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Fix interaction between unread and mark #208

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merged 3 commits into from
May 4, 2024
Merged

Fix interaction between unread and mark #208

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088637a
unread noop tests
nhz2 Apr 9, 2024
c61e12e
fix tests
nhz2 May 4, 2024
fb7aa5a
doc markpos invariant
nhz2 May 4, 2024
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32 changes: 22 additions & 10 deletions src/buffer.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
# position 1 markpos bufferpos marginpos lastindex(data)
#
# `markpos` is positive iff there are marked data; otherwise it is set to zero.
# `markpos` ≤ `bufferpos` ≤ `marginpos` must hold whenever possible.
# `markpos` ≤ `marginpos` and `bufferpos` ≤ `marginpos` must hold.

mutable struct Buffer
# data and positions (see above)
Expand Down Expand Up @@ -87,6 +87,7 @@ end

function reset!(buf::Buffer)
@assert buf.markpos > 0
@assert buf.markpos ≤ buf.marginpos
buf.bufferpos = buf.markpos
buf.markpos = 0
return buf.bufferpos
Expand Down Expand Up @@ -119,7 +120,8 @@ end

# Remove all buffered data.
function emptybuffer!(buf::Buffer)
buf.marginpos = buf.bufferpos
buf.markpos = 0
buf.bufferpos = buf.marginpos = 1
return buf
end

Expand All @@ -133,16 +135,14 @@ function makemargin!(buf::Buffer, minsize::Integer; eager::Bool = false)
if marginsize(buf) < minsize || eager
# datapos refer to the leftmost position of data that must not be
# discarded. We can left-shift to discard all data before this
if buf.markpos == 0
datapos = if iszero(buf.markpos)
# If data is not marked we must not discard buffered (nonconsumed) data
datapos = buf.bufferpos
datasize = buffersize(buf)
buf.bufferpos
else
# Else, we must not consume marked data
# (Since markpos ≤ bufferpos, we do not consume buffered data either)
datapos = buf.markpos
datasize = buf.marginpos - buf.markpos
# Else, we must not consume marked or buffered data
min(buf.markpos, buf.bufferpos)
end
datasize = buf.marginpos - datapos
# Shift data left in buffer to make space for new data
copyto!(buf.data, 1, buf.data, datapos, datasize)
shift = datapos - 1
Expand Down Expand Up @@ -204,9 +204,21 @@ end
# Insert data to the current buffer.
function insertdata!(buf::Buffer, data::Ptr{UInt8}, nbytes::Integer)
makemargin!(buf, nbytes)
copyto!(buf.data, buf.bufferpos + nbytes, buf.data, buf.bufferpos, buffersize(buf))
datapos = if iszero(buf.markpos)
# If data is not marked we must not discard buffered (nonconsumed) data
buf.bufferpos
else
# Else, we must not consume marked or buffered data
min(buf.markpos, buf.bufferpos)
end
datasize = buf.marginpos - datapos
copyto!(buf.data, datapos + nbytes, buf.data, datapos, datasize)
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These changes ensure the marked data and buffered data stay together.

GC.@preserve buf unsafe_copyto!(bufferptr(buf), data, nbytes)
supplied!(buf, nbytes)
if !iszero(buf.markpos)
buf.markpos += nbytes
end
@assert buf.markpos ≤ buf.marginpos
return buf
end

Expand Down
94 changes: 61 additions & 33 deletions test/codecnoop.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -274,44 +274,72 @@
@test !iswritable(stream)
end

stream = NoopStream(IOBuffer(""))
@test TranscodingStreams.unread(stream, b"foo") === nothing
@test read(stream, 3) == b"foo"
close(stream)
@testset "unread" begin
stream = NoopStream(IOBuffer(""))
@test TranscodingStreams.unread(stream, b"foo") === nothing
@test read(stream, 3) == b"foo"
close(stream)

stream = NoopStream(IOBuffer("foo"))
@test read(stream, 3) == b"foo"
@test TranscodingStreams.unread(stream, b"bar") === nothing
@test read(stream, 3) == b"bar"
close(stream)
stream = NoopStream(IOBuffer("foo"))
@test read(stream, 3) == b"foo"
@test TranscodingStreams.unread(stream, b"bar") === nothing
@test read(stream, 3) == b"bar"
close(stream)

stream = NoopStream(IOBuffer("foobar"))
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test read(stream, 3) == b"foo"
@test read(stream, 3) == b"bar"
@test eof(stream)
close(stream)
stream = NoopStream(IOBuffer("foobar"))
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test read(stream, 3) == b"foo"
@test read(stream, 3) == b"bar"
@test eof(stream)
close(stream)

stream = NoopStream(IOBuffer("foobar"))
@test read(stream, 3) == b"foo"
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test read(stream, 3) == b"bar"
@test eof(stream)
close(stream)
stream = NoopStream(IOBuffer("foobar"))
@test read(stream, 3) == b"foo"
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test read(stream, 3) == b"bar"
@test eof(stream)
close(stream)

stream = NoopStream(IOBuffer("foobar"))
@test read(stream, 3) == b"foo"
@test read(stream, 3) == b"bar"
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test eof(stream)
close(stream)
stream = NoopStream(IOBuffer("foobar"))
@test read(stream, 3) == b"foo"
@test read(stream, 3) == b"bar"
@test TranscodingStreams.unread(stream, b"baz") === nothing
@test read(stream, 3) == b"baz"
@test eof(stream)
close(stream)

stream = NoopStream(IOBuffer("foobar"))
@test_throws ArgumentError TranscodingStreams.unsafe_unread(stream, pointer(b"foo"), -1)
close(stream)
for bufsize in (1, 2, 3, 4, 100)
for n in (1, 100)
stream = NoopStream(IOBuffer("foo"^n*"bar"^n); bufsize)
@test mark(stream) == 0
@test read(stream, 3n) == codeunits("foo"^n)
@test read(stream, 3n) == codeunits("bar"^n)
TranscodingStreams.unread(stream, codeunits("baz"^n))
@test reset(stream) == 0
@test read(stream, 3n) == codeunits("foo"^n)
@test read(stream, 3n) == codeunits("baz"^n)
@test eof(stream)
close(stream)
end
end

# unread before mark
stream = NoopStream(IOBuffer("foobar"); bufsize=16)
@test read(stream, String) == "foobar"
mark(stream)
for i in 1:100
TranscodingStreams.unread(stream, b"foo")
end
@test read(stream, String) == "foo"^100
@test reset(stream) == 6
@test eof(stream)

stream = NoopStream(IOBuffer("foobar"))
@test_throws ArgumentError TranscodingStreams.unsafe_unread(stream, pointer(b"foo"), -1)
close(stream)
end

stream = NoopStream(IOBuffer(""))
unsafe_write(stream, C_NULL, 0)
Expand Down
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