Remove unsafe annotations for the options API.

These used to have safety considerations although none do anymore, but
they require validation or there could be runtime panics.

- Addresses #100
- Addresses #138

lexical-util/src/algorithm.rs

@@ -8,9 +8,9 @@ use crate::num::Integer;
 /// performance isn't the highest consideration here.
 #[inline(always)]
 #[cfg(feature = "write")]
-pub fn copy_to_dst<Bytes: AsRef<[u8]>>(dst: &mut [u8], src: Bytes) -> usize {
+pub fn copy_to_dst<T: Copy, Bytes: AsRef<[T]>>(dst: &mut [T], src: Bytes) -> usize {
     let src = src.as_ref();
-    dst[..src.len()].clone_from_slice(src);
+    dst[..src.len()].copy_from_slice(src);
 
     src.len()
 }

lexical-util/src/iterator.rs

@@ -49,13 +49,6 @@ pub unsafe trait BytesIter<'a>: Iterator<Item = &'a u8> + Buffer<'a> {
     /// does not set the cursor within skipped characters.
     unsafe fn set_cursor(&mut self, index: usize);
 
-    /// Set the cursor to the start of the buffer.
-    #[inline(always)]
-    fn seek_start(&mut self) {
-        // SAFETY: 0 is alwatys <= any usize value.
-        unsafe { self.set_cursor(0) };
-    }
-
     /// Get a slice to the full buffer, which may or may not be the same as
     /// `as_slice`.
     fn as_full_slice(&self) -> &'a [u8];
@@ -157,6 +150,9 @@ pub unsafe trait BytesIter<'a>: Iterator<Item = &'a u8> + Buffer<'a> {
     /// expected one.
     #[inline(always)]
     fn read_if<Pred: FnOnce(&u8) -> bool>(&mut self, pred: Pred) -> Option<Self::Item> {
+        // NOTE: This was implemented to remove usage of unsafe throughout to code
+        // base, however, performance was really not up to scratch. I'm not sure
+        // the cause of this.
         if let Some(peeked) = self.peek() {
             if pred(peeked) {
                 // SAFETY: the slice cannot be empty because we peeked a value.