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module Gitlab
module EncodingHelper
extend self
# This threshold is carefully tweaked to prevent usage of encodings detected
# by CharlockHolmes with low confidence. If CharlockHolmes confidence is low,
# we're better off sticking with utf8 encoding.
# Reason: git diff can return strings with invalid utf8 byte sequences if it
# truncates a diff in the middle of a multibyte character. In this case
# CharlockHolmes will try to guess the encoding and will likely suggest an
# obscure encoding with low confidence.
# There is a lot more info with this merge request:
# https://gitlab.com/gitlab-org/gitlab_git/merge_requests/77#note_4754193
ENCODING_CONFIDENCE_THRESHOLD = 50
def encode!(message)
return nil unless message.respond_to? :force_encoding
# if message is utf-8 encoding, just return it
message.force_encoding("UTF-8")
return message if message.valid_encoding?
# return message if message type is binary
detect = CharlockHolmes::EncodingDetector.detect(message)
return message.force_encoding("BINARY") if detect_binary?(message, detect)
if detect && detect[:encoding] && detect[:confidence] > ENCODING_CONFIDENCE_THRESHOLD
# force detected encoding if we have sufficient confidence.
message.force_encoding(detect[:encoding])
end
# encode and clean the bad chars
message.replace clean(message)
rescue
encoding = detect ? detect[:encoding] : "unknown"
"--broken encoding: #{encoding}"
end
def detect_binary?(data, detect = nil)
detect ||= CharlockHolmes::EncodingDetector.detect(data)
detect && detect[:type] == :binary && detect[:confidence] == 100
end
def detect_libgit2_binary?(data)
# EncodingDetector checks the first 1024 * 1024 bytes for NUL byte, libgit2 checks
# only the first 8000 (https://github.com/libgit2/libgit2/blob/2ed855a9e8f9af211e7274021c2264e600c0f86b/src/filter.h#L15),
# which is what we use below to keep a consistent behavior.
detect = CharlockHolmes::EncodingDetector.new(8000).detect(data)
detect && detect[:type] == :binary
end
def encode_utf8(message)
detect = CharlockHolmes::EncodingDetector.detect(message)
if detect && detect[:encoding]
begin
CharlockHolmes::Converter.convert(message, detect[:encoding], 'UTF-8')
rescue ArgumentError => e
Rails.logger.warn("Ignoring error converting #{detect[:encoding]} into UTF8: #{e.message}")
''
end
else
clean(message)
end
end
# Convert all characters to the desired encoding, and drop the characters not available in that encoding
def lossy_encode(message, encoding)
message.encode(encoding, invalid: :replace, undef: :replace, replace: '')
end
private
def clean(message)
message.encode("UTF-16BE", undef: :replace, invalid: :replace, replace: "")
.encode("UTF-8")
.gsub("\0".encode("UTF-8"), "")
end
end
end
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