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Honor read overrides on IO subclasses when sniffing #180

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Honor read overrides on IO subclasses when sniffing #180

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feba7f2
Honor read overrides on IO subclasses when sniffing
OskarEichler Aug 28, 2026
b10450b
test: cover overridden StringIO read methods
OskarEichler Aug 29, 2026
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5 changes: 3 additions & 2 deletions lib/marcel/magic.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -317,9 +317,10 @@ def self.io_read(io, length, buffer, mode)
end

def self.read_mode(io)
return :native if io.is_a?(IO) || io.is_a?(StringIO)
reader = io.method(:read)
return :native if reader.owner == IO || reader.owner == StringIO

parameters = io.method(:read).parameters
parameters = reader.parameters
supports_buffer = parameters.any? { |kind,| kind == :rest } ||
parameters.count { |kind,| kind == :req || kind == :opt } >= 2
supports_buffer ? :buffer : :single
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14 changes: 14 additions & 0 deletions test/magic_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,20 @@ def read(*)
end
end

test "StringIO subclasses can override read without accepting a buffer" do
io_class = Class.new(StringIO) do
def read(length)
super(length)
end
end
io = io_class.new("abcdef")
buffer = String.new(encoding: Encoding::BINARY)
mode = Marcel::Magic.send(:read_mode, io)

assert_equal :single, mode
assert_equal "abc", Marcel::Magic.send(:io_read, io, 3, buffer, mode)
end

# Before Tika 4.0.0, the timestamped-data magic matched any 11-byte OID under the
# 1.2.840.113549 arc, so sibling CMS content types (compressedData, authData, ...) in
# 1.2.840.113549.1.9.16.1.* were misdetected as application/timestamped-data. The 4.0.0
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