local unicode_printability_boundaries = require "luacheck.unicode_printability_boundaries"
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local unicode = {}
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-- unicode_printability_boundaries is an array of first codepoints of
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-- each continuous block of codepoints that are all printable or all not printable.
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function unicode.is_printable(codepoint)
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-- Binary search for index of the first boundary less than or equal to given codepoint.
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local floor_boundary_index
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-- Target index is always in [begin_index..end_index).
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local begin_index = 1
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local end_index = #unicode_printability_boundaries + 1
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while end_index - begin_index > 1 do
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local mid_index = math.floor((begin_index + end_index) / 2)
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local mid_codepoint = unicode_printability_boundaries[mid_index]
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if codepoint < mid_codepoint then
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end_index = mid_index
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elseif codepoint > mid_codepoint then
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begin_index = mid_index
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else
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floor_boundary_index = mid_index
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break
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end
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end
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floor_boundary_index = floor_boundary_index or begin_index
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-- floor_boundary_index is the number of the block containing codepoint.
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-- Printable and not printable blocks alternate and the first one is not printable (zero is not printable).
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return floor_boundary_index % 2 == 0
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end
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return unicode
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