Add test for SubString

src/basic.jl

@@ -1,5 +1,3 @@
-memory(v::MemoryView) = v.ref.mem
-
 function Base.setindex!(v::MutableMemoryView{T}, x, i::Int) where {T}
     @boundscheck checkbounds(v, i)
     xT = x isa T ? x : convert(T, x)::T
@@ -8,6 +6,9 @@ function Base.setindex!(v::MutableMemoryView{T}, x, i::Int) where {T}
     return v
 end
 
+# TODO: This uses the internal `.mem` field of `MemoryRef`, but AFAIK there is no
+# API in Base to get the memory from a `MemoryRef`
+Base.parent(v::MemoryView) = v.ref.mem
 Base.size(v::MemoryView) = (v.len,)
 Base.IndexStyle(::Type{<:MemoryView}) = Base.IndexLinear()
 

src/construction.jl

@@ -9,14 +9,8 @@ MemoryView(A::Array{T}) where {T} = MutableMemoryView{T}(unsafe, A.ref, length(A
 # Strings
 MemoryView(s::String) = ImmutableMemoryView(unsafe_wrap(Memory{UInt8}, s))
 function MemoryView(s::SubString)
-    memview = MemoryView(parent(s))
-    codesize = sizeof(codeunit(s))
-    offset = codesize * s.offset
-    len = s.ncodeunits * codesize
-    mem = memview.ref.mem
-    span = (offset + 1):len
-    @boundscheck checkbounds(mem, span)
-    @inbounds typeof(memview)(unsafe, memoryref(mem, offset + 1), s.ncodeunits * codesize)
+    v = ImmutableMemoryView(parent(s))
+    @inbounds v[(s.offset + 1):(s.offset + s.ncodeunits)]
 end
 
 # Special implementation for SubString{String}, which we can guarantee never

test/runtests.jl

@@ -91,6 +91,64 @@ end
     @test mem == v
 end
 
+struct CharString <: AbstractString
+    x::Vector{Char}
+end
+Base.codeunit(s::CharString, i::Int) = reinterpret(UInt32, s.x[i])
+Base.codeunit(s::CharString) = UInt32
+Base.ncodeunits(s::CharString) = length(s.x)
+Base.thisind(s::CharString, i) = i
+Base.isvalid(s::CharString, i::Integer) = in(i, 1:ncodeunits(s))
+CharString(s::String) = CharString(collect(s))
+
+function Base.nextind(s::CharString, i::Int, n::Int)
+    if iszero(n)
+        if !(iszero(i) || in(i, eachindex(s.x)))
+            throw(BoundsError(s, i))
+        else
+            i
+        end
+    else
+        in(i, 0:lastindex(s.x)) ? i + n : throw(BoundsError(s, i))
+    end
+end
+
+function Base.iterate(s::CharString, i::Int=1)
+    i > ncodeunits(s) ? nothing : (s.x[i], i + 1)
+end
+
+MemoryView(s::CharString) = MemoryView(s.x)
+
+@testset "Substrings" begin
+    for (s, i) in [
+        ("æøåac", 1:5),
+        ("æøåac", 2:4),
+        ("æøåac", 4:3),
+        ("æøåac", 1:1),
+        ("", 1:0),
+        ("儒家孟子", 2:4),
+    ]
+        ss = SubString(CharString(s), i)
+        v1 = MemoryView(ss)
+        @test v1 isa ImmutableMemoryView{Char}
+        v2 = ImmutableMemoryView(collect(s)[i])
+        @test v1 == v2
+    end
+
+    for (s, i) in [
+        ("æøåac", 1:8),
+        ("æøåac", 3:7),
+        ("æøåac", 5:4),
+        ("æøåac", 1:1),
+        ("", 1:0),
+        ("儒家孟子", 4:10),
+    ]
+        ss = SubString(s, i)
+        @test MemoryView(ss) isa ImmutableMemoryView{UInt8}
+        @test MemoryView(ss) == MemoryView(String(ss))
+    end
+end
+
 memlen(x) = length(MemoryView(x))
 @testset "Zero allocation" begin
     for v in MUT_BACKINGS
@@ -330,6 +388,14 @@ end
             @test cmp(MemoryView(a), MemoryView(b)) == y
         end
     end
+
+    @testset "Parent" begin
+        mem = Memory{UInt16}(undef, 3)
+        vec = Base.wrap(Array, mem, (3,))
+        v = MemoryView(vec)
+        @test parent(v) === mem
+        @test parent(ImmutableMemoryView(mem)) === mem
+    end
 end
 
 @testset "Equality" begin