Use binary search to discover closest sync sample index, replace
assertions with runtime errors in case the file's table of sync sample
indices is not sorted properly.
Change-Id: Ie4446a44e613a8d329ac680c37361d4407d22520
related-to-bug: 5549855
diff --git a/media/libstagefright/SampleTable.cpp b/media/libstagefright/SampleTable.cpp
index 1451c16..8e790fc 100644
--- a/media/libstagefright/SampleTable.cpp
+++ b/media/libstagefright/SampleTable.cpp
@@ -618,27 +618,26 @@
}
uint32_t left = 0;
- while (left < mNumSyncSamples) {
- uint32_t x = mSyncSamples[left];
+ uint32_t right = mNumSyncSamples;
+ while (left < right) {
+ uint32_t center = left + (right - left) / 2;
+ uint32_t x = mSyncSamples[center];
- if (x >= start_sample_index) {
+ if (start_sample_index < x) {
+ right = center;
+ } else if (start_sample_index > x) {
+ left = center + 1;
+ } else {
+ left = center;
break;
}
-
- ++left;
- }
- if (left > 0) {
- --left;
}
- uint32_t x;
- if (mDataSource->readAt(
- mSyncSampleOffset + 8 + left * 4, &x, 4) != 4) {
- return ERROR_IO;
- }
+ // Now ssi[left] is the sync sample index just before (or at)
+ // start_sample_index.
+ // Also start_sample_index < ssi[left + 1], if left + 1 < mNumSyncSamples.
- x = ntohl(x);
- --x;
+ uint32_t x = mSyncSamples[left];
if (left + 1 < mNumSyncSamples) {
uint32_t y = mSyncSamples[left + 1];
@@ -679,15 +678,13 @@
if (x > start_sample_index) {
CHECK(left > 0);
- if (mDataSource->readAt(
- mSyncSampleOffset + 8 + (left - 1) * 4, &x, 4) != 4) {
- return ERROR_IO;
+ x = mSyncSamples[left - 1];
+
+ if (x > start_sample_index) {
+ // The table of sync sample indices was not sorted
+ // properly.
+ return ERROR_MALFORMED;
}
-
- x = ntohl(x);
- --x;
-
- CHECK(x <= start_sample_index);
}
break;
}
@@ -701,7 +698,11 @@
x = mSyncSamples[left + 1];
- CHECK(x >= start_sample_index);
+ if (x < start_sample_index) {
+ // The table of sync sample indices was not sorted
+ // properly.
+ return ERROR_MALFORMED;
+ }
}
break;