Module: RedQuilt::Indentation

Defined in:
lib/red_quilt/indentation.rb

Overview

Stateless CommonMark indentation / column arithmetic, shared by the block parser and its collaborator parsers (List, Blockquote, Footnote). Tabs expand to the next multiple of 4 columns.

Class Method Summary collapse

Class Method Details

.leading_columns(text) ⇒ Object

Leading-whitespace width of ‘text` in columns (tabs expanded to the next tab stop of 4).



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# File 'lib/red_quilt/indentation.rb', line 12

def leading_columns(text)
  col = 0
  i = 0
  bytes = text.bytesize
  while i < bytes
    b = text.getbyte(i)
    if b == 0x20
      col += 1
    elsif b == 0x09
      col = ((col / 4) + 1) * 4
    else
      break
    end
    i += 1
  end
  col
end

.leading_ws_bytes(text) ⇒ Object

Bytes of literal leading 0x20 / 0x09 in ‘text`.



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# File 'lib/red_quilt/indentation.rb', line 61

def leading_ws_bytes(text)
  i = 0
  bytes = text.bytesize
  while i < bytes
    b = text.getbyte(i)
    break unless b == 0x20 || b == 0x09

    i += 1
  end
  i
end

.strip_columns(text, n) ⇒ Object

Strips up to ‘n` columns of leading whitespace from `text` and returns the rest. Leading whitespace is normalised to spaces in the returned string so subsequent strips compose correctly regardless of where they land relative to the original tab stops.



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# File 'lib/red_quilt/indentation.rb', line 34

def strip_columns(text, n)
  return text if n <= 0

  col = 0
  i = 0
  bytes = text.bytesize
  while i < bytes
    b = text.getbyte(i)
    if b == 0x20
      col += 1
    elsif b == 0x09
      col = ((col / 4) + 1) * 4
    else
      break
    end
    i += 1
  end
  # text[0...i] is all leading whitespace representing `col` cols.
  if n >= col
    i.zero? ? text : text.byteslice(i..)
  else
    # Keep the unstripped portion as a run of spaces.
    (" " * (col - n)) + text.byteslice(i..)
  end
end