Method: IO#advise

Defined in:
io.c

#advise(advice, offset = 0, len = 0) ⇒ nil

Invokes Posix system call posix_fadvise(2), which announces an intention to access data from the current file in a particular manner.

The arguments and results are platform-dependent.

The relevant data is specified by:

  • offset: The offset of the first byte of data.

  • len: The number of bytes to be accessed; if len is zero, or is larger than the number of bytes remaining, all remaining bytes will be accessed.

Argument advice is one of the following symbols:

  • :normal: The application has no advice to give about its access pattern for the specified data. If no advice is given for an open file, this is the default assumption.

  • :sequential: The application expects to access the specified data sequentially (with lower offsets read before higher ones).

  • :random: The specified data will be accessed in random order.

  • :noreuse: The specified data will be accessed only once.

  • :willneed: The specified data will be accessed in the near future.

  • :dontneed: The specified data will not be accessed in the near future.

Not implemented on all platforms.

Returns:

  • (nil) 


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# File 'io.c', line 10942

static VALUE
rb_io_advise(int argc, VALUE *argv, VALUE io)
{
    VALUE advice, offset, len;
    rb_off_t off, l;
    rb_io_t *fptr;

    rb_scan_args(argc, argv, "12", &advice, &offset, &len);
    advice_arg_check(advice);

    io = GetWriteIO(io);
    GetOpenFile(io, fptr);

    off = NIL_P(offset) ? 0 : NUM2OFFT(offset);
    l   = NIL_P(len)    ? 0 : NUM2OFFT(len);

#ifdef HAVE_POSIX_FADVISE
    return do_io_advise(fptr, advice, off, l);
#else
    ((void)off, (void)l); /* Ignore all hint */
    return Qnil;
#endif
}