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$NetBSD: patch-af,v 1.2 2009/02/11 08:06:17 obache Exp $
--- ars.c.orig 2003-07-28 09:00:54.000000000 +0000
+++ ars.c
@@ -372,7 +372,7 @@ u_int16_t ars_cksum(void *vbuf, size_t n
}
if (nbytes == 1) {
oddbyte = 0;
- *((u_int16_t *) &oddbyte) = *(u_int8_t *) buf;
+ *((u_int8_t *) &oddbyte) = *((u_int8_t *) buf);
sum += oddbyte;
}
sum = (sum >> 16) + (sum & 0xffff);
@@ -381,6 +381,13 @@ u_int16_t ars_cksum(void *vbuf, size_t n
}
/* Multiple buffers checksum facility */
+/*
+ * Important facts about the checksum (sum = ~cksum, Ai are bytes):
+ * 1. sum(A0...A2i-1,A2i...A2n-1) = sum(A0...A2i-1) + sum(A2i...B2n-1),
+ * 2. sum(A0...A2i,A2i+1...A2n-1) = sum(A0...A2i,0) + sum(0,A2i+1...A2n-1)
+ * 3. sum(A0...A2n-1,A2n) = sum(A0...A2n-1,A2n,0) (ex definitiones)
+ * 4. sum(0,A0...Ak) = swap_bytes(sum(A0...Ak))
+ */
u_int16_t ars_multi_cksum(struct mc_context *c, int op, void *vbuf,
size_t nbytes)
{
@@ -394,38 +401,27 @@ u_int16_t ars_multi_cksum(struct mc_cont
c->old = 0;
return -ARS_OK;
} else if (op == ARS_MC_UPDATE) {
- if (c->oddbyte_flag) {
- u_int8_t *x = (u_int8_t*)&oddbyte;
- oddbyte = 0;
- *((u_int16_t *) &oddbyte) = c->oddbyte << 8;
- *((u_int16_t *) &oddbyte) |= *(u_int8_t *) buf;
- oddbyte = (x[0] << 8) | x[1]; /* fix endianess */
- c->old += oddbyte;
- nbytes--;
- c->oddbyte_flag = 0;
- /* We need to stay aligned -- bad slowdown, fix? */
- tmp = alloca(nbytes);
- memcpy(tmp, vbuf+1, nbytes);
- buf = tmp;
- }
- sum = c->old;
+ sum = 0;
while (nbytes > 1) {
sum += *buf++;
nbytes -= 2;
}
- c->old = sum;
if (nbytes == 1) {
- c->oddbyte = *(u_int8_t*) buf;
- c->oddbyte_flag++;
+ oddbyte = 0;
+ *((u_int8_t *) &oddbyte) = *((u_int8_t *) buf);
+ sum += oddbyte;
+ }
+ if (c->oddbyte_flag) {
+ /* reverse checksum endianness */
+ sum = (sum >> 16) + (sum & 0xffff);
+ sum += (sum >> 16);
+ sum = ((sum & 0xff00) >> 8) | ((sum & 0xff) << 8);
}
+ c->old += sum;
+ c->oddbyte_flag ^= (nbytes == 1 ? 1 : 0);
return -ARS_OK;
} else if (op == ARS_MC_FINAL) {
sum = c->old;
- if (c->oddbyte_flag == 1) {
- oddbyte = 0;
- *((u_int16_t *) &oddbyte) = c->oddbyte;
- sum += oddbyte;
- }
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return (u_int16_t) ~sum;
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