Emit 4 byte UTF-sequences in place of encoded surrogate pairs.
Symmetric with a5afcfc73141e5e378d79a326d0 which converts 4 byte UTF-8
sequences to surrogate pairs.
bug: 18848397
Change-Id: I42adc275b7e0df0cbbd9d8a799e8b0447d8f5cae
diff --git a/runtime/utf.cc b/runtime/utf.cc
index 39c8d15..3d13c3e 100644
--- a/runtime/utf.cc
+++ b/runtime/utf.cc
@@ -67,15 +67,39 @@
void ConvertUtf16ToModifiedUtf8(char* utf8_out, const uint16_t* utf16_in, size_t char_count) {
while (char_count--) {
- uint16_t ch = *utf16_in++;
+ const uint16_t ch = *utf16_in++;
if (ch > 0 && ch <= 0x7f) {
*utf8_out++ = ch;
} else {
+ // char_count == 0 here implies we've encountered an unpaired
+ // surrogate and we have no choice but to encode it as 3-byte UTF
+ // sequence. Note that unpaired surrogates can occur as a part of
+ // "normal" operation.
+ if ((ch >= 0xd800 && ch <= 0xdbff) && (char_count > 0)) {
+ const uint16_t ch2 = *utf16_in;
+
+ // Check if the other half of the pair is within the expected
+ // range. If it isn't, we will have to emit both "halves" as
+ // separate 3 byte sequences.
+ if (ch2 >= 0xdc00 && ch2 <= 0xdfff) {
+ utf16_in++;
+ char_count--;
+ const uint32_t code_point = (ch << 10) + ch2 - 0x035fdc00;
+ *utf8_out++ = (code_point >> 18) | 0xf0;
+ *utf8_out++ = ((code_point >> 12) & 0x3f) | 0x80;
+ *utf8_out++ = ((code_point >> 6) & 0x3f) | 0x80;
+ *utf8_out++ = (code_point & 0x3f) | 0x80;
+ continue;
+ }
+ }
+
if (ch > 0x07ff) {
+ // Three byte encoding.
*utf8_out++ = (ch >> 12) | 0xe0;
*utf8_out++ = ((ch >> 6) & 0x3f) | 0x80;
*utf8_out++ = (ch & 0x3f) | 0x80;
} else /*(ch > 0x7f || ch == 0)*/ {
+ // Two byte encoding.
*utf8_out++ = (ch >> 6) | 0xc0;
*utf8_out++ = (ch & 0x3f) | 0x80;
}
@@ -147,15 +171,32 @@
size_t CountUtf8Bytes(const uint16_t* chars, size_t char_count) {
size_t result = 0;
while (char_count--) {
- uint16_t ch = *chars++;
+ const uint16_t ch = *chars++;
if (ch > 0 && ch <= 0x7f) {
++result;
- } else {
- if (ch > 0x7ff) {
- result += 3;
+ } else if (ch >= 0xd800 && ch <= 0xdbff) {
+ if (char_count > 0) {
+ const uint16_t ch2 = *chars;
+ // If we find a properly paired surrogate, we emit it as a 4 byte
+ // UTF sequence. If we find an unpaired leading or trailing surrogate,
+ // we emit it as a 3 byte sequence like would have done earlier.
+ if (ch2 >= 0xdc00 && ch2 <= 0xdfff) {
+ chars++;
+ char_count--;
+
+ result += 4;
+ } else {
+ result += 3;
+ }
} else {
- result += 2;
+ // This implies we found an unpaired trailing surrogate at the end
+ // of a string.
+ result += 3;
}
+ } else if (ch > 0x7ff) {
+ result += 3;
+ } else {
+ result += 2;
}
}
return result;