Module: OpenC3IO

Included in:
IO, StringIO
Defined in:
lib/openc3/core_ext/openc3_io.rb,
ext/openc3/ext/openc3_io/openc3_io.c

Overview

OpenC3 specific additions to the Ruby IO and StringIO classes

Instance Method Summary collapse

Instance Method Details

#read_length_bytes(*args) ⇒ String

Reads a length field and then return the String resulting from reading the number of bytes the length field indicates

For example:

io = StringIO.new
# where io is "\x02\x01\x02\x03\x04...."
result = io.read_length_bytes(1)
# result will be "\x01x02" because the length field was given
# to be 1 byte. We read 1 byte which is a 2. So we then read two
# bytes and return.

Parameters:

  • length_num_bytes (Integer) —

    Number of bytes in the length field

Returns:

  • (String) —

    A String of “length field” number of bytes



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# File 'lib/openc3/core_ext/openc3_io.rb', line 42

def read_length_bytes(length_num_bytes, max_read_size = nil)
  return nil unless (length_num_bytes == 1) || (length_num_bytes == 2) or (length_num_bytes == 4)

  # Read bytes for string length
  temp_string_length = self.read(length_num_bytes)
  return nil if (temp_string_length.nil?) || (temp_string_length.length != length_num_bytes)

  string_length = OpenC3::BinaryAccessor.read(0, length_num_bytes * 8, :UINT, temp_string_length, :BIG_ENDIAN)

  # Read String
  return nil if max_read_size and string_length > max_read_size

  string = self.read(string_length)
  return nil if (string.nil?) || (string.length != string_length)

  return string
end