Method: XZ::StreamReader#read

Defined in:

lib/facter/util/ruby-xz-1.0.0/lib/xz/stream_reader.rb

#read(length = nil, outbuf = String.new) ⇒ Object

Mostly like IO#read. The length parameter refers to the amount of decompressed bytes to read, not the amount of bytes to read from the compressed data. That is, if you request a read of 50 bytes, you will receive a string with a maximum length of 50 bytes, regardless of how many bytes this was in compressed form.

Return values are as per IO#read.

# File 'lib/facter/util/ruby-xz-1.0.0/lib/xz/stream_reader.rb', line 203

def read(length = nil, outbuf = String.new)
  return "".force_encoding(Encoding::BINARY) if length == 0 # Shortcut; retval as per IO#read.

  # Note: Querying the underlying IO as early as possible allows to
  # have Ruby's own IO exceptions to bubble up.
  if length
    return nil if eof? # In line with IO#read
    outbuf.force_encoding(Encoding::BINARY) # As per IO#read docs

    # The user's request is in decompressed bytes, so it doesn't matter
    # how much is actually read from the compressed file.
    if @delegate_io.eof?
      data   = ""
      action = XZ::LibLZMA::LZMA_FINISH
    else
      data   = @delegate_io.read(XZ::CHUNK_SIZE)
      action = @delegate_io.eof? ? XZ::LibLZMA::LZMA_FINISH : XZ::LibLZMA::LZMA_RUN
    end

    lzma_code(data, action) { |decompressed| @readbuf << decompressed }

    # If the requested amount has been read, return it.
    # Also return if EOF has been reached. Note that
    # String#slice! will clear the string to an empty one
    # if `length' is greater than the string length.
    # If EOF is not yet reached, try reading and decompresing
    # more data.
    if @readbuf.bytesize >= length || @delegate_io.eof?
      result = @readbuf.slice!(0, length)
      @pos += result.bytesize
      return outbuf.replace(result)
    else
      return read(length, outbuf)
    end
  else
    # Read the entire file and decompress it into memory, returning it.
    while chunk = @delegate_io.read(XZ::CHUNK_SIZE)
      action = @delegate_io.eof? ? XZ::LibLZMA::LZMA_FINISH : XZ::LibLZMA::LZMA_RUN
      lzma_code(chunk, action) { |decompressed| @readbuf << decompressed }
    end

    @pos += @readbuf.bytesize

    # Apply encoding conversion.
    # First, tag the read data with the external encoding.
    @readbuf.force_encoding(@external_encoding)

    # Now, transcode it to the internal encoding if that was requested.
    # Otherwise return it with the external encoding as-is.
    if @internal_encoding
      @readbuf.encode!(@internal_encoding, @transcode_options)
      outbuf.force_encoding(@internal_encoding)
    else
      outbuf.force_encoding(@external_encoding)
    end

    outbuf.replace(@readbuf)
    @readbuf.clear
    @readbuf.force_encoding(Encoding::BINARY) # Back to binary mode for further reading

    return outbuf
  end
end