1 files changed, 232 insertions, 0 deletions
diff --git a/libs/utils/BlobCache.cpp b/libs/utils/BlobCache.cpp
new file mode 100644
index 0000000..1298fa7
--- /dev/null
+++ b/libs/utils/BlobCache.cpp
@@ -0,0 +1,232 @@
+/*
+ ** 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.
+ */
+
+#define LOG_TAG "BlobCache"
+//#define LOG_NDEBUG 0
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <utils/BlobCache.h>
+#include <utils/Log.h>
+
+namespace android {
+
+BlobCache::BlobCache(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize):
+        mMaxKeySize(maxKeySize),
+        mMaxValueSize(maxValueSize),
+        mMaxTotalSize(maxTotalSize),
+        mTotalSize(0) {
+    nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
+    mRandState[0] = (now >> 0) & 0xFFFF;
+    mRandState[1] = (now >> 16) & 0xFFFF;
+    mRandState[2] = (now >> 32) & 0xFFFF;
+    LOGV("initializing random seed using %lld", now);
+}
+
+void BlobCache::set(const void* key, size_t keySize, const void* value,
+        size_t valueSize) {
+    if (mMaxKeySize < keySize) {
+        LOGV("set: not caching because the key is too large: %d (limit: %d)",
+                keySize, mMaxKeySize);
+        return;
+    }
+    if (mMaxValueSize < valueSize) {
+        LOGV("set: not caching because the value is too large: %d (limit: %d)",
+                valueSize, mMaxValueSize);
+        return;
+    }
+    if (mMaxTotalSize < keySize + valueSize) {
+        LOGV("set: not caching because the combined key/value size is too "
+                "large: %d (limit: %d)", keySize + valueSize, mMaxTotalSize);
+        return;
+    }
+    if (keySize == 0) {
+        LOGW("set: not caching because keySize is 0");
+        return;
+    }
+    if (valueSize <= 0) {
+        LOGW("set: not caching because valueSize is 0");
+        return;
+    }
+
+    Mutex::Autolock lock(mMutex);
+    sp<Blob> dummyKey(new Blob(key, keySize, false));
+    CacheEntry dummyEntry(dummyKey, NULL);
+
+    while (true) {
+
+        ssize_t index = mCacheEntries.indexOf(dummyEntry);
+        if (index < 0) {
+            // Create a new cache entry.
+            sp<Blob> keyBlob(new Blob(key, keySize, true));
+            sp<Blob> valueBlob(new Blob(value, valueSize, true));
+            size_t newTotalSize = mTotalSize + keySize + valueSize;
+            if (mMaxTotalSize < newTotalSize) {
+                if (isCleanable()) {
+                    // Clean the cache and try again.
+                    clean();
+                    continue;
+                } else {
+                    LOGV("set: not caching new key/value pair because the "
+                            "total cache size limit would be exceeded: %d "
+                            "(limit: %d)",
+                            keySize + valueSize, mMaxTotalSize);
+                    break;
+                }
+            }
+            mCacheEntries.add(CacheEntry(keyBlob, valueBlob));
+            mTotalSize = newTotalSize;
+            LOGV("set: created new cache entry with %d byte key and %d byte value",
+                    keySize, valueSize);
+        } else {
+            // Update the existing cache entry.
+            sp<Blob> valueBlob(new Blob(value, valueSize, true));
+            sp<Blob> oldValueBlob(mCacheEntries[index].getValue());
+            size_t newTotalSize = mTotalSize + valueSize - oldValueBlob->getSize();
+            if (mMaxTotalSize < newTotalSize) {
+                if (isCleanable()) {
+                    // Clean the cache and try again.
+                    clean();
+                    continue;
+                } else {
+                    LOGV("set: not caching new value because the total cache "
+                            "size limit would be exceeded: %d (limit: %d)",
+                            keySize + valueSize, mMaxTotalSize);
+                    break;
+                }
+            }
+            mCacheEntries.editItemAt(index).setValue(valueBlob);
+            mTotalSize = newTotalSize;
+            LOGV("set: updated existing cache entry with %d byte key and %d byte "
+                    "value", keySize, valueSize);
+        }
+        break;
+    }
+}
+
+size_t BlobCache::get(const void* key, size_t keySize, void* value,
+        size_t valueSize) {
+    if (mMaxKeySize < keySize) {
+        LOGV("get: not searching because the key is too large: %d (limit %d)",
+                keySize, mMaxKeySize);
+        return 0;
+    }
+    Mutex::Autolock lock(mMutex);
+    sp<Blob> dummyKey(new Blob(key, keySize, false));
+    CacheEntry dummyEntry(dummyKey, NULL);
+    ssize_t index = mCacheEntries.indexOf(dummyEntry);
+    if (index < 0) {
+        LOGV("get: no cache entry found for key of size %d", keySize);
+        return 0;
+    }
+
+    // The key was found. Return the value if the caller's buffer is large
+    // enough.
+    sp<Blob> valueBlob(mCacheEntries[index].getValue());
+    size_t valueBlobSize = valueBlob->getSize();
+    if (valueBlobSize <= valueSize) {
+        LOGV("get: copying %d bytes to caller's buffer", valueBlobSize);
+        memcpy(value, valueBlob->getData(), valueBlobSize);
+    } else {
+        LOGV("get: caller's buffer is too small for value: %d (needs %d)",
+                valueSize, valueBlobSize);
+    }
+    return valueBlobSize;
+}
+
+void BlobCache::clean() {
+    // Remove a random cache entry until the total cache size gets below half
+    // the maximum total cache size.
+    while (mTotalSize > mMaxTotalSize / 2) {
+        size_t i = size_t(nrand48(mRandState) % (mCacheEntries.size()));
+        const CacheEntry& entry(mCacheEntries[i]);
+        mTotalSize -= entry.getKey()->getSize() + entry.getValue()->getSize();
+        mCacheEntries.removeAt(i);
+    }
+}
+
+bool BlobCache::isCleanable() const {
+    return mTotalSize > mMaxTotalSize / 2;
+}
+
+BlobCache::Blob::Blob(const void* data, size_t size, bool copyData):
+        mData(copyData ? malloc(size) : data),
+        mSize(size),
+        mOwnsData(copyData) {
+    if (copyData) {
+        memcpy(const_cast<void*>(mData), data, size);
+    }
+}
+
+BlobCache::Blob::~Blob() {
+    if (mOwnsData) {
+        free(const_cast<void*>(mData));
+    }
+}
+
+bool BlobCache::Blob::operator<(const Blob& rhs) const {
+    if (mSize == rhs.mSize) {
+        return memcmp(mData, rhs.mData, mSize) < 0;
+    } else {
+        return mSize < rhs.mSize;
+    }
+}
+
+const void* BlobCache::Blob::getData() const {
+    return mData;
+}
+
+size_t BlobCache::Blob::getSize() const {
+    return mSize;
+}
+
+BlobCache::CacheEntry::CacheEntry() {
+}
+
+BlobCache::CacheEntry::CacheEntry(const sp<Blob>& key, const sp<Blob>& value):
+        mKey(key),
+        mValue(value) {
+}
+
+BlobCache::CacheEntry::CacheEntry(const CacheEntry& ce):
+        mKey(ce.mKey),
+        mValue(ce.mValue) {
+}
+
+bool BlobCache::CacheEntry::operator<(const CacheEntry& rhs) const {
+    return *mKey < *rhs.mKey;
+}
+
+const BlobCache::CacheEntry& BlobCache::CacheEntry::operator=(const CacheEntry& rhs) {
+    mKey = rhs.mKey;
+    mValue = rhs.mValue;
+    return *this;
+}
+
+sp<BlobCache::Blob> BlobCache::CacheEntry::getKey() const {
+    return mKey;
+}
+
+sp<BlobCache::Blob> BlobCache::CacheEntry::getValue() const {
+    return mValue;
+}
+
+void BlobCache::CacheEntry::setValue(const sp<Blob>& value) {
+    mValue = value;
+}
+
+} // namespace android