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Added some more fixes to the lwip_standard_chksum() comments.

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This commit is contained in:
christiaans 2005-12-14 12:55:12 +00:00
parent 5088a38b9f
commit 61cdbb30a6
1 changed files with 7 additions and 4 deletions
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11
src/core/inet.c
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@ -63,7 +63,7 @@
* *
* @param dataptr points to start of data to be summed at any boundary * @param dataptr points to start of data to be summed at any boundary
* @param len length of data to be summed * @param len length of data to be summed
* @return network order (!) lwip checksum (non-inverted Internet sum) * @return host order (!) lwip checksum (non-inverted Internet sum)
* *
* @note accumulator size limits summable lenght to 64k * @note accumulator size limits summable lenght to 64k
* @note host endianess is irrelevant (p3 RFC1071) * @note host endianess is irrelevant (p3 RFC1071)
@ -80,10 +80,11 @@ lwip_standard_chksum(void *dataptr, u16_t len)
octetptr = (u8_t*)dataptr; octetptr = (u8_t*)dataptr;
while (len > 1) while (len > 1)
{ {
/* first octet is most significant */ /* delacre first octet as most significant
thus assume network order, ignoring host order */
src = (*octetptr) << 8; src = (*octetptr) << 8;
octetptr++; octetptr++;
/* second octet is least significant */ /* declare second octet as least significant */
src |= (*octetptr); src |= (*octetptr);
octetptr++; octetptr++;
acc += src; acc += src;
@ -99,7 +100,9 @@ lwip_standard_chksum(void *dataptr, u16_t len)
if ((acc & 0xffff0000) != 0) { if ((acc & 0xffff0000) != 0) {
acc = (acc >> 16) + (acc & 0x0000ffffUL); acc = (acc >> 16) + (acc & 0x0000ffffUL);
} }
/* caller must invert bits for Internet sum ! */ /* This maybe a little confusing: reorder sum using htons()
instead of ntohs() since it has a little less call overhead.
The caller must invert bits for Internet sum ! */
return htons((u16_t)acc); return htons((u16_t)acc);
} }