From 01be289d0da6225a81e8064eacbff5dcc1c90a9f Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@alum.mit.edu>
Date: Mon, 9 Jan 2017 08:26:02 -0500
Subject: [PATCH] faster push and unshift to Vector for splatted arguments,
 support offset arrays in append and prepend, and support iterators in prepend

---
 base/array.jl    | 37 ++++++++++++++++++++++++++++++++-----
 test/arrayops.jl | 32 +++++++++++++++++++++++++-------
 2 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/base/array.jl b/base/array.jl
index f5bc45fe00af5..9d0e73d2c9e8b 100644
--- a/base/array.jl
+++ b/base/array.jl
@@ -554,15 +554,17 @@ function push!(a::Array{Any,1}, item::ANY)
 end
 
 function append!{T}(a::Array{T,1}, items::AbstractVector)
-    n = length(items)
+    itemindices = eachindex(items)
+    n = length(itemindices)
     ccall(:jl_array_grow_end, Void, (Any, UInt), a, n)
-    copy!(a, length(a)-n+1, items, 1, n)
+    copy!(a, length(a)-n+1, items, first(itemindices), n)
     return a
 end
 
 append!(a::Vector, iter) = _append!(a, iteratorsize(iter), iter)
+push!(a::Vector, iter...) = append!(a, iter)
 
-function _append!(a, ::HasLength, iter)
+function _append!(a, ::Union{HasLength,HasShape}, iter)
     n = length(a)
     resize!(a, n+length(iter))
     @inbounds for (i,item) in zip(n+1:length(a), iter)
@@ -591,17 +593,42 @@ julia> prepend!([3],[1,2])
  3
 ```
 """
+function prepend! end
+
 function prepend!{T}(a::Array{T,1}, items::AbstractVector)
-    n = length(items)
+    itemindices = eachindex(items)
+    n = length(itemindices)
     ccall(:jl_array_grow_beg, Void, (Any, UInt), a, n)
     if a === items
         copy!(a, 1, items, n+1, n)
     else
-        copy!(a, 1, items, 1, n)
+        copy!(a, 1, items, first(itemindices), n)
     end
     return a
 end
 
+prepend!(a::Vector, iter) = _prepend!(a, iteratorsize(iter), iter)
+unshift!(a::Vector, iter...) = prepend!(a, iter)
+
+function _prepend!(a, ::Union{HasLength,HasShape}, iter)
+    n = length(iter)
+    ccall(:jl_array_grow_beg, Void, (Any, UInt), a, n)
+    i = 0
+    for item in iter
+        @inbounds a[i += 1] = item
+    end
+    a
+end
+function _prepend!(a, ::IteratorSize, iter)
+    n = 0
+    for item in iter
+        n += 1
+        unshift!(a, item)
+    end
+    reverse!(a, 1, n)
+    a
+end
+
 
 """
     resize!(a::Vector, n::Integer) -> Vector
diff --git a/test/arrayops.jl b/test/arrayops.jl
index c073f0b21751a..b2cd9fb77b861 100644
--- a/test/arrayops.jl
+++ b/test/arrayops.jl
@@ -1122,10 +1122,31 @@ A = [[i i; i i] for i=1:2]
 @test cumsum(A) == Any[[1 1; 1 1], [3 3; 3 3]]
 @test cumprod(A) == Any[[1 1; 1 1], [4 4; 4 4]]
 
-# PR #4627
-A = [1,2]
-@test append!(A, A) == [1,2,1,2]
-@test prepend!(A, A) == [1,2,1,2,1,2,1,2]
+isdefined(Main, :TestHelpers) || eval(Main, :(include("TestHelpers.jl")))
+using TestHelpers.OAs
+
+@testset "prepend/append" begin
+    # PR #4627
+    A = [1,2]
+    @test append!(A, A) == [1,2,1,2]
+    @test prepend!(A, A) == [1,2,1,2,1,2,1,2]
+
+    # iterators with length:
+    @test append!([1,2], (9,8)) == [1,2,9,8] == push!([1,2], (9,8)...)
+    @test prepend!([1,2], (9,8)) == [9,8,1,2] == unshift!([1,2], (9,8)...)
+    @test append!([1,2], ()) == [1,2] == prepend!([1,2], ())
+    # iterators without length:
+    g = (i for i = 1:10 if iseven(i))
+    @test append!([1,2], g) == [1,2,2,4,6,8,10] == push!([1,2], g...)
+    @test prepend!([1,2], g) == [2,4,6,8,10,1,2] == unshift!([1,2], g...)
+    g = (i for i = 1:2:10 if iseven(i)) # isempty(g) == true
+    @test append!([1,2], g) == [1,2] == push!([1,2], g...)
+    @test prepend!([1,2], g) == [1,2] == unshift!([1,2], g...)
+
+    # offset array
+    @test append!([1,2], OffsetArray([9,8], (-3,))) == [1,2,9,8]
+    @test prepend!([1,2], OffsetArray([9,8], (-3,))) == [9,8,1,2]
+end
 
 A = [1,2]
 s = Set([1,2,3])
@@ -1880,9 +1901,6 @@ end
     end
 end
 
-isdefined(Main, :TestHelpers) || eval(Main, :(include("TestHelpers.jl")))
-using TestHelpers.OAs
-
 @testset "accumulate, accumulate!" begin
 
     @test accumulate(+, [1,2,3]) == [1, 3, 6]