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Message-ID: <CAL3m8eCdz_eUGptYsn5NDPho0PQ_=wH+F4aY9eSmgsPj+vS00w@mail.gmail.com>
Date: Sun, 14 Apr 2013 23:10:55 -0500
From: Strake <strake888@...il.com>
To: musl@...ts.openwall.com
Subject: Re: [patch] add ether_(aton, ntoa)
On 14/04/2013, Rich Felker <dalias@...ifal.cx> wrote:
> I would put the static object inside the function that uses it rather
> than outside, but this is purely a stylistic consideration.
Yeah, I just like to define closure-bound free variables without the
closure scope itself, and automatics within.
> Also, it
> _might_ be better to separate the functions with static storage out so
> that programs using the _r interfaces don't pull in extra .bss, but
> it's a tradeoff -- if we do this for every ugly nonstandard function,
> we just end up making the .a file a lot larger and making build time a
> lot slower. So I think I'm okay with the way you did it; we might even
> want to go the other direction and put all 4 functions in one file.
I would've done, but I wished to match how inet_* are organized.
>> +char *ether_ntoa_r (const struct ether_addr *p_a, char *x) {
>> + char *y;
>> + y = x;
>> + for (int ii = 0; ii < 6; ii++) {
>> + x += sprintf (x, ii == 0 ? "%0hhX" : ":%0hhX",
>> (*p_a).ether_addr_octet[ii]);
>
> The hh is unnecessary here. The argument has type int (due to default
> promotions) so just "%X" is fine. Also, as far as I can tell, the 0
> was not doing anything since no width was specified. If your intent is
> to always have 2 hex digits, "%.2X" is the right format to use.
Thanks. New patch follows message.
> Could you compare and see if it generates smaller code if we use a
> single snprintf/sscanf to implement these functions rather than a
> loop? I'm not sure which is better, but since they're not widely used,
> my main interest is keeping them small.
ntoa: same size
aton: mine is smaller
> Also, how are these functions
> documented to handle malformed input, and are you matching the
> documentation on that?
Linux docs say that ether_aton return 0 on malformed input, as mine does.
ether_ntoa is infallible.
Cheers,
Strake
>From ad5ab07c6ec15b8b98717750888947634c2fa039 Mon Sep 17 00:00:00 2001
From: Strake <strake888@...il.com>
Date: Sun, 14 Apr 2013 12:09:30 -0500
Subject: [PATCH] add ether_(aton, ntoa)
---
include/netinet/ether.h | 14 ++++++++++++++
src/network/ether_aton.c | 23 +++++++++++++++++++++++
src/network/ether_ntoa.c | 17 +++++++++++++++++
3 files changed, 54 insertions(+)
create mode 100644 include/netinet/ether.h
create mode 100644 src/network/ether_aton.c
create mode 100644 src/network/ether_ntoa.c
diff --git a/include/netinet/ether.h b/include/netinet/ether.h
new file mode 100644
index 0000000..c5179d5
--- /dev/null
+++ b/include/netinet/ether.h
@@ -0,0 +1,14 @@
+#ifndef _NETINET_ETHER_H
+#define _NETINET_ETHER_H
+
+#include <netinet/if_ether.h>
+
+char *ether_ntoa (const struct ether_addr *);
+
+struct ether_addr *ether_aton (const char *);
+
+char *ether_ntoa_r (const struct ether_addr *, char *);
+
+struct ether_addr *ether_aton_r (const char *, struct ether_addr *);
+
+#endif
diff --git a/src/network/ether_aton.c b/src/network/ether_aton.c
new file mode 100644
index 0000000..4270872
--- /dev/null
+++ b/src/network/ether_aton.c
@@ -0,0 +1,23 @@
+#include <stdlib.h>
+#include <netinet/ether.h>
+
+static struct ether_addr a;
+
+struct ether_addr *ether_aton_r (const char *x, struct ether_addr *p_a) {
+ for (int ii = 0; ii < 6; ii++) {
+ unsigned long int n;
+ if (ii != 0) {
+ if (x[0] != ':') return 0; /* bad format */
+ else x++;
+ }
+ n = strtoul (x, &x, 16);
+ if (n > 0xFF) return 0; /* bad byte */
+ (*p_a).ether_addr_octet[ii] = n;
+ }
+ if (x[0] != 0) return 0; /* bad format */
+ return p_a;
+}
+
+struct ether_addr *ether_aton (const char *x) {
+ return ether_aton_r (x, &a);
+}
diff --git a/src/network/ether_ntoa.c b/src/network/ether_ntoa.c
new file mode 100644
index 0000000..468ac48
--- /dev/null
+++ b/src/network/ether_ntoa.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <netinet/ether.h>
+
+static char x[18];
+
+char *ether_ntoa_r (const struct ether_addr *p_a, char *x) {
+ char *y;
+ y = x;
+ for (int ii = 0; ii < 6; ii++) {
+ x += sprintf (x, ii == 0 ? "%.2X" : ":%.2X", (*p_a).ether_addr_octet[ii]);
+ }
+ return y;
+}
+
+char *ether_ntoa (const struct ether_addr *p_a) {
+ return ether_ntoa_r (p_a, x);
+}
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