[PATCH] domain_codec: optimize call to dname_enc

[Denys Vlasenko]

Thanks. I addressed this a bit differently. Looks good now?

On Tue, Jun 9, 2020 at 4:55 PM Martin Lewis <martin.lewis.x84 at gmail.com> wrote:
>
> The only call to dname_enc is with cstr = NULL, so most of dname_enc's logic is not used.
> Therefore, we can directly call convert_dname and shrink the binary size.
>
> function                                             old     new   delta
> convert_dname                                          -     143    +143
> attach_option                                        463     493     +30
> dname_enc                                            445       -    -445
> ------------------------------------------------------------------------------
> (add/remove: 1/1 grow/shrink: 1/0 up/down: 173/-445)         Total: -272
> bytes
>    text    data     bss     dec     hex filename
>  993252   16923    1872 1012047   f714f busybox_old
>  992980   16923    1872 1011775   f703f busybox_unstripped
>
> Signed-off-by: Martin Lewis <martin.lewis.x84 at gmail.com>
> ---
>  networking/udhcp/common.c       | 6 +++++-
>  networking/udhcp/common.h       | 1 +
>  networking/udhcp/domain_codec.c | 2 +-
>  3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
> index 9ec752dfc..f609bcfdb 100644
> --- a/networking/udhcp/common.c
> +++ b/networking/udhcp/common.c
> @@ -431,7 +431,11 @@ static NOINLINE void attach_option(
>  #if ENABLE_FEATURE_UDHCP_RFC3397
>         if ((optflag->flags & OPTION_TYPE_MASK) == OPTION_DNS_STRING) {
>                 /* reuse buffer and length for RFC1035-formatted string */
> -               allocated = buffer = (char *)dname_enc(NULL, 0, buffer, &length);
> +               allocated = buffer = (char *)convert_dname(buffer);
> +               if (buffer == NULL)
> +                       length = 0;
> +               else
> +                       length = strlen(buffer) + 1; /* including NUL */
>         }
>  #endif
>
> diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
> index 60255eefa..7aeeb5152 100644
> --- a/networking/udhcp/common.h
> +++ b/networking/udhcp/common.h
> @@ -219,6 +219,7 @@ void udhcp_add_simple_option(struct dhcp_packet *packet, uint8_t code, uint32_t
>  #if ENABLE_FEATURE_UDHCP_RFC3397 || ENABLE_FEATURE_UDHCPC6_RFC3646 || ENABLE_FEATURE_UDHCPC6_RFC4704
>  char *dname_dec(const uint8_t *cstr, int clen, const char *pre) FAST_FUNC;
>  uint8_t *dname_enc(const uint8_t *cstr, int clen, const char *src, int *retlen) FAST_FUNC;
> +uint8_t *convert_dname(const char *src);
>  #endif
>  struct option_set *udhcp_find_option(struct option_set *opt_list, uint8_t code) FAST_FUNC;
>
> diff --git a/networking/udhcp/domain_codec.c b/networking/udhcp/domain_codec.c
> index b7a3a5353..b5df48d87 100644
> --- a/networking/udhcp/domain_codec.c
> +++ b/networking/udhcp/domain_codec.c
> @@ -113,7 +113,7 @@ char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre)
>   * RFC1035 encoding "\003foo\004blah\003com\000". Return allocated string, or
>   * NULL if an error occurs.
>   */
> -static uint8_t *convert_dname(const char *src)
> +uint8_t *convert_dname(const char *src)
>  {
>         uint8_t c, *res, *lenptr, *dst;
>         int len;
> --
> 2.11.0
>
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