Be more lenient with 4 byte UTF-8 sequences.

Accept 4 byte sequences and convert them into surrogate
pairs instead of expecting 2 separate 3 byte sequences
each encoding one half of a surrogate pair.

Note that in addition to supporting 4 byte sequences in
strings from JNI, we also tolerate them in dex files. This
is mainly for consistency, and there's no need to claim any
sort of official support.

bug: 18848397
bug: https://code.google.com/p/android/issues/detail?id=81341
Change-Id: Ibc98d29e59d98803e640f2489ea4c56912a59b29

1 files changed, 19 insertions, 3 deletions

diff --git a/runtime/utf.h b/runtime/utf.h
index 3ee07fe65d..dd38afa172 100644
--- a/runtime/utf.h
+++ b/runtime/utf.h
@@ -85,12 +85,16 @@ int32_t ComputeUtf16Hash(const uint16_t* chars, size_t char_count);
 size_t ComputeModifiedUtf8Hash(const char* chars);
 
 /*
- * Retrieve the next UTF-16 character from a UTF-8 string.
+ * Retrieve the next UTF-16 character or surrogate pair from a UTF-8 string.
+ * single byte, 2-byte and 3-byte UTF-8 sequences result in a single UTF-16
+ * character whereas 4-byte UTF-8 sequences result in a surrogate pair. Use
+ * GetLeadingUtf16Char and GetTrailingUtf16Char to process the return value
+ * of this function.
  *
  * Advances "*utf8_data_in" to the start of the next character.
  *
  * WARNING: If a string is corrupted by dropping a '\0' in the middle
- * of a 3-byte sequence, you can end up overrunning the buffer with
+ * of a multi byte sequence, you can end up overrunning the buffer with
  * reads (and possibly with the writes if the length was computed and
  * cached before the damage). For performance reasons, this function
  * assumes that the string being parsed is known to be valid (e.g., by
@@ -98,7 +102,19 @@ size_t ComputeModifiedUtf8Hash(const char* chars);
  * out of dex files or other internal translations, so the only real
  * risk comes from the JNI NewStringUTF call.
  */
-uint16_t GetUtf16FromUtf8(const char** utf8_data_in);
+uint32_t GetUtf16FromUtf8(const char** utf8_data_in);
+
+/**
+ * Gets the leading UTF-16 character from a surrogate pair, or the sole
+ * UTF-16 character from the return value of GetUtf16FromUtf8.
+ */
+ALWAYS_INLINE uint16_t GetLeadingUtf16Char(uint32_t maybe_pair);
+
+/**
+ * Gets the trailing UTF-16 character from a surrogate pair, or 0 otherwise
+ * from the return value of GetUtf16FromUtf8.
+ */
+ALWAYS_INLINE uint16_t GetTrailingUtf16Char(uint32_t maybe_pair);
 
 }  // namespace art