diff options
Diffstat (limited to 'include/utils/BlobCache.h')
| -rw-r--r-- | include/utils/BlobCache.h | 251 |
1 files changed, 0 insertions, 251 deletions
diff --git a/include/utils/BlobCache.h b/include/utils/BlobCache.h deleted file mode 100644 index 4f342a2..0000000 --- a/include/utils/BlobCache.h +++ /dev/null @@ -1,251 +0,0 @@ -/* - ** 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. - */ - -#ifndef ANDROID_BLOB_CACHE_H -#define ANDROID_BLOB_CACHE_H - -#include <stddef.h> - -#include <utils/Flattenable.h> -#include <utils/RefBase.h> -#include <utils/SortedVector.h> -#include <utils/threads.h> - -namespace android { - -// A BlobCache is an in-memory cache for binary key/value pairs. A BlobCache -// does NOT provide any thread-safety guarantees. -// -// The cache contents can be serialized to an in-memory buffer or mmap'd file -// and then reloaded in a subsequent execution of the program. This -// serialization is non-portable and the data should only be used by the device -// that generated it. -class BlobCache : public RefBase, public Flattenable { -public: - - // Create an empty blob cache. The blob cache will cache key/value pairs - // with key and value sizes less than or equal to maxKeySize and - // maxValueSize, respectively. The total combined size of ALL cache entries - // (key sizes plus value sizes) will not exceed maxTotalSize. - BlobCache(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize); - - // set inserts a new binary value into the cache and associates it with the - // given binary key. If the key or value are too large for the cache then - // the cache remains unchanged. This includes the case where a different - // value was previously associated with the given key - the old value will - // remain in the cache. If the given key and value are small enough to be - // put in the cache (based on the maxKeySize, maxValueSize, and maxTotalSize - // values specified to the BlobCache constructor), then the key/value pair - // will be in the cache after set returns. Note, however, that a subsequent - // call to set may evict old key/value pairs from the cache. - // - // Preconditions: - // key != NULL - // 0 < keySize - // value != NULL - // 0 < valueSize - void set(const void* key, size_t keySize, const void* value, - size_t valueSize); - - // get retrieves from the cache the binary value associated with a given - // binary key. If the key is present in the cache then the length of the - // binary value associated with that key is returned. If the value argument - // is non-NULL and the size of the cached value is less than valueSize bytes - // then the cached value is copied into the buffer pointed to by the value - // argument. If the key is not present in the cache then 0 is returned and - // the buffer pointed to by the value argument is not modified. - // - // Note that when calling get multiple times with the same key, the later - // calls may fail, returning 0, even if earlier calls succeeded. The return - // value must be checked for each call. - // - // Preconditions: - // key != NULL - // 0 < keySize - // 0 <= valueSize - size_t get(const void* key, size_t keySize, void* value, size_t valueSize); - - // getFlattenedSize returns the number of bytes needed to store the entire - // serialized cache. - virtual size_t getFlattenedSize() const; - - // getFdCount returns the number of file descriptors that will result from - // flattening the cache. This will always return 0 so as to allow the - // flattened cache to be saved to disk and then later restored. - virtual size_t getFdCount() const; - - // flatten serializes the current contents of the cache into the memory - // pointed to by 'buffer'. The serialized cache contents can later be - // loaded into a BlobCache object using the unflatten method. The contents - // of the BlobCache object will not be modified. - // - // Preconditions: - // size >= this.getFlattenedSize() - // count == 0 - virtual status_t flatten(void* buffer, size_t size, int fds[], - size_t count) const; - - // unflatten replaces the contents of the cache with the serialized cache - // contents in the memory pointed to by 'buffer'. The previous contents of - // the BlobCache will be evicted from the cache. If an error occurs while - // unflattening the serialized cache contents then the BlobCache will be - // left in an empty state. - // - // Preconditions: - // count == 0 - virtual status_t unflatten(void const* buffer, size_t size, int fds[], - size_t count); - -private: - // Copying is disallowed. - BlobCache(const BlobCache&); - void operator=(const BlobCache&); - - // A random function helper to get around MinGW not having nrand48() - long int blob_random(); - - // clean evicts a randomly chosen set of entries from the cache such that - // the total size of all remaining entries is less than mMaxTotalSize/2. - void clean(); - - // isCleanable returns true if the cache is full enough for the clean method - // to have some effect, and false otherwise. - bool isCleanable() const; - - // A Blob is an immutable sized unstructured data blob. - class Blob : public RefBase { - public: - Blob(const void* data, size_t size, bool copyData); - ~Blob(); - - bool operator<(const Blob& rhs) const; - - const void* getData() const; - size_t getSize() const; - - private: - // Copying is not allowed. - Blob(const Blob&); - void operator=(const Blob&); - - // mData points to the buffer containing the blob data. - const void* mData; - - // mSize is the size of the blob data in bytes. - size_t mSize; - - // mOwnsData indicates whether or not this Blob object should free the - // memory pointed to by mData when the Blob gets destructed. - bool mOwnsData; - }; - - // A CacheEntry is a single key/value pair in the cache. - class CacheEntry { - public: - CacheEntry(); - CacheEntry(const sp<Blob>& key, const sp<Blob>& value); - CacheEntry(const CacheEntry& ce); - - bool operator<(const CacheEntry& rhs) const; - const CacheEntry& operator=(const CacheEntry&); - - sp<Blob> getKey() const; - sp<Blob> getValue() const; - - void setValue(const sp<Blob>& value); - - private: - - // mKey is the key that identifies the cache entry. - sp<Blob> mKey; - - // mValue is the cached data associated with the key. - sp<Blob> mValue; - }; - - // A Header is the header for the entire BlobCache serialization format. No - // need to make this portable, so we simply write the struct out. - struct Header { - // mMagicNumber is the magic number that identifies the data as - // serialized BlobCache contents. It must always contain 'Blb$'. - uint32_t mMagicNumber; - - // mBlobCacheVersion is the serialization format version. - uint32_t mBlobCacheVersion; - - // mDeviceVersion is the device-specific version of the cache. This can - // be used to invalidate the cache. - uint32_t mDeviceVersion; - - // mNumEntries is number of cache entries following the header in the - // data. - size_t mNumEntries; - }; - - // An EntryHeader is the header for a serialized cache entry. No need to - // make this portable, so we simply write the struct out. Each EntryHeader - // is followed imediately by the key data and then the value data. - // - // The beginning of each serialized EntryHeader is 4-byte aligned, so the - // number of bytes that a serialized cache entry will occupy is: - // - // ((sizeof(EntryHeader) + keySize + valueSize) + 3) & ~3 - // - struct EntryHeader { - // mKeySize is the size of the entry key in bytes. - size_t mKeySize; - - // mValueSize is the size of the entry value in bytes. - size_t mValueSize; - - // mData contains both the key and value data for the cache entry. The - // key comes first followed immediately by the value. - uint8_t mData[]; - }; - - // mMaxKeySize is the maximum key size that will be cached. Calls to - // BlobCache::set with a keySize parameter larger than mMaxKeySize will - // simply not add the key/value pair to the cache. - const size_t mMaxKeySize; - - // mMaxValueSize is the maximum value size that will be cached. Calls to - // BlobCache::set with a valueSize parameter larger than mMaxValueSize will - // simply not add the key/value pair to the cache. - const size_t mMaxValueSize; - - // mMaxTotalSize is the maximum size that all cache entries can occupy. This - // includes space for both keys and values. When a call to BlobCache::set - // would otherwise cause this limit to be exceeded, either the key/value - // pair passed to BlobCache::set will not be cached or other cache entries - // will be evicted from the cache to make room for the new entry. - const size_t mMaxTotalSize; - - // mTotalSize is the total combined size of all keys and values currently in - // the cache. - size_t mTotalSize; - - // mRandState is the pseudo-random number generator state. It is passed to - // nrand48 to generate random numbers when needed. - unsigned short mRandState[3]; - - // mCacheEntries stores all the cache entries that are resident in memory. - // Cache entries are added to it by the 'set' method. - SortedVector<CacheEntry> mCacheEntries; -}; - -} - -#endif // ANDROID_BLOB_CACHE_H |