diff --git a/src/ddsrt/include/dds/ddsrt/string.h b/src/ddsrt/include/dds/ddsrt/string.h
index 7fca58c..5c8d600 100644
--- a/src/ddsrt/include/dds/ddsrt/string.h
+++ b/src/ddsrt/include/dds/ddsrt/string.h
@@ -176,6 +176,25 @@ ddsrt_strerror_r(
     char *buf,
     size_t buflen);
 
+/**
+ * @brief Replace substring of null terminated string
+ *
+ * @param[in]   str     pointer to string
+ * @param[in]   srch    non-empty string to replace
+ * @param[in]   subst   string to substitute character "srch" with
+ * @param[in]   max     maximum number of times to replace search, or 0 for unlimited
+ *
+ * @returns Pointer to newly allocated string with max occurrences of srch replaced, or
+ * NULL on allocation failure or if srch is an empty string.
+ */
+DDS_EXPORT char *
+ddsrt_str_replace(
+    const char *str,
+    const char *srch,
+    const char *subst,
+    size_t max)
+ddsrt_nonnull_all;
+
 #if defined (__cplusplus)
 }
 #endif
diff --git a/src/ddsrt/include/dds/ddsrt/strtol.h b/src/ddsrt/include/dds/ddsrt/strtol.h
index c4cb059..07860c2 100644
--- a/src/ddsrt/include/dds/ddsrt/strtol.h
+++ b/src/ddsrt/include/dds/ddsrt/strtol.h
@@ -21,6 +21,19 @@
 extern "C" {
 #endif
 
+/**
+ * @brief Convert a character to an integer value
+ *
+ * Translates the numeric value of the provided character. For characters in range
+ * '0' to '9' the returned integer value is 0-9. For the range 'a' to 'z' and 'A'
+ * to 'Z', the numeric return value is 10-36.
+ *
+ * @param[in] chr   The character
+ *
+ * @returns The integer value for the character, or -1 in case @chr cannot be translated to a numeric value
+ */
+DDS_EXPORT int32_t ddsrt_todigit(const int chr);
+
 /**
  * @brief Convert a string to a long long integer.
  *
diff --git a/src/ddsrt/src/string.c b/src/ddsrt/src/string.c
index d048e5f..e625535 100644
--- a/src/ddsrt/src/string.c
+++ b/src/ddsrt/src/string.c
@@ -15,7 +15,9 @@
 #include <string.h>
 
 #include "dds/ddsrt/heap.h"
+#include "dds/ddsrt/misc.h"
 #include "dds/ddsrt/string.h"
+#include "dds/ddsrt/types.h"
 
 int
 ddsrt_strcasecmp(
@@ -162,3 +164,41 @@ ddsrt_strdup(
 
   return ddsrt_memdup(str, strlen(str) + 1);
 }
+
+char *
+ddsrt_str_replace(
+    const char *str,
+    const char *srch,
+    const char *subst,
+    size_t max)
+{
+  const size_t lsrch = strlen(srch);
+  if (lsrch == 0) /* empty search string is treated as failure */
+    return NULL;
+
+  const size_t lsubst = strlen(subst);
+  const size_t lstr = strlen(str);
+  const char *cur = str;
+  char *res;
+  size_t cnt;
+
+  if (max == 0)
+    max = SIZE_MAX;
+  for (cnt = 0; (cur = strstr(cur, srch)) != NULL && cnt < max; cnt++)
+    cur += lsrch;
+  if ((res = ddsrt_malloc(lstr + cnt * (lsubst - lsrch) + 1)) == NULL)
+    return NULL;
+  char *tmp = res;
+  cur = str;
+  while (cnt--)
+  {
+    const char *found = strstr(cur, srch);
+    const size_t skip = (size_t)(found - cur);
+    memcpy(tmp, cur, skip);
+    memcpy(tmp + skip, subst, lsubst);
+    tmp += skip + lsubst;
+    cur += skip + lsrch;
+  }
+  memcpy(tmp, cur, lstr - (size_t) (cur - str) + 1);
+  return res;
+}
diff --git a/src/ddsrt/src/strtol.c b/src/ddsrt/src/strtol.c
index 5269d96..f8d4223 100644
--- a/src/ddsrt/src/strtol.c
+++ b/src/ddsrt/src/strtol.c
@@ -16,7 +16,7 @@
 
 #include "dds/ddsrt/strtol.h"
 
-static int ddsrt_todigit(const int chr)
+int32_t ddsrt_todigit(const int chr)
 {
   if (chr >= '0' && chr <= '9') {
     return chr - '0';
diff --git a/src/ddsrt/tests/string.c b/src/ddsrt/tests/string.c
index eae2cc7..babe9af 100644
--- a/src/ddsrt/tests/string.c
+++ b/src/ddsrt/tests/string.c
@@ -12,6 +12,7 @@
 #include <string.h>
 
 #include "CUnit/Theory.h"
+#include "dds/ddsrt/heap.h"
 #include "dds/ddsrt/string.h"
 
 typedef enum { eq, lt, gt } eq_t;
@@ -67,3 +68,26 @@ CU_Theory((const char *s1, const char *s2, size_t n, eq_t e), ddsrt_strncasecmp,
   CU_ASSERT((e == eq && r == 0) || (e == lt && r < 0) || (e == gt && r > 0));
 }
 
+CU_TheoryDataPoints(ddsrt_str_replace, basic) = {
+  CU_DataPoints(const char *,  "",  "a", "aaa",  "aaa",   "aaa", "aaa",   "a", "aa",    "acaca", "aacaacaa", "aaa"),
+  CU_DataPoints(const char *, "a",   "",   "a",    "a",     "a",  "aa", "aaa",  "a",        "a",       "aa",   "a"),
+  CU_DataPoints(const char *, "b",  "b",   "b",   "bb",    "bb",   "b",   "b",  "b",       "bb",        "b",    ""),
+  CU_DataPoints(size_t,         0,    0,     0,      1,       2,     0,     0,   10,          0,          2,     0),
+  CU_DataPoints(const char *,  "", NULL, "bbb", "bbaa", "bbbba",  "ba",   "a", "bb", "bbcbbcbb",   "bcbcaa",    ""),
+};
+
+CU_Theory((const char *str, const char *srch, const char *subst, size_t max, const char * exp), ddsrt_str_replace, basic)
+{
+  char * r = ddsrt_str_replace(str, srch, subst, max);
+  if (exp != NULL)
+  {
+    CU_ASSERT_FATAL(r != NULL);
+    CU_ASSERT(strcmp(r, exp) == 0);
+    ddsrt_free(r);
+  }
+  else
+  {
+    CU_ASSERT_FATAL(r == NULL);
+  }
+}
+