Class: AppInfo::PngUncrush::PngReader

Inherits:
Object
  • Object
show all
Defined in:
lib/app_info/png_uncrush.rb

Overview

:nodoc:

Constant Summary collapse

PNG_HEADER = 
"\x89PNG\r\n\x1a\n".bytes
CHUNK = 
1024

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(raw) ⇒ PngReader

Returns a new instance of PngReader.



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# File 'lib/app_info/png_uncrush.rb', line 21

def initialize(raw)
  @io = if raw.is_a?(String)
          StringIO.new(raw)
        elsif raw.respond_to?(:read) && raw.respond_to?(:eof?)
          raw
        else
          raise ArgumentError, "expected data as String or an object
                                responding to read, got #{raw.class}"
        end

  @data = String.new
end

Instance Attribute Details

#data ⇒ Object (readonly)

Returns the value of attribute data.



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# File 'lib/app_info/png_uncrush.rb', line 19

def data
  @data
end

Instance Method Details

#[](offset, length) ⇒ Object 



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# File 'lib/app_info/png_uncrush.rb', line 50

def [](offset, length)
  while !@io.eof? && @data.length < offset + length
    data = @io.read(CHUNK)
    break unless data

    data.force_encoding(@data.encoding) if data.respond_to?(:encoding)
    @data << data
  end

  @data[offset, length]
end

#header ⇒ Object 



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# File 'lib/app_info/png_uncrush.rb', line 42

def header
  @header ||= self[0, 8]
end

#png? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/app_info/png_uncrush.rb', line 46

def png?
  PNG_HEADER == header.bytes
end

#size ⇒ Object 



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# File 'lib/app_info/png_uncrush.rb', line 34

def size
  @io.size
end

#unpack(format) ⇒ Object 



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# File 'lib/app_info/png_uncrush.rb', line 38

def unpack(format)
  @io.unpack(format)
end