Module: CosmosIO

Included in:
IO, StringIO
Defined in:
lib/cosmos/core_ext/cosmos_io.rb,
ext/cosmos/ext/cosmos_io/cosmos_io.c

Overview

COSMOS specific additions to the Ruby IO and StringIO classes

Instance Method Summary collapse

Instance Method Details

#read_length_bytes(param_length_num_bytes) ⇒ 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 'ext/cosmos/ext/cosmos_io/cosmos_io.c', line 37

static VALUE read_length_bytes(VALUE self, VALUE param_length_num_bytes)
{
  int length_num_bytes = FIX2INT(param_length_num_bytes);
  unsigned char* string = NULL;
  long string_length = 0;
  unsigned short short_length = 0;
  unsigned char* length_ptr = NULL;
  volatile VALUE temp_string = Qnil;
  volatile VALUE temp_string_length = Qnil;
  volatile VALUE return_value = Qnil;

  /* Read bytes for string length */
  temp_string = rb_funcall(self, id_method_read, 1, param_length_num_bytes);
  if (NIL_P(temp_string) || (RSTRING_LEN(temp_string) != length_num_bytes))
  {
    return Qnil;
  }

  string = (unsigned char*) RSTRING_PTR(temp_string);
  switch (length_num_bytes)
  {
    case 1:
      string_length = (unsigned int) string[0];
      break;
    case 2:
      length_ptr = (unsigned char*) &short_length;
      if (HOST_ENDIANNESS == COSMOS_BIG_ENDIAN)
      {
        length_ptr[1] = string[1];
        length_ptr[0] = string[0];
      }
      else
      {
        length_ptr[0] = string[1];
        length_ptr[1] = string[0];
      }
      string_length = short_length;
      break;
    case 4:
      length_ptr = (unsigned char*) &string_length;
      if (HOST_ENDIANNESS == COSMOS_BIG_ENDIAN)
      {
        length_ptr[3] = string[3];
        length_ptr[2] = string[2];
        length_ptr[1] = string[1];
        length_ptr[0] = string[0];
      }
      else
      {
        length_ptr[0] = string[3];
        length_ptr[1] = string[2];
        length_ptr[2] = string[1];
        length_ptr[3] = string[0];
      }
      break;
    default:
      return Qnil;
      break;
  };

  /* Read String */
  temp_string_length = UINT2NUM(string_length);
  return_value = rb_funcall(self, id_method_read, 1, temp_string_length);
  if (NIL_P(return_value) || (RSTRING_LEN(return_value) != string_length))
  {
    return Qnil;
  }

  return return_value;
}