Class: SFML::InputStream

Inherits:
Object
  • Object
show all
Defined in:
lib/sfml/system/input_stream.rb

Overview

Bridge between a Ruby IO-like object (anything with #read(n), #seek(pos), #pos / #tell, and #size) and CSFML's sfInputStream* parameter on *_createFromStream loader functions.

Typical use is indirect — pass a Ruby IO to the .from_stream factory on Font, Image, Texture, Shader, Music, or SoundBuffer:

File.open("assets/hero.png", "rb") do |io|
tex = SFML::Texture.from_stream(io)
end

Direct use is for advanced cases (custom virtual filesystems, network streams, etc.). Subclass or build with .new(io):

wrapped = SFML::InputStream.new(my_random_access_io)
font    = SFML::Font.send(:_load_from_stream_handle, wrapped.struct)

The InputStream object must outlive the loader call — keep a reference until the CSFML factory returns. The wrapped IO is not closed automatically; close it yourself.

Instance Method Summary collapse

Constructor Details

#initialize(io) ⇒ InputStream

io must respond to: read(n), seek(pos, IO::SEEK_SET), pos/tell, size. Ruby's File, StringIO, and Tempfile all qualify.



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# File 'lib/sfml/system/input_stream.rb', line 27

def initialize(io)
  @io = io

  # Strong refs so the GC doesn't free our callbacks before CSFML
  # is done with the struct. CSFML calls them synchronously
  # during the loader function, but may also call them later
  # (Music streams from disk on its audio thread).
  @read_cb = FFI::Function.new(:int64, [:pointer, :size_t, :pointer]) do |buf, size, _user|
    begin
      bytes = @io.read(size) || ""
      buf.write_bytes(bytes) unless bytes.empty?
      bytes.bytesize
    rescue StandardError
      -1
    end
  end

  @seek_cb = FFI::Function.new(:int64, [:size_t, :pointer]) do |pos, _user|
    begin
      @io.seek(pos, IO::SEEK_SET)
      pos
    rescue StandardError
      -1
    end
  end

  @tell_cb = FFI::Function.new(:int64, [:pointer]) do |_user|
    begin
      @io.respond_to?(:pos) ? @io.pos : @io.tell
    rescue StandardError
      -1
    end
  end

  @size_cb = FFI::Function.new(:int64, [:pointer]) do |_user|
    begin
      @io.size
    rescue StandardError
      -1
    end
  end

  @struct = C::System::InputStream.new
  @struct[:read]      = @read_cb
  @struct[:seek]      = @seek_cb
  @struct[:tell]      = @tell_cb
  @struct[:get_size]  = @size_cb
  @struct[:user_data] = FFI::Pointer::NULL
end

Instance Method Details

#to_ptr ⇒ Object

Pointer suitable for the sfInputStream* parameter on *_createFromStream loaders.



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# File 'lib/sfml/system/input_stream.rb', line 84

def to_ptr
  @struct.pointer
end