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Refactoring tidy_bytes, part 2
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Felipe
GitHub
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@ -1,136 +1,69 @@
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# frozen_string_literal: true
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module TidyBytes
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# Using a frozen array so we have a O(1) lookup time
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CP1252_MAP = Array.new(160) do |i|
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case i
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when 128 then [226, 130, 172]
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when 130 then [226, 128, 154]
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when 131 then [198, 146]
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when 132 then [226, 128, 158]
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when 133 then [226, 128, 166]
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when 134 then [226, 128, 160]
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when 135 then [226, 128, 161]
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when 136 then [203, 134]
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when 137 then [226, 128, 176]
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when 138 then [197, 160]
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when 139 then [226, 128, 185]
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when 140 then [197, 146]
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when 142 then [197, 189]
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when 145 then [226, 128, 152]
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when 146 then [226, 128, 153]
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when 147 then [226, 128, 156]
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when 148 then [226, 128, 157]
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when 149 then [226, 128, 162]
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when 150 then [226, 128, 147]
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when 151 then [226, 128, 148]
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when 152 then [203, 156]
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when 153 then [226, 132, 162]
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when 154 then [197, 161]
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when 155 then [226, 128, 186]
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when 156 then [197, 147]
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when 158 then [197, 190]
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when 159 then [197, 184]
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# precomputing CP1252 to UTF-8 mappings for bytes 128-159
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CP1252_MAP = (128..159).map do |byte|
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case byte
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when 128 then [226, 130, 172] # EURO SIGN
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when 130 then [226, 128, 154] # SINGLE LOW-9 QUOTATION MARK
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when 131 then [198, 146] # LATIN SMALL LETTER F WITH HOOK
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when 132 then [226, 128, 158] # DOUBLE LOW-9 QUOTATION MARK
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when 133 then [226, 128, 166] # HORIZONTAL ELLIPSIS
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when 134 then [226, 128, 160] # DAGGER
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when 135 then [226, 128, 161] # DOUBLE DAGGER
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when 136 then [203, 134] # MODIFIER LETTER CIRCUMFLEX ACCENT
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when 137 then [226, 128, 176] # PER MILLE SIGN
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when 138 then [197, 160] # LATIN CAPITAL LETTER S WITH CARON
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when 139 then [226, 128, 185] # SINGLE LEFT-POINTING ANGLE QUOTATION MARK
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when 140 then [197, 146] # LATIN CAPITAL LIGATURE OE
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when 142 then [197, 189] # LATIN CAPITAL LETTER Z WITH CARON
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when 145 then [226, 128, 152] # LEFT SINGLE QUOTATION MARK
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when 146 then [226, 128, 153] # RIGHT SINGLE QUOTATION MARK
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when 147 then [226, 128, 156] # LEFT DOUBLE QUOTATION MARK
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when 148 then [226, 128, 157] # RIGHT DOUBLE QUOTATION MARK
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when 149 then [226, 128, 162] # BULLET
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when 150 then [226, 128, 147] # EN DASH
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when 151 then [226, 128, 148] # EM DASH
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when 152 then [203, 156] # SMALL TILDE
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when 153 then [226, 132, 162] # TRADE MARK SIGN
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when 154 then [197, 161] # LATIN SMALL LETTER S WITH CARON
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when 155 then [226, 128, 186] # SINGLE RIGHT-POINTING ANGLE QUOTATION MARK
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when 156 then [197, 147] # LATIN SMALL LIGATURE OE
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when 158 then [197, 190] # LATIN SMALL LETTER Z WITH CARON
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when 159 then [197, 184] # LATIN SMALL LETTER Y WITH DIAERESIS
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end
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end.freeze
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# precomputing all possible byte conversions
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CP1252_TO_UTF8 = Array.new(256) do |b|
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if (128..159).cover?(b)
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CP1252_MAP[b - 128]&.pack('C*')
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elsif b < 128
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b.chr
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else
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b < 192 ? [194, b].pack('C*') : [195, b - 64].pack('C*')
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end
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end.freeze
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def self.included(base)
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base.class_eval do
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private
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def tidy_byte(byte)
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if byte < 160
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CP1252_MAP[byte]
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else
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byte < 192 ? [194, byte] : [195, byte - 64]
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end
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end
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public
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# Attempt to replace invalid UTF-8 bytes with valid ones. This method
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# naively assumes if you have invalid UTF8 bytes, they are either Windows
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# CP-1252 or ISO8859-1. In practice this isn't a bad assumption, but may not
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# always work.
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#
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# Passing +true+ will forcibly tidy all bytes, assuming that the string's
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# encoding is CP-1252 or ISO-8859-1.
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def tidy_bytes(force = false)
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return nil if empty?
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if force
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buffer = String.new(capacity: bytesize)
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each_byte do |b|
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cleaned = tidy_byte(b)
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buffer << cleaned.pack("C*") if cleaned
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end
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each_byte { |b| buffer << CP1252_TO_UTF8[b] }
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return buffer.force_encoding(Encoding::UTF_8)
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end
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buffer = String.new(capacity: bytesize)
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bytes = each_byte.to_a
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conts_expected = 0
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last_lead = 0
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bytes.each_with_index do |byte, i|
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if byte < 128 # ASCII
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buffer << byte
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next
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end
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if byte > 244 || byte > 240 # invalid bytes
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cleaned = tidy_byte(byte)
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buffer << cleaned.pack("C*") if cleaned
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next
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end
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is_cont = byte > 127 && byte < 192
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is_lead = byte > 191 && byte < 245
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if is_cont
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# Not expecting continuation byte? Clean up. Otherwise, now expect one less.
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if conts_expected == 0
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cleaned = tidy_byte(byte)
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buffer << cleaned.pack("C*") if cleaned
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else
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buffer << byte
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conts_expected -= 1
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end
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else
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if conts_expected > 0
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# Expected continuation, but got ASCII or leading? Clean backwards up to
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# the leading byte.
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(1..(i - last_lead)).each do |j|
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back_byte = bytes[i - j]
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cleaned = tidy_byte(back_byte)
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buffer << cleaned.pack("C*") if cleaned
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end
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conts_expected = 0
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end
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if is_lead
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# Final byte is leading? Clean it.
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if i == bytes.length - 1
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cleaned = tidy_byte(byte)
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buffer << cleaned.pack("C*") if cleaned
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else
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# Valid leading byte? Expect continuations determined by position of
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# first zero bit, with max of 3.
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buffer << byte
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conts_expected = byte < 224 ? 1 : byte < 240 ? 2 : 3
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last_lead = i
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end
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end
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end
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begin
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encode('UTF-8')
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rescue Encoding::UndefinedConversionError, Encoding::InvalidByteSequenceError
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buffer = String.new(capacity: bytesize)
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scrub { |b| CP1252_TO_UTF8[b.ord] }
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end
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buffer.force_encoding(Encoding::UTF_8)
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rescue
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nil
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end
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# Tidy bytes in place.
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def tidy_bytes!(force = false)
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result = tidy_bytes(force)
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result ? replace(result) : self
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