Simplify some casts

Avoid try_from ... unwrap. We can just use 'as', which is easier to understand.

Author: thejpster

src/fat/volume.rs

@@ -587,8 +587,8 @@ impl FatVolume {
                         // Can quit early
                         return Ok(());
                     } else if dir_entry.is_valid() && !dir_entry.is_lfn() {
-                        // Safe, since Block::LEN always fits on a u32
-                        let start = u32::try_from(start).unwrap();
+                        // Block::LEN always fits on a u32
+                        let start = start as u32;
                         let entry = dir_entry.get_entry(FatType::Fat16, block_idx, start);
                         func(&entry);
                     }
@@ -642,8 +642,8 @@ impl FatVolume {
                         // Can quit early
                         return Ok(());
                     } else if dir_entry.is_valid() && !dir_entry.is_lfn() {
-                        // Safe, since Block::LEN always fits on a u32
-                        let start = u32::try_from(start).unwrap();
+                        // Block::LEN always fits on a u32
+                        let start = start as u32;
                         let entry = dir_entry.get_entry(FatType::Fat32, block, start);
                         func(&entry);
                     }
@@ -769,8 +769,8 @@ impl FatVolume {
                 break;
             } else if dir_entry.matches(match_name) {
                 // Found it
-                // Safe, since Block::LEN always fits on a u32
-                let start = u32::try_from(start).unwrap();
+                // Block::LEN always fits on a u32
+                let start = start as u32;
                 return Ok(dir_entry.get_entry(fat_type, block, start));
             }
         }

src/filesystem/directory.rs

@@ -1,5 +1,3 @@
-use core::convert::TryFrom;
-
 use crate::blockdevice::BlockIdx;
 use crate::fat::{FatType, OnDiskDirEntry};
 use crate::filesystem::{Attributes, ClusterId, SearchId, ShortFileName, Timestamp};
@@ -262,16 +260,12 @@ impl DirEntry {
             [0u8; 2]
         } else {
             // Safe due to the AND operation
-            u16::try_from((cluster_number >> 16) & 0x0000_FFFF)
-                .unwrap()
-                .to_le_bytes()
+            (((cluster_number >> 16) & 0x0000_FFFF) as u16).to_le_bytes()
         };
         data[20..22].copy_from_slice(&cluster_hi[..]);
         data[22..26].copy_from_slice(&self.mtime.serialize_to_fat()[..]);
         // Safe due to the AND operation
-        let cluster_lo = u16::try_from(cluster_number & 0x0000_FFFF)
-            .unwrap()
-            .to_le_bytes();
+        let cluster_lo = ((cluster_number & 0x0000_FFFF) as u16).to_le_bytes();
         data[26..28].copy_from_slice(&cluster_lo[..]);
         data[28..32].copy_from_slice(&self.size.to_le_bytes()[..]);
         data