Module: Postsvg::Svg::PathData::Parser

Defined in:
lib/postsvg/svg/path_data/parser.rb

Overview

Tokenizer + parser for SVG path data. Handles the standard grammar from SVG 1.1 ยง8.3. Output is a list of Command value objects with normalized argument counts.

Constant Summary collapse

COMMAND_RE = 
/([MmLlHhVvCcSsQqTtAaZz])/
ARG_RE = 
/(-?\d+(?:\.\d+)?(?:[eE][-+]?\d+)?)/.freeze
NUMBER_ONLY_RE = 
/\A-?\d+(?:\.\d+)?(?:[eE][-+]?\d+)?\z/.freeze

Class Method Summary collapse

Class Method Details

.arity_for(opcode) ⇒ Object 



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# File 'lib/postsvg/svg/path_data/parser.rb', line 47

def arity_for(opcode)
  case opcode.upcase
  when "M", "L", "T" then 2
  when "H", "V" then 1
  when "C" then 6
  when "S", "Q" then 4
  when "A" then 7
  when "Z" then 0
  else 0
  end
end

.parse(text) ⇒ Object 



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# File 'lib/postsvg/svg/path_data/parser.rb', line 15

def parse(text)
  return [] if text.nil? || text.empty?

  commands = []
  tokens = tokenize(text)
  i = 0
  while i < tokens.length
    opcode = tokens[i]
    i += 1
    arity = arity_for(opcode)
    if arity.zero?
      commands << Command.new(opcode: opcode, args: [])
      next
    end

    # Repeat: M / L / C etc. can have multiple coordinate
    # tuples after a single opcode. Consume in groups of arity.
    loop do
      args, consumed = take_args(tokens, i, arity)
      break unless consumed == arity

      commands << Command.new(opcode: opcode, args: args)
      i += consumed
      # After moveto, implicit lineto for subsequent tuples.
      opcode = (opcode == "M") ? "L" : (opcode == "m" ? "l" : opcode)
      # For H/V/Z, no implicit repetition.
      break if %w[H V Z h v z].include?(opcode)
    end
  end
  commands
end

.take_args(tokens, start, count) ⇒ Object 



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# File 'lib/postsvg/svg/path_data/parser.rb', line 67

def take_args(tokens, start, count)
  args = []
  consumed = 0
  while consumed < count && start + consumed < tokens.length
    tok = tokens[start + consumed]
    break unless NUMBER_ONLY_RE.match?(tok.to_s)

    args << tok.to_f
    consumed += 1
  end
  [args, consumed]
end

.tokenize(text) ⇒ Object 



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# File 'lib/postsvg/svg/path_data/parser.rb', line 59

def tokenize(text)
  text.to_s.gsub(/-/, " -")
       .scan(/([MmLlHhVvCcSsQqTtAaZz])|(-?\d+(?:\.\d+)?(?:[eE][-+]?\d+)?)/)
       .flatten.compact
end