From 7e0af1b8f6bed94d46bf8de2d88f5336e8b3e616 Mon Sep 17 00:00:00 2001
From: Szymon Walter <walter.szymon.98@gmail.com>
Date: Tue, 20 Mar 2018 11:05:56 +0100
Subject: [PATCH] add generic `Idx` type argument to `Buffer` and `Length`

---
 src/buffer/length.rs   | 74 ++++++++++++++++++++++--------------------
 src/buffer/mod.rs      | 17 +++++-----
 src/fs.rs              |  9 ++---
 src/sys/block_group.rs | 12 +++----
 src/sys/inode.rs       |  6 ++--
 src/sys/superblock.rs  |  6 ++--
 6 files changed, 65 insertions(+), 59 deletions(-)

diff --git a/src/buffer/length.rs b/src/buffer/length.rs
index e198377..a370002 100644
--- a/src/buffer/length.rs
+++ b/src/buffer/length.rs
@@ -2,28 +2,30 @@ use core::fmt::{self, Debug, Display};
 use core::cmp::Ordering;
 
 #[derive(Clone, Copy, Debug, Hash)]
-pub enum Length {
+pub enum Length<Idx> {
     Unbounded,
-    Bounded(usize),
+    Bounded(Idx),
 }
 
-impl Length {
-    pub fn try_len(&self) -> Option<usize> {
+impl<Idx: Copy> Length<Idx> {
+    pub fn try_len(&self) -> Option<Idx> {
         match *self {
             Length::Unbounded => None,
             Length::Bounded(n) => Some(n),
         }
     }
 
-    pub unsafe fn len(&self) -> usize {
+    pub unsafe fn len(&self) -> Idx {
         match *self {
-            Length::Unbounded => {
-                panic!("attempt to convert `Length::Unbounded` to `usize`")
-            }
+            Length::Unbounded => panic!(
+                "attempt to convert `Length::Unbounded` to `Length::Idx`"
+            ),
             Length::Bounded(n) => n,
         }
     }
+}
 
+impl<Idx> Length<Idx> {
     pub fn is_bounded(&self) -> bool {
         match *self {
             Length::Unbounded => false,
@@ -32,62 +34,64 @@ impl Length {
     }
 }
 
-impl Display for Length {
+impl<Idx: Debug> Display for Length<Idx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         Debug::fmt(self, f)
     }
 }
 
-impl PartialEq for Length {
-    fn eq(&self, rhs: &Length) -> bool {
-        match (*self, *rhs) {
-            (Length::Unbounded, _) => false,
-            (_, Length::Unbounded) => false,
-            (Length::Bounded(a), Length::Bounded(ref b)) => a.eq(b),
+impl<Idx: PartialEq> PartialEq for Length<Idx> {
+    fn eq(&self, rhs: &Self) -> bool {
+        match (self, rhs) {
+            (&Length::Unbounded, _) => false,
+            (_, &Length::Unbounded) => false,
+            (&Length::Bounded(ref a), &Length::Bounded(ref b)) => a.eq(b),
         }
     }
 
-    fn ne(&self, rhs: &Length) -> bool {
-        match (*self, *rhs) {
-            (Length::Unbounded, _) => false,
-            (_, Length::Unbounded) => false,
-            (Length::Bounded(a), Length::Bounded(ref b)) => a.ne(b),
+    fn ne(&self, rhs: &Self) -> bool {
+        match (self, rhs) {
+            (&Length::Unbounded, _) => false,
+            (_, &Length::Unbounded) => false,
+            (&Length::Bounded(ref a), &Length::Bounded(ref b)) => a.ne(b),
         }
     }
 }
 
-impl PartialEq<usize> for Length {
-    fn eq(&self, rhs: &usize) -> bool {
+impl<Idx: PartialEq> PartialEq<Idx> for Length<Idx> {
+    fn eq(&self, rhs: &Idx) -> bool {
         match *self {
             Length::Unbounded => false,
-            Length::Bounded(n) => n.eq(rhs),
+            Length::Bounded(ref n) => n.eq(rhs),
         }
     }
 
-    fn ne(&self, rhs: &usize) -> bool {
+    fn ne(&self, rhs: &Idx) -> bool {
         match *self {
             Length::Unbounded => false,
-            Length::Bounded(n) => n.eq(rhs),
+            Length::Bounded(ref n) => n.eq(rhs),
         }
     }
 }
 
-impl PartialOrd for Length {
-    fn partial_cmp(&self, rhs: &Length) -> Option<Ordering> {
-        match (*self, *rhs) {
-            (Length::Unbounded, Length::Unbounded) => None,
-            (Length::Unbounded, _) => Some(Ordering::Greater),
-            (_, Length::Unbounded) => Some(Ordering::Less),
-            (Length::Bounded(a), Length::Bounded(ref b)) => a.partial_cmp(b),
+impl<Idx: PartialOrd> PartialOrd for Length<Idx> {
+    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
+        match (self, rhs) {
+            (&Length::Unbounded, &Length::Unbounded) => None,
+            (&Length::Unbounded, _) => Some(Ordering::Greater),
+            (_, &Length::Unbounded) => Some(Ordering::Less),
+            (&Length::Bounded(ref a), &Length::Bounded(ref b)) => {
+                a.partial_cmp(b)
+            }
         }
     }
 }
 
-impl PartialOrd<usize> for Length {
-    fn partial_cmp(&self, rhs: &usize) -> Option<Ordering> {
+impl<Idx: PartialOrd> PartialOrd<Idx> for Length<Idx> {
+    fn partial_cmp(&self, rhs: &Idx) -> Option<Ordering> {
         match *self {
             Length::Unbounded => Some(Ordering::Greater),
-            Length::Bounded(n) => n.partial_cmp(rhs),
+            Length::Bounded(ref n) => n.partial_cmp(rhs),
         }
     }
 }
diff --git a/src/buffer/mod.rs b/src/buffer/mod.rs
index 6a7d137..7b52be0 100644
--- a/src/buffer/mod.rs
+++ b/src/buffer/mod.rs
@@ -11,23 +11,24 @@ use error::Infallible;
 pub mod length;
 use self::length::Length;
 
-pub trait Buffer<T>
+pub trait Buffer<T, Idx>
 where
     [T]: ToOwned,
+    Idx: PartialEq + PartialOrd,
 {
     type Error;
 
-    fn len(&self) -> Length;
+    fn len(&self) -> Length<Idx>;
     fn commit(
         &mut self,
         slice: Option<BufferCommit<T>>,
     ) -> Result<(), Self::Error>;
     unsafe fn slice_unchecked<'a>(
         &'a self,
-        range: Range<usize>,
+        range: Range<Idx>,
     ) -> BufferSlice<'a, T>;
 
-    fn slice<'a>(&'a self, range: Range<usize>) -> Option<BufferSlice<'a, T>> {
+    fn slice<'a>(&'a self, range: Range<Idx>) -> Option<BufferSlice<'a, T>> {
         if self.len() >= range.end && self.len() > range.start {
             unsafe { Some(self.slice_unchecked(range)) }
         } else {
@@ -214,14 +215,14 @@ impl<T> DerefMut for BufferCommit<T> {
 
 macro_rules! impl_slice {
     (@inner $buffer:ty $( , $lt:lifetime )* ) => {
-        impl<$( $lt, )* T> Buffer<T> for $buffer
+        impl<$( $lt, )* T> Buffer<T, usize> for $buffer
         where
             T: Clone,
             [T]: ToOwned,
         {
             type Error = Infallible;
 
-            fn len(&self) -> Length {
+            fn len(&self) -> Length<usize> {
                 Length::Bounded(<Self as AsRef<[T]>>::as_ref(self).len())
             }
 
@@ -272,10 +273,10 @@ mod file {
     use super::{Buffer, BufferCommit, BufferSlice};
     use super::length::Length;
 
-    impl Buffer<u8> for RefCell<File> {
+    impl Buffer<u8, usize> for RefCell<File> {
         type Error = io::Error;
 
-        fn len(&self) -> Length {
+        fn len(&self) -> Length<usize> {
             Length::Bounded(
                 self.borrow()
                     .metadata()
diff --git a/src/fs.rs b/src/fs.rs
index 837a550..2acc507 100644
--- a/src/fs.rs
+++ b/src/fs.rs
@@ -2,6 +2,7 @@ use core::mem;
 use alloc::Vec;
 
 use error::Error;
+use block::Address; // TODO
 use buffer::{Buffer, BufferSlice};
 use sys::superblock::Superblock;
 use sys::block_group::BlockGroupDescriptor;
@@ -20,13 +21,13 @@ impl<T> From<(T, usize)> for Struct<T> {
 }
 
 /// Safe wrapper for raw sys structs
-pub struct Ext2<B: Buffer<u8>> {
+pub struct Ext2<B: Buffer<u8, usize>> {
     buffer: B,
     superblock: Struct<Superblock>,
     block_groups: Struct<Vec<BlockGroupDescriptor>>,
 }
 
-impl<B: Buffer<u8>> Ext2<B>
+impl<B: Buffer<u8, usize>> Ext2<B>
 where
     Error: From<B::Error>,
 {
@@ -164,7 +165,7 @@ where
     }
 }
 
-pub struct Inodes<'a, B: 'a + Buffer<u8>> {
+pub struct Inodes<'a, B: 'a + Buffer<u8, usize>> {
     buffer: &'a B,
     block_groups: &'a [BlockGroupDescriptor],
     block_size: usize,
@@ -174,7 +175,7 @@ pub struct Inodes<'a, B: 'a + Buffer<u8>> {
     index: usize,
 }
 
-impl<'a, B: 'a + Buffer<u8>> Iterator for Inodes<'a, B>
+impl<'a, B: 'a + Buffer<u8, usize>> Iterator for Inodes<'a, B>
 where
     Error: From<B::Error>,
 {
diff --git a/src/sys/block_group.rs b/src/sys/block_group.rs
index a856fbf..6963bc5 100644
--- a/src/sys/block_group.rs
+++ b/src/sys/block_group.rs
@@ -51,12 +51,12 @@ impl Debug for BlockGroupDescriptor {
 }
 
 impl BlockGroupDescriptor {
-    pub unsafe fn find_descriptor<'a, E>(
-        haystack: &'a Buffer<u8, Error = E>,
+    pub unsafe fn find_descriptor<B: Buffer<u8, usize>>(
+        haystack: &B,
         offset: usize,
     ) -> Result<(BlockGroupDescriptor, usize), Error>
     where
-        Error: From<E>,
+        Error: From<B::Error>,
     {
         let end = offset + mem::size_of::<BlockGroupDescriptor>();
         if haystack.len() < end {
@@ -70,13 +70,13 @@ impl BlockGroupDescriptor {
         Ok(descr)
     }
 
-    pub unsafe fn find_descriptor_table<'a, E>(
-        haystack: &'a Buffer<u8, Error = E>,
+    pub unsafe fn find_descriptor_table<B: Buffer<u8, usize>>(
+        haystack: &B,
         offset: usize,
         count: usize,
     ) -> Result<(Vec<BlockGroupDescriptor>, usize), Error>
     where
-        Error: From<E>,
+        Error: From<B::Error>,
     {
         let end = offset + count * mem::size_of::<BlockGroupDescriptor>();
         if haystack.len() < end {
diff --git a/src/sys/inode.rs b/src/sys/inode.rs
index 3e6241b..52ba803 100644
--- a/src/sys/inode.rs
+++ b/src/sys/inode.rs
@@ -96,13 +96,13 @@ impl Debug for Inode {
 }
 
 impl Inode {
-    pub unsafe fn find_inode<'a, E>(
-        haystack: &'a Buffer<u8, Error = E>,
+    pub unsafe fn find_inode<B: Buffer<u8, usize>>(
+        haystack: &B,
         offset: usize,
         size: usize,
     ) -> Result<(Inode, usize), Error>
     where
-        Error: From<E>,
+        Error: From<B::Error>,
     {
         if size != mem::size_of::<Inode>() {
             unimplemented!("inodes with a size != 128");
diff --git a/src/sys/superblock.rs b/src/sys/superblock.rs
index 77cb82a..d2cb36c 100644
--- a/src/sys/superblock.rs
+++ b/src/sys/superblock.rs
@@ -194,11 +194,11 @@ impl Debug for Superblock {
 }
 
 impl Superblock {
-    pub unsafe fn find<'a, E>(
-        haystack: &'a Buffer<u8, Error = E>,
+    pub unsafe fn find<B: Buffer<u8, usize>>(
+        haystack: &B,
     ) -> Result<(Superblock, usize), Error>
     where
-        Error: From<E>,
+        Error: From<B::Error>,
     {
         let offset = 1024;
         let end = offset + mem::size_of::<Superblock>();