Merge pull request #60 from Nemo157/macro-🚫type

Allow inferring array type for macro constructors

Cargo.toml

@@ -40,6 +40,14 @@ all-features = true
 [workspace]
 members = ["fuzz"]
 
+[dev-dependencies]
+criterion = "0.3.0"
+
 [[test]]
 name = "tinyvec"
 required-features = ["alloc"]
+
+[[bench]]
+name = "macros"
+harness = false
+required-features = ["alloc"]

benches/macros.rs

@@ -0,0 +1,48 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+
+use tinyvec::tiny_vec;
+
+fn bench_tinyvec_macro(c: &mut Criterion) {
+  let mut g = c.benchmark_group("tinyvec_macro");
+
+  g.bench_function("0 of 32", |b| {
+    b.iter(|| tiny_vec!([u8; 32]));
+  });
+
+  g.bench_function("16 of 32", |b| {
+    b.iter(||
+      tiny_vec!([u8; 32],
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+      ));
+  });
+
+  g.bench_function("32 of 32", |b| {
+    b.iter(||
+      tiny_vec!([u8; 32],
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+      ));
+  });
+
+  g.bench_function("33 of 32", |b| {
+    b.iter(||
+      tiny_vec!([u8; 32],
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+        33,
+      ));
+  });
+
+  g.bench_function("64 of 32", |b| {
+    b.iter(||
+      tiny_vec!([u8; 32],
+        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+        33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+        49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
+      ));
+  });
+}
+
+criterion_group!(benches, bench_tinyvec_macro);
+criterion_main!(benches);

src/arrayvec.rs

@@ -11,25 +11,35 @@ use super::*;
 /// ```rust
 /// use tinyvec::*;
 ///
+/// // The backing array type can be specified in the macro call
 /// let empty_av = array_vec!([u8; 16]);
-///
 /// let some_ints = array_vec!([i32; 4], 1, 2, 3);
+///
+/// // Or left to inference
+/// let empty_av: ArrayVec<[u8; 10]> = array_vec!();
+/// let some_ints: ArrayVec<[u8; 10]> = array_vec!(5, 6, 7, 8);
 /// ```
 #[macro_export]
 macro_rules! array_vec {
   ($array_type:ty) => {
     {
-      let av: ArrayVec<$array_type> = Default::default();
+      let av: $crate::ArrayVec<$array_type> = Default::default();
       av
     }
   };
   ($array_type:ty, $($elem:expr),*) => {
     {
-      let mut av: ArrayVec<$array_type> = Default::default();
+      let mut av: $crate::ArrayVec<$array_type> = Default::default();
       $( av.push($elem); )*
       av
     }
   };
+  () => {
+    array_vec!(_)
+  };
+  ($($elem:expr),*) => {
+    array_vec!(_, $($elem),*)
+  };
 }
 
 /// An array-backed, vector-like data structure.
@@ -251,7 +261,7 @@ impl<A: Array> ArrayVec<A> {
   }
 
   /// Clone each element of the slice into this `ArrayVec`.
-  /// 
+  ///
   /// ## Panics
   /// * If the `ArrayVec` would overflow, this will panic.
   #[inline]

src/lib.rs

@@ -75,7 +75,8 @@ use core::{
 };
 
 #[cfg(feature = "alloc")]
-extern crate alloc;
+#[doc(hidden)] // re-export for macros
+pub extern crate alloc;
 
 mod array;
 pub use array::*;

src/tinyvec.rs

@@ -15,21 +15,25 @@ use alloc::vec::Vec;
 /// ```rust
 /// use tinyvec::*;
 ///
+/// // The backing array type can be specified in the macro call
 /// let empty_tv = tiny_vec!([u8; 16]);
-///
 /// let some_ints = tiny_vec!([i32; 4], 1, 2, 3);
-///
 /// let many_ints = tiny_vec!([i32; 4], 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+///
+/// // Or left to inference
+/// let empty_tv: TinyVec<[u8; 16]> = tiny_vec!();
+/// let some_ints: TinyVec<[i32; 4]> = tiny_vec!(1, 2, 3);
+/// let many_ints: TinyVec<[i32; 4]> = tiny_vec!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
 /// ```
 #[macro_export]
 macro_rules! tiny_vec {
   ($array_type:ty) => {
     {
-      let mut tv: TinyVec<$array_type> = Default::default();
+      let mut tv: $crate::TinyVec<$array_type> = Default::default();
       tv
     }
   };
-  ($array_type:ty, $($elem:expr),*) => {
+  ($array_type:ty, $($elem:expr),* $(,)?) => {
     {
       // Note(Lokathor): This goofy looking thing will count the number of
       // `$elem` entries we were given. We can't spit out the "+1"s on their
@@ -42,14 +46,19 @@ macro_rules! tiny_vec {
       const INVOKED_ELEM_COUNT: usize = 0 $( + { let _ = stringify!($elem); 1 })*;
       // If we have more `$elem` than the `CAPACITY` we will simply go directly
       // to constructing on the heap.
-      let av: TinyVec<$array_type> = if INVOKED_ELEM_COUNT <= <$array_type as Array>::CAPACITY {
-        TinyVec::<$array_type>::Inline(array_vec!($array_type, $($elem),*))
-      } else {
-        TinyVec::<$array_type>::Heap(vec!($($elem),*))
-      };
+      let av: $crate::TinyVec<$array_type> = $crate::TinyVec::from_either_with_capacity(
+        INVOKED_ELEM_COUNT,
+        #[inline(always)] || $crate::array_vec!($array_type, $($elem),*),
+        #[inline(always)] || vec!($($elem),*));
       av
     }
   };
+  () => {
+    tiny_vec!(_)
+  };
+  ($($elem:expr),*) => {
+    tiny_vec!(_, $($elem),*)
+  };
 }
 
 /// A vector that starts inline, but can automatically move to the heap.
@@ -65,9 +74,9 @@ macro_rules! tiny_vec {
 ///
 /// Because it's an enum, you can construct a `TinyVec` simply by making an
 /// `ArrayVec` or `Vec` and then putting it into the enum.
-/// 
+///
 /// There is also a macro
-/// 
+///
 /// ```rust
 /// # use tinyvec::*;
 /// let empty_tv = tiny_vec!([u8; 16]);
@@ -333,6 +342,20 @@ impl<A: Array> TinyVec<A> {
     }
   }
 
+  #[inline(always)]
+  #[doc(hidden)] // Internal implementation details of `tiny_vec!`
+  pub fn from_either_with_capacity(
+    cap: usize,
+    make_array: impl FnOnce() -> ArrayVec<A>,
+    make_vec: impl FnOnce() -> Vec<A::Item>,
+  ) -> Self {
+    if cap <= A::CAPACITY {
+      TinyVec::Inline(make_array())
+    } else {
+      TinyVec::Heap(make_vec())
+    }
+  }
+
   /// Inserts an item at the position given, moving all following elements +1
   /// index.
   ///