Add GC.@preserve when using pointers (#221)

Author: nhz2

docs/src/examples.md

@@ -178,7 +178,7 @@ using CodecZlib
 
 function decompress(input, output)
     buffer = Vector{UInt8}(undef, 16 * 1024)
-    while !eof(input)
+    GC.@preserve buffer while !eof(input)
         n = min(bytesavailable(input), length(buffer))
         unsafe_read(input, pointer(buffer), n)
         unsafe_write(output, pointer(buffer), n)

src/memory.jl

@@ -11,6 +11,7 @@ struct Memory
     size::UInt
 end
 
+# TODO remove this method
 function Memory(data::ByteData)
     return Memory(pointer(data), sizeof(data))
 end

src/stream.jl

@@ -343,16 +343,18 @@ function Base.readuntil(stream::TranscodingStream, delim::UInt8; keep::Bool=fals
     local ret::Vector{UInt8}
     filled = 0
     while !eof(stream)
-        p = findbyte(buffer1, delim)
-        found = false
-        if p < marginptr(buffer1)
-            found = true
-            sz = Int(p + 1 - bufferptr(buffer1))
-            if !keep
-                sz -= 1
+        GC.@preserve buffer1 begin
+            p = findbyte(buffer1, delim)
+            found = false
+            if p < marginptr(buffer1)
+                found = true
+                sz = Int(p + 1 - bufferptr(buffer1))
+                if !keep
+                    sz -= 1
+                end
+            else
+                sz = buffersize(buffer1)
             end
-        else
-            sz = buffersize(buffer1)
         end
         if @isdefined(ret)
             resize!(ret, filled + sz)
@@ -703,9 +705,11 @@ end
 # Call `process` with prologue and epilogue.
 function callprocess(stream::TranscodingStream, inbuf::Buffer, outbuf::Buffer)
     state = stream.state
-    input = buffermem(inbuf)
-    GC.@preserve inbuf makemargin!(outbuf, minoutsize(stream.codec, input))
-    Δin::Int, Δout::Int, state.code = GC.@preserve inbuf outbuf process(stream.codec, input, marginmem(outbuf), state.error)
+    makemargin!(
+        outbuf,
+        GC.@preserve(inbuf, minoutsize(stream.codec, buffermem(inbuf))),
+    )
+    Δin::Int, Δout::Int, state.code = GC.@preserve inbuf outbuf process(stream.codec, buffermem(inbuf), marginmem(outbuf), state.error)
     @debug(
         "called process()",
         code = state.code,

src/transcode.jl

@@ -46,10 +46,10 @@ function Base.transcode(codec::Type{C}, src::String) where {C<:Codec}
 end
 
 _default_output_buffer(codec, input) = Buffer(
-    initial_output_size(
+    GC.@preserve(input, initial_output_size(
         codec,
         buffermem(input)
-    )
+    ))
 )
 
 """
@@ -125,8 +125,7 @@ function transcode!(
     Base.mightalias(input.data, output.data) && error(
         "input and outbut buffers must be independent"
     )
-    # GC.@preserve since unsafe_transcode! may convert to raw pointers
-    GC.@preserve input output codec unsafe_transcode!(output, codec, input)
+    unsafe_transcode!(output, codec, input)
 end
 
 """
@@ -148,10 +147,10 @@ function unsafe_transcode!(
     if code === :error
         @goto error
     end
-    n = minoutsize(codec, buffermem(input))
+    n = GC.@preserve input minoutsize(codec, buffermem(input))
     @label process
     makemargin!(output, n)
-    Δin, Δout, code = process(codec, buffermem(input), marginmem(output), error)
+    Δin, Δout, code = GC.@preserve input output process(codec, buffermem(input), marginmem(output), error)
     @debug(
         "called process()",
         code = code,
@@ -169,13 +168,13 @@ function unsafe_transcode!(
             if startproc(codec, :write, error) === :error
                 @goto error
             end
-            n = minoutsize(codec, buffermem(input))
+            n = GC.@preserve input minoutsize(codec, buffermem(input))
             @goto process
         end
         resize!(output.data, output.marginpos - 1)
         return output.data
     else
-        n = max(Δout, minoutsize(codec, buffermem(input)))
+        n = GC.@preserve input max(Δout, minoutsize(codec, buffermem(input)))
         @goto process
     end
     @label error

test/codecnoop.jl

@@ -24,13 +24,14 @@ using FillArrays: Zeros
 
     stream = TranscodingStream(Noop(), IOBuffer())
     @test_throws EOFError read(stream, UInt8)
-    @test_throws EOFError unsafe_read(stream, pointer(Vector{UInt8}(undef, 3)), 3)
+    data = Vector{UInt8}(undef, 3)
+    @test_throws EOFError GC.@preserve data unsafe_read(stream, pointer(data), 3)
     close(stream)
 
     stream = TranscodingStream(Noop(), IOBuffer("foobar"), bufsize=1)
     @test read(stream, UInt8) === UInt8('f')
     data = Vector{UInt8}(undef, 5)
-    unsafe_read(stream, pointer(data), 5) === nothing
+    GC.@preserve data unsafe_read(stream, pointer(data), 5) === nothing
     @test data == b"oobar"
     close(stream)
 
@@ -122,7 +123,7 @@ using FillArrays: Zeros
     stream = TranscodingStream(Noop(), IOBuffer("foo"))
     out = zeros(UInt8, 3)
     @test bytesavailable(stream) == 0
-    @test TranscodingStreams.unsafe_read(stream, pointer(out), 10) == 3
+    @test GC.@preserve out TranscodingStreams.unsafe_read(stream, pointer(out), 10) == 3
     @test out == b"foo"
     close(stream)
 
@@ -384,7 +385,8 @@ using FillArrays: Zeros
         @test eof(stream)
 
         stream = NoopStream(IOBuffer("foobar"))
-        @test_throws ArgumentError TranscodingStreams.unsafe_unread(stream, pointer(b"foo"), -1)
+        data = b"foo"
+        @test_throws ArgumentError GC.@preserve data TranscodingStreams.unsafe_unread(stream, pointer(data), -1)
         close(stream)
 
         stream = NoopStream(IOBuffer("foo"))

test/codecquadruple.jl

@@ -81,7 +81,8 @@ end
     close(stream2)
 
     stream = TranscodingStream(QuadrupleCodec(), IOBuffer("foo"))
-    @test_throws EOFError unsafe_read(stream, pointer(Vector{UInt8}(undef, 13)), 13)
+    data = Vector{UInt8}(undef, 13)
+    @test_throws EOFError GC.@preserve data unsafe_read(stream, pointer(data), 13)
     close(stream)
 
     @testset "position" begin

test/runtests.jl

@@ -26,13 +26,15 @@ using TranscodingStreams:
 
     data = Vector{UInt8}(b"foobar")
     buf = Buffer(data)
-    @test buf isa Buffer
-    @test bufferptr(buf) === pointer(data)
-    @test buffersize(buf) === 6
-    @test buffermem(buf) === Memory(pointer(data), 6)
-    @test marginptr(buf) === pointer(data) + 6
-    @test marginsize(buf) === 0
-    @test marginmem(buf) === Memory(pointer(data)+6, 0)
+    GC.@preserve data buf begin
+        @test buf isa Buffer
+        @test bufferptr(buf) === pointer(data)
+        @test buffersize(buf) === 6
+        @test buffermem(buf) === Memory(pointer(data), 6)
+        @test marginptr(buf) === pointer(data) + 6
+        @test marginsize(buf) === 0
+        @test marginmem(buf) === Memory(pointer(data)+6, 0)
+    end
 
     buf = Buffer(2)
     writebyte!(buf, 0x34)
@@ -72,31 +74,33 @@ end
 
 @testset "Memory" begin
     data = Vector{UInt8}(b"foobar")
-    mem = TranscodingStreams.Memory(pointer(data), sizeof(data))
-    @test mem isa TranscodingStreams.Memory
-    @test mem.ptr === pointer(data)
-    @test mem.size === length(mem) === UInt(sizeof(data))
-    @test lastindex(mem) === 6
-    @test mem[1] === UInt8('f')
-    @test mem[2] === UInt8('o')
-    @test mem[3] === UInt8('o')
-    @test mem[4] === UInt8('b')
-    @test mem[5] === UInt8('a')
-    @test mem[6] === UInt8('r')
-    @test_throws BoundsError mem[7]
-    @test_throws BoundsError mem[0]
-    mem[1] = UInt8('z')
-    @test mem[1] === UInt8('z')
-    mem[3] = UInt8('!')
-    @test mem[3] === UInt8('!')
-    @test_throws BoundsError mem[7] = 0x00
-    @test_throws BoundsError mem[0] = 0x00
+    GC.@preserve data let mem = TranscodingStreams.Memory(pointer(data), sizeof(data))
+        @test mem isa TranscodingStreams.Memory
+        @test mem.ptr === pointer(data)
+        @test mem.size === length(mem) === UInt(sizeof(data))
+        @test lastindex(mem) === 6
+        @test mem[1] === UInt8('f')
+        @test mem[2] === UInt8('o')
+        @test mem[3] === UInt8('o')
+        @test mem[4] === UInt8('b')
+        @test mem[5] === UInt8('a')
+        @test mem[6] === UInt8('r')
+        @test_throws BoundsError mem[7]
+        @test_throws BoundsError mem[0]
+        mem[1] = UInt8('z')
+        @test mem[1] === UInt8('z')
+        mem[3] = UInt8('!')
+        @test mem[3] === UInt8('!')
+        @test_throws BoundsError mem[7] = 0x00
+        @test_throws BoundsError mem[0] = 0x00
+    end
 
     data = Vector{UInt8}(b"foobar")
-    mem = TranscodingStreams.Memory(data)
-    @test mem isa TranscodingStreams.Memory
-    @test mem.ptr == pointer(data)
-    @test mem.size == sizeof(data)
+    GC.@preserve data let mem = TranscodingStreams.Memory(pointer(data), sizeof(data))
+        @test mem isa TranscodingStreams.Memory
+        @test mem.ptr == pointer(data)
+        @test mem.size == sizeof(data)
+    end
 end
 
 @testset "Stats" begin