Re: [PATCH v2 09/13] env: Use string pointer instead of indexes in env_get_f()

Simon Glass
2021-10-15T00:40:24Z

Hi Marek,

On Wed, 13 Oct 2021 at 09:46, Marek Behún <kabel@kernel.org> wrote:
>
> From: Marek Behún <marek.behun@nic.cz>
>
> Since we no longer use env_get_char() to access n-th character of
> linearized environment data, but rather access the arrays themselves, we
> can convert the iteration to use string pointers instead of position
> indexes.
>
> Signed-off-by: Marek Behún <marek.behun@nic.cz>
> ---
> cmd/nvedit.c | 34 +++++++++++++++++-----------------
> 1 file changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/cmd/nvedit.c b/cmd/nvedit.c
> index 7c99a693ea..6eabd51209 100644
> --- a/cmd/nvedit.c
> +++ b/cmd/nvedit.c
> @@ -706,17 +706,17 @@ char *from_env(const char *envvar)
> return ret;
> }
>
> -static int env_match(const char *env, const char *s1, int i2)
> +static const char *matching_name_get_value(const char *p, const char *name)

OK so this is the function where I would like a nice comment, please.

> {
> - while (*s1 == env[i2++] && *s1 != '\0')
> - if (*s1++ == '=')
> - return i2;
> + while (*name == *p++ && *name != '\0')
> + if (*name++ == '=')
> + return p;
>
> - /* We can look at env[i2-1] because i2 was incremented at least once. */
> - if (*s1 == '\0' && env[i2-1] == '=')
> - return i2;
> + /* We can look at p[-1] because p was incremented at least once. */
> + if (*name == '\0' && p[-1] == '=')
> + return p;
>
> - return -1;
> + return NULL;
> }
>
> /*
> @@ -724,8 +724,7 @@ static int env_match(const char *env, const char *s1, int i2)
> */
> int env_get_f(const char *name, char *buf, unsigned len)
> {
> - const char *env;
> - int i, nxt;
> + const char *env, *p, *nxt;
>
> if (name == NULL || *name == '\0')
> return -1;
> @@ -735,20 +734,21 @@ int env_get_f(const char *name, char *buf, unsigned len)
> else
> env = (const char *)gd->env_addr;
>
> - for (i = 0; env[i] != '\0'; i = nxt + 1) {
> - int val, n;
> + for (p = env; *p != '\0'; p = nxt + 1) {
> + const char *value;
> + int n;
>
> - for (nxt = i; env[nxt] != '\0'; ++nxt)
> - if (nxt >= CONFIG_ENV_SIZE)
> + for (nxt = p; *nxt != '\0'; ++nxt)
> + if (nxt - env >= CONFIG_ENV_SIZE)
> return -1;
>
> - val = env_match(env, name, i);
> - if (val < 0)
> + value = matching_name_get_value(p, name);
> + if (value == NULL)
> continue;
>
> /* found; copy out */
> for (n = 0; n < len; ++n, ++buf) {
> - *buf = env[val++];
> + *buf = *value++;
> if (*buf == '\0')
> return n;
> }
> --
> 2.32.0
>

Regards,
Simon