Method: IO#ungetbyte

Defined in:
io.c

#ungetbyte(string) ⇒ nil #ungetbyte(integer) ⇒ nil

Pushes back bytes (passed as a parameter) onto ios, such that a subsequent buffered read will return it. Only one byte may be pushed back before a subsequent read operation (that is, you will be able to read only the last of several bytes that have been pushed back). Has no effect with unbuffered reads (such as IO#sysread).

f = File.new("testfile")   #=> #<File:testfile>
b = f.getbyte              #=> 0x38
f.ungetbyte(b)             #=> nil
f.getbyte                  #=> 0x38

Overloads:

  • #ungetbyte(string) ⇒ nil

    Returns:

    • (nil)
  • #ungetbyte(integer) ⇒ nil

    Returns:

    • (nil) 


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# File 'io.c', line 4275

VALUE
rb_io_ungetbyte(VALUE io, VALUE b)
{
    rb_io_t *fptr;

    GetOpenFile(io, fptr);
    rb_io_check_byte_readable(fptr);
    switch (TYPE(b)) {
      case T_NIL:
        return Qnil;
      case T_FIXNUM:
      case T_BIGNUM: ;
        VALUE v = rb_int_modulo(b, INT2FIX(256));
        unsigned char c = NUM2INT(v) & 0xFF;
        b = rb_str_new((const char *)&c, 1);
        break;
      default:
        SafeStringValue(b);
    }
    io_ungetbyte(b, fptr);
    return Qnil;
}