Class: Ppr::Macro

Inherits:
Object
  • Object
show all
Defined in:
lib/ppr/ppr_core.rb

Overview

Describes a macro of the ruby preprocessor.

Direct Known Subclasses

Assign, If, LoadRequire

Constant Summary collapse

E_NUMBER =

Regular expression for identifying a line number inside an exception message.

/:[1-9][0-9]*:/
E_TYPE =

Type of exception which correspond to a macro execution.

/\(eval\)\s*/

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, num, ppr, *variables, expand: ":<", final: true) ⇒ Macro

Creates a new macro named name, starting at line number num, generated from preprocessor ppr and with possible variables.

Other parameters:

expand

used to redefine the expand operator

final

indicates that the result of the macro expansion

shall not be preprocessed again.



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# File 'lib/ppr/ppr_core.rb', line 48

def initialize(name, num, ppr, *variables, expand: ":<", final: true)
    # Check and set the name.
    @name = name.to_str
    # Check and set the line number of the begining of the macro.
    @start_num = num.to_i
    # Check and set the preprocessor
    unless ppr.is_a?(Preprocessor) then
        raise "Invalid class for a preprocessor: #{ppr.class}"
    end
    @ppr = ppr
    # The start of the macro code is unknown at first (will be known
    # when generating the code).
    @code_num = nil
    # Check and set the variables.
    # print "variables=#{variables}\n"
    @variables = variables.map do |variable|
        variable = variable.to_str
        unless variable.match(/^[a-z_][a-z0-9_]*$/)
            raise "Invalid string for a macro variable: #{variable}"
        end
        variable
    end

    # Initialize the content of the macro as an array of lines.
    @lines = []

    # Set the default expansion operator string.
    @expand = expand

    # Set the macro code expansion result status: when final, no
    # other macro is applied on it, otherwise, it is preprocessed again.
    @final = final ? true : false
end

Instance Attribute Details

#name ⇒ Object (readonly)

The name of the macro.



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# File 'lib/ppr/ppr_core.rb', line 39

def name
  @name
end

Class Method Details

.e_message(name, message, i_number, number = nil) ⇒ Object

Update an exception message to refer macro name invoked at line number i_number and adds a possible macro line number.



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# File 'lib/ppr/ppr_core.rb', line 191

def Macro.e_message(name, message, i_number, number = nil)
    result = "Ppr error (#{name}:#{i_number})"
    result << ":#{number}: " if number
    result << message
    return result
end

Instance Method Details

#add(line) ⇒ Object Also known as: <<

Adds a line to the macro.



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# File 'lib/ppr/ppr_core.rb', line 97

def add(line)
    # Process the line.
    # Remove the ending newline if any.
    @lines << line.chomp
end

#apply(i_number, *arguments) ⇒ Object

Applies the macro invoked at line number i_number with arguments.



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# File 'lib/ppr/ppr_core.rb', line 205

def apply(i_number,*arguments)
    # Generate the code of the macro.
    code = self.generate(i_number,*arguments)
    # Evaluate the code in the safe context of ppr.
    # print "code=#{code}\n"
    begin
        return @ppr.run do |__stream__|
            __ppr__ = @ppr
            begin
                __stream__ << eval(code) 
            # rescue Exception => e
            #     raise e
            end
        end
    rescue Exception => e
        if e.is_a?(SaferGenerator::SaferException) then
            # An exception happened while executing the macro code,
            # get the cause (which contains the exception which has
            # been raised while executing the macro).
            cause = e.cause
            message = cause.message
            # Update the line number in the message if any.
            if e_number(message) then
                # There is a line number, update it in the context of
                # the processed file.
                message = e_shift_number(message, @start_num - @code_num)
                # Raise the exception again with the updated message.
                raise cause, e_message(message.gsub(E_TYPE,""),i_number)
            else
                # There was not any line number in the message, look
                # for it into the backtrack message.
                number = cause.backtrace.find do |trace|
                    found = e_number(trace)
                    if found and e_type?(trace,E_TYPE)
                        break found
                    else
                        next nil
                    end
                end
                if number then
                    # Update the line number in the context of the processed
                    # file.
                    number += @start_num - @code_num
                    # The number found, raise the exception again with
                    # the message updated with the number.
                    raise cause,
                        e_message(message.gsub(E_TYPE,""),i_number,number)
                else
                    # No number, use the macro start instead for
                    # raising the exception.
                    raise cause, e_message(message,i_number,@start_num)
                end
            end        
        else
            # An exception happened due to an internal error of the
            # SaferGenerator class, raise it as is.
            raise e
        end
    end
end

#e_message(message, i_number, number = nil) ⇒ Object

Update an exception message to refer the macro invoked at line number i_number and adds a possible macro line number.



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# File 'lib/ppr/ppr_core.rb', line 200

def e_message(message, i_number, number = nil)
    Macro.e_message(@name,message,i_number,number)
end

#e_number(message) ⇒ Object

Tells if an exception message includes a line number.



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# File 'lib/ppr/ppr_core.rb', line 155

def e_number(message)
    found = E_NUMBER.match(message)
    if found then
        # The number is found, return it.
        return found.to_s[1..-2].to_i
    else
        # The number is not found.
        return nil
    end
end

#e_shift_number(message, sh) ⇒ Object

Shifts the line number inside an exception message by sh.



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# File 'lib/ppr/ppr_core.rb', line 172

def e_shift_number(message,sh)
    # Edit the message to fix the line number and raise then.
    return message.gsub(E_NUMBER) { |str|
        # Remove the ':'
        str = str[1..-2]
        # Get and check the line number.
        num = str.to_i
        # print "num=#{num}\n"
        if num.to_s == str then
            # This is really a line number.
            ":#{num+sh}:"
        else
            ":#{str}:"
        end
    }
end

#e_type?(message, type) ⇒ Boolean

Tells if an exception message is of a given type.

Returns:

  • (Boolean) 


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# File 'lib/ppr/ppr_core.rb', line 167

def e_type?(message,type)
    return message =~ Regexp.new(type)
end

#empty? ⇒ Boolean

Checks if the macro is empty (no code line yet).

Returns:

  • (Boolean) 


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# File 'lib/ppr/ppr_core.rb', line 105

def empty?
    return @lines.empty?
end

#final? ⇒ Boolean

Tells if the maco expansion result is final (i.e., it is not preprocessed again) or not.

Returns:

  • (Boolean) 


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# File 'lib/ppr/ppr_core.rb', line 92

def final?
    return @final
end

#generate(i_number, *values) ⇒ Object

Generates the code of the macro invoked at line number i_number using values for the variables.



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# File 'lib/ppr/ppr_core.rb', line 111

def generate(i_number,*values)
    # First generate a variable for the resulting text.
    result = "result_"
    count = 0
    # Ensure the variable is not used in the code.
    count += 1 while (@lines.find {|line| line.include?(name + count.to_s)})
    result = result + count.to_s
    # The process the lines and join them into the resulting string code.
    buffer = StringIO.new("")
    # Adds the prologue initializing the result text string and setting
    # the values.
    buffer << result + " = StringIO.new(\"\")\n"
    # Update the macro code start line.
    @code_num = 1
    unless @variables.size == values.size
        raise Macro.e_message(@name,
            "invalid number of argument: got #{values.size}, but expecting #{@variables.size}.",i_number,@start_num)
    end
    @variables.each.with_index do |var,i|
        buffer << "#{var} = #{to_quoted(values[i])}\n"
        @code_num += 1
    end
    # Add each line of the macros.
    @lines.each do |line|
        # If any, replace the expand command by a concatenation to the
        # resulting string buffer.
        line = line.sub(@expand,"#{result} << ")
        # Add the line
        buffer << line << "\n"
    end
    # Adds the epilogue
    buffer << result << ".string"
    return buffer.string
end

#to_quoted(string) ⇒ Object

Converts a string to a quoted string.



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# File 'lib/ppr/ppr_core.rb', line 83

def to_quoted(string)
    return "\"" + 
        string.gsub(/[\"]|#\{/, "\"" => "\\\"", "\#{" => "\\\#{") +
        "\""
        #}}} This comment is just to avoid confusing the text editor.
end