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

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(-)

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(-)

Reviewed-by: Simon Glass <sjg@chromium.org>

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

Hi Simon,

On Thu, 14 Oct 2021 18:40:02 -0600
Simon Glass <sjg@chromium.org> wrote:

> > -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.

Now that I look at it, I notice that it also works for cases when name
is "abc=def" (it matches just "abc"). This was the purpose of
env_match() before, but env_get_f() does not use it that way, and this
functionality can now be removed.

This would simplify the code to something like
  len = strlen(name);
  if (p[len] == '=' && !strncmp(p, name, len))
    return &p[len + 1];
  return NULL;

And this is simple enough to be inlined into env_get_f().

I will refactor this and send v3.

Marek