Class: Daedalus::DependencyGrapher::ExpressionEvaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/daedalus/dependency_grapher.rb

Instance Method Summary collapse

Constructor Details

#initialize(expression) ⇒ ExpressionEvaluator

Returns a new instance of ExpressionEvaluator.



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# File 'lib/daedalus/dependency_grapher.rb', line 27

def initialize(expression)
  @expression = expression
end

Instance Method Details

#evaluate(defines) ⇒ Object 



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# File 'lib/daedalus/dependency_grapher.rb', line 31

def evaluate(defines)
  # Stage0: eliminate comments
  @expression.gsub!(/(\/\/.*)$/, "")
  @expression.gsub!(/(\/\*.*\*\/)/, "")

  # Stage1: find 'defined's and evaluate
  #         replace defined with boolean evaluation value
  re = /((!|\s*)?defined((\(|\s+)(\s*[^) ]+)(\)|\s|$)))/o
  @expression.gsub!(re) do |expr|
    m = expr.match(re)
    negate = m[2] == "!"
    key = m[5].strip

    value = defines.include? key
    value = !value if negate
    value ? "true" : "false"
  end

  # Stage2: scan macro-defined keywords
  #         replace with actual value (true or false)
  # this covers patterns like __clang__ and __x86_64__
  @expression.gsub!(/__[A-Za-z0-9_]+__/) do |expr|
    if defines.include?(expr)
      defines[expr].to_s
    elsif integer?(expr)
      expr
    else
      '0'
    end
  end

  # this covers other patters.
  @expression.gsub!(/[A-Z0-9_]{4,}/) do |expr|
    if defines.include?(expr)
      defines[expr].to_s
    elsif integer?(expr)
      expr
    else
      '0'
    end
  end

  # Stage3: Evaluate with ruby eval()
  eval(@expression)
end