sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Add some comments to inet_ntop()

Browse Source 
Endian-ness issues are mind boggling sometimes.  I have been confused by the logic in inet_ntop() a few times so I thought I would add some comments so that I (and others) will understand the endian-ness issues in the future.  No change to logic, only comments changed.
This commit is contained in:
Gregory Nutt 2020-10-04 11:22:32 -06:00 committed by Xiang Xiao
parent e4094eff12
commit 32b0562375
1 changed files with 32 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
libs/libc/net/lib_inetntop.c
View File

@ -98,7 +98,8 @@
****************************************************************************/
#if defined(CONFIG_NET_IPv4) || defined(CONFIG_LIBC_IPv4_ADDRCONV)
static int inet_ipv4_ntop(FAR const void *src, FAR char *dest, socklen_t size)
static int inet_ipv4_ntop(FAR const void *src, FAR char *dest,
socklen_t size)
{
FAR uint8_t *ptr;
@ -108,8 +109,33 @@ static int inet_ipv4_ntop(FAR const void *src, FAR char *dest, socklen_t size)
}
ptr = (FAR uint8_t *)src;
/* Data is in network order. However, indexed access is the same in both
* big and little endian cases:
*
* Big Endian:
* +---+---+---+---+
* Network Order: | 0 | 1 | 2 | 3 | n=Network byte order
* |192|168| 1 | 2 | Example
* +---+---+---+---+
* Host Index: | 0 | 1 | 2 | 3 | n=Host Index
* |192|168| 1 | 2 | Example
* +---+---+---+---+
*
* Little Endian:
*
* +---+---+---+---+
* Network Order: | 0 | 1 | 2 | 3 | n=Network byte order
* |192|168| 1 | 2 | Example
* +---+---+---+---+
* Host Index: | 3 | 2 | 1 | 0 | n=Host Index
* | 2 | 1 |168|192| Example
* +---+---+---+---+
*/
snprintf(dest, INET_ADDRSTRLEN, "%u.%u.%u.%u",
ptr[0], ptr[1], ptr[2], ptr[3]);
return OK;
}
#endif
@ -143,7 +169,8 @@ static int inet_ipv4_ntop(FAR const void *src, FAR char *dest, socklen_t size)
****************************************************************************/
#if defined(CONFIG_NET_IPv6) || defined(CONFIG_LIBC_IPv6_ADDRCONV)
static int inet_ipv6_ntop(FAR const void *src, FAR char *dest, socklen_t size)
static int inet_ipv6_ntop(FAR const void *src, FAR char *dest,
socklen_t size)
{
FAR const struct in6_addr *in6_addr;
uint16_t warray[8];
@ -180,6 +207,7 @@ static int inet_ipv6_ntop(FAR const void *src, FAR char *dest, socklen_t size)
{
break;
}
offset++;
count++;
}
@ -190,6 +218,7 @@ static int inet_ipv6_ntop(FAR const void *src, FAR char *dest, socklen_t size)
maxcount = count;
}
}
offset++;
}
@ -260,7 +289,7 @@ FAR const char *inet_ntop(int af, FAR const void *src, FAR char *dest,
{
int ret;
DEBUGASSERT(src && dest);
DEBUGASSERT(src != NULL && dest != NULL);
/* Do the conversion according to the IP version */