[lttng-dev] [lttng-tools PATCH 1/2] Introduce a new utils_resolve_relative function

[David Goulet]

On 07 Nov (23:32:13), Raphaël Beamonte wrote:
> This functions allows to resolve relative path such as './'
> and '../' inside a path string. This allows to use paths such
> as '~/../test' that are received as '/home/x/../test' for
> instance.
> 
> Signed-off-by: Raphaël Beamonte <raphael.beamonte at gmail.com>
> ---
>  src/common/utils.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>  src/common/utils.h |    1 +
>  2 files changed, 49 insertions(+)
> 
> diff --git a/src/common/utils.c b/src/common/utils.c
> index da4c036..7b52760 100644
> --- a/src/common/utils.c
> +++ b/src/common/utils.c
> @@ -36,6 +36,54 @@
>  #include "defaults.h"
>  
>  /*
> + * Resolve the './' and '../' strings inside a path using our
> + * very own way to do it, so that it works even if the directory
> + * does not exist
> + */
> +LTTNG_HIDDEN
> +int utils_resolve_relative(char *path)
> +{
> +	char *next, *previous, *slash, *start_path;
> +
> +	/* As long as we find '/./' in the path string */
> +	while ((next = strstr(path, "/./"))) {
> +
> +		/* We prepare the start_path not containing it */
> +		start_path = strndup(path, next - path);
> +
> +		/* And we concatenate it with the part after this string */
> +		snprintf(path, PATH_MAX, "%s%s", start_path, next + 2);
> +
> +		free(start_path);
> +	}
> +
> +	while ((next = strstr(path, "/../"))) {
> +		/* If the path starts with '/../', there's a problem */
> +		if (next == path) {
> +			ERR("%s: Path cannot be resolved", path);
> +			return 1;
> +		}
> +
> +		/* We find the last level of directory */
> +		previous = path;
> +		while ((slash = strpbrk(previous + 1, "/")) && slash != next) {
> +			previous = slash;
> +		}
> +
> +		/* Then we prepare the start_path not containing it */
> +		start_path = strndup(path, previous - path);
> +
> +		/* And we concatenate it with the part after the '/../' */
> +		snprintf(path, PATH_MAX, "%s%s", start_path, next + 3);

I'm not to keen with modifying directly the given path. I would really
prefer having this function return a newly allocated char * and taking a
const char *.  We could want to keep the path given for whatever reason
and also you have no idea if the path given is NULL terminated or not
nor its size.

Also, a small unit test testing this function and the other one in the
next patch would be awesome if you have 2 minutes for that. Those
functions are not that trivial to follow for a human :P, there is a lot
of string mangling and it's getting confusing after a while.

Thanks!
David

> +
> +		free(start_path);
> +	}
> +
> +	return 0;
> +}
> +
> +
> +/*
>   * Return the realpath(3) of the path even if the last directory token does not
>   * exist. For example, with /tmp/test1/test2, if test2/ does not exist but the
>   * /tmp/test1 does, the real path is returned. In normal time, realpath(3)
> diff --git a/src/common/utils.h b/src/common/utils.h
> index 52f2798..ced3584 100644
> --- a/src/common/utils.h
> +++ b/src/common/utils.h
> @@ -26,6 +26,7 @@
>  #define MEBI_LOG2 20
>  #define GIBI_LOG2 30
>  
> +int utils_resolve_relative(char *path);
>  char *utils_expand_path(const char *path);
>  int utils_create_pipe(int *dst);
>  int utils_create_pipe_cloexec(int *dst);
> -- 
> 1.7.10.4
> 
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