Vladimir Kotal writes: > random(3C) returns long which is 4 bytes in /usr/bin/nc (nc is delivered > only as 32-bit prog).
Actually, the random(3C) man page indicates that it returns a value in the range 0 to 2^31-1. In other words, it's a 31 bit non-negative value, and it doesn't matter how the application is compiled. > This means (random() & 0xFFFF) will be just the 2 > less significant bytes of the 4 returned by random(). Yes, but why? > The purpose of the expression on line 792 is preparation for permuting > the numbers in (lo,hi) interval. It seems that the goal of the binary > operation is to cap the random number returned from random() to 16 bits > (so it fits in the range of usable TCP/UDP ports) and then further limit > it with the range 'hi - lo'. That sounds wrong to me. This code is tossing away 15 bits of the randomness, and (much worse yet) is biasing the results. The first 65536 - (65535 MOD (hi - lo + 1)) values will be hit preferentially, something like (1 + 65536 / (hi - lo + 1)) times as often. That's possibly an annoying skew, if the range is large, and it happens precisely because the random value is truncated before being used for the modulo (%) selection. > Although without the binary operation this will remain functional > (thanks to the modulo operation), IMHO the idea is logical and should be > preserved. There is probably a better way how to do it, though. (cast to > in_port_t ?) I don't actually understand the logic behind it. I would have thought that it was just randomizing over a range, but it seems to have some inner logic that escapes me. I don't think it can be right. Perhaps someone thought that random(3C) was able to return negative numbers? -- James Carlson, Solaris Networking <[EMAIL PROTECTED]> Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ opensolaris-code mailing list opensolaris-code@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/opensolaris-code
