Class: GObject::GValue

Inherits:
FFI::ManagedStruct
  • Object
show all
Defined in:
lib/vips/gvalue.rb

Overview

Represent a GValue. Example use:

gvalue = GValue::alloc
gvalue.init GObject::GDOUBLE_TYPE
gvalue.set 3.1415
value = gvalue.get
# optional -- drop any ref the gvalue had
gvalue.unset

Lifetime is managed automatically. It doesn't know about all GType values, but it does know the ones that libvips uses.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.alloc ⇒ GValue

Allocate memory for a GValue and return a class wrapper. Memory will be freed automatically when it goes out of scope. The GValue is inited to 0, use #init to set a type.

Returns:

  • (GValue) —

    a new gvalue set to 0



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# File 'lib/vips/gvalue.rb', line 63

def self.alloc
  # allocate memory
  memory = FFI::MemoryPointer.new GValue

  # make this alloc autorelease ... we mustn't release in
  # GValue::release, since we are used to wrap GValue pointers
  # made by other people
  pointer = FFI::Pointer.new GValue, memory

  # ... and wrap in a GValue
  GValue.new pointer
end

.from_nick(gtype, value) ⇒ Object

convert an enum value (str/symb/int) into an int ready for libvips



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# File 'lib/vips/gvalue.rb', line 28

def self.from_nick(gtype, value)
  value = value.to_s if value.is_a? Symbol

  if value.is_a? String
    # libvips expects "-" as a separator in enum names, but "_" is more
    # convenient for ruby, eg. :b_w
    value = Vips.vips_enum_from_nick "ruby-vips", gtype, value.tr("_", "-")
    if value == -1
      raise Vips::Error
    end
  end

  value
end

.release(ptr) ⇒ Object 



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# File 'lib/vips/gvalue.rb', line 53

def self.release ptr
  # GLib::logger.debug("GObject::GValue::release") {"ptr = #{ptr}"}
  ::GObject.g_value_unset ptr
end

.to_nick(gtype, enum_value) ⇒ Object

convert an int enum back into a symbol



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# File 'lib/vips/gvalue.rb', line 44

def self.to_nick(gtype, enum_value)
  enum_name = Vips.vips_enum_nick gtype, enum_value
  if enum_name.nil?
    raise Vips::Error
  end

  enum_name.to_sym
end

Instance Method Details

#get ⇒ Any

Get the value of a GValue. The value is converted to a Ruby type in the obvious way.

Returns:

  • (Any) —

    the value held by the GValue



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# File 'lib/vips/gvalue.rb', line 171

def get
  gtype = self[:gtype]
  fundamental = ::GObject.g_type_fundamental gtype
  result = nil

  case gtype
  when GBOOL_TYPE
    result = ::GObject.g_value_get_boolean(self) != 0

  when GINT_TYPE
    result = ::GObject.g_value_get_int self

  when GUINT64_TYPE
    result = ::GObject.g_value_get_uint64 self

  when GDOUBLE_TYPE
    result = ::GObject.g_value_get_double self

  when GSTR_TYPE
    result = ::GObject.g_value_get_string self

  when Vips::REFSTR_TYPE
    len = Vips::SizeStruct.new
    result = ::Vips.vips_value_get_ref_string self, len

  when Vips::ARRAY_INT_TYPE
    len = Vips::IntStruct.new
    array = Vips.vips_value_get_array_int self, len
    result = array.get_array_of_int32 0, len[:value]

  when Vips::ARRAY_DOUBLE_TYPE
    len = Vips::IntStruct.new
    array = Vips.vips_value_get_array_double self, len
    result = array.get_array_of_double 0, len[:value]

  when Vips::ARRAY_IMAGE_TYPE
    len = Vips::IntStruct.new
    array = Vips.vips_value_get_array_image self, len
    result = array.get_array_of_pointer 0, len[:value]
    result.map! do |pointer|
      ::GObject.g_object_ref pointer
      Vips::Image.new pointer
    end

  when Vips::BLOB_TYPE
    len = Vips::SizeStruct.new
    array = Vips.vips_value_get_blob self, len
    result = array.get_bytes 0, len[:value]

  else
    case fundamental
    when GFLAGS_TYPE
      result = ::GObject.g_value_get_flags self

    when GENUM_TYPE
      enum_value = ::GObject.g_value_get_enum(self)
      result = GValue.to_nick self[:gtype], enum_value

    when GOBJECT_TYPE
      obj = ::GObject.g_value_get_object self
      # g_value_get_object() does not add a ref ... we need to add
      # one to match the unref in gobject release
      ::GObject.g_object_ref obj
      result = Vips::Image.new obj

    else
      raise Vips::Error, "unimplemented gtype for get: " \
        "#{::GObject.g_type_name gtype} (#{gtype})"
    end
  end

  # GLib::logger.debug("GObject::GValue.get") {
  #     "result = #{result.inspect[0..50]}"
  # }

  result
end

#init(gtype) ⇒ Object

Set the type of thing a gvalue can hold.

Parameters:

  • gtype (GType) —

    the type of thing this GValue can hold.



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# File 'lib/vips/gvalue.rb', line 79

def init gtype
  ::GObject.g_value_init self, gtype
end

#set(value) ⇒ Object

Set the value of a GValue. The value is converted to the type of the GValue, if possible.

Parameters:

  • value (Any) —

    The value to set



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# File 'lib/vips/gvalue.rb', line 87

def set value
  # GLib::logger.debug("GObject::GValue.set") {
  #     "value = #{value.inspect[0..50]}"
  # }

  gtype = self[:gtype]
  fundamental = ::GObject.g_type_fundamental gtype

  case gtype
  when GBOOL_TYPE
    ::GObject.g_value_set_boolean self, (value ? 1 : 0)

  when GINT_TYPE
    ::GObject.g_value_set_int self, value

  when GUINT64_TYPE
    ::GObject.g_value_set_uint64 self, value

  when GDOUBLE_TYPE
    ::GObject.g_value_set_double self, value

  when GSTR_TYPE
    ::GObject.g_value_set_string self, value

  when Vips::REFSTR_TYPE
    ::Vips.vips_value_set_ref_string self, value

  when Vips::ARRAY_INT_TYPE
    value = [value] unless value.is_a? Array

    Vips.vips_value_set_array_int self, nil, value.length
    ptr = Vips.vips_value_get_array_int self, nil
    ptr.write_array_of_int32 value

  when Vips::ARRAY_DOUBLE_TYPE
    value = [value] unless value.is_a? Array

    # this will allocate an array in the gvalue
    Vips.vips_value_set_array_double self, nil, value.length

    # pull the array out and fill it
    ptr = Vips.vips_value_get_array_double self, nil

    ptr.write_array_of_double value

  when Vips::ARRAY_IMAGE_TYPE
    value = [value] unless value.is_a? Array

    Vips.vips_value_set_array_image self, value.length
    ptr = Vips.vips_value_get_array_image self, nil
    ptr.write_array_of_pointer value

    # the gvalue needs a ref on each of the images
    value.each { |image| ::GObject.g_object_ref image }

  when Vips::BLOB_TYPE
    len = value.bytesize
    ptr = GLib.g_malloc len
    Vips.vips_value_set_blob self, GLib::G_FREE, ptr, len
    ptr.write_bytes value

  else
    case fundamental
    when GFLAGS_TYPE
      ::GObject.g_value_set_flags self, value

    when GENUM_TYPE
      enum_value = GValue.from_nick(self[:gtype], value)
      ::GObject.g_value_set_enum self, enum_value

    when GOBJECT_TYPE
      ::GObject.g_value_set_object self, value

    else
      raise Vips::Error, "unimplemented gtype for set: " \
        "#{::GObject.g_type_name gtype} (#{gtype})"
    end
  end
end

#unset ⇒ Object

Clear the thing held by a GValue.

This happens automatically when a GValue is GCed, but this method can be handy if you need to drop a reference explicitly for some reason.



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# File 'lib/vips/gvalue.rb', line 253

def unset
  ::GObject.g_value_unset self
end