Merge pull request #784 from johannes-fischer/circular_buffer_resize

Implement resize! for CircularBuffer

Author: oxinabox

src/circular_buffer.jl

@@ -225,3 +225,25 @@ Base.@propagate_inbounds function Base.last(cb::CircularBuffer)
     @boundscheck (cb.length == 0) && throw(BoundsError(cb, 1))
     return cb.buffer[_buffer_index(cb, cb.length)]
 end
+
+"""
+    resize!(cb::CircularBuffer, n)
+
+Resize CircularBuffer to the maximum capacity of n elements.
+If n is smaller than the current buffer length, the first n elements will be retained.
+"""
+function Base.resize!(cb::CircularBuffer, n::Integer)
+    if n != capacity(cb)
+        buf_new = Vector{eltype(cb)}(undef, n)
+        len_new = min(length(cb), n)
+        for i in 1:len_new
+            @inbounds buf_new[i] = cb[i]
+        end
+
+        cb.capacity = n
+        cb.first = 1
+        cb.length = len_new
+        cb.buffer = buf_new
+    end
+    return cb
+end

test/test_circular_buffer.jl

@@ -164,4 +164,28 @@
             @test Array(cb) == [21, 42, 42]
         end
     end
+
+    @testset "resize!" begin
+        @testset "resize an empty buffer" begin
+            cb = CircularBuffer{Int}(3)
+            resize!(cb, 10)
+            @test isempty(cb) && capacity(cb) == 10
+        end
+        @testset "resize a non empty buffer to smaller size" begin
+            cb = CircularBuffer{Int}(10)
+            append!(cb, -7:10)
+            resize!(cb, 6)
+            @test cb == 1:6
+            append!(cb, 7:8)
+            @test cb == 3:8
+        end
+        @testset "resize a non empty buffer to larger size" begin
+            cb = CircularBuffer{Int}(10)
+            append!(cb, -7:10)
+            resize!(cb, 15)
+            @test cb == 1:10
+            append!(cb, 11:20)
+            @test cb == 6:20
+        end
+    end
 end