Factorize describeDifferences
Fixes: 259479229
Test: new test for this in this patch
Change-Id: Iecbccd10b04ada49f3485097dfcf3511c26c0925
diff --git a/common/framework/com/android/net/module/util/BitUtils.java b/common/framework/com/android/net/module/util/BitUtils.java
index 2b32e86..3062d8c 100644
--- a/common/framework/com/android/net/module/util/BitUtils.java
+++ b/common/framework/com/android/net/module/util/BitUtils.java
@@ -17,6 +17,7 @@
package com.android.net.module.util;
import android.annotation.NonNull;
+import android.annotation.Nullable;
/**
* @hide
@@ -107,4 +108,33 @@
++bitPos;
}
}
+
+ /**
+ * Returns a short but human-readable string of updates between an old and a new bit fields.
+ *
+ * @param oldVal the old bit field to diff from
+ * @param newVal the new bit field to diff to
+ * @return a string fit for logging differences, or null if no differences.
+ * this method cannot return the empty string.
+ */
+ @Nullable
+ public static String describeDifferences(final long oldVal, final long newVal,
+ @NonNull final NameOf nameFetcher) {
+ final long changed = oldVal ^ newVal;
+ if (0 == changed) return null;
+ // If the control reaches here, there are changes (additions, removals, or both) so
+ // the code below is guaranteed to add something to the string and can't return "".
+ final long removed = oldVal & changed;
+ final long added = newVal & changed;
+ final StringBuilder sb = new StringBuilder();
+ if (0 != removed) {
+ sb.append("-");
+ appendStringRepresentationOfBitMaskToStringBuilder(sb, removed, nameFetcher, "-");
+ }
+ if (0 != added) {
+ sb.append("+");
+ appendStringRepresentationOfBitMaskToStringBuilder(sb, added, nameFetcher, "+");
+ }
+ return sb.toString();
+ }
}
diff --git a/common/tests/unit/src/com/android/net/module/util/BitUtilsTests.kt b/common/tests/unit/src/com/android/net/module/util/BitUtilsTests.kt
index 0236716..49940ea 100644
--- a/common/tests/unit/src/com/android/net/module/util/BitUtilsTests.kt
+++ b/common/tests/unit/src/com/android/net/module/util/BitUtilsTests.kt
@@ -17,11 +17,13 @@
package com.android.net.module.util
import com.android.net.module.util.BitUtils.appendStringRepresentationOfBitMaskToStringBuilder
+import com.android.net.module.util.BitUtils.describeDifferences
import com.android.net.module.util.BitUtils.packBits
import com.android.net.module.util.BitUtils.unpackBits
-import org.junit.Test
import kotlin.test.assertEquals
+import kotlin.test.assertNull
import kotlin.test.assertTrue
+import org.junit.Test
class BitUtilsTests {
@Test
@@ -58,4 +60,23 @@
assertEquals(expected, it.toString())
}
}
+
+ @Test
+ fun testDescribeDifferences() {
+ fun describe(a: Long, b: Long) = describeDifferences(a, b, Integer::toString)
+ assertNull(describe(0, 0))
+ assertNull(describe(5, 5))
+ assertNull(describe(Long.MAX_VALUE, Long.MAX_VALUE))
+
+ assertEquals("+0", describe(0, 1))
+ assertEquals("-0", describe(1, 0))
+
+ assertEquals("+0+2", describe(0, 5))
+ assertEquals("+2", describe(1, 5))
+ assertEquals("-0+2", describe(1, 4))
+
+ fun makeField(vararg i: Int) = i.sumOf { 1L shl it }
+ assertEquals("-0-4-6-9+1+3+11", describe(makeField(0, 4, 6, 9), makeField(1, 3, 11)))
+ assertEquals("-1-5-9+6+8", describe(makeField(0, 1, 3, 4, 5, 9), makeField(0, 3, 4, 6, 8)))
+ }
}
