[PATCH v2] dm: Add support for escaped characters in str_field_delimit()

Abhinav Jain
2024-06-13T16:26:43Z

Remove all the escape characters that come before separator.
Tested this code by writing a dummy program containing the two
functions and testing it on below input, sharing results:

Original string: "field1\,with\,commas,field2\,with\,more\,commas"
Field: "field1"
Field: "with"
Field: "commas"
Field: "field2"
Field: "with"
Field: "more"
Field: "commas"

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
---
PATCH v1:
https://lore.kernel.org/all/20240609141721.52344-1-jain.abhinav177@gmail.com/

Changes since v1:
- Modified the str_field_delimit function as per shared feedback
- Added remove_escaped_characters function
---
---
drivers/md/dm-init.c | 53 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 47 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
index 2a71bcdba92d..0e31ecf1b48e 100644
--- a/drivers/md/dm-init.c
+++ b/drivers/md/dm-init.c
@@ -76,6 +76,24 @@ static void __init dm_setup_cleanup(struct list_head *devices)
}
}

+/* Remove escape characters from a given field string. */
+static void __init remove_escape_characters(char *field)
+{
+ char *src = field;
+ char *dest = field;
+
+ while (*src) {
+ if (*src == '\\') {
+ src++;
+ if (*src)
+ *dest++ = *src++;
+ } else {
+ *dest++ = *src++;
+ }
+ }
+ *dest = '\0';
+}
+
/**
* str_field_delimit - delimit a string based on a separator char.
* @str: the pointer to the string to delimit.
@@ -87,16 +105,39 @@ static void __init dm_setup_cleanup(struct list_head *devices)
*/
static char __init *str_field_delimit(char **str, char separator)
{
- char *s;
+ char *s, *escaped, *field;

- /* TODO: add support for escaped characters */
*str = skip_spaces(*str);
s = strchr(*str, separator);
- /* Delimit the field and remove trailing spaces */
- if (s)
+
+ /* Check for escaped character */
+ escaped = strchr(*str, '\\');
+ while (escaped && (s == NULL || escaped < s)) {
+ /*
+ * Move the separator search ahead if escaped
+ * character comes before.
+ */
+ s = strchr(escaped + 1, separator);
+ escaped = strchr(escaped + 1, '\\');
+ }
+
+ /* If we found a separator, we need to handle escape characters */
+ if (s) {
+ *s = '\0';
+
+ remove_escape_characters(*str);
+ field = *str;
+ *str = s + 1;
+ } else {
+ /* Handle the last field when no separator is present */
+ s = *str + strlen(*str);
*s = '\0';
- *str = strim(*str);
- return s ? ++s : NULL;
+
+ remove_escape_characters(*str);
+ field = *str;
+ *str = s;
+ }
+ return field;
}

/**
--
2.34.1