uint32_t
utf16_to_code_point_prev(const uint16_t *chars, size_t len, ssize_t *iter) {
const uint16_t v = chars[(*iter)--];
if (HB_IsLowSurrogate(v)) {
// surrogate pair
if (*iter < 0) {
// the surrogate is incomplete.
return HB_InvalidCodePoint;
}
const uint16_t v2 = chars[(*iter)--];
if (!HB_IsHighSurrogate(v2)) {
// invalidate surrogate pair.
return HB_InvalidCodePoint;
}
return HB_SurrogateToUcs4(v2, v);
}
if (HB_IsHighSurrogate(v)) {
// this isn't a valid code point
return HB_InvalidCodePoint;
}
return v;
}
static HB_UChar32 getChar(const HB_UChar16 *string, hb_uint32 length, hb_uint32 &i)
{
HB_UChar32 ch;
if (HB_IsHighSurrogate(string[i])
&& i < length - 1
&& HB_IsLowSurrogate(string[i + 1])) {
ch = HB_SurrogateToUcs4(string[i], string[i + 1]);
++i;
} else {
ch = string[i];
}
return ch;
}