Add range-based Parcel::hasFileDescriptorsInRange(offset, len)

To be used by lazy values in bundle. I also reused the new code in
scanForFds().

Test: atest -d android.os.cts.ParcelTest android.os.cts.BundleTest android.os.BundleTest android.os.ParcelTest
Bug: 195622897
Change-Id: Icce738d4c87d086bffb7dfeb1b39a6bbce8f9af3
diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 6ce0922..609e969 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -566,6 +566,36 @@
     return mHasFds;
 }
 
+status_t Parcel::hasFileDescriptorsInRange(size_t offset, size_t len, bool& result) const {
+    if (len > INT32_MAX || offset > INT32_MAX) {
+        // Don't accept size_t values which may have come from an inadvertent conversion from a
+        // negative int.
+        return BAD_VALUE;
+    }
+    size_t limit = offset + len;
+    if (offset > mDataSize || len > mDataSize || limit > mDataSize || offset > limit) {
+        return BAD_VALUE;
+    }
+    result = hasFileDescriptorsInRangeUnchecked(offset, len);
+    return NO_ERROR;
+}
+
+bool Parcel::hasFileDescriptorsInRangeUnchecked(size_t offset, size_t len) const {
+    for (size_t i = 0; i < mObjectsSize; i++) {
+        size_t pos = mObjects[i];
+        if (pos < offset) continue;
+        if (pos + sizeof(flat_binder_object) > offset + len) {
+          if (mObjectsSorted) break;
+          else continue;
+        }
+        const flat_binder_object* flat = reinterpret_cast<const flat_binder_object*>(mData + pos);
+        if (flat->hdr.type == BINDER_TYPE_FD) {
+            return true;
+        }
+    }
+    return false;
+}
+
 void Parcel::markSensitive() const
 {
     mDeallocZero = true;
@@ -2559,16 +2589,7 @@
 
 void Parcel::scanForFds() const
 {
-    bool hasFds = false;
-    for (size_t i=0; i<mObjectsSize; i++) {
-        const flat_binder_object* flat
-            = reinterpret_cast<const flat_binder_object*>(mData + mObjects[i]);
-        if (flat->hdr.type == BINDER_TYPE_FD) {
-            hasFds = true;
-            break;
-        }
-    }
-    mHasFds = hasFds;
+    mHasFds = hasFileDescriptorsInRangeUnchecked(0, dataSize());
     mFdsKnown = true;
 }