[U-Boot] [PATCH v5 05/26] env: Simplify the reverse_strstr() interface

Joe Hershberger
2015-05-20T19:27:18Z

The logic to find the whole matching name was split needlessly between
the reverse_strstr function and its caller. Fully contain it to make the
interface for calling it more consistent.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

---

Changes in v5: None
Changes in v4: None
Changes in v3: None
Changes in v2:
-Fix bisectability issue
-Fix corner case in reverse_name_search() where searched starts with ' '

common/env_attr.c | 87 ++++++++++++++++++++++++++++++-------------------------
1 file changed, 47 insertions(+), 40 deletions(-)

diff --git a/common/env_attr.c b/common/env_attr.c
index e791f44..6e13184 100644
--- a/common/env_attr.c
+++ b/common/env_attr.c
@@ -109,33 +109,59 @@ int env_attr_walk(const char *attr_list,
}

/*
- * Search for the last matching string in another string with the option to
- * start looking at a certain point (i.e. ignore anything beyond that point).
+ * Search for the last exactly matching name in an attribute list
*/
-static char *reverse_strstr(const char *searched, const char *search_for,
- const char *searched_start)
+static int reverse_name_search(const char *searched, const char *search_for,
+ const char **result)
{
- char *result = NULL;
+ int result_size = 0;
+ const char *cur_searched = searched;

- if (*search_for == '\0')
- return (char *)searched;
+ if (result)
+ *result = NULL;
+
+ if (*search_for == '\0') {
+ if (result)
+ *result = searched;
+ return strlen(searched);
+ }

for (;;) {
- char *match = strstr(searched, search_for);
-
- /*
- * Stop looking if no new match is found or looking past the
- * searched_start pointer
- */
- if (match == NULL || (searched_start != NULL &&
- match + strlen(search_for) > searched_start))
+ const char *match = strstr(cur_searched, search_for);
+ const char *prevch;
+ const char *nextch;
+
+ /* Stop looking if no new match is found */
+ if (match == NULL)
break;

- result = match;
- searched = match + 1;
+ prevch = match - 1;
+ nextch = match + strlen(search_for);
+
+ /* Skip spaces */
+ while (*prevch == ' ' && prevch >= searched)
+ prevch--;
+ while (*nextch == ' ')
+ nextch++;
+
+ /* Start looking past the current match so last is found */
+ cur_searched = match + 1;
+ /* Check for an exact match */
+ if (match != searched &&
+ *prevch != ENV_ATTR_LIST_DELIM &&
+ prevch != searched - 1)
+ continue;
+ if (*nextch != ENV_ATTR_SEP &&
+ *nextch != ENV_ATTR_LIST_DELIM &&
+ *nextch != '\0')
+ continue;
+
+ if (result)
+ *result = match;
+ result_size = strlen(search_for);
}

- return result;
+ return result_size;
}

/*
@@ -145,6 +171,7 @@ static char *reverse_strstr(const char *searched, const char *search_for,
int env_attr_lookup(const char *attr_list, const char *name, char *attributes)
{
const char *entry = NULL;
+ int entry_len;

if (!attributes)
/* bad parameter */
@@ -153,32 +180,12 @@ int env_attr_lookup(const char *attr_list, const char *name, char *attributes)
/* list not found */
return -EINVAL;

- entry = reverse_strstr(attr_list, name, NULL);
- while (entry != NULL) {
- const char *prevch = entry - 1;
- const char *nextch = entry + strlen(name);
-
- /* Skip spaces */
- while (*prevch == ' ')
- prevch--;
- while (*nextch == ' ')
- nextch++;
-
- /* check for an exact match */
- if ((entry == attr_list ||
- *prevch == ENV_ATTR_LIST_DELIM) &&
- (*nextch == ENV_ATTR_SEP ||
- *nextch == ENV_ATTR_LIST_DELIM ||
- *nextch == '\0'))
- break;
-
- entry = reverse_strstr(attr_list, name, entry);
- }
+ entry_len = reverse_name_search(attr_list, name, &entry);
if (entry != NULL) {
int len;

/* skip the name */
- entry += strlen(name);
+ entry += entry_len;
/* skip spaces */
while (*entry == ' ')
entry++;
--
1.7.11.5