621 lines
18 KiB
Ruby
621 lines
18 KiB
Ruby
# coding: utf-8
|
|
# typed: true
|
|
# frozen_string_literal: true
|
|
|
|
require 'tempfile'
|
|
|
|
class PDF::Reader
|
|
# 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
|
|
#
|
|
class ObjectHash
|
|
include Enumerable
|
|
|
|
attr_accessor :default
|
|
attr_reader :trailer, :pdf_version
|
|
attr_reader :sec_handler
|
|
|
|
# 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
|
|
#
|
|
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
|
|
|
|
# returns the type of object a ref points to
|
|
def obj_type(ref)
|
|
self[ref].class.to_s.to_sym
|
|
rescue
|
|
nil
|
|
end
|
|
|
|
# returns true if the supplied references points to an object with a stream
|
|
def stream?(ref)
|
|
self.has_key?(ref) && self[ref].is_a?(PDF::Reader::Stream)
|
|
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.
|
|
#
|
|
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
|
|
|
|
# If key is a PDF::Reader::Reference object, lookup the corresponding
|
|
# object in the PDF and return it. Otherwise return key untouched.
|
|
#
|
|
def object(key)
|
|
key.is_a?(PDF::Reader::Reference) ? self[key] : key
|
|
end
|
|
alias :deref :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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# 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.
|
|
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
|
|
|
|
# Recursively dereferences the object refered to be +key+. If +key+ is not
|
|
# a PDF::Reader::Reference, the key is returned unchanged.
|
|
#
|
|
def deref!(key)
|
|
deref_internal!(key, {})
|
|
end
|
|
|
|
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
|
|
|
|
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
|
|
|
|
# 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.
|
|
#
|
|
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
|
|
|
|
# iterate over each key, value. Just like a ruby hash.
|
|
#
|
|
def each(&block)
|
|
@xref.each do |ref|
|
|
yield ref, self[ref]
|
|
end
|
|
end
|
|
alias :each_pair :each
|
|
|
|
# iterate over each key. Just like a ruby hash.
|
|
#
|
|
def each_key(&block)
|
|
each do |id, obj|
|
|
yield id
|
|
end
|
|
end
|
|
|
|
# iterate over each value. Just like a ruby hash.
|
|
#
|
|
def each_value(&block)
|
|
each do |id, obj|
|
|
yield obj
|
|
end
|
|
end
|
|
|
|
# return the number of objects in the file. An object with multiple generations
|
|
# is counted once.
|
|
def size
|
|
xref.size
|
|
end
|
|
alias :length :size
|
|
|
|
# return true if there are no objects in this file
|
|
#
|
|
def empty?
|
|
size == 0 ? true : false
|
|
end
|
|
|
|
# return true if the specified key exists in the file. key
|
|
# can be an int or a PDF::Reader::Reference
|
|
#
|
|
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
|
|
alias :include? :has_key?
|
|
alias :key? :has_key?
|
|
alias :member? :has_key?
|
|
|
|
# return true if the specifiedvalue exists in the file
|
|
#
|
|
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
|
|
alias :value? :has_key?
|
|
|
|
def to_s
|
|
"<PDF::Reader::ObjectHash size: #{self.size}>"
|
|
end
|
|
|
|
# return an array of all keys in the file
|
|
#
|
|
def keys
|
|
ret = []
|
|
each_key { |k| ret << k }
|
|
ret
|
|
end
|
|
|
|
# return an array of all values in the file
|
|
#
|
|
def values
|
|
ret = []
|
|
each_value { |v| ret << v }
|
|
ret
|
|
end
|
|
|
|
# return an array of all values from the specified keys
|
|
#
|
|
def values_at(*ids)
|
|
ids.map { |id| self[id] }
|
|
end
|
|
|
|
# return an array of arrays. Each sub array contains a key/value pair.
|
|
#
|
|
def to_a
|
|
ret = []
|
|
each do |id, obj|
|
|
ret << [id, obj]
|
|
end
|
|
ret
|
|
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.
|
|
#
|
|
def page_references
|
|
root = fetch(trailer[:Root])
|
|
@page_references ||= begin
|
|
pages_root = deref_hash(root[:Pages]) || {}
|
|
get_page_objects(pages_root)
|
|
end
|
|
end
|
|
|
|
def encrypted?
|
|
trailer.has_key?(:Encrypt)
|
|
end
|
|
|
|
def sec_handler?
|
|
!!sec_handler
|
|
end
|
|
|
|
private
|
|
|
|
# parse a traditional object from the PDF, starting from the byte offset indicated
|
|
# in the xref table
|
|
#
|
|
def fetch_object(key)
|
|
if xref[key].is_a?(Integer)
|
|
buf = new_buffer(xref[key])
|
|
decrypt(key, Parser.new(buf, self).object(key.id, key.gen))
|
|
end
|
|
end
|
|
|
|
# parse a object that's embedded in an object stream in the PDF
|
|
#
|
|
def fetch_object_stream(key)
|
|
if xref[key].is_a?(PDF::Reader::Reference)
|
|
container_key = xref[key]
|
|
stream = deref_stream(container_key)
|
|
raise MalformedPDFError, "Object Stream cannot be nil" if stream.nil?
|
|
object_streams[container_key] ||= PDF::Reader::ObjectStream.new(stream)
|
|
object_streams[container_key][key.id]
|
|
end
|
|
end
|
|
|
|
# Private implementation of deref!, which exists to ensure the `seen` argument
|
|
# isn't publicly available. It's used to avoid endless loops in the recursion, and
|
|
# doesn't need to be part of the public API.
|
|
#
|
|
def deref_internal!(key, seen)
|
|
seen_key = key.is_a?(PDF::Reader::Reference) ? key : key.object_id
|
|
|
|
return seen[seen_key] if seen.key?(seen_key)
|
|
|
|
case object = deref(key)
|
|
when Hash
|
|
seen[seen_key] ||= {}
|
|
object.each do |k, value|
|
|
seen[seen_key][k] = deref_internal!(value, seen)
|
|
end
|
|
seen[seen_key]
|
|
when PDF::Reader::Stream
|
|
seen[seen_key] ||= PDF::Reader::Stream.new({}, object.data)
|
|
object.hash.each do |k,value|
|
|
seen[seen_key].hash[k] = deref_internal!(value, seen)
|
|
end
|
|
seen[seen_key]
|
|
when Array
|
|
seen[seen_key] ||= []
|
|
object.each do |value|
|
|
seen[seen_key] << deref_internal!(value, seen)
|
|
end
|
|
seen[seen_key]
|
|
else
|
|
object
|
|
end
|
|
end
|
|
|
|
def decrypt(ref, obj)
|
|
case obj
|
|
when PDF::Reader::Stream then
|
|
# PDF 32000-1:2008 7.5.8.2: "The cross-reference stream shall not be encrypted [...]."
|
|
# Therefore we shouldn't try to decrypt it.
|
|
obj.data = sec_handler.decrypt(obj.data, ref) unless obj.hash[:Type] == :XRef
|
|
obj
|
|
when Hash then
|
|
arr = obj.map { |key,val| [key, decrypt(ref, val)] }
|
|
arr.each_with_object({}) { |(k,v), accum|
|
|
accum[k] = v
|
|
}
|
|
when Array then
|
|
obj.collect { |item| decrypt(ref, item) }
|
|
when String
|
|
sec_handler.decrypt(obj, ref)
|
|
else
|
|
obj
|
|
end
|
|
end
|
|
|
|
def new_buffer(offset = 0)
|
|
PDF::Reader::Buffer.new(@io, :seek => offset)
|
|
end
|
|
|
|
def xref
|
|
@xref
|
|
end
|
|
|
|
def object_streams
|
|
@object_streams ||= {}
|
|
end
|
|
|
|
# returns an array of object references for all pages in this object store. The ordering of
|
|
# the Array is significant and matches the page ordering of the document
|
|
#
|
|
def get_page_objects(obj)
|
|
derefed_obj = deref_hash(obj)
|
|
|
|
if derefed_obj.nil?
|
|
raise MalformedPDFError, "Expected Page or Pages object, got nil"
|
|
elsif derefed_obj[:Type] == :Page
|
|
[obj]
|
|
elsif derefed_obj[:Kids]
|
|
kids = deref_array(derefed_obj[:Kids]) || []
|
|
kids.map { |kid|
|
|
get_page_objects(kid)
|
|
}.flatten
|
|
else
|
|
raise MalformedPDFError, "Expected Page or Pages object"
|
|
end
|
|
end
|
|
|
|
def read_version
|
|
@io.seek(0)
|
|
_m, version = *@io.read(10).to_s.match(/PDF-(\d.\d)/)
|
|
@io.seek(0)
|
|
version.to_f
|
|
end
|
|
|
|
def extract_io_from(input)
|
|
if input.is_a?(IO) || input.is_a?(StringIO) || input.is_a?(Tempfile)
|
|
input
|
|
elsif File.file?(input.to_s)
|
|
StringIO.new read_as_binary(input.to_s)
|
|
else
|
|
raise ArgumentError, "input must be an IO-like object or a filename (#{input.class})"
|
|
end
|
|
end
|
|
|
|
def read_as_binary(input)
|
|
if File.respond_to?(:binread)
|
|
File.binread(input.to_s)
|
|
else
|
|
File.open(input.to_s,"rb") { |f| f.read }
|
|
end
|
|
end
|
|
|
|
end
|
|
end
|