Class: PDF::Reader::ObjectHash

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/pdf/reader/object_hash.rb

Overview

Provides low level access to the objects in a PDF file via a hash-like object.

A PDF file can be viewed as a large hash map. It is a series of objects stored at precise byte offsets, and a table that maps object IDs to byte offsets. Given an object ID, looking up an object is an O(1) operation.

Each PDF object can be mapped to a ruby object, so by passing an object ID to the [] method, a ruby representation of that object will be retrieved.

The class behaves much like a standard Ruby hash, including the use of the Enumerable mixin. The key difference is no []= method - the hash is read only.

Basic Usage

h = PDF::Reader::ObjectHash.new("somefile.pdf")
h[1]
=> 3469

h[PDF::Reader::Reference.new(1,0)]
=> 3469

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(input, opts = {}) ⇒ ObjectHash

Creates a new ObjectHash object. Input can be a string with a valid filename or an IO-like object.

Valid options:

:password - the user password to decrypt the source PDF



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# File 'lib/pdf/reader/object_hash.rb', line 44

def initialize(input, opts = {})
  @io          = extract_io_from(input)
  @xref        = PDF::Reader::XRef.new(@io)
  @pdf_version = read_version
  @trailer     = @xref.trailer
  @cache       = opts[:cache] || PDF::Reader::ObjectCache.new
  @sec_handler = NullSecurityHandler.new
  @sec_handler = SecurityHandlerFactory.build(
    deref(trailer[:Encrypt]),
    deref(trailer[:ID]),
    opts[:password]
  )
end

Instance Attribute Details

#default ⇒ Object

Returns the value of attribute default.



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# File 'lib/pdf/reader/object_hash.rb', line 33

def default
  @default
end

#pdf_version ⇒ Object (readonly)

Returns the value of attribute pdf_version.



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# File 'lib/pdf/reader/object_hash.rb', line 34

def pdf_version
  @pdf_version
end

#sec_handler ⇒ Object (readonly)

Returns the value of attribute sec_handler.



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# File 'lib/pdf/reader/object_hash.rb', line 35

def sec_handler
  @sec_handler
end

#trailer ⇒ Object (readonly)

Returns the value of attribute trailer.



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# File 'lib/pdf/reader/object_hash.rb', line 34

def trailer
  @trailer
end

Instance Method Details

#[](key) ⇒ Object

Access an object from the PDF. key can be an int or a PDF::Reader::Reference object.

If an int is used, the object with that ID and a generation number of 0 will be returned.

If a PDF::Reader::Reference object is used the exact ID and generation number can be specified.



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# File 'lib/pdf/reader/object_hash.rb', line 79

def [](key)
  return default if key.to_i <= 0

  unless key.is_a?(PDF::Reader::Reference)
    key = PDF::Reader::Reference.new(key.to_i, 0)
  end

  @cache[key] ||= fetch_object(key) || fetch_object_stream(key)
rescue InvalidObjectError
  return default
end

#deref!(key) ⇒ Object

Recursively dereferences the object refered to be key. If key is not a PDF::Reader::Reference, the key is returned unchanged.



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# File 'lib/pdf/reader/object_hash.rb', line 314

def deref!(key)
  deref_internal!(key, {})
end

#deref_array(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return an Array or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.



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# File 'lib/pdf/reader/object_hash.rb', line 105

def deref_array(key)
  obj = deref(key)

  return obj if obj.nil?

  obj.tap { |obj|
    raise MalformedPDFError, "expected object to be an Array or nil" if !obj.is_a?(Array)
  }
end

#deref_array!(key) ⇒ Object 



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# File 'lib/pdf/reader/object_hash.rb', line 318

def deref_array!(key)
  deref!(key).tap { |obj|
    if !obj.nil? && !obj.is_a?(Array)
      raise MalformedPDFError, "expected object (#{obj.inspect}) to be an Array or nil"
    end
  }
end

#deref_array_of_numbers(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return an Array of Numerics or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.

Some effort to cast array elements to a number is made for any non-numeric elements.

Raises:



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# File 'lib/pdf/reader/object_hash.rb', line 123

def deref_array_of_numbers(key)
  arr = deref(key)

  return arr if arr.nil?

  raise MalformedPDFError, "expected object to be an Array" unless arr.is_a?(Array)

  arr.map { |item|
    if item.is_a?(Numeric)
      item
    elsif item.respond_to?(:to_f)
      item.to_f
    elsif item.respond_to?(:to_i)
      item.to_i
    else
      raise MalformedPDFError, "expected object to be a number"
    end
  }
end

#deref_hash(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a Hash or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.



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# File 'lib/pdf/reader/object_hash.rb', line 149

def deref_hash(key)
  obj = deref(key)

  return obj if obj.nil?

  obj.tap { |obj|
    raise MalformedPDFError, "expected object to be a Hash or nil" if !obj.is_a?(Hash)
  }
end

#deref_hash!(key) ⇒ Object 



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# File 'lib/pdf/reader/object_hash.rb', line 326

def deref_hash!(key)
  deref!(key).tap { |obj|
    if !obj.nil? && !obj.is_a?(Hash)
      raise MalformedPDFError, "expected object (#{obj.inspect}) to be a Hash or nil"
    end
  }
end

#deref_integer(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return an Integer or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.

Some effort to cast to an int is made when the reference points to a non-integer.



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# File 'lib/pdf/reader/object_hash.rb', line 191

def deref_integer(key)
  obj = deref(key)

  return obj if obj.nil?

  if !obj.is_a?(Integer)
    if obj.respond_to?(:to_i)
      obj = obj.to_i
    else
      raise MalformedPDFError, "expected object to be an Integer"
    end
  end

  obj
end

#deref_name(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a PDF name (Symbol) or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.

Some effort to cast to a symbol is made when the reference points to a non-symbol.



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# File 'lib/pdf/reader/object_hash.rb', line 167

def deref_name(key)
  obj = deref(key)

  return obj if obj.nil?

  if !obj.is_a?(Symbol)
    if obj.respond_to?(:to_sym)
      obj = obj.to_sym
    else
      raise MalformedPDFError, "expected object to be a Name"
    end
  end

  obj
end

#deref_name_or_array(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a PDF Name (symbol), Array or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting a Name or Array and no other type will do.



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# File 'lib/pdf/reader/object_hash.rb', line 281

def deref_name_or_array(key)
  obj = deref(key)

  return obj if obj.nil?

  obj.tap { |obj|
    if !obj.is_a?(Symbol) && !obj.is_a?(Array)
      raise MalformedPDFError, "expected object to be an Array or Name"
    end
  }
end

#deref_number(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a Numeric or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting an Array and no other type will do.

Some effort to cast to a number is made when the reference points to a non-number.



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# File 'lib/pdf/reader/object_hash.rb', line 215

def deref_number(key)
  obj = deref(key)

  return obj if obj.nil?

  if !obj.is_a?(Numeric)
    if obj.respond_to?(:to_f)
      obj = obj.to_f
    elsif obj.respond_to?(:to_i)
      obj.to_i
    else
      raise MalformedPDFError, "expected object to be a number"
    end
  end

  obj
end

#deref_stream(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a PDF::Reader::Stream or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting a stream and no other type will do.



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# File 'lib/pdf/reader/object_hash.rb', line 239

def deref_stream(key)
  obj = deref(key)

  return obj if obj.nil?

  obj.tap { |obj|
    if !obj.is_a?(PDF::Reader::Stream)
      raise MalformedPDFError, "expected object to be a Stream or nil"
    end
  }
end

#deref_stream_or_array(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a PDF::Reader::Stream, Array or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting a stream or Array and no other type will do.



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# File 'lib/pdf/reader/object_hash.rb', line 299

def deref_stream_or_array(key)
  obj = deref(key)

  return obj if obj.nil?

  obj.tap { |obj|
    if !obj.is_a?(PDF::Reader::Stream) && !obj.is_a?(Array)
      raise MalformedPDFError, "expected object to be an Array or Stream"
    end
  }
end

#deref_string(key) ⇒ Object

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.

Guaranteed to only return a String or nil. If the dereference results in any other type then a MalformedPDFError exception will raise. Useful when expecting a string and no other type will do.

Some effort to cast to a string is made when the reference points to a non-string.



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# File 'lib/pdf/reader/object_hash.rb', line 259

def deref_string(key)
  obj = deref(key)

  return obj if obj.nil?

  if !obj.is_a?(String)
    if obj.respond_to?(:to_s)
      obj = obj.to_s
    else
      raise MalformedPDFError, "expected object to be a string"
    end
  end

  obj
end

#each(&block) ⇒ Object Also known as: each_pair

iterate over each key, value. Just like a ruby hash.



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# File 'lib/pdf/reader/object_hash.rb', line 359

def each(&block)
  @xref.each do |ref|
    yield ref, self[ref]
  end
end

#each_key(&block) ⇒ Object

iterate over each key. Just like a ruby hash.



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# File 'lib/pdf/reader/object_hash.rb', line 368

def each_key(&block)
  each do |id, obj|
    yield id
  end
end

#each_value(&block) ⇒ Object

iterate over each value. Just like a ruby hash.



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# File 'lib/pdf/reader/object_hash.rb', line 376

def each_value(&block)
  each do |id, obj|
    yield obj
  end
end

#empty? ⇒ Boolean

return true if there are no objects in this file

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 391

def empty?
  size == 0 ? true : false
end

#encrypted? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 474

def encrypted?
  trailer.has_key?(:Encrypt)
end

#fetch(key, local_default = nil) ⇒ Object

Access an object from the PDF. key can be an int or a PDF::Reader::Reference object.

If an int is used, the object with that ID and a generation number of 0 will be returned.

If a PDF::Reader::Reference object is used the exact ID and generation number can be specified.

local_default is the object that will be returned if the requested key doesn’t exist.



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# File 'lib/pdf/reader/object_hash.rb', line 346

def fetch(key, local_default = nil)
  obj = self[key]
  if obj
    return obj
  elsif local_default
    return local_default
  else
    raise IndexError, "#{key} is invalid" if key.to_i <= 0
  end
end

#has_key?(check_key) ⇒ Boolean Also known as: include?, key?, member?, value?

return true if the specified key exists in the file. key can be an int or a PDF::Reader::Reference

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 398

def has_key?(check_key)
  # TODO update from O(n) to O(1)
  each_key do |key|
    if check_key.kind_of?(PDF::Reader::Reference)
      return true if check_key == key
    else
      return true if check_key.to_i == key.id
    end
  end
  return false
end

#has_value?(value) ⇒ Boolean

return true if the specifiedvalue exists in the file

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 415

def has_value?(value)
  # TODO update from O(n) to O(1)
  each_value do |obj|
    return true if obj == value
  end
  return false
end

#keys ⇒ Object

return an array of all keys in the file



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# File 'lib/pdf/reader/object_hash.rb', line 430

def keys
  ret = []
  each_key { |k| ret << k }
  ret
end

#obj_type(ref) ⇒ Object

returns the type of object a ref points to



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# File 'lib/pdf/reader/object_hash.rb', line 59

def obj_type(ref)
  self[ref].class.to_s.to_sym
rescue
  nil
end

#object(key) ⇒ Object Also known as: deref

If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.



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# File 'lib/pdf/reader/object_hash.rb', line 94

def object(key)
  key.is_a?(PDF::Reader::Reference) ? self[key] : key
end

#page_references ⇒ Object

returns an array of PDF::Reader::References. Each reference in the array points a Page object, one for each page in the PDF. The first reference is page 1, second reference is page 2, etc.

Useful for apps that want to extract data from specific pages.



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# File 'lib/pdf/reader/object_hash.rb', line 466

def page_references
  root  = fetch(trailer[:Root])
  @page_references ||= begin
                         pages_root = deref_hash(root[:Pages]) || {}
                         get_page_objects(pages_root)
                       end
end

#sec_handler? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 478

def sec_handler?
  !!sec_handler
end

#size ⇒ Object Also known as: length

return the number of objects in the file. An object with multiple generations is counted once.



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# File 'lib/pdf/reader/object_hash.rb', line 384

def size
  xref.size
end

#stream?(ref) ⇒ Boolean

returns true if the supplied references points to an object with a stream

Returns:

  • (Boolean) 


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# File 'lib/pdf/reader/object_hash.rb', line 66

def stream?(ref)
  self.has_key?(ref) && self[ref].is_a?(PDF::Reader::Stream)
end

#to_a ⇒ Object

return an array of arrays. Each sub array contains a key/value pair.



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# File 'lib/pdf/reader/object_hash.rb', line 452

def to_a
  ret = []
  each do |id, obj|
    ret << [id, obj]
  end
  ret
end

#to_s ⇒ Object 



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# File 'lib/pdf/reader/object_hash.rb', line 424

def to_s
  "<PDF::Reader::ObjectHash size: #{self.size}>"
end

#values ⇒ Object

return an array of all values in the file



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# File 'lib/pdf/reader/object_hash.rb', line 438

def values
  ret = []
  each_value { |v| ret << v }
  ret
end

#values_at(*ids) ⇒ Object

return an array of all values from the specified keys



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# File 'lib/pdf/reader/object_hash.rb', line 446

def values_at(*ids)
  ids.map { |id| self[id] }
end