wrapper for raw sys structs
-pub struct Ext2<B: Buffer<u8, usize>> {
+pub struct Ext2<S: Size, B: Buffer<u8, Address<S>>> {
     buffer: B,
-    superblock: Struct<Superblock>,
-    block_groups: Struct<Vec<BlockGroupDescriptor>>,
+    superblock: Struct<Superblock, S>,
+    block_groups: Struct<Vec<BlockGroupDescriptor>, S>,
 }
 
-impl<B: Buffer<u8, usize>> Ext2<B>
+impl<S: Size + Copy, B: Buffer<u8, Address<S>>> Ext2<S, B>
 where
     Error: From<B::Error>,
 {
-    pub fn new(buffer: B) -> Result<Ext2<B>, Error> {
+    pub fn new(buffer: B) -> Result<Ext2<S, B>, Error> {
         let superblock = unsafe { Struct::from(Superblock::find(&buffer)?) };
-        let block_size = superblock.inner.block_size();
-        let block_groups_offset =
-            (superblock.inner.first_data_block as usize + 1) * block_size;
+        let block_groups_offset = Address::with_block_size(
+            superblock.inner.first_data_block as usize + 1,
+            0,
+            superblock.inner.log_block_size + 10,
+        );
         let block_groups_count = superblock
             .inner
             .block_group_count()
@@ -74,7 +78,8 @@ where
             let slice = BufferSlice::from_cast(descr, offset);
             let commit = slice.commit();
             self.buffer.commit(commit).map_err(|err| Error::from(err))?;
-            offset += mem::size_of::<BlockGroupDescriptor>();
+            offset =
+                offset + Address::from(mem::size_of::<BlockGroupDescriptor>());
         }
 
         Ok(())
@@ -83,35 +88,36 @@ where
     #[allow(dead_code)]
     fn update_inode(
         &mut self,
-        &(ref inode, offset): &(Inode, usize),
+        &(ref inode, offset): &(Inode, Address<S>),
     ) -> Result<(), Error> {
         let slice = BufferSlice::from_cast(inode, offset);
         let commit = slice.commit();
         self.buffer.commit(commit).map_err(|err| Error::from(err))
     }
 
-    pub fn root_inode(&self) -> (Inode, usize) {
+    pub fn root_inode(&self) -> (Inode, Address<S>) {
         self.inode_nth(2).unwrap()
     }
 
-    pub fn inode_nth(&self, index: usize) -> Option<(Inode, usize)> {
+    pub fn inode_nth(&self, index: usize) -> Option<(Inode, Address<S>)> {
         self.inodes_nth(index).next()
     }
 
-    pub fn inodes<'a>(&'a self) -> Inodes<'a, B> {
+    pub fn inodes<'a>(&'a self) -> Inodes<'a, S, B> {
         self.inodes_nth(1)
     }
 
-    pub fn inodes_nth<'a>(&'a self, index: usize) -> Inodes<'a, B> {
+    pub fn inodes_nth<'a>(&'a self, index: usize) -> Inodes<'a, S, B> {
         assert!(index > 0, "inodes are 1-indexed");
         Inodes {
             buffer: &self.buffer,
             block_groups: &self.block_groups.inner,
-            block_size: self.block_size(),
+            log_block_size: self.log_block_size(),
             inode_size: self.inode_size(),
             inodes_per_group: self.inodes_count(),
             inodes_count: self.total_inodes_count(),
             index,
+            _phantom: PhantomData,
         }
     }
 
@@ -163,23 +169,29 @@ where
     pub fn block_size(&self) -> usize {
         self.superblock().block_size()
     }
+
+    pub fn log_block_size(&self) -> u32 {
+        self.superblock().log_block_size
+    }
 }
 
-pub struct Inodes<'a, B: 'a + Buffer<u8, usize>> {
+pub struct Inodes<'a, S: Size, B: 'a + Buffer<u8, Address<S>>> {
     buffer: &'a B,
     block_groups: &'a [BlockGroupDescriptor],
-    block_size: usize,
+    log_block_size: u32,
     inode_size: usize,
     inodes_per_group: usize,
     inodes_count: usize,
     index: usize,
+    _phantom: PhantomData<S>,
 }
 
-impl<'a, B: 'a + Buffer<u8, usize>> Iterator for Inodes<'a, B>
+impl<'a, S: Size + Copy, B: 'a + Buffer<u8, Address<S>>> Iterator
+    for Inodes<'a, S, B>
 where
     Error: From<B::Error>,
 {
-    type Item = (Inode, usize);
+    type Item = (Inode, Address<S>);
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.index < self.inodes_count {
@@ -190,8 +202,11 @@ where
             let inodes_block =
                 self.block_groups[block_group].inode_table_block as usize;
 
-            let offset =
-                inodes_block * self.block_size + index * self.inode_size;
+            let offset = Address::with_block_size(
+                inodes_block,
+                index * self.inode_size,
+                self.log_block_size,
+            );
             unsafe {
                 Inode::find_inode(self.buffer, offset, self.inode_size).ok()
             }
@@ -206,6 +221,7 @@ mod tests {
     use std::fs::File;
     use std::cell::RefCell;
 
+    use block::{Address, Size512};
     use buffer::Buffer;
 
     use super::Ext2;
@@ -213,13 +229,21 @@ mod tests {
     #[test]
     fn file_len() {
         let file = RefCell::new(File::open("ext2.img").unwrap());
-        assert_eq!(unsafe { file.slice_unchecked(1024..2048).len() }, 1024);
+        assert_eq!(
+            unsafe {
+                file.slice_unchecked(
+                    Address::<Size512>::from(1024_usize)
+                        ..Address::<Size512>::from(2048_usize),
+                ).len()
+            },
+            1024
+        );
     }
 
     #[test]
     fn file() {
         let file = RefCell::new(File::open("ext2.img").unwrap());
-        let fs = Ext2::new(file);
+        let fs = Ext2::<Size512, _>::new(file);
 
         assert!(
             fs.is_ok(),
@@ -237,7 +261,7 @@ mod tests {
     #[test]
     fn inodes() {
         let file = RefCell::new(File::open("ext2.img").unwrap());
-        let fs = Ext2::new(file);
+        let fs = Ext2::<Size512, _>::new(file);
 
         assert!(
             fs.is_ok(),
diff --git a/src/sys/block_group.rs b/src/sys/block_group.rs
index 6963bc5..aeb8738 100644
--- a/src/sys/block_group.rs
+++ b/src/sys/block_group.rs
@@ -4,6 +4,7 @@ use core::fmt::{self, Debug};
 use alloc::Vec;
 
 use error::Error;
+use block::{Address, Size};
 use buffer::Buffer;
 
 /// The Block Group Descriptor Table contains a descriptor for each block group
@@ -51,16 +52,24 @@ impl Debug for BlockGroupDescriptor {
 }
 
 impl BlockGroupDescriptor {
-    pub unsafe fn find_descriptor<B: Buffer<u8, usize>>(
+    pub unsafe fn find_descriptor<
+        S: Size + Copy + PartialOrd,
+        B: Buffer<u8, Address<S>>,
+    >(
         haystack: &B,
-        offset: usize,
-    ) -> Result<(BlockGroupDescriptor, usize), Error>
+        offset: Address<S>,
+    ) -> Result<(BlockGroupDescriptor, Address<S>), Error>
     where
         Error: From<B::Error>,
     {
-        let end = offset + mem::size_of::<BlockGroupDescriptor>();
+        let end =
+            offset + Address::from(mem::size_of::<BlockGroupDescriptor>());
         if haystack.len() < end {
-            return Err(Error::OutOfBounds(end));
+            return Err(Error::AddressOutOfBounds(
+                end.block(),
+                end.offset(),
+                end.block_size(),
+            ));
         }
 
         let descr = haystack
@@ -70,22 +79,31 @@ impl BlockGroupDescriptor {
         Ok(descr)
     }
 
-    pub unsafe fn find_descriptor_table<B: Buffer<u8, usize>>(
+    pub unsafe fn find_descriptor_table<
+        S: Size + Copy + PartialOrd,
+        B: Buffer<u8, Address<S>>,
+    >(
         haystack: &B,
-        offset: usize,
+        offset: Address<S>,
         count: usize,
-    ) -> Result<(Vec<BlockGroupDescriptor>, usize), Error>
+    ) -> Result<(Vec<BlockGroupDescriptor>, Address<S>), Error>
     where
         Error: From<B::Error>,
     {
-        let end = offset + count * mem::size_of::<BlockGroupDescriptor>();
+        let end = offset
+            + Address::from(count * mem::size_of::<BlockGroupDescriptor>());
         if haystack.len() < end {
-            return Err(Error::OutOfBounds(end));
+            return Err(Error::AddressOutOfBounds(
+                end.block(),
+                end.offset(),
+                end.block_size(),
+            ));
         }
 
         let mut vec = Vec::with_capacity(count);
         for i in 0..count {
-            let offset = offset + i * mem::size_of::<BlockGroupDescriptor>();
+            let offset = offset
+                + Address::from(i * mem::size_of::<BlockGroupDescriptor>());
             vec.push({
                 BlockGroupDescriptor::find_descriptor(haystack, offset)?.0
             });
@@ -97,13 +115,18 @@ impl BlockGroupDescriptor {
 
 #[cfg(test)]
 mod tests {
+    use block::{Address, Size512};
     use super::*;
 
     #[test]
     fn find() {
         let buffer = vec![0_u8; 4096];
         let table = unsafe {
-            BlockGroupDescriptor::find_descriptor_table(&buffer, 2048, 8)
+            BlockGroupDescriptor::find_descriptor_table(
+                &buffer,
+                Address::<Size512>::new(4, 0),
+                8,
+            )
         };
         assert!(
             table.is_ok(),
diff --git a/src/sys/inode.rs b/src/sys/inode.rs
index 52ba803..bd37647 100644
--- a/src/sys/inode.rs
+++ b/src/sys/inode.rs
@@ -2,6 +2,7 @@ use core::mem;
 use core::fmt::{self, Debug};
 
 use error::Error;
+use block::{Address, Size};
 use buffer::Buffer;
 
 /// An inode is a structure on the disk that represents a file, directory,
@@ -96,11 +97,14 @@ impl Debug for Inode {
 }
 
 impl Inode {
-    pub unsafe fn find_inode<B: Buffer<u8, usize>>(
+    pub unsafe fn find_inode<
+        S: Size + Copy + PartialOrd,
+        B: Buffer<u8, Address<S>>,
+    >(
         haystack: &B,
-        offset: usize,
+        offset: Address<S>,
         size: usize,
-    ) -> Result<(Inode, usize), Error>
+    ) -> Result<(Inode, Address<S>), Error>
     where
         Error: From<B::Error>,
     {
@@ -108,9 +112,13 @@ impl Inode {
             unimplemented!("inodes with a size != 128");
         }
 
-        let end = offset + size;
+        let end = offset + Address::from(size);
         if haystack.len() < end {
-            return Err(Error::OutOfBounds(end));
+            return Err(Error::AddressOutOfBounds(
+                end.block(),
+                end.offset(),
+                end.block_size(),
+            ));
         }
 
         let inode = haystack
diff --git a/src/sys/superblock.rs b/src/sys/superblock.rs
index d2cb36c..8db45f3 100644
--- a/src/sys/superblock.rs
+++ b/src/sys/superblock.rs
@@ -2,6 +2,7 @@ use core::mem;
 use core::fmt::{self, Debug};
 
 use error::Error;
+use block::{Address, Size};
 use buffer::Buffer;
 
 /// Ext2 signature (0xef53), used to help confirm the presence of Ext2 on a
@@ -194,16 +195,20 @@ impl Debug for Superblock {
 }
 
 impl Superblock {
-    pub unsafe fn find<B: Buffer<u8, usize>>(
+    pub unsafe fn find<S: Size + Copy + PartialOrd, B: Buffer<u8, Address<S>>>(
         haystack: &B,
-    ) -> Result<(Superblock, usize), Error>
+    ) -> Result<(Superblock, Address<S>), Error>
     where
         Error: From<B::Error>,
     {
-        let offset = 1024;
-        let end = offset + mem::size_of::<Superblock>();
+        let offset = Address::from(1024_usize);
+        let end = offset + Address::from(mem::size_of::<Superblock>());
         if haystack.len() < end {
-            return Err(Error::OutOfBounds(end));
+            return Err(Error::AddressOutOfBounds(
+                end.block(),
+                end.offset(),
+                end.block_size(),
+            ));
         }
 
         let superblock = {
@@ -291,6 +296,7 @@ bitflags! {
 
 #[cfg(test)]
 mod tests {
+    use block::Size512;
     use super::*;
 
     #[test]
@@ -299,7 +305,7 @@ mod tests {
         // magic
         buffer[1024 + 56] = EXT2_MAGIC as u8;
         buffer[1024 + 57] = (EXT2_MAGIC >> 8) as u8;
-        let superblock = unsafe { Superblock::find(&buffer) };
+        let superblock = unsafe { Superblock::find::<Size512, _>(&buffer) };
         assert!(
             superblock.is_ok(),
             "Err({:?})",
@@ -314,7 +320,7 @@ mod tests {
         use std::fs::File;
 
         let file = RefCell::new(File::open("ext2.img").unwrap());
-        let superblock = unsafe { Superblock::find(&file) };
+        let superblock = unsafe { Superblock::find::<Size512, _>(&file) };
         assert!(
             superblock.is_ok(),
             "Err({:?})",