Fix position for NoopStream in :write mode (#118)

src/noop.jl

@@ -51,7 +51,16 @@ Note that this method may return a wrong position when
 - the position of the wrapped stream has been changed outside of this package.
 """
 function Base.position(stream::NoopStream)
-    return position(stream.stream) - buffersize(stream.state.buffer1)
+    mode = stream.state.mode
+    @checkmode (:idle, :read, :write)
+    if mode === :idle
+        return Int64(0)
+    elseif mode === :write
+        return position(stream.stream) + buffersize(stream.state.buffer1)
+    elseif mode === :read
+        return position(stream.stream) - buffersize(stream.state.buffer1)
+    end
+    @assert false "unreachable"
 end
 
 function Base.seek(stream::NoopStream, pos::Integer)
@@ -126,7 +135,7 @@ function stats(stream::NoopStream)
     mode = state.mode
     @checkmode (:idle, :read, :write)
     buffer = state.buffer1
-    @assert buffer == stream.state.buffer2
+    @assert buffer === stream.state.buffer2
     if mode == :idle
         consumed = supplied = 0
     elseif mode == :read

test/codecnoop.jl

@@ -283,4 +283,29 @@
     @test_throws ArgumentError NoopStream(let s = IOBuffer(); close(s); s; end)
     @test_throws ArgumentError TranscodingStream(Noop(), IOBuffer(), bufsize=0)
     @test_throws ArgumentError TranscodingStream(Noop(), IOBuffer(), sharedbuf=true)
+
+    @testset "position" begin
+        iob = IOBuffer()
+        sink = IOBuffer()
+        stream = NoopStream(sink, bufsize=16)
+        @test position(stream) == position(iob)
+        for len in 0:10:100
+            write(stream, repeat("x", len))
+            write(iob, repeat("x", len))
+            @test position(stream) == position(iob)
+        end
+        @test position(stream) == position(sink) == position(iob)
+        close(stream)
+        close(iob)
+
+        mktemp() do path, sink
+            stream = NoopStream(sink, bufsize=16)
+            pos = 0
+            for len in 0:10:100
+                write(stream, repeat("x", len))
+                pos += len
+                @test position(stream) == pos
+            end
+        end
+    end
 end

test/codecquadruple.jl

@@ -83,4 +83,28 @@ end
     stream = TranscodingStream(QuadrupleCodec(), IOBuffer("foo"))
     @test_throws EOFError unsafe_read(stream, pointer(Vector{UInt8}(undef, 13)), 13)
     close(stream)
+
+    @testset "position" begin
+        iob = IOBuffer()
+        sink = IOBuffer()
+        stream = TranscodingStream(QuadrupleCodec(), sink, bufsize=16)
+        @test position(stream) == position(iob)
+        for len in 0:10:100
+            write(stream, repeat("x", len))
+            write(iob, repeat("x", len))
+            @test position(stream) == position(iob)
+        end
+        close(stream)
+        close(iob)
+
+        mktemp() do path, sink
+            stream = TranscodingStream(QuadrupleCodec(), sink, bufsize=16)
+            pos = 0
+            for len in 0:10:100
+                write(stream, repeat("x", len))
+                pos += len
+                @test position(stream) == pos
+            end
+        end
+    end
 end