BlobCache: implement cache serialization

This change adds serialization and deserialization functionality to
BlobCache, conforming to the Flattenable interface.

Change-Id: Ibc99cb1c3d015f363d57d0713eabccec07ff975e

2 files changed, 302 insertions, 2 deletions

diff --git a/libs/utils/BlobCache.cpp b/libs/utils/BlobCache.cpp
index 15155b2..d38aae9 100644
--- a/libs/utils/BlobCache.cpp
+++ b/libs/utils/BlobCache.cpp
@@ -21,10 +21,20 @@
 #include <string.h>
 
 #include <utils/BlobCache.h>
+#include <utils/Errors.h>
 #include <utils/Log.h>
 
 namespace android {
 
+// BlobCache::Header::mMagicNumber value
+static const uint32_t blobCacheMagic = '_Bb$';
+
+// BlobCache::Header::mBlobCacheVersion value
+static const uint32_t blobCacheVersion = 1;
+
+// BlobCache::Header::mDeviceVersion value
+static const uint32_t blobCacheDeviceVersion = 1;
+
 BlobCache::BlobCache(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize):
         mMaxKeySize(maxKeySize),
         mMaxValueSize(maxValueSize),
@@ -71,7 +81,6 @@ void BlobCache::set(const void* key, size_t keySize, const void* value,
     CacheEntry dummyEntry(dummyKey, NULL);
 
     while (true) {
-
         ssize_t index = mCacheEntries.indexOf(dummyEntry);
         if (index < 0) {
             // Create a new cache entry.
@@ -150,6 +159,133 @@ size_t BlobCache::get(const void* key, size_t keySize, void* value,
     return valueBlobSize;
 }
 
+static inline size_t align4(size_t size) {
+    return (size + 3) & ~3;
+}
+
+size_t BlobCache::getFlattenedSize() const {
+    size_t size = sizeof(Header);
+    for (size_t i = 0; i < mCacheEntries.size(); i++) {
+        const CacheEntry& e(mCacheEntries[i]);
+        sp<Blob> keyBlob = e.getKey();
+        sp<Blob> valueBlob = e.getValue();
+        size = align4(size);
+        size += sizeof(EntryHeader) + keyBlob->getSize() +
+                valueBlob->getSize();
+    }
+    return size;
+}
+
+size_t BlobCache::getFdCount() const {
+    return 0;
+}
+
+status_t BlobCache::flatten(void* buffer, size_t size, int fds[], size_t count)
+        const {
+    if (count != 0) {
+        LOGE("flatten: nonzero fd count: %d", count);
+        return BAD_VALUE;
+    }
+
+    // Write the cache header
+    if (size < sizeof(Header)) {
+        LOGE("flatten: not enough room for cache header");
+        return BAD_VALUE;
+    }
+    Header* header = reinterpret_cast<Header*>(buffer);
+    header->mMagicNumber = blobCacheMagic;
+    header->mBlobCacheVersion = blobCacheVersion;
+    header->mDeviceVersion = blobCacheDeviceVersion;
+    header->mNumEntries = mCacheEntries.size();
+
+    // Write cache entries
+    uint8_t* byteBuffer = reinterpret_cast<uint8_t*>(buffer);
+    off_t byteOffset = align4(sizeof(Header));
+    for (size_t i = 0; i < mCacheEntries.size(); i++) {
+        const CacheEntry& e(mCacheEntries[i]);
+        sp<Blob> keyBlob = e.getKey();
+        sp<Blob> valueBlob = e.getValue();
+        size_t keySize = keyBlob->getSize();
+        size_t valueSize = valueBlob->getSize();
+
+        size_t entrySize = sizeof(EntryHeader) + keySize + valueSize;
+        if (byteOffset + entrySize > size) {
+            LOGE("flatten: not enough room for cache entries");
+            return BAD_VALUE;
+        }
+
+        EntryHeader* eheader = reinterpret_cast<EntryHeader*>(
+            &byteBuffer[byteOffset]);
+        eheader->mKeySize = keySize;
+        eheader->mValueSize = valueSize;
+
+        memcpy(eheader->mData, keyBlob->getData(), keySize);
+        memcpy(eheader->mData + keySize, valueBlob->getData(), valueSize);
+
+        byteOffset += align4(entrySize);
+    }
+
+    return OK;
+}
+
+status_t BlobCache::unflatten(void const* buffer, size_t size, int fds[],
+        size_t count) {
+    // All errors should result in the BlobCache being in an empty state.
+    mCacheEntries.clear();
+
+    if (count != 0) {
+        LOGE("unflatten: nonzero fd count: %d", count);
+        return BAD_VALUE;
+    }
+
+    // Read the cache header
+    if (size < sizeof(Header)) {
+        LOGE("unflatten: not enough room for cache header");
+        return BAD_VALUE;
+    }
+    const Header* header = reinterpret_cast<const Header*>(buffer);
+    if (header->mMagicNumber != blobCacheMagic) {
+        LOGE("unflatten: bad magic number: %d", header->mMagicNumber);
+        return BAD_VALUE;
+    }
+    if (header->mBlobCacheVersion != blobCacheVersion ||
+            header->mDeviceVersion != blobCacheDeviceVersion) {
+        // We treat version mismatches as an empty cache.
+        return OK;
+    }
+
+    // Read cache entries
+    const uint8_t* byteBuffer = reinterpret_cast<const uint8_t*>(buffer);
+    off_t byteOffset = align4(sizeof(Header));
+    size_t numEntries = header->mNumEntries;
+    for (size_t i = 0; i < numEntries; i++) {
+        if (byteOffset + sizeof(EntryHeader) > size) {
+            mCacheEntries.clear();
+            LOGE("unflatten: not enough room for cache entry headers");
+            return BAD_VALUE;
+        }
+
+        const EntryHeader* eheader = reinterpret_cast<const EntryHeader*>(
+                &byteBuffer[byteOffset]);
+        size_t keySize = eheader->mKeySize;
+        size_t valueSize = eheader->mValueSize;
+        size_t entrySize = sizeof(EntryHeader) + keySize + valueSize;
+
+        if (byteOffset + entrySize > size) {
+            mCacheEntries.clear();
+            LOGE("unflatten: not enough room for cache entry headers");
+            return BAD_VALUE;
+        }
+
+        const uint8_t* data = eheader->mData;
+        set(data, keySize, data + keySize, valueSize);
+
+        byteOffset += align4(entrySize);
+    }
+
+    return OK;
+}
+
 long int BlobCache::blob_random() {
 #ifdef _WIN32
     return rand();
@@ -177,7 +313,7 @@ BlobCache::Blob::Blob(const void* data, size_t size, bool copyData):
         mData(copyData ? malloc(size) : data),
         mSize(size),
         mOwnsData(copyData) {
-    if (copyData) {
+    if (data != NULL && copyData) {
         memcpy(const_cast<void*>(mData), data, size);
     }
 }
diff --git a/libs/utils/tests/BlobCache_test.cpp b/libs/utils/tests/BlobCache_test.cpp
index 653ea5e..b64cc39 100644
--- a/libs/utils/tests/BlobCache_test.cpp
+++ b/libs/utils/tests/BlobCache_test.cpp
@@ -14,9 +14,13 @@
  ** limitations under the License.
  */
 
+#include <fcntl.h>
+#include <stdio.h>
+
 #include <gtest/gtest.h>
 
 #include <utils/BlobCache.h>
+#include <utils/Errors.h>
 
 namespace android {
 
@@ -254,4 +258,164 @@ TEST_F(BlobCacheTest, ExceedingTotalLimitHalvesCacheSize) {
     ASSERT_EQ(maxEntries/2 + 1, numCached);
 }
 
+class BlobCacheFlattenTest : public BlobCacheTest {
+protected:
+    virtual void SetUp() {
+        BlobCacheTest::SetUp();
+        mBC2 = new BlobCache(MAX_KEY_SIZE, MAX_VALUE_SIZE, MAX_TOTAL_SIZE);
+    }
+
+    virtual void TearDown() {
+        mBC2.clear();
+        BlobCacheTest::TearDown();
+    }
+
+    void roundTrip() {
+        size_t size = mBC->getFlattenedSize();
+        uint8_t* flat = new uint8_t[size];
+        ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+        ASSERT_EQ(OK, mBC2->unflatten(flat, size, NULL, 0));
+        delete[] flat;
+    }
+
+    sp<BlobCache> mBC2;
+};
+
+TEST_F(BlobCacheFlattenTest, FlattenOneValue) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+    roundTrip();
+    ASSERT_EQ(size_t(4), mBC2->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(BlobCacheFlattenTest, FlattenFullCache) {
+    // 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, &k, 1);
+    }
+
+    roundTrip();
+
+    // Verify the deserialized cache
+    for (int i = 0; i < maxEntries; i++) {
+        uint8_t k = i;
+        uint8_t v = 0xee;
+        ASSERT_EQ(size_t(1), mBC2->get(&k, 1, &v, 1));
+        ASSERT_EQ(k, v);
+    }
+}
+
+TEST_F(BlobCacheFlattenTest, FlattenDoesntChangeCache) {
+    // 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, &k, 1);
+    }
+
+    size_t size = mBC->getFlattenedSize();
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+    delete[] flat;
+
+    // Verify the cache that we just serialized
+    for (int i = 0; i < maxEntries; i++) {
+        uint8_t k = i;
+        uint8_t v = 0xee;
+        ASSERT_EQ(size_t(1), mBC->get(&k, 1, &v, 1));
+        ASSERT_EQ(k, v);
+    }
+}
+
+TEST_F(BlobCacheFlattenTest, FlattenCatchesBufferTooSmall) {
+    // 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, &k, 1);
+    }
+
+    size_t size = mBC->getFlattenedSize() - 1;
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(BAD_VALUE, mBC->flatten(flat, size, NULL, 0));
+    delete[] flat;
+}
+
+TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadMagic) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+
+    size_t size = mBC->getFlattenedSize();
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+    flat[1] = ~flat[1];
+
+    // Bad magic should cause an error.
+    ASSERT_EQ(BAD_VALUE, mBC2->unflatten(flat, size, NULL, 0));
+    delete[] flat;
+
+    // The error should cause the unflatten to result in an empty cache
+    ASSERT_EQ(size_t(0), mBC2->get("abcd", 4, buf, 4));
+}
+
+TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadBlobCacheVersion) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+
+    size_t size = mBC->getFlattenedSize();
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+    flat[5] = ~flat[5];
+
+    // Version mismatches shouldn't cause errors, but should not use the
+    // serialized entries
+    ASSERT_EQ(OK, mBC2->unflatten(flat, size, NULL, 0));
+    delete[] flat;
+
+    // The version mismatch should cause the unflatten to result in an empty
+    // cache
+    ASSERT_EQ(size_t(0), mBC2->get("abcd", 4, buf, 4));
+}
+
+TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadBlobCacheDeviceVersion) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+
+    size_t size = mBC->getFlattenedSize();
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+    flat[10] = ~flat[10];
+
+    // Version mismatches shouldn't cause errors, but should not use the
+    // serialized entries
+    ASSERT_EQ(OK, mBC2->unflatten(flat, size, NULL, 0));
+    delete[] flat;
+
+    // The version mismatch should cause the unflatten to result in an empty
+    // cache
+    ASSERT_EQ(size_t(0), mBC2->get("abcd", 4, buf, 4));
+}
+
+TEST_F(BlobCacheFlattenTest, UnflattenCatchesBufferTooSmall) {
+    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    mBC->set("abcd", 4, "efgh", 4);
+
+    size_t size = mBC->getFlattenedSize();
+    uint8_t* flat = new uint8_t[size];
+    ASSERT_EQ(OK, mBC->flatten(flat, size, NULL, 0));
+
+    // A buffer truncation shouldt cause an error
+    ASSERT_EQ(BAD_VALUE, mBC2->unflatten(flat, size-1, NULL, 0));
+    delete[] flat;
+
+    // The error should cause the unflatten to result in an empty cache
+    ASSERT_EQ(size_t(0), mBC2->get("abcd", 4, buf, 4));
+}
+
 } // namespace android