[TeX] Added telemetry express utility static lib

- to be used by AdServices

Bug: 271127104
Test: atest ExpressLogApisTests
Ignore-AOSP-First: has to be merged with TeX changes into framework
Change-Id: I914d6ac88e5b4445c51c09109a79ff828ada3e9b

17 files changed, 1000 insertions, 0 deletions

diff --git a/java/com/android/modules/expresslog/Android.bp b/java/com/android/modules/expresslog/Android.bp
new file mode 100644
index 0000000..cacc7f8
--- /dev/null
+++ b/java/com/android/modules/expresslog/Android.bp
@@ -0,0 +1,39 @@
+//
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+java_library {
+    name: "modules-utils-expresslog",
+    defaults: ["modules-utils-defaults"],
+    min_sdk_version: "30",
+    srcs: [
+        "*.java",
+        ":statslog-expresslog-java-gen",
+    ],
+    libs: [
+        "framework-statsd",
+    ],
+}
+
+genrule {
+    name: "statslog-expresslog-java-gen",
+    tools: ["stats-log-api-gen"],
+    cmd: "$(location stats-log-api-gen) --java $(out) --module expresslog" +
+        " --javaPackage com.android.modules.expresslog --javaClass StatsExpressLog",
+    out: ["com/android/modules/expresslog/StatsExpressLog.java"],
+}
diff --git a/java/com/android/modules/expresslog/Counter.java b/java/com/android/modules/expresslog/Counter.java
new file mode 100644
index 0000000..b788c3f
--- /dev/null
+++ b/java/com/android/modules/expresslog/Counter.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.modules.expresslog;
+
+import android.annotation.NonNull;
+
+import com.android.modules.expresslog.StatsExpressLog;
+
+/** Counter encapsulates StatsD write API calls */
+public final class Counter {
+
+    // Not instantiable.
+    private Counter() {}
+
+    /**
+     * Increments Telemetry Express Counter metric by 1
+     * @param metricId to log, no-op if metricId is not defined in the TeX catalog
+     */
+    public static void logIncrement(@NonNull String metricId) {
+        logIncrement(metricId, 1);
+    }
+
+    /**
+     * Increments Telemetry Express Counter metric by 1
+     * @param metricId to log, no-op if metricId is not defined in the TeX catalog
+     * @param uid used as a dimension for the count metric
+     */
+    public static void logIncrementWithUid(@NonNull String metricId, int uid) {
+        logIncrementWithUid(metricId, uid, 1);
+    }
+
+    /**
+     * Increments Telemetry Express Counter metric by arbitrary value
+     * @param metricId to log, no-op if metricId is not defined in the TeX catalog
+     * @param amount to increment counter
+     */
+    public static void logIncrement(@NonNull String metricId, long amount) {
+        final long metricIdHash = Utils.hashString(metricId);
+        StatsExpressLog.write(StatsExpressLog.EXPRESS_EVENT_REPORTED, metricIdHash, amount);
+    }
+
+    /**
+     * Increments Telemetry Express Counter metric by arbitrary value
+     * @param metricId to log, no-op if metricId is not defined in the TeX catalog
+     * @param uid used as a dimension for the count metric
+     * @param amount to increment counter
+     */
+    public static void logIncrementWithUid(@NonNull String metricId, int uid, long amount) {
+        final long metricIdHash = Utils.hashString(metricId);
+        StatsExpressLog.write(
+            StatsExpressLog.EXPRESS_UID_EVENT_REPORTED, metricIdHash, amount, uid);
+    }
+}
diff --git a/java/com/android/modules/expresslog/Histogram.java b/java/com/android/modules/expresslog/Histogram.java
new file mode 100644
index 0000000..be300bf
--- /dev/null
+++ b/java/com/android/modules/expresslog/Histogram.java
@@ -0,0 +1,227 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.modules.expresslog;
+
+import android.annotation.FloatRange;
+import android.annotation.IntRange;
+import android.annotation.NonNull;
+
+import com.android.modules.expresslog.StatsExpressLog;
+
+import java.util.Arrays;
+
+/** Histogram encapsulates StatsD write API calls */
+public final class Histogram {
+
+    private final long mMetricIdHash;
+    private final BinOptions mBinOptions;
+
+    /**
+     * Creates Histogram metric logging wrapper
+     *
+     * @param metricId   to log, logging will be no-op if metricId is not defined in the TeX catalog
+     * @param binOptions to calculate bin index for samples
+     */
+    public Histogram(@NonNull String metricId, @NonNull BinOptions binOptions) {
+        mMetricIdHash = Utils.hashString(metricId);
+        mBinOptions = binOptions;
+    }
+
+    /**
+     * Logs increment sample count for automatically calculated bin
+     *
+     * @param sample value
+     */
+    public void logSample(float sample) {
+        final int binIndex = mBinOptions.getBinForSample(sample);
+        StatsExpressLog.write(StatsExpressLog.EXPRESS_HISTOGRAM_SAMPLE_REPORTED, mMetricIdHash,
+                /*count*/ 1, binIndex);
+    }
+
+    /**
+     * Logs increment sample count for automatically calculated bin
+     *
+     * @param uid used as a dimension for the count metric
+     * @param sample value
+     */
+    public void logSampleWithUid(int uid, float sample) {
+        final int binIndex = mBinOptions.getBinForSample(sample);
+        StatsExpressLog.write(StatsExpressLog.EXPRESS_UID_HISTOGRAM_SAMPLE_REPORTED,
+                mMetricIdHash, /*count*/ 1, binIndex, uid);
+    }
+
+    /** Used by Histogram to map data sample to corresponding bin */
+    public interface BinOptions {
+        /**
+         * Returns bins count to be used by a histogram
+         *
+         * @return bins count used to initialize Options, including overflow & underflow bins
+         */
+        int getBinsCount();
+
+        /**
+         * Returns bin index for the input sample value
+         * index == 0 stands for underflow
+         * index == getBinsCount() - 1 stands for overflow
+         *
+         * @return zero based index
+         */
+        int getBinForSample(float sample);
+    }
+
+    /** Used by Histogram to map data sample to corresponding bin for uniform bins */
+    public static final class UniformOptions implements BinOptions {
+
+        private final int mBinCount;
+        private final float mMinValue;
+        private final float mExclusiveMaxValue;
+        private final float mBinSize;
+
+        /**
+         * Creates options for uniform (linear) sized bins
+         *
+         * @param binCount          amount of histogram bins. 2 bin indexes will be calculated
+         *                          automatically to represent underflow & overflow bins
+         * @param minValue          is included in the first bin, values less than minValue
+         *                          go to underflow bin
+         * @param exclusiveMaxValue is included in the overflow bucket. For accurate
+         *                          measure up to kMax, then exclusiveMaxValue
+         *                          should be set to kMax + 1
+         */
+        public UniformOptions(@IntRange(from = 1) int binCount, float minValue,
+                float exclusiveMaxValue) {
+            if (binCount < 1) {
+                throw new IllegalArgumentException("Bin count should be positive number");
+            }
+
+            if (exclusiveMaxValue <= minValue) {
+                throw new IllegalArgumentException("Bins range invalid (maxValue < minValue)");
+            }
+
+            mMinValue = minValue;
+            mExclusiveMaxValue = exclusiveMaxValue;
+            mBinSize = (mExclusiveMaxValue - minValue) / binCount;
+
+            // Implicitly add 2 for the extra underflow & overflow bins
+            mBinCount = binCount + 2;
+        }
+
+        @Override
+        public int getBinsCount() {
+            return mBinCount;
+        }
+
+        @Override
+        public int getBinForSample(float sample) {
+            if (sample < mMinValue) {
+                // goes to underflow
+                return 0;
+            } else if (sample >= mExclusiveMaxValue) {
+                // goes to overflow
+                return mBinCount - 1;
+            }
+            return (int) ((sample - mMinValue) / mBinSize + 1);
+        }
+    }
+
+    /** Used by Histogram to map data sample to corresponding bin for scaled bins */
+    public static final class ScaledRangeOptions implements BinOptions {
+        // store minimum value per bin
+        final long[] mBins;
+
+        /**
+         * Creates options for scaled range bins
+         *
+         * @param binCount      amount of histogram bins. 2 bin indexes will be calculated
+         *                      automatically to represent underflow & overflow bins
+         * @param minValue      is included in the first bin, values less than minValue
+         *                      go to underflow bin
+         * @param firstBinWidth used to represent first bin width and as a reference to calculate
+         *                      width for consecutive bins
+         * @param scaleFactor   used to calculate width for consecutive bins
+         */
+        public ScaledRangeOptions(@IntRange(from = 1) int binCount, int minValue,
+                @FloatRange(from = 1.f) float firstBinWidth,
+                @FloatRange(from = 1.f) float scaleFactor) {
+            if (binCount < 1) {
+                throw new IllegalArgumentException("Bin count should be positive number");
+            }
+
+            if (firstBinWidth < 1.f) {
+                throw new IllegalArgumentException(
+                        "First bin width invalid (should be 1.f at minimum)");
+            }
+
+            if (scaleFactor < 1.f) {
+                throw new IllegalArgumentException(
+                        "Scaled factor invalid (should be 1.f at minimum)");
+            }
+
+            // precalculating bins ranges (no need to create a bin for underflow reference value)
+            mBins = initBins(binCount + 1, minValue, firstBinWidth, scaleFactor);
+        }
+
+        @Override
+        public int getBinsCount() {
+            return mBins.length + 1;
+        }
+
+        @Override
+        public int getBinForSample(float sample) {
+            if (sample < mBins[0]) {
+                // goes to underflow
+                return 0;
+            } else if (sample >= mBins[mBins.length - 1]) {
+                // goes to overflow
+                return mBins.length;
+            }
+
+            return lower_bound(mBins, (long) sample) + 1;
+        }
+
+        // To find lower bound using binary search implementation of Arrays utility class
+        private static int lower_bound(long[] array, long sample) {
+            int index = Arrays.binarySearch(array, sample);
+            // If key is not present in the array
+            if (index < 0) {
+                // Index specify the position of the key when inserted in the sorted array
+                // so the element currently present at this position will be the lower bound
+                return Math.abs(index) - 2;
+            }
+            return index;
+        }
+
+        private static long[] initBins(int count, int minValue, float firstBinWidth,
+                float scaleFactor) {
+            long[] bins = new long[count];
+            bins[0] = minValue;
+            double lastWidth = firstBinWidth;
+            for (int i = 1; i < count; i++) {
+                // current bin minValue = previous bin width * scaleFactor
+                double currentBinMinValue = bins[i - 1] + lastWidth;
+                if (currentBinMinValue > Integer.MAX_VALUE) {
+                    throw new IllegalArgumentException(
+                        "Attempted to create a bucket larger than maxint");
+                }
+
+                bins[i] = (long) currentBinMinValue;
+                lastWidth *= scaleFactor;
+            }
+            return bins;
+        }
+    }
+}
diff --git a/java/com/android/modules/expresslog/OWNERS b/java/com/android/modules/expresslog/OWNERS
new file mode 100644
index 0000000..d3a5812
--- /dev/null
+++ b/java/com/android/modules/expresslog/OWNERS
@@ -0,0 +1,10 @@
+# Bug component: 719316
+# Stats/expresslog
+
+jeffreyhuang@google.com
+muhammadq@google.com
+rslawik@google.com
+sharaienko@google.com
+singhtejinder@google.com
+tsaichristine@google.com
+yaochen@google.com
diff --git a/java/com/android/modules/expresslog/TEST_MAPPING b/java/com/android/modules/expresslog/TEST_MAPPING
new file mode 100644
index 0000000..e658d7a
--- /dev/null
+++ b/java/com/android/modules/expresslog/TEST_MAPPING
@@ -0,0 +1,12 @@
+{
+  "presubmit": [
+    {
+      "name": "ExpressLogApisTests",
+      "options": [
+        {
+          "exclude-annotation": "org.junit.Ignore"
+        }
+      ]
+    }
+  ]
+}
diff --git a/java/com/android/modules/expresslog/Utils.java b/java/com/android/modules/expresslog/Utils.java
new file mode 100644
index 0000000..fde90fc
--- /dev/null
+++ b/java/com/android/modules/expresslog/Utils.java
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.modules.expresslog;
+
+final class Utils {
+    static native long hashString(String stringToHash);
+}
diff --git a/javatests/com/android/modules/expresslog/Android.bp b/javatests/com/android/modules/expresslog/Android.bp
new file mode 100644
index 0000000..dd52750
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/Android.bp
@@ -0,0 +1,76 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+android_test {
+    name: "ExpressLogApisTests",
+
+    sdk_version: "module_current",
+    min_sdk_version: "30",
+
+    srcs: [
+        "*.java",
+    ],
+
+    static_libs: [
+        "androidx.test.rules",
+        "androidx.test.runner",
+        "modules-utils-expresslog",
+    ],
+
+    libs: [
+        "android.test.base",
+        "android.test.runner",
+    ],
+
+    jni_libs: [
+        "libexpresslog_test_jni",
+    ],
+
+    test_suites: [
+        "general-tests",
+    ],
+}
+
+cc_library_shared {
+    name: "libexpresslog_test_jni",
+
+    sdk_version: "current",
+    min_sdk_version: "30",
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-Wextra",
+
+        "-DNAMESPACE_FOR_HASH_FUNCTIONS=farmhash",
+    ],
+    srcs: [
+        "jni/onload.cpp",
+    ],
+    header_libs: [
+        "liblog_headers",
+        "libnativehelper_header_only",
+    ],
+    shared_libs: [
+        "liblog",
+    ],
+    static_libs: [
+        "libexpresslog_jni",
+        "libtextclassifier_hash_static",
+    ],
+}
diff --git a/javatests/com/android/modules/expresslog/AndroidManifest.xml b/javatests/com/android/modules/expresslog/AndroidManifest.xml
new file mode 100644
index 0000000..9128796
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/AndroidManifest.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2023 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          android:installLocation="internalOnly"
+          package="com.android.modules.expresslog" >
+
+    <application android:debuggable="true">
+        <uses-library android:name="android.test.runner" />
+    </application>
+
+    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
+            android:targetPackage="com.android.modules.expresslog"
+            android:label="Telemetry Express Logging Helper Tests" />
+
+</manifest>
diff --git a/javatests/com/android/modules/expresslog/OWNERS b/javatests/com/android/modules/expresslog/OWNERS
new file mode 100644
index 0000000..fe9652e
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/OWNERS
@@ -0,0 +1,3 @@
+# Bug component: 719316
+# Stats/expresslog
+file:/java/com/android/modules/expresslog/OWNERS
diff --git a/javatests/com/android/modules/expresslog/ScaledRangeOptionsTest.java b/javatests/com/android/modules/expresslog/ScaledRangeOptionsTest.java
new file mode 100644
index 0000000..8defce7
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/ScaledRangeOptionsTest.java
@@ -0,0 +1,171 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.modules.expresslog;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import androidx.test.filters.SmallTest;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+@SmallTest
+public class ScaledRangeOptionsTest {
+    static {
+        System.loadLibrary("expresslog_test_jni");
+    }
+
+    private static final String TAG = ScaledRangeOptionsTest.class.getSimpleName();
+
+    @Test
+    public void testGetBinsCount() {
+        Histogram.ScaledRangeOptions options1 = new Histogram.ScaledRangeOptions(1, 100, 100, 2);
+        assertEquals(3, options1.getBinsCount());
+
+        Histogram.ScaledRangeOptions options10 = new Histogram.ScaledRangeOptions(10, 100, 100, 2);
+        assertEquals(12, options10.getBinsCount());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructZeroBinsCount() {
+        new Histogram.ScaledRangeOptions(0, 100, 100, 2);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructNegativeBinsCount() {
+        new Histogram.ScaledRangeOptions(-1, 100, 100, 2);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructNegativeFirstBinWidth() {
+        new Histogram.ScaledRangeOptions(10, 100, -100, 2);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructTooSmallFirstBinWidth() {
+        new Histogram.ScaledRangeOptions(10, 100, 0.5f, 2);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructNegativeScaleFactor() {
+        new Histogram.ScaledRangeOptions(10, 100, 100, -2);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructTooSmallScaleFactor() {
+        new Histogram.ScaledRangeOptions(10, 100, 100, 0.5f);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructTooBigScaleFactor() {
+        new Histogram.ScaledRangeOptions(10, 100, 100, 500.f);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructTooBigBinRange() {
+        new Histogram.ScaledRangeOptions(100, 100, 100, 10.f);
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual1() {
+        Histogram.ScaledRangeOptions options = new Histogram.ScaledRangeOptions(10, 1, 1, 1);
+        assertEquals(12, options.getBinsCount());
+
+        assertEquals(11, options.getBinForSample(11));
+
+        for (int i = 0, bins = options.getBinsCount(); i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i));
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual2() {
+        // this should produce bin otpions similar to linear histogram with bin width 2
+        Histogram.ScaledRangeOptions options = new Histogram.ScaledRangeOptions(10, 1, 2, 1);
+        assertEquals(12, options.getBinsCount());
+
+        for (int i = 0, bins = options.getBinsCount(); i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i * 2));
+            assertEquals(i, options.getBinForSample(i * 2 - 1));
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual5() {
+        Histogram.ScaledRangeOptions options = new Histogram.ScaledRangeOptions(2, 0, 5, 1);
+        assertEquals(4, options.getBinsCount());
+        for (int i = 0; i < 2; i++) {
+            for (int sample = 0; sample < 5; sample++) {
+                assertEquals(i + 1, options.getBinForSample(i * 5 + sample));
+            }
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual10() {
+        Histogram.ScaledRangeOptions options = new Histogram.ScaledRangeOptions(10, 1, 10, 1);
+        assertEquals(0, options.getBinForSample(0));
+        assertEquals(options.getBinsCount() - 2, options.getBinForSample(100));
+        assertEquals(options.getBinsCount() - 1, options.getBinForSample(101));
+
+        final float binSize = (101 - 1) / 10f;
+        for (int i = 1, bins = options.getBinsCount() - 1; i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i * binSize));
+        }
+    }
+
+    @Test
+    public void testBinIndexForScaleFactor2() {
+        final int binsCount = 10;
+        final int minValue = 10;
+        final int firstBinWidth = 5;
+        final int scaledFactor = 2;
+
+        Histogram.ScaledRangeOptions options = new Histogram.ScaledRangeOptions(
+                binsCount, minValue, firstBinWidth, scaledFactor);
+        assertEquals(binsCount + 2, options.getBinsCount());
+        long[] binCounts = new long[10];
+
+        // precalculate max valid value - start value for the overflow bin
+        int lastBinStartValue = minValue; //firstBinMin value
+        int lastBinWidth = firstBinWidth;
+        for (int binIdx = 2; binIdx <= binsCount + 1; binIdx++) {
+            lastBinStartValue = lastBinStartValue + lastBinWidth;
+            lastBinWidth *= scaledFactor;
+        }
+
+        // underflow bin
+        for (int i = 1; i < minValue; i++) {
+            assertEquals(0, options.getBinForSample(i));
+        }
+
+        for (int i = 10; i < lastBinStartValue; i++) {
+            assertTrue(options.getBinForSample(i) > 0);
+            assertTrue(options.getBinForSample(i) <= binsCount);
+            binCounts[options.getBinForSample(i) - 1]++;
+        }
+
+        // overflow bin
+        assertEquals(binsCount + 1, options.getBinForSample(lastBinStartValue));
+
+        for (int i = 1; i < binsCount; i++) {
+            assertEquals(binCounts[i], binCounts[i - 1] * 2L);
+        }
+    }
+}
diff --git a/javatests/com/android/modules/expresslog/TEST_MAPPING b/javatests/com/android/modules/expresslog/TEST_MAPPING
new file mode 100644
index 0000000..e658d7a
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/TEST_MAPPING
@@ -0,0 +1,12 @@
+{
+  "presubmit": [
+    {
+      "name": "ExpressLogApisTests",
+      "options": [
+        {
+          "exclude-annotation": "org.junit.Ignore"
+        }
+      ]
+    }
+  ]
+}
diff --git a/javatests/com/android/modules/expresslog/UniformOptionsTest.java b/javatests/com/android/modules/expresslog/UniformOptionsTest.java
new file mode 100644
index 0000000..3cc03ec
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/UniformOptionsTest.java
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.modules.expresslog;
+
+import androidx.test.filters.SmallTest;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+@SmallTest
+public class UniformOptionsTest {
+    static {
+        System.loadLibrary("expresslog_test_jni");
+    }
+
+    private static final String TAG = UniformOptionsTest.class.getSimpleName();
+
+    @Test
+    public void testGetBinsCount() {
+        Histogram.UniformOptions options1 = new Histogram.UniformOptions(1, 100, 1000);
+        assertEquals(3, options1.getBinsCount());
+
+        Histogram.UniformOptions options10 = new Histogram.UniformOptions(10, 100, 1000);
+        assertEquals(12, options10.getBinsCount());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructZeroBinsCount() {
+        new Histogram.UniformOptions(0, 100, 1000);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructNegativeBinsCount() {
+        new Histogram.UniformOptions(-1, 100, 1000);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testConstructMaxValueLessThanMinValue() {
+        new Histogram.UniformOptions(10, 1000, 100);
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual1() {
+        Histogram.UniformOptions options = new Histogram.UniformOptions(10, 1, 11);
+        for (int i = 0, bins = options.getBinsCount(); i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i));
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual2() {
+        Histogram.UniformOptions options = new Histogram.UniformOptions(10, 1, 21);
+        for (int i = 0, bins = options.getBinsCount(); i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i * 2));
+            assertEquals(i, options.getBinForSample(i * 2 - 1));
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual5() {
+        Histogram.UniformOptions options = new Histogram.UniformOptions(2, 0, 10);
+        assertEquals(4, options.getBinsCount());
+        for (int i = 0; i < 2; i++) {
+            for (int sample = 0; sample < 5; sample++) {
+                assertEquals(i + 1, options.getBinForSample(i * 5 + sample));
+            }
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual10() {
+        Histogram.UniformOptions options = new Histogram.UniformOptions(10, 1, 101);
+        assertEquals(0, options.getBinForSample(0));
+        assertEquals(options.getBinsCount() - 2, options.getBinForSample(100));
+        assertEquals(options.getBinsCount() - 1, options.getBinForSample(101));
+
+        final float binSize = (101 - 1) / 10f;
+        for (int i = 1, bins = options.getBinsCount() - 1; i < bins; i++) {
+            assertEquals(i, options.getBinForSample(i * binSize));
+        }
+    }
+
+    @Test
+    public void testBinIndexForRangeEqual90() {
+        final int binCount = 10;
+        final int minValue = 100;
+        final int maxValue = 100000;
+
+        Histogram.UniformOptions options = new Histogram.UniformOptions(binCount, minValue,
+                maxValue);
+
+        // logging underflow sample
+        assertEquals(0, options.getBinForSample(minValue - 1));
+
+        // logging overflow sample
+        assertEquals(binCount + 1, options.getBinForSample(maxValue));
+        assertEquals(binCount + 1, options.getBinForSample(maxValue + 1));
+
+        // logging min edge sample
+        assertEquals(1, options.getBinForSample(minValue));
+
+        // logging max edge sample
+        assertEquals(binCount, options.getBinForSample(maxValue - 1));
+
+        // logging single valid sample per bin
+        final int binSize = (maxValue - minValue) / binCount;
+
+        for (int i = 0; i < binCount; i++) {
+            assertEquals(i + 1, options.getBinForSample(minValue + binSize * i));
+        }
+    }
+}
diff --git a/javatests/com/android/modules/expresslog/jni/.clang-format b/javatests/com/android/modules/expresslog/jni/.clang-format
new file mode 100644
index 0000000..cead3a0
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/jni/.clang-format
@@ -0,0 +1,17 @@
+BasedOnStyle: Google
+AllowShortIfStatementsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: false
+AllowShortLoopsOnASingleLine: true
+BinPackArguments: true
+BinPackParameters: true
+ColumnLimit: 100
+CommentPragmas: NOLINT:.*
+ContinuationIndentWidth: 8
+DerivePointerAlignment: false
+IndentWidth: 4
+PointerAlignment: Left
+TabWidth: 4
+AccessModifierOffset: -4
+IncludeCategories:
+  - Regex:    '^"Log\.h"'
+    Priority:    -1
diff --git a/javatests/com/android/modules/expresslog/jni/onload.cpp b/javatests/com/android/modules/expresslog/jni/onload.cpp
new file mode 100644
index 0000000..a112467
--- /dev/null
+++ b/javatests/com/android/modules/expresslog/jni/onload.cpp
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "TeX"
+
+#include <jni.h>
+#include <log/log.h>
+
+namespace android {
+extern int register_com_android_modules_expresslog_Utils(JNIEnv* env);
+}  // namespace android
+
+using namespace android;
+
+extern "C" jint JNI_OnLoad(JavaVM* vm, void* /* reserved */) {
+    JNIEnv* env = NULL;
+    jint result = -1;
+
+    if (vm->GetEnv((void**)&env, JNI_VERSION_1_4) != JNI_OK) {
+        ALOGE("GetEnv failed!");
+        return result;
+    }
+    ALOG_ASSERT(env, "Could not retrieve the env!");
+
+    register_com_android_modules_expresslog_Utils(env);
+    return JNI_VERSION_1_4;
+}
diff --git a/jni/expresslog/.clang-format b/jni/expresslog/.clang-format
new file mode 100644
index 0000000..cead3a0
--- /dev/null
+++ b/jni/expresslog/.clang-format
@@ -0,0 +1,17 @@
+BasedOnStyle: Google
+AllowShortIfStatementsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: false
+AllowShortLoopsOnASingleLine: true
+BinPackArguments: true
+BinPackParameters: true
+ColumnLimit: 100
+CommentPragmas: NOLINT:.*
+ContinuationIndentWidth: 8
+DerivePointerAlignment: false
+IndentWidth: 4
+PointerAlignment: Left
+TabWidth: 4
+AccessModifierOffset: -4
+IncludeCategories:
+  - Regex:    '^"Log\.h"'
+    Priority:    -1
diff --git a/jni/expresslog/Android.bp b/jni/expresslog/Android.bp
new file mode 100644
index 0000000..b477c7b
--- /dev/null
+++ b/jni/expresslog/Android.bp
@@ -0,0 +1,49 @@
+//
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// JNI library for Utils.hashString
+cc_library_static {
+    name: "libexpresslog_jni",
+
+    sdk_version: "current",
+    min_sdk_version: "30",
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-Wextra",
+
+        "-DNAMESPACE_FOR_HASH_FUNCTIONS=farmhash",
+    ],
+    srcs: [
+        "com_android_modules_expresslog_Utils.cpp",
+    ],
+    header_libs: [
+        "liblog_headers",
+        "libnativehelper_header_only",
+        "libtextclassifier_hash_headers",
+    ],
+    shared_libs: [
+        "liblog",
+    ],
+    static_libs: [
+        "libtextclassifier_hash_static",
+    ],
+    visibility: ["//visibility:public"],
+    apex_available: [
+        "//apex_available:anyapex",
+        "//apex_available:platform",
+    ],
+}
diff --git a/jni/expresslog/com_android_modules_expresslog_Utils.cpp b/jni/expresslog/com_android_modules_expresslog_Utils.cpp
new file mode 100644
index 0000000..973d946
--- /dev/null
+++ b/jni/expresslog/com_android_modules_expresslog_Utils.cpp
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_NAMESPACE "TeX.tag."
+#define LOG_TAG "TeX"
+
+#include <log/log.h>
+#include <nativehelper/scoped_local_ref.h>
+#include <nativehelper/scoped_utf_chars.h>
+#include <utils/hash/farmhash.h>
+
+// ----------------------------------------------------------------------------
+// JNI Glue
+// ----------------------------------------------------------------------------
+
+static jclass gStringClass = nullptr;
+
+/**
+ * Class:     com_android_modules_expresslog_Utils
+ * Method:    hashString
+ * Signature: (Ljava/lang/String;)J
+ */
+static jlong hashString(JNIEnv* env, jclass /*class*/, jstring metricNameObj) {
+    ScopedUtfChars name(env, metricNameObj);
+    if (name.c_str() == nullptr) {
+        return 0;
+    }
+
+    return static_cast<jlong>(farmhash::Fingerprint64(name.c_str(), name.size()));
+}
+
+static const JNINativeMethod gMethods[] = {
+        {"hashString", "(Ljava/lang/String;)J", (void*)hashString},
+};
+
+namespace android {
+
+int register_com_android_modules_expresslog_Utils(JNIEnv* env) {
+    static const char* const kUtilsClassName = "com/android/modules/expresslog/Utils";
+    static const char* const kStringClassName = "java/lang/String";
+
+    ScopedLocalRef<jclass> utilsCls(env, env->FindClass(kUtilsClassName));
+    if (utilsCls.get() == nullptr) {
+        ALOGE("jni expresslog registration failure, class not found '%s'", kUtilsClassName);
+        return JNI_ERR;
+    }
+
+    jclass stringClass = env->FindClass(kStringClassName);
+    if (stringClass == nullptr) {
+        ALOGE("jni expresslog registration failure, class not found '%s'", kStringClassName);
+        return JNI_ERR;
+    }
+    gStringClass = static_cast<jclass>(env->NewGlobalRef(stringClass));
+    if (gStringClass == nullptr) {
+        ALOGE("jni expresslog Unable to create global reference '%s'", kStringClassName);
+        return JNI_ERR;
+    }
+
+    const jint count = sizeof(gMethods) / sizeof(gMethods[0]);
+    int status = env->RegisterNatives(utilsCls.get(), gMethods, count);
+    if (status < 0) {
+        ALOGE("jni expresslog registration failure, status: %d", status);
+        return JNI_ERR;
+    }
+    return JNI_VERSION_1_4;
+}
+
+}  // namespace android