[lwip-users] TCP_SEQ_BETWEEN

[Leon Woestenberg]

Hello,

I have just reverted the TCP_SEQ_BETWEEN macro as suggested by Bill
Knight, as it fails on his ARM target.

In reviewing the macro, I got lost in simple math. The aim of the
macro is to verify that:

(b<=a<=c)
==
(b<=a) and (a<=c)
==
(0<=a-b) and (0<=c-a)

However, the current macro TCP_SEQ_BETWEEN

(c-b>=a-b) merely checks that (c>=a)

Was this an intentional simplification?

Regards,

Leon Woestenberg.

#define TCP_SEQ_LT(a,b)     ((s32_t)((a)-(b)) < 0)
#define TCP_SEQ_LEQ(a,b)    ((s32_t)((a)-(b)) <= 0)
#define TCP_SEQ_GT(a,b)     ((s32_t)((a)-(b)) > 0)
#define TCP_SEQ_GEQ(a,b)    ((s32_t)((a)-(b)) >= 0)
/* is b<=a<=c? */
#if 0 /* see bug #10548 */
#define TCP_SEQ_BETWEEN(a,b,c) ((c)-(b) >= (a)-(b))
#endif
#define TCP_SEQ_BETWEEN(a,b,c) (TCP_SEQ_GEQ(a,b) && TCP_SEQ_LEQ(a,c))