Implement tag omission optimization

decoder/src/decoder.rs

@@ -73,14 +73,11 @@ impl<'t, 'b> Decoder<'t, 'b> {
  &mut self,
  num_elements: usize,
  ) -> Result<Vec<FormatSliceElement<'t>>, DecodeError> {
- if num_elements == 0 {
- return Ok(vec![]);
- }
+ let format = self.get_format()?;
+ let is_enum = format.contains('|');
 
  let mut elements = Vec::with_capacity(num_elements);
  for i in 0..num_elements {
- let format = self.get_format()?;
- let is_enum = format.contains('|');
  let format = if is_enum {
  self.get_variant(format)?
  } else {

src/export.rs

@@ -275,10 +275,11 @@ pub fn isize(b: isize) {
 }
 
 /// Implementation detail
-pub fn fmt_slice(values: &[impl Format]) {
+pub fn fmt_slice<T: Format>(values: &[T]) {
  usize(values.len());
+ istr(T::_format_tag());
  for value in values {
- fmt(value);
+ value._format_data();
  }
 }
 
@@ -349,9 +350,10 @@ pub fn u8_array(a: &[u8]) {
 }
 
 // NOTE: This is passed `&[u8; N]` – it's just coerced to a slice.
-pub fn fmt_array(a: &[impl Format]) {
+pub fn fmt_array<T: Format>(a: &[T]) {
+ istr(T::_format_tag());
  for value in a {
- fmt(value);
+ value._format_data();
  }
 }
 

src/impls/primitives.rs

@@ -52,11 +52,7 @@ where
 
  #[inline]
  fn _format_data(&self) {
- export::usize(self.len());
- for value in self {
- export::istr(T::_format_tag());
- value._format_data();
- }
+ export::fmt_slice(self);
  }
 }