Object
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 an exact 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.
h = PDF::Reader::ObjectHash.new("somefile.pdf") h[1] => 3469 h[PDF::Reader::Reference.new(1,0)] => 3469
Creates a new ObjectHash object. input can be a string with a valid filename, a string containing a PDF file, or an IO object.
# File lib/pdf/reader/object_hash.rb, line 36 def initialize(input) if input.respond_to?(:seek) && input.respond_to?(:read) @io = input elsif File.file?(input.to_s) if File.respond_to?(:binread) input = File.binread(input.to_s) else input = File.read(input.to_s) end @io = StringIO.new(input) else raise ArgumentError, "input must be an IO-like object or a filename" end @pdf_version = read_version @xref = PDF::Reader::XRef.new(@io) @trailer = @xref.trailer end
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.
# File lib/pdf/reader/object_hash.rb, line 77 def [](key) return default if key.to_i <= 0 begin unless key.kind_of?(PDF::Reader::Reference) key = PDF::Reader::Reference.new(key.to_i, 0) end if xref[key].is_a?(Fixnum) buf = new_buffer(xref[key]) Parser.new(buf, self).object(key.id, key.gen) elsif xref[key].is_a?(PDF::Reader::Reference) container_key = xref[key] object_streams[container_key] ||= PDF::Reader::ObjectStream.new(object(container_key)) object_streams[container_key][key.id] end rescue InvalidObjectError return default end end
iterate over each key, value. Just like a ruby hash.
# File lib/pdf/reader/object_hash.rb, line 128 def each(&block) @xref.each do |ref| yield ref, self[ref] end end
iterate over each key. Just like a ruby hash.
# File lib/pdf/reader/object_hash.rb, line 137 def each_key(&block) each do |id, obj| yield id end end
iterate over each value. Just like a ruby hash.
# File lib/pdf/reader/object_hash.rb, line 145 def each_value(&block) each do |id, obj| yield obj end end
return true if there are no objects in this file
# File lib/pdf/reader/object_hash.rb, line 160 def empty? size == 0 ? true : false end
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.
# File lib/pdf/reader/object_hash.rb, line 115 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
return true if the specified key exists in the file. key can be an int or a PDF::Reader::Reference
# File lib/pdf/reader/object_hash.rb, line 167 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
return true if the specifiedvalue exists in the file
# File lib/pdf/reader/object_hash.rb, line 184 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
return an array of all keys in the file
# File lib/pdf/reader/object_hash.rb, line 199 def keys ret = [] each_key { |k| ret << k } ret end
returns the type of object a ref points to
# File lib/pdf/reader/object_hash.rb, line 55 def obj_type(ref) self[ref].class.to_s.to_sym rescue nil end
If key is a PDF::Reader::Reference object, lookup the corresponding object in the PDF and return it. Otherwise return key untouched.
# File lib/pdf/reader/object_hash.rb, line 99 def object(key) key.is_a?(PDF::Reader::Reference) ? self[key] : key end
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.
# File lib/pdf/reader/object_hash.rb, line 235 def page_references root = fetch(trailer[:Root]) @page_references ||= get_page_objects(root[:Pages]).flatten end
return the number of objects in the file. An object with multiple generations is counted once.
# File lib/pdf/reader/object_hash.rb, line 153 def size xref.size end
returns true if the supplied references points to an object with a stream
# File lib/pdf/reader/object_hash.rb, line 62 def stream?(ref) self[ref].class == PDF::Reader::Stream rescue false end
return an array of arrays. Each sub array contains a key/value pair.
# File lib/pdf/reader/object_hash.rb, line 221 def to_a ret = [] each do |id, obj| ret << [id, obj] end ret end
# File lib/pdf/reader/object_hash.rb, line 193 def to_s "<PDF::Reader::ObejctHash size: #{self.size}>" end
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