libutils: add a binary blob cache implementation.

This change adds an implementation of a cache that stores key/value
pairs of unstructured binary blobs.

Change-Id: Idd01fdabedfa3aed6d359a6efb0592967af52651

1 files changed, 257 insertions, 0 deletions

diff --git a/libs/utils/tests/BlobCache_test.cpp b/libs/utils/tests/BlobCache_test.cpp
new file mode 100644
index 0000000..653ea5e
--- /dev/null
+++ b/libs/utils/tests/BlobCache_test.cpp
@@ -0,0 +1,257 @@
+/*
+ ** Copyright 2011, 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.
+ */
+
+#include <gtest/gtest.h>
+
+#include <utils/BlobCache.h>
+
+namespace android {
+
+class BlobCacheTest : public ::testing::Test {
+protected:
+    enum {
+        MAX_KEY_SIZE = 6,
+        MAX_VALUE_SIZE = 8,
+        MAX_TOTAL_SIZE = 13,
+    };
+
+    virtual void SetUp() {
+        mBC = new BlobCache(MAX_KEY_SIZE, MAX_VALUE_SIZE, MAX_TOTAL_SIZE);
+    }
+
+    virtual void TearDown() {
+        mBC.clear();
+    }
+
+    sp<BlobCache> mBC;
+};
+
+TEST_F(BlobCacheTest, CacheSingleValueSucceeds) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
+    ASSERT_EQ('e', buf[0]);
+    ASSERT_EQ('f', buf[1]);
+    ASSERT_EQ('g', buf[2]);
+    ASSERT_EQ('h', buf[3]);
+}
+
+TEST_F(BlobCacheTest, CacheTwoValuesSucceeds) {
+    char buf[2] = { 0xee, 0xee };
+    mBC->set("ab", 2, "cd", 2);
+    mBC->set("ef", 2, "gh", 2);
+    ASSERT_EQ(size_t(2), mBC->get("ab", 2, buf, 2));
+    ASSERT_EQ('c', buf[0]);
+    ASSERT_EQ('d', buf[1]);
+    ASSERT_EQ(size_t(2), mBC->get("ef", 2, buf, 2));
+    ASSERT_EQ('g', buf[0]);
+    ASSERT_EQ('h', buf[1]);
+}
+
+TEST_F(BlobCacheTest, GetOnlyWritesInsideBounds) {
+    char buf[6] = { 0xee, 0xee, 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf+1, 4));
+    ASSERT_EQ(0xee, buf[0]);
+    ASSERT_EQ('e', buf[1]);
+    ASSERT_EQ('f', buf[2]);
+    ASSERT_EQ('g', buf[3]);
+    ASSERT_EQ('h', buf[4]);
+    ASSERT_EQ(0xee, buf[5]);
+}
+
+TEST_F(BlobCacheTest, GetOnlyWritesIfBufferIsLargeEnough) {
+    char buf[3] = { 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 3));
+    ASSERT_EQ(0xee, buf[0]);
+    ASSERT_EQ(0xee, buf[1]);
+    ASSERT_EQ(0xee, buf[2]);
+}
+
+TEST_F(BlobCacheTest, GetDoesntAccessNullBuffer) {
+    mBC->set("abcd", 4, "efgh", 4);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, NULL, 0));
+}
+
+TEST_F(BlobCacheTest, MultipleSetsCacheLatestValue) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    mBC->set("abcd", 4, "ijkl", 4);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
+    ASSERT_EQ('i', buf[0]);
+    ASSERT_EQ('j', buf[1]);
+    ASSERT_EQ('k', buf[2]);
+    ASSERT_EQ('l', buf[3]);
+}
+
+TEST_F(BlobCacheTest, SecondSetKeepsFirstValueIfTooLarge) {
+    char buf[MAX_VALUE_SIZE+1] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    mBC->set("abcd", 4, buf, MAX_VALUE_SIZE+1);
+    ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
+    ASSERT_EQ('e', buf[0]);
+    ASSERT_EQ('f', buf[1]);
+    ASSERT_EQ('g', buf[2]);
+    ASSERT_EQ('h', buf[3]);
+}
+
+TEST_F(BlobCacheTest, DoesntCacheIfKeyIsTooBig) {
+    char key[MAX_KEY_SIZE+1];
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    for (int i = 0; i < MAX_KEY_SIZE+1; i++) {
+        key[i] = 'a';
+    }
+    mBC->set(key, MAX_KEY_SIZE+1, "bbbb", 4);
+    ASSERT_EQ(size_t(0), mBC->get(key, MAX_KEY_SIZE+1, buf, 4));
+    ASSERT_EQ(0xee, buf[0]);
+    ASSERT_EQ(0xee, buf[1]);
+    ASSERT_EQ(0xee, buf[2]);
+    ASSERT_EQ(0xee, buf[3]);
+}
+
+TEST_F(BlobCacheTest, DoesntCacheIfValueIsTooBig) {
+    char buf[MAX_VALUE_SIZE+1];
+    for (int i = 0; i < MAX_VALUE_SIZE+1; i++) {
+        buf[i] = 'b';
+    }
+    mBC->set("abcd", 4, buf, MAX_VALUE_SIZE+1);
+    for (int i = 0; i < MAX_VALUE_SIZE+1; i++) {
+        buf[i] = 0xee;
+    }
+    ASSERT_EQ(size_t(0), mBC->get("abcd", 4, buf, MAX_VALUE_SIZE+1));
+    for (int i = 0; i < MAX_VALUE_SIZE+1; i++) {
+        SCOPED_TRACE(i);
+        ASSERT_EQ(0xee, buf[i]);
+    }
+}
+
+TEST_F(BlobCacheTest, DoesntCacheIfKeyValuePairIsTooBig) {
+    // Check a testing assumptions
+    ASSERT_TRUE(MAX_TOTAL_SIZE < MAX_KEY_SIZE + MAX_VALUE_SIZE);
+    ASSERT_TRUE(MAX_KEY_SIZE < MAX_TOTAL_SIZE);
+
+    enum { bufSize = MAX_TOTAL_SIZE - MAX_KEY_SIZE + 1 };
+
+    char key[MAX_KEY_SIZE];
+    char buf[bufSize];
+    for (int i = 0; i < MAX_KEY_SIZE; i++) {
+        key[i] = 'a';
+    }
+    for (int i = 0; i < bufSize; i++) {
+        buf[i] = 'b';
+    }
+
+    mBC->set(key, MAX_KEY_SIZE, buf, MAX_VALUE_SIZE);
+    ASSERT_EQ(size_t(0), mBC->get(key, MAX_KEY_SIZE, NULL, 0));
+}
+
+TEST_F(BlobCacheTest, CacheMaxKeySizeSucceeds) {
+    char key[MAX_KEY_SIZE];
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    for (int i = 0; i < MAX_KEY_SIZE; i++) {
+        key[i] = 'a';
+    }
+    mBC->set(key, MAX_KEY_SIZE, "wxyz", 4);
+    ASSERT_EQ(size_t(4), mBC->get(key, MAX_KEY_SIZE, buf, 4));
+    ASSERT_EQ('w', buf[0]);
+    ASSERT_EQ('x', buf[1]);
+    ASSERT_EQ('y', buf[2]);
+    ASSERT_EQ('z', buf[3]);
+}
+
+TEST_F(BlobCacheTest, CacheMaxValueSizeSucceeds) {
+    char buf[MAX_VALUE_SIZE];
+    for (int i = 0; i < MAX_VALUE_SIZE; i++) {
+        buf[i] = 'b';
+    }
+    mBC->set("abcd", 4, buf, MAX_VALUE_SIZE);
+    for (int i = 0; i < MAX_VALUE_SIZE; i++) {
+        buf[i] = 0xee;
+    }
+    ASSERT_EQ(size_t(MAX_VALUE_SIZE), mBC->get("abcd", 4, buf,
+            MAX_VALUE_SIZE));
+    for (int i = 0; i < MAX_VALUE_SIZE; i++) {
+        SCOPED_TRACE(i);
+        ASSERT_EQ('b', buf[i]);
+    }
+}
+
+TEST_F(BlobCacheTest, CacheMaxKeyValuePairSizeSucceeds) {
+    // Check a testing assumption
+    ASSERT_TRUE(MAX_KEY_SIZE < MAX_TOTAL_SIZE);
+
+    enum { bufSize = MAX_TOTAL_SIZE - MAX_KEY_SIZE };
+
+    char key[MAX_KEY_SIZE];
+    char buf[bufSize];
+    for (int i = 0; i < MAX_KEY_SIZE; i++) {
+        key[i] = 'a';
+    }
+    for (int i = 0; i < bufSize; i++) {
+        buf[i] = 'b';
+    }
+
+    mBC->set(key, MAX_KEY_SIZE, buf, bufSize);
+    ASSERT_EQ(size_t(bufSize), mBC->get(key, MAX_KEY_SIZE, NULL, 0));
+}
+
+TEST_F(BlobCacheTest, CacheMinKeyAndValueSizeSucceeds) {
+    char buf[1] = { 0xee };
+    mBC->set("x", 1, "y", 1);
+    ASSERT_EQ(size_t(1), mBC->get("x", 1, buf, 1));
+    ASSERT_EQ('y', buf[0]);
+}
+
+TEST_F(BlobCacheTest, CacheSizeDoesntExceedTotalLimit) {
+    for (int i = 0; i < 256; i++) {
+        uint8_t k = i;
+        mBC->set(&k, 1, "x", 1);
+    }
+    int numCached = 0;
+    for (int i = 0; i < 256; i++) {
+        uint8_t k = i;
+        if (mBC->get(&k, 1, NULL, 0) == 1) {
+            numCached++;
+        }
+    }
+    ASSERT_GE(MAX_TOTAL_SIZE / 2, numCached);
+}
+
+TEST_F(BlobCacheTest, ExceedingTotalLimitHalvesCacheSize) {
+    // Fill up the entire cache with 1 char key/value pairs.
+    const int maxEntries = MAX_TOTAL_SIZE / 2;
+    for (int i = 0; i < maxEntries; i++) {
+        uint8_t k = i;
+        mBC->set(&k, 1, "x", 1);
+    }
+    // Insert one more entry, causing a cache overflow.
+    {
+        uint8_t k = maxEntries;
+        mBC->set(&k, 1, "x", 1);
+    }
+    // Count the number of entries in the cache.
+    int numCached = 0;
+    for (int i = 0; i < maxEntries+1; i++) {
+        uint8_t k = i;
+        if (mBC->get(&k, 1, NULL, 0) == 1) {
+            numCached++;
+        }
+    }
+    ASSERT_EQ(maxEntries/2 + 1, numCached);
+}
+
+} // namespace android