1 files changed, 108 insertions, 0 deletions
diff --git a/src/iter.rs b/src/iter.rs
new file mode 100644
index 0000000..c004f41
--- /dev/null
+++ b/src/iter.rs
@@ -0,0 +1,108 @@
+use core::slice;
+use core::convert::TryInto;
+use core::convert::TryFrom;
+
+pub struct Bytes<'a> {
+    slice: &'a [u8],
+    pos: usize
+}
+
+impl<'a> Bytes<'a> {
+    #[inline]
+    pub fn new(slice: &'a [u8]) -> Bytes<'a> {
+        Bytes {
+            slice,
+            pos: 0
+        }
+    }
+
+    #[inline]
+    pub fn pos(&self) -> usize {
+        self.pos
+    }
+
+    #[inline]
+    pub fn peek(&self) -> Option<u8> {
+        self.peek_ahead(0)
+    }
+
+    #[inline]
+    pub fn peek_ahead(&self, n: usize) -> Option<u8> {
+        self.slice.get(self.pos + n).copied()
+    }
+
+    #[inline]
+    pub fn peek_n<U: TryFrom<&'a[u8]>>(&self, n: usize) -> Option<U> {
+        self.slice.get(self.pos..self.pos + n)?.try_into().ok()
+    }
+
+    #[inline]
+    pub unsafe fn bump(&mut self) {
+        debug_assert!(self.pos < self.slice.len(), "overflow");
+        self.pos += 1;
+    }
+
+    #[allow(unused)]
+    #[inline]
+    pub unsafe fn advance(&mut self, n: usize) {
+        debug_assert!(self.pos + n <= self.slice.len(), "overflow");
+        self.pos += n;
+    }
+
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.slice.len()
+    }
+
+    #[inline]
+    pub fn slice(&mut self) -> &'a [u8] {
+        // not moving position at all, so it's safe
+        unsafe {
+            self.slice_skip(0)
+        }
+    }
+
+    #[inline]
+    pub unsafe fn slice_skip(&mut self, skip: usize) -> &'a [u8] {
+        debug_assert!(self.pos >= skip);
+        let head_pos = self.pos - skip;
+        let ptr = self.slice.as_ptr();
+        let head = slice::from_raw_parts(ptr, head_pos);
+        let tail = slice::from_raw_parts(ptr.add(self.pos), self.slice.len() - self.pos);
+        self.pos = 0;
+        self.slice = tail;
+        head
+    }
+
+    #[inline]
+    pub unsafe fn advance_and_commit(&mut self, n: usize) {
+        debug_assert!(self.pos + n <= self.slice.len(), "overflow");
+        self.pos += n;
+        let ptr = self.slice.as_ptr();
+        let tail = slice::from_raw_parts(ptr.add(n), self.slice.len() - n);
+        self.pos = 0;
+        self.slice = tail;
+    }
+}
+
+impl<'a> AsRef<[u8]> for Bytes<'a> {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        &self.slice[self.pos..]
+    }
+}
+
+impl<'a> Iterator for Bytes<'a> {
+    type Item = u8;
+
+    #[inline]
+    fn next(&mut self) -> Option<u8> {
+        if self.slice.len() > self.pos {
+            let b = unsafe { *self.slice.get_unchecked(self.pos) };
+            self.pos += 1;
+            Some(b)
+        } else {
+            None
+        }
+    }
+}