media.bufferpool2: ensure message-ids are safe from overflow/underflow
Since message-ids can be wrapped, they are not safe from
overflow/underflow. Change them to be safe from overflow/underflow.
Bug: 321674574
Change-Id: I39a4baf057fc81389925e0fe358894f62ade9423
diff --git a/media/bufferpool/aidl/default/BufferStatus.cpp b/media/bufferpool/aidl/default/BufferStatus.cpp
index 19caa1e..fecbe3f 100644
--- a/media/bufferpool/aidl/default/BufferStatus.cpp
+++ b/media/bufferpool/aidl/default/BufferStatus.cpp
@@ -26,8 +26,17 @@
using aidl::android::hardware::media::bufferpool2::BufferStatus;
+uint32_t wrappedMinus(uint32_t a, uint32_t b) {
+ if (a >= b) {
+ return a - b;
+ } else {
+ return ~(b - a) + 1;
+ }
+}
+
bool isMessageLater(uint32_t curMsgId, uint32_t prevMsgId) {
- return curMsgId != prevMsgId && curMsgId - prevMsgId < prevMsgId - curMsgId;
+ return curMsgId != prevMsgId &&
+ wrappedMinus(curMsgId, prevMsgId) < wrappedMinus(prevMsgId, curMsgId);
}
bool isBufferInRange(BufferId from, BufferId to, BufferId bufferId) {