lib: add string replace function

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

2 files changed, 48 insertions, 0 deletions

diff --git a/lib/frrstr.c b/lib/frrstr.c
index fd337073f..fbbc890ec 100644
--- a/lib/frrstr.c
+++ b/lib/frrstr.c
@@ -152,6 +152,32 @@ void frrstr_strvec_free(vector v)
 	vector_free(v);
 }
 
+char *frrstr_replace(const char *str, const char *find, const char *replace)
+{
+	char *ch;
+	char *nustr = XSTRDUP(MTYPE_TMP, str);
+
+	size_t findlen = strlen(find);
+	size_t repllen = strlen(replace);
+
+	while ((ch = strstr(nustr, find))) {
+		if (repllen > findlen) {
+			size_t nusz = strlen(nustr) + repllen - findlen + 1;
+			nustr = XREALLOC(MTYPE_TMP, nustr, nusz);
+			ch = strstr(nustr, find);
+		}
+
+		size_t nustrlen = strlen(nustr);
+		size_t taillen = (nustr + nustrlen) - (ch + findlen);
+
+		memmove(ch + findlen + (repllen - findlen), ch + findlen,
+			taillen + 1);
+		memcpy(ch, replace, repllen);
+	}
+
+	return nustr;
+}
+
 bool begins_with(const char *str, const char *prefix)
 {
 	if (!str || !prefix)
diff --git a/lib/frrstr.h b/lib/frrstr.h
index 8b591849a..d40ca14ba 100644
--- a/lib/frrstr.h
+++ b/lib/frrstr.h
@@ -88,6 +88,28 @@ void frrstr_filter_vec(vector v, regex_t *filter);
 void frrstr_strvec_free(vector v);
 
 /*
+ * Given a string, replaces all occurrences of a substring with a different
+ * string. The result is a new string. The original string is not modified.
+ *
+ * If 'replace' is longer than 'find', this function performs N+1 allocations,
+ * where N is the number of times 'find' occurs in 'str'. If 'replace' is equal
+ * in length or shorter than 'find', only 1 allocation is performed.
+ *
+ * str
+ *    String to perform replacement on.
+ *
+ * find
+ *    Substring to replace.
+ *
+ * replace
+ *    String to replace 'find' with.
+ *
+ * Returns:
+ *    A new string, allocated with MTYPE_TMP, that is the result of performing
+ *    the replacement on 'str'. This must be freed by the caller.
+ */
+char *frrstr_replace(const char *str, const char *find, const char *replace);
+/*
  * Prefix match for string.
  *
  * str