transcode data without copying (#11)

* transcode data without copying

* test reusability of encoder and decoder

Author: bicycle1885

src/buffer.jl

@@ -182,6 +182,15 @@ function copymarked(buf::Buffer)
     return buf.data[buf.markpos:buf.marginpos-1]
 end
 
+# Take the ownership of the marked data.
+function takemarked!(buf::Buffer)
+    @assert buf.markpos > 0
+    sz = buf.marginpos - buf.markpos
+    copy!(buf.data, 1, buf.data, buf.markpos, sz)
+    initbuffer!(buf)
+    return resize!(buf.data, sz)
+end
+
 # Read as much data as possbile from `input` to the margin of `output`.
 # This function will not block if `input` has buffered data.
 function readdata!(input::IO, output::Buffer)

src/stream.jl

@@ -327,7 +327,7 @@ function Base.transcode(codec::Codec, data::Vector{UInt8})
     mark!(buffer2)
     stream = TranscodingStream(codec, DevNull, State(Buffer(data), buffer2))
     write(stream, TOKEN_END)
-    transcoded = copymarked(buffer2)
+    transcoded = takemarked!(buffer2)
     changestate!(stream, :idle)
     return transcoded
 end

src/testtools.jl

@@ -26,9 +26,11 @@ end
 
 function test_roundtrip_transcode(encode, decode)
     srand(12345)
+    encoder = encode()
+    decoder = decode()
     for n in vcat(0:30, sort!(rand(500:100_000, 30))), alpha in (0x00:0xff, 0x00:0x0f)
         data = rand(alpha, n)
-        Base.Test.@test hash(transcode(decode(), transcode(encode(), data))) == hash(data)
+        Base.Test.@test hash(transcode(decoder, transcode(encoder, data))) == hash(data)
     end
 end