Class: Android::AXMLParser

Inherits:
Object
  • Object
show all
Defined in:
lib/android/axml_parser.rb

Overview

Note:

refer to Android OS framework code:

/frameworks/base/include/androidfw/ResourceTypes.h,

/frameworks/base/libs/androidfw/ResourceTypes.cpp

binary AXML parser

See Also:

Direct Known Subclasses

AXMLWriter

Defined Under Namespace

Classes: ReadError

Constant Summary collapse

HEADER = 
"\x03\x00\x08\x00"
TAG_START_NAMESPACE = 
0x00100100
TAG_END_NAMESPACE = 
0x00100101
TAG_START = 
0x00100102
TAG_END = 
0x00100103
TAG_TEXT = 
0x00100104
TAG_CDSECT = 
0x00100105
TAG_ENTITY_REF = 
0x00100106
VAL_TYPE_NULL = 
0
VAL_TYPE_REFERENCE = 
1
VAL_TYPE_ATTRIBUTE = 
2
VAL_TYPE_STRING = 
3
VAL_TYPE_FLOAT = 
4
VAL_TYPE_DIMENSION = 
5
VAL_TYPE_FRACTION = 
6
VAL_TYPE_INT_DEC = 
16
VAL_TYPE_INT_HEX = 
17
VAL_TYPE_INT_BOOLEAN = 
18
VAL_TYPE_INT_COLOR_ARGB8 = 
28
VAL_TYPE_INT_COLOR_RGB8 = 
29
VAL_TYPE_INT_COLOR_ARGB4 = 
30
VAL_TYPE_INT_COLOR_RGB4 = 
31

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(axml) ⇒ AXMLParser

Returns a new instance of AXMLParser.

Parameters:

  • axml (String) —

    binary xml data



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# File 'lib/android/axml_parser.rb', line 52

def initialize(axml)
  @io = StringIO.new(axml, "rb")
  @strings = []
end

Instance Attribute Details

#metadata ⇒ Array<String> (readonly)

Returns strings defined in axml.

Returns:

  • (Array<String>) —

    strings defined in axml



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# File 'lib/android/axml_parser.rb', line 49

def metadata
  @metadata
end

#strings ⇒ Array<String> (readonly)

Returns strings defined in axml.

Returns:

  • (Array<String>) —

    strings defined in axml



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# File 'lib/android/axml_parser.rb', line 49

def strings
  @strings
end

Class Method Details

.axml?(data) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/android/axml_parser.rb', line 18

def self.axml?(data)
  (data[0..3] == HEADER)
end

Instance Method Details

#convert_value(val_str_id, flags, val) ⇒ Object 



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# File 'lib/android/axml_parser.rb', line 219

def convert_value(val_str_id, flags, val)
  unless val_str_id == 0xFFFFFFFF
    value = @strings[val_str_id]
  else
    type = flags >> 24
    case type
    when VAL_TYPE_NULL
      value = nil
    when VAL_TYPE_REFERENCE
      value = "@%#x" % val # refered resource id.
    when VAL_TYPE_INT_DEC
      value = val
    when VAL_TYPE_INT_HEX
      value = "%#x" % val
    when VAL_TYPE_INT_BOOLEAN
      value = ((val == 0xFFFFFFFF) || (val==1)) ? true : false
    else
      value = "[%#x, flag=%#x]" % [val, flags]
    end
  end
end

#current_nesting_level ⇒ Object 



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# File 'lib/android/axml_parser.rb', line 215

def current_nesting_level
  @parents.length
end

#get_namespace_prefix(ns_uri) ⇒ Object

find the first declared namespace prefix for a URI



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# File 'lib/android/axml_parser.rb', line 188

def get_namespace_prefix(ns_uri)
  # a namespace might be given as a URI or as a reference to a previously defined namespace.
  # E.g. like this:
  # <tag1 xmlns:android="http://schemas.android.com/apk/res/android">
  #   <tag2 xmlns:n0="android" />
  # </tag1>

  # Walk recursively through the namespaces to
  # transitively resolve URIs that just pointed to previous namespace prefixes
  current_uri = ns_uri
  @namespaces.reverse.each do |ns|
    if ns[:prefix] == current_uri
      # we found a previous namespace declaration that was referenced to by
      # the current_uri. Proceed with this namespace’s URI and try to see if this
      # is also just a reference to a previous namespace
      current_uri = ns[:uri]
    end
  end

  # current_uri now contains the URI of the topmost namespace declaration.
  # We’ll take the prefix of this and return it.
  @namespaces.reverse.each do |ns|
    return ns[:prefix] if ns[:uri] == current_uri
  end
  raise "Could not resolve URI #{ns_uri} to a namespace prefix"
end

#parse ⇒ REXML::Document

parse binary xml

Returns:

  • (REXML::Document) 


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# File 'lib/android/axml_parser.rb', line 59

def parse
  @doc = REXML::Document.new
  @doc << REXML::XMLDecl.new

  @num_str = word(4*4)
  @xml_offset = word(3*4)

  @parents = [@doc]
  @namespaces = []
  @metadata = []
  parse_strings
  parse_tags
  @doc
end

#parse_attribute ⇒ Object

parse attribute of a element



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# File 'lib/android/axml_parser.rb', line 175

def parse_attribute
  ns_id, name_id, val_str_id, flags, val = @io.read(4*5).unpack("V*")
  key = @strings[name_id]
  unless ns_id == 0xFFFFFFFF
    namespace_uri = @strings[ns_id]
    prefix = get_namespace_prefix(namespace_uri)
    key = "#{prefix}:#{key}"
  end
  value = convert_value(val_str_id, flags, val)
  return key, value, (flags >> 24)
end

#parse_strings ⇒ Object

relace string table parser



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# File 'lib/android/axml_parser.rb', line 92

def parse_strings
  strpool = Resource::ResStringPool.new(@io.string, 8) # ugh!
  @strings = strpool.strings
end

#parse_tags ⇒ Object

parse tag



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# File 'lib/android/axml_parser.rb', line 98

def parse_tags
  # skip until first TAG_START_NAMESPACE
  pos = @xml_offset
  pos += 4 until (word(pos) == TAG_START_NAMESPACE)
  @io.pos -= 4

  # read tags
  #puts "start tag parse: %d(%#x)" % [@io.pos, @io.pos]
  until @io.eof?
    last_pos = @io.pos
    tag, tag1, line, tag3, ns_id, name_id = @io.read(4*6).unpack("V*")
    case tag
    when TAG_START
      tag6, num_attrs, tag8  = @io.read(4*3).unpack("V*")

      prefix = ''
      if ns_id != 0xFFFFFFFF
        namespace_uri = @strings[ns_id]
        prefix = get_namespace_prefix(namespace_uri) + ':'
      end
      elem = REXML::Element.new(prefix + @strings[name_id])

      meta_tag = if @strings[name_id] == 'meta-data'
                    @metadata << {}
                    true
                  end

      # If this element is a direct descendent of a namespace declaration
      # we add the namespace definition as an attribute.
      if @namespaces.last[:nesting_level] == current_nesting_level
        elem.add_namespace(@namespaces.last[:prefix], @namespaces.last[:uri])
      end
      #puts "start tag %d(%#x): #{@strings[name_id]} attrs:#{num_attrs}" % [last_pos, last_pos]
      @parents.last.add_element elem
      num_attrs.times do
        key, val, type = parse_attribute

        if meta_tag
          @metadata.last[key] = {
            value: val,
            position: @io.pos - 4,
            val_str_id: @io.pos - 12,
            is_string: type == VAL_TYPE_STRING
          }
        end

        if val.is_a?(String)
          # drop invalid chars that would be rejected by REXML from string
          val = val.scan(REXML::Text::VALID_XML_CHARS).join
        end
        elem.add_attribute(key, val)
      end
      @parents.push elem
    when TAG_END
      @parents.pop
    when TAG_END_NAMESPACE
      @namespaces.pop
      break if @namespaces.empty? # if the topmost namespace (usually 'android:') has been closed, we‘re done.
    when TAG_TEXT
      text = REXML::Text.new(@strings[ns_id])
      @parents.last.text = text
      dummy = @io.read(4*1).unpack("V*") # skip 4bytes
    when TAG_START_NAMESPACE
      prefix = @strings[ns_id]
      uri = @strings[name_id]
      @namespaces.push({ prefix: prefix, uri: uri, nesting_level: current_nesting_level })
    when TAG_CDSECT
      raise ReadError, "TAG_CDSECT not implemented"
    when TAG_ENTITY_REF
      raise ReadError, "TAG_ENTITY_REF not implemented"
    else
      raise ReadError, "pos=%d(%#x)[tag:%#x]" % [last_pos, last_pos, tag]
    end
  end
end

#short(offset) ⇒ Integer

read 2byte as short integer

Parameters:

  • offset (Integer) —

    offset from top position. current position is used if ofset is nil

Returns:

  • (Integer) —

    little endian unsign short value



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# File 'lib/android/axml_parser.rb', line 86

def short(offset)
  @io.pos = offset unless offset.nil?
  @io.read(2).unpack("v")[0]
end

#word(offset = nil) ⇒ Integer

read one word(4byte) as integer

Parameters:

  • offset (Integer) (defaults to: nil) —

    offset from top position. current position is used if ofset is nil

Returns:

  • (Integer) —

    little endian word value



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# File 'lib/android/axml_parser.rb', line 78

def word(offset=nil)
  @io.pos = offset unless offset.nil?
  @io.read(4).unpack("V")[0]
end