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



46
47
48
49
50
51
52
53
54
55
56
57
58
 
# File 'lib/pdf/reader/object_hash.rb', line 46

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.



35
36
37
 
# File 'lib/pdf/reader/object_hash.rb', line 35

def default
  @default
end

#pdf_version ⇒ Object (readonly)

Returns the value of attribute pdf_version.



36
37
38
 
# File 'lib/pdf/reader/object_hash.rb', line 36

def pdf_version
  @pdf_version
end

#sec_handler ⇒ Object (readonly)

Returns the value of attribute sec_handler.



37
38
39
 
# File 'lib/pdf/reader/object_hash.rb', line 37

def sec_handler
  @sec_handler
end

#trailer ⇒ Object (readonly)

Returns the value of attribute trailer.



36
37
38
 
# File 'lib/pdf/reader/object_hash.rb', line 36

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.



81
82
83
84
85
86
87
88
89
90
91
 
# File 'lib/pdf/reader/object_hash.rb', line 81

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.



316
317
318
 
# File 'lib/pdf/reader/object_hash.rb', line 316

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.



107
108
109
110
111
112
113
114
115
 
# File 'lib/pdf/reader/object_hash.rb', line 107

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 



320
321
322
323
324
325
326
 
# File 'lib/pdf/reader/object_hash.rb', line 320

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:



125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
 
# File 'lib/pdf/reader/object_hash.rb', line 125

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.



151
152
153
154
155
156
157
158
159
 
# File 'lib/pdf/reader/object_hash.rb', line 151

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 



328
329
330
331
332
333
334
 
# File 'lib/pdf/reader/object_hash.rb', line 328

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.



193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
 
# File 'lib/pdf/reader/object_hash.rb', line 193

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.



169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
 
# File 'lib/pdf/reader/object_hash.rb', line 169

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.



283
284
285
286
287
288
289
290
291
292
293
 
# File 'lib/pdf/reader/object_hash.rb', line 283

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.



217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
 
# File 'lib/pdf/reader/object_hash.rb', line 217

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.



241
242
243
244
245
246
247
248
249
250
251
 
# File 'lib/pdf/reader/object_hash.rb', line 241

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.



301
302
303
304
305
306
307
308
309
310
311
 
# File 'lib/pdf/reader/object_hash.rb', line 301

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.



261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
 
# File 'lib/pdf/reader/object_hash.rb', line 261

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.



361
362
363
364
365
 
# File 'lib/pdf/reader/object_hash.rb', line 361

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.



370
371
372
373
374
 
# File 'lib/pdf/reader/object_hash.rb', line 370

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.



378
379
380
381
382
 
# File 'lib/pdf/reader/object_hash.rb', line 378

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) 


393
394
395
 
# File 'lib/pdf/reader/object_hash.rb', line 393

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

#encrypted? ⇒ Boolean

Returns:

  • (Boolean) 


476
477
478
 
# File 'lib/pdf/reader/object_hash.rb', line 476

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.



348
349
350
351
352
353
354
355
356
357
 
# File 'lib/pdf/reader/object_hash.rb', line 348

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) 


400
401
402
403
404
405
406
407
408
409
410
 
# File 'lib/pdf/reader/object_hash.rb', line 400

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) 


417
418
419
420
421
422
423
 
# File 'lib/pdf/reader/object_hash.rb', line 417

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



432
433
434
435
436
 
# File 'lib/pdf/reader/object_hash.rb', line 432

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

#obj_type(ref) ⇒ Object

returns the type of object a ref points to



61
62
63
64
65
 
# File 'lib/pdf/reader/object_hash.rb', line 61

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.



96
97
98
 
# File 'lib/pdf/reader/object_hash.rb', line 96

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.



468
469
470
471
472
473
474
 
# File 'lib/pdf/reader/object_hash.rb', line 468

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) 


480
481
482
 
# File 'lib/pdf/reader/object_hash.rb', line 480

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.



386
387
388
 
# File 'lib/pdf/reader/object_hash.rb', line 386

def size
  xref.size
end

#stream?(ref) ⇒ Boolean

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

Returns:

  • (Boolean) 


68
69
70
 
# File 'lib/pdf/reader/object_hash.rb', line 68

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.



454
455
456
457
458
459
460
 
# File 'lib/pdf/reader/object_hash.rb', line 454

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

#to_s ⇒ Object 



426
427
428
 
# File 'lib/pdf/reader/object_hash.rb', line 426

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

#values ⇒ Object

return an array of all values in the file



440
441
442
443
444
 
# File 'lib/pdf/reader/object_hash.rb', line 440

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

#values_at(*ids) ⇒ Object

return an array of all values from the specified keys



448
449
450
 
# File 'lib/pdf/reader/object_hash.rb', line 448

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