+typedef unsigned int utf32;
+#define UTF32_PRINTF_FORMAT "%u"
+
+/**
+ * "parse" an utf8 character from a string.
+ * Warning: This function only works for valid utf-8 inputs. The behaviour
+ * is undefined for invalid utf-8 input.
+ *
+ * @param p A pointer to a pointer into the string. The pointer
+ * is incremented for each consumed char
+ */
+static inline utf32 read_utf8_char(const char **p)
+{
+ const unsigned char *c = (const unsigned char *) *p;
+ utf32 result;
+
+ if ((*c & 0x80) == 0) {
+ /* 1 character encoding: 0b0??????? */
+ result = *c++;
+ } else if ((*c & 0xE0) == 0xC0) {
+ /* 2 character encoding: 0b110?????, 0b10?????? */
+ result = *c++ & 0x1F;
+ result = (result << 6) | (*c++ & 0x3F);
+ } else if ((*c & 0xF0) == 0xE0) {
+ /* 3 character encoding: 0b1110????, 0b10??????, 0b10?????? */
+ result = *c++ & 0x0F;
+ result = (result << 6) | (*c++ & 0x3F);
+ result = (result << 6) | (*c++ & 0x3F);
+ } else {
+ /* 4 character enc.: 0b11110???, 0b10??????, 0b10??????, 0b10?????? */
+ assert((*c & 0xF8) == 0xF0);
+ result = *c++ & 0x07;
+ result = (result << 6) | (*c++ & 0x3F);
+ result = (result << 6) | (*c++ & 0x3F);
+ result = (result << 6) | (*c++ & 0x3F);
+ }
+
+ *p = (const char*) c;
+ return result;
+}
+
+static inline size_t wstrlen(const string_t *string)
+{
+ size_t result = 0;
+ const char *p = string->begin;
+ const char *end = p + string->size;
+ while (p < end) {
+ read_utf8_char(&p);
+ ++result;
+ }
+ return result;
+}