CircularBuffer: Added first/last methods that slightly improve performance (JuliaCollections#543)

* Added first/last methods that slightly improve performance

* Added reset! for circular buffer

* vestion+

* Revert "Added reset! for circular buffer"

This reverts commit e43b3b2.

Author: sairus7

Project.toml

@@ -1,6 +1,6 @@
 name = "DataStructures"
 uuid = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
-version = "0.17.2"
+version = "0.17.3"
 
 [deps]
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"

src/circular_buffer.jl

@@ -193,3 +193,26 @@ capacity(cb::CircularBuffer) = cb.capacity
 Test whether the buffer is full.
 """
 isfull(cb::CircularBuffer) = length(cb) == cb.capacity
+
+"""
+    first(cb)
+
+Get the first element of CircularBuffer.
+"""
+Base.@propagate_inbounds function Base.first(cb::CircularBuffer)
+    @boundscheck if cb.length == 0
+        throw(BoundsError(cb, 1))
+    end
+    cb.buffer[cb.first]
+end
+"""
+    last(cb)
+
+Get the last element of CircularBuffer.
+"""
+Base.@propagate_inbounds function Base.last(cb::CircularBuffer)
+    @boundscheck if cb.length == 0
+        throw(BoundsError(cb, 1))
+    end
+    cb.buffer[_buffer_index(cb, cb.length)]
+end

test/test_circular_buffer.jl

@@ -6,6 +6,7 @@
             @test length(cb) == 0
             @test capacity(cb) == 5
             @test_throws BoundsError first(cb)
+            @test_throws BoundsError last(cb)
             @test isempty(cb) == true
             @test isfull(cb) == false
             @test eltype(cb) == Int
@@ -17,6 +18,7 @@
             @test length(cb) == 1
             @test capacity(cb) == 5
             @test isfull(cb) == false
+            @test first(cb) == last(cb)
         end
 
         @testset "Appending many elements" begin
@@ -38,6 +40,8 @@
             @test_throws BoundsError cb[3:6]
             @test cb[3:4] == Int[6,7]
             @test cb[[1,5]] == Int[4,8]
+            @test first(cb) == 4
+            @test last(cb) == 8
         end
 
         @testset "setindex" begin