AAPT2: Fix issue with styled string indices

Styled strings use spans to denote which part
is styled (<b>, <i>, etc). Spans are simply a range
of indices into the original string.

In Java, we use String and its internal representation, meaning
we must encode the indices using UTF16 lengths.

When the internal AAPT2 representation of strings switched to UTF8,
the indices also began to index into the UTF8 string.

This change reverts the indices to use UTF16 lengths.

Bug:31170115
Change-Id: I07b8b5b67d2542c7e0a855b601cdbd3ac4ebffb0

1 files changed, 15 insertions, 5 deletions

diff --git a/tools/aapt2/util/Util.cpp b/tools/aapt2/util/Util.cpp
index e743247be8a9..b0bec624cc9c 100644
--- a/tools/aapt2/util/Util.cpp
+++ b/tools/aapt2/util/Util.cpp
@@ -314,6 +314,9 @@ StringBuilder& StringBuilder::append(const StringPiece& str) {
         return *this;
     }
 
+    // Where the new data will be appended to.
+    size_t newDataIndex = mStr.size();
+
     const char* const end = str.end();
     const char* start = str.begin();
     const char* current = start;
@@ -422,6 +425,16 @@ StringBuilder& StringBuilder::append(const StringPiece& str) {
         current++;
     }
     mStr.append(start, end - start);
+
+    // Accumulate the added string's UTF-16 length.
+    ssize_t len = utf8_to_utf16_length(
+            reinterpret_cast<const uint8_t*>(mStr.data()) + newDataIndex,
+            mStr.size() - newDataIndex);
+    if (len < 0) {
+        mError = "invalid unicode code point";
+        return *this;
+    }
+    mUtf16Len += len;
     return *this;
 }
 
@@ -434,11 +447,8 @@ std::u16string utf8ToUtf16(const StringPiece& utf8) {
 
     std::u16string utf16;
     utf16.resize(utf16Length);
-    utf8_to_utf16(
-            reinterpret_cast<const uint8_t*>(utf8.data()),
-            utf8.length(),
-            &*utf16.begin(),
-            (size_t) utf16Length + 1);
+    utf8_to_utf16(reinterpret_cast<const uint8_t*>(utf8.data()), utf8.length(),
+                  &*utf16.begin(), utf16Length + 1);
     return utf16;
 }