commit bee1df883d3770c0edc5c171435641a82c9e8a81
author Raph Levien <raph@google.com> Wed Feb 17 15:04:17 2016 -0800
committer Raph Levien <raph@google.com> Fri Feb 19 10:05:07 2016 -0800
tree a5eb15594078a78b47c66641234f35b1f0f8b197
parent 468dcf57c026a5eebac700479b518ed8c35f4c6b

Finer grained character boundaries in computing SMS fragment lengths

The standard Java character iterator has potentially unbounded
distance between character boundaries, meaning that when breaking an
SMS message into fragments it's not safe to assume that the fragment
will contain such a boundary. This patch special-cases flags (pairs of
Regional Indicator Symbols) and also guarantees some progress in the
case of no boundary found.

Bug: 26210851
Change-Id: Ic16637a834af0dfe40197fbcdb3471c1bf5cd6d2

src/java/com/android/internal/telephony/SmsMessageBase.java

diff --git a/src/java/com/android/internal/telephony/SmsMessageBase.java b/src/java/com/android/internal/telephony/SmsMessageBase.java
index 1d50834..3338772 100644
--- a/src/java/com/android/internal/telephony/SmsMessageBase.java
+++ b/src/java/com/android/internal/telephony/SmsMessageBase.java
@@ -24,6 +24,7 @@
 
 import android.provider.Telephony;
 import android.telephony.SmsMessage;
+import android.text.Emoji;
 
 /**
  * Base class declaring the specific methods and members for SmsMessage.
@@ -367,7 +368,21 @@
             BreakIterator breakIterator = BreakIterator.getCharacterInstance();
             breakIterator.setText(msgBody.toString());
             if (!breakIterator.isBoundary(nextPos)) {
-                nextPos = breakIterator.preceding(nextPos);
+                int breakPos = breakIterator.preceding(nextPos);
+                while (breakPos + 4 <= nextPos
+                        && Emoji.isRegionalIndicatorSymbol(
+                            Character.codePointAt(msgBody, breakPos))
+                        && Emoji.isRegionalIndicatorSymbol(
+                            Character.codePointAt(msgBody, breakPos + 2))) {
+                    // skip forward over flags (pairs of Regional Indicator Symbol)
+                    breakPos += 4;
+                }
+                if (breakPos > currentPosition) {
+                    nextPos = breakPos;
+                } else if (Character.isHighSurrogate(msgBody.charAt(nextPos - 1))) {
+                    // no character boundary in this fragment, try to at least land on a code point
+                    nextPos -= 1;
+                }
             }
         }
         return nextPos;