misc: Add ssh_strreplace()

Pair-Programmed-With: Sahana Prasad <sahana@redhat.com>
Signed-Off-by: Sahana Prasad <sahana@redhat.com>
Signed-Off-By: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

src/misc.c

@@ -1786,4 +1786,54 @@ err:
     return -1;
 }
 
+/**
+ * @internal
+ *
+ * @brief Finds the first occurence of a patterm in a string and replaces it.
+ *
+ * @param[in]  src          Source string containing the patern to be replaced.
+ * @param[in]  pattern      Pattern to be replaced in the source string.
+ *                          Note: this function replaces the first occurence of pattern only.
+ * @param[in]  replace      String to be replaced is stored in replace.
+ *
+ * @returns  src_replaced a pointer that points to the replaced string.
+ * NULL if allocation fails.
+ */
+char *ssh_strreplace(char *src, const char *pattern, const char *replace)
+{
+    char *p = NULL;
+    char *src_replaced = NULL;
+    size_t len_replaced;
+
+    if (pattern == NULL || replace == NULL) {
+        return src;
+    }
+
+    if ((p = strstr(src, pattern)) != NULL) {
+        size_t offset = p - src;
+        size_t len  = strlen(src);
+        size_t pattern_len = strlen(pattern);
+        size_t replace_len = strlen(replace);
+
+        if (replace_len != pattern_len) {
+            len_replaced = strlen(src) + replace_len - pattern_len + 1;
+        } else {
+            len_replaced = strlen(src) + 1;
+        }
+
+        src_replaced = (char *)malloc(len_replaced);
+
+        if (src_replaced == NULL) {
+            return NULL;
+        }
+
+        memset(src_replaced, 0, len_replaced);
+        memcpy(src_replaced, src, offset);
+        memcpy(src_replaced + offset, replace, replace_len);
+        memcpy(src_replaced + offset + replace_len, src + offset + pattern_len, len - offset - pattern_len);
+    }
+
+    return src_replaced; /* free in the caller */
+}
+
 /** @} */