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Optimise unescape #457

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Optimise unescape #457

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14 changes: 9 additions & 5 deletions lib/rdf/ntriples/reader.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,8 @@ def self.parse_literal(input, **options)
ESCAPE_CHARS_ESCAPED_REGEXP = Regexp.union(
ESCAPE_CHARS_ESCAPED.keys
).freeze
# Combined pattern for a single-pass unescape (UCHAR first, then escape chars)
UNESCAPE_COMBINED = Regexp.union(UCHAR, ESCAPE_CHARS_ESCAPED_REGEXP).freeze

##
# @param [String] string
Expand All @@ -190,11 +192,13 @@ def self.unescape(string)
# greatly reduces the number of allocations and the processing time.
string = string.dup.force_encoding(Encoding::UTF_8) unless string.encoding == Encoding::UTF_8

string
.gsub(UCHAR) do
[($1 || $2).hex].pack('U*')
end
.gsub(ESCAPE_CHARS_ESCAPED_REGEXP, ESCAPE_CHARS_ESCAPED)
# Early return when nothing to unescape: avoids string allocation entirely.
return string unless string.match?(UNESCAPE_COMBINED)

# Single pass handles both \uXXXX/\UXXXXXXXX and backslash escape chars.
string.gsub(UNESCAPE_COMBINED) do |match|
($1 || $2) ? [($1 || $2).hex].pack('U*') : ESCAPE_CHARS_ESCAPED[match]
end
end

##
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