From f9f192c35e913d5068c8636eba341828dc88f417 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rafa=C5=82=20Harabie=C5=84?= <rafalh1992@o2.pl>
Date: Sun, 1 Oct 2017 21:31:44 +0200
Subject: [PATCH] Add FAT table iterator.

---
 src/dir.rs   |  2 +-
 src/file.rs  |  7 +++----
 src/table.rs | 25 ++++++++++++++++++++++++-
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/dir.rs b/src/dir.rs
index fb80337..f104679 100644
--- a/src/dir.rs
+++ b/src/dir.rs
@@ -262,7 +262,7 @@ impl <'a, 'b> FatDir<'a, 'b> {
 impl <'a, 'b> Iterator for FatDir<'a, 'b> {
     type Item = io::Result<FatDirEntry<'a, 'b>>;
 
-    fn next(&mut self) -> Option<io::Result<FatDirEntry<'a, 'b>>> {
+    fn next(&mut self) -> Option<Self::Item> {
         let mut lfn_buf = Vec::<u16>::new();
         loop {
             let res = self.read_dir_entry_data();
diff --git a/src/file.rs b/src/file.rs
index a2256ff..a1bdad4 100644
--- a/src/file.rs
+++ b/src/file.rs
@@ -4,7 +4,6 @@ use std::io::{SeekFrom, ErrorKind};
 use std::io;
 
 use fs::FatSharedStateRef;
-use table::FatNextCluster;
 
 
 pub struct FatFile<'a, 'b: 'a> {
@@ -49,7 +48,7 @@ impl <'a, 'b> Read for FatFile<'a, 'b> {
             self.offset += read_bytes as u32;
             buf_offset += read_bytes;
             if self.offset % cluster_size == 0 {
-                self.current_cluster = state.table.get_next_cluster(current_cluster);
+                self.current_cluster = state.table.cluster_iter(current_cluster).skip(1).next();
             }
         }
         Ok(buf_offset)
@@ -70,8 +69,8 @@ impl <'a, 'b> Seek for FatFile<'a, 'b> {
         let cluster_count = (new_offset / cluster_size as i64) as usize;
         let mut new_cluster = Some(self.first_cluster);
         let state = self.state.borrow_mut();
-        for _ in 0..cluster_count {
-            new_cluster = state.table.get_next_cluster(new_cluster.unwrap());
+        if cluster_count > 0 {
+            new_cluster = state.table.cluster_iter(new_cluster.unwrap()).skip(cluster_count).next();
         }
         self.offset = new_offset as u32;
         self.current_cluster = new_cluster;
diff --git a/src/table.rs b/src/table.rs
index 30032c3..a8e002f 100644
--- a/src/table.rs
+++ b/src/table.rs
@@ -2,6 +2,7 @@ use std::io::prelude::*;
 use std::io;
 use byteorder::{LittleEndian, ReadBytesExt};
 use fs::FatType;
+use core::iter;
 
 pub(crate) struct FatTableData<T> {
     table: Box<[T]>,
@@ -35,9 +36,17 @@ impl FatTable {
         };
         Ok(table)
     }
+    
+    pub fn cluster_iter(&self, cluster: u32) -> iter::Chain<iter::Once<u32>, FatClusterIterator> {
+        let iter = FatClusterIterator {
+            table: self,
+            cluster: Some(cluster),
+        };
+        iter::once(cluster).chain(iter)
+    }
 }
 
-pub(crate) trait FatNextCluster {
+trait FatNextCluster {
     fn get_next_cluster(&self, cluster: u32) -> Option<u32>;
 }
 
@@ -115,3 +124,17 @@ impl FatNextCluster for FatTable32 {
         }
     }
 }
+
+pub(crate) struct FatClusterIterator<'a> {
+    table: &'a FatTable,
+    cluster: Option<u32>,
+}
+
+impl <'a> Iterator for FatClusterIterator<'a> {
+    type Item = u32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.cluster = self.table.get_next_cluster(self.cluster.unwrap());
+        self.cluster
+    }
+}