feat(string_utils): insert_into

src/utils/string_utils/string_utils.c

@@ -1,7 +1,8 @@
 #include "string_utils.h"
 
 #include <ctype.h>
-#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
 
 char *trim_blank_left(char *str)
 {
@@ -13,3 +14,31 @@ char *trim_blank_left(char *str)
 
     return str;
 }
+
+char *insert_into(char *dest, const char *src, size_t pos, size_t len)
+{
+    size_t res_len = strlen(dest);
+    size_t prefix_len = pos;
+    size_t suffix_len = res_len - (pos + len);
+    size_t src_len = strlen(src);
+    size_t new_len = prefix_len + src_len + suffix_len;
+
+    if (dest == NULL || src == NULL || pos + len > res_len)
+        return NULL;
+
+    if (res_len < new_len)
+    {
+        char *p = realloc(dest, new_len + 1);
+        if (p == NULL)
+            return NULL; // allocation failure
+        dest = p;
+    }
+
+    memmove(dest + pos + src_len, dest + pos + len, suffix_len);
+    memcpy(dest + pos, src, src_len);
+    dest[new_len] = 0;
+
+    if (res_len > new_len)
+        return realloc(dest, new_len + 1);
+    return dest;
+}

src/utils/string_utils/string_utils.h

@@ -12,4 +12,10 @@
  */
 char *trim_blank_left(char *str);
 
+/**
+ * Inserts a substring into a destination string at a specified position,
+ * replacing a specified length of characters.
+ */
+char *insert_into(char *dest, const char *src, size_t pos, size_t len);
+
 #endif /* STRING_UTILS_H */