370 lines
13 KiB
C++
370 lines
13 KiB
C++
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/*
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** Copyright 2011, The Android Open Source Project
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**
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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**
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** http://www.apache.org/licenses/LICENSE-2.0
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**
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*/
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//#define LOG_NDEBUG 0
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#include "BlobCache.h"
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#include <android-base/properties.h>
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#include <errno.h>
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#include <inttypes.h>
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#include <log/log.h>
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#include <chrono>
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namespace android {
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// BlobCache::Header::mMagicNumber value
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static const uint32_t blobCacheMagic = ('_' << 24) + ('B' << 16) + ('b' << 8) + '$';
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// BlobCache::Header::mBlobCacheVersion value
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static const uint32_t blobCacheVersion = 3;
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// BlobCache::Header::mDeviceVersion value
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static const uint32_t blobCacheDeviceVersion = 1;
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BlobCache::BlobCache(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize)
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: mMaxTotalSize(maxTotalSize),
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mMaxKeySize(maxKeySize),
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mMaxValueSize(maxValueSize),
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mTotalSize(0) {
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int64_t now = std::chrono::steady_clock::now().time_since_epoch().count();
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#ifdef _WIN32
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srand(now);
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#else
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mRandState[0] = (now >> 0) & 0xFFFF;
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mRandState[1] = (now >> 16) & 0xFFFF;
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mRandState[2] = (now >> 32) & 0xFFFF;
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#endif
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ALOGV("initializing random seed using %lld", (unsigned long long)now);
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}
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BlobCache::InsertResult BlobCache::set(const void* key, size_t keySize, const void* value,
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size_t valueSize) {
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if (mMaxKeySize < keySize) {
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ALOGV("set: not caching because the key is too large: %zu (limit: %zu)", keySize,
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mMaxKeySize);
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return InsertResult::kKeyTooBig;
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}
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if (mMaxValueSize < valueSize) {
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ALOGV("set: not caching because the value is too large: %zu (limit: %zu)", valueSize,
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mMaxValueSize);
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return InsertResult::kValueTooBig;
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}
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if (mMaxTotalSize < keySize + valueSize) {
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ALOGV("set: not caching because the combined key/value size is too "
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"large: %zu (limit: %zu)",
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keySize + valueSize, mMaxTotalSize);
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return InsertResult::kCombinedTooBig;
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}
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if (keySize == 0) {
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ALOGW("set: not caching because keySize is 0");
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return InsertResult::kInvalidKeySize;
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}
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if (valueSize == 0) {
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ALOGW("set: not caching because valueSize is 0");
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return InsertResult::kInvalidValueSize;
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}
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std::shared_ptr<Blob> cacheKey(new Blob(key, keySize, false));
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CacheEntry cacheEntry(cacheKey, nullptr);
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bool didClean = false;
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while (true) {
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auto index = std::lower_bound(mCacheEntries.begin(), mCacheEntries.end(), cacheEntry);
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if (index == mCacheEntries.end() || cacheEntry < *index) {
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// Create a new cache entry.
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std::shared_ptr<Blob> keyBlob(new Blob(key, keySize, true));
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std::shared_ptr<Blob> valueBlob(new Blob(value, valueSize, true));
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size_t newTotalSize = mTotalSize + keySize + valueSize;
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if (mMaxTotalSize < newTotalSize) {
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if (isCleanable()) {
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// Clean the cache and try again.
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clean();
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didClean = true;
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continue;
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} else {
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ALOGV("set: not caching new key/value pair because the "
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"total cache size limit would be exceeded: %zu "
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"(limit: %zu)",
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keySize + valueSize, mMaxTotalSize);
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return InsertResult::kNotEnoughSpace;
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}
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}
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mCacheEntries.insert(index, CacheEntry(keyBlob, valueBlob));
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mTotalSize = newTotalSize;
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ALOGV("set: created new cache entry with %zu byte key and %zu byte value", keySize,
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valueSize);
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} else {
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// Update the existing cache entry.
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std::shared_ptr<Blob> valueBlob(new Blob(value, valueSize, true));
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std::shared_ptr<Blob> oldValueBlob(index->getValue());
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size_t newTotalSize = mTotalSize + valueSize - oldValueBlob->getSize();
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if (mMaxTotalSize < newTotalSize) {
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if (isCleanable()) {
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// Clean the cache and try again.
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clean();
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didClean = true;
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continue;
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} else {
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ALOGV("set: not caching new value because the total cache "
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"size limit would be exceeded: %zu (limit: %zu)",
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keySize + valueSize, mMaxTotalSize);
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return InsertResult::kNotEnoughSpace;
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}
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}
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index->setValue(valueBlob);
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mTotalSize = newTotalSize;
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ALOGV("set: updated existing cache entry with %zu byte key and %zu byte "
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"value",
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keySize, valueSize);
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}
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return didClean ? InsertResult::kDidClean : InsertResult::kInserted;
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}
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}
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size_t BlobCache::get(const void* key, size_t keySize, void* value, size_t valueSize) {
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if (mMaxKeySize < keySize) {
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ALOGV("get: not searching because the key is too large: %zu (limit %zu)", keySize,
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mMaxKeySize);
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return 0;
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}
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std::shared_ptr<Blob> cacheKey(new Blob(key, keySize, false));
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CacheEntry cacheEntry(cacheKey, nullptr);
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auto index = std::lower_bound(mCacheEntries.begin(), mCacheEntries.end(), cacheEntry);
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if (index == mCacheEntries.end() || cacheEntry < *index) {
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ALOGV("get: no cache entry found for key of size %zu", keySize);
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return 0;
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}
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// The key was found. Return the value if the caller's buffer is large
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// enough.
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std::shared_ptr<Blob> valueBlob(index->getValue());
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size_t valueBlobSize = valueBlob->getSize();
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if (valueBlobSize <= valueSize) {
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ALOGV("get: copying %zu bytes to caller's buffer", valueBlobSize);
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memcpy(value, valueBlob->getData(), valueBlobSize);
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} else {
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ALOGV("get: caller's buffer is too small for value: %zu (needs %zu)", valueSize,
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valueBlobSize);
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}
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return valueBlobSize;
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}
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static inline size_t align4(size_t size) {
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return (size + 3) & ~3;
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}
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size_t BlobCache::getFlattenedSize() const {
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auto buildId = base::GetProperty("ro.build.id", "");
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size_t size = align4(sizeof(Header) + buildId.size());
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for (const CacheEntry& e : mCacheEntries) {
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std::shared_ptr<Blob> const& keyBlob = e.getKey();
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std::shared_ptr<Blob> const& valueBlob = e.getValue();
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size += align4(sizeof(EntryHeader) + keyBlob->getSize() + valueBlob->getSize());
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}
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return size;
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}
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int BlobCache::flatten(void* buffer, size_t size) const {
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// Write the cache header
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if (size < sizeof(Header)) {
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ALOGE("flatten: not enough room for cache header");
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return 0;
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}
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Header* header = reinterpret_cast<Header*>(buffer);
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header->mMagicNumber = blobCacheMagic;
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header->mBlobCacheVersion = blobCacheVersion;
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header->mDeviceVersion = blobCacheDeviceVersion;
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header->mNumEntries = mCacheEntries.size();
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auto buildId = base::GetProperty("ro.build.id", "");
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header->mBuildIdLength = buildId.size();
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memcpy(header->mBuildId, buildId.c_str(), header->mBuildIdLength);
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// Write cache entries
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uint8_t* byteBuffer = reinterpret_cast<uint8_t*>(buffer);
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off_t byteOffset = align4(sizeof(Header) + header->mBuildIdLength);
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for (const CacheEntry& e : mCacheEntries) {
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std::shared_ptr<Blob> const& keyBlob = e.getKey();
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std::shared_ptr<Blob> const& valueBlob = e.getValue();
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size_t keySize = keyBlob->getSize();
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size_t valueSize = valueBlob->getSize();
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size_t entrySize = sizeof(EntryHeader) + keySize + valueSize;
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size_t totalSize = align4(entrySize);
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if (byteOffset + totalSize > size) {
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ALOGE("flatten: not enough room for cache entries");
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return -EINVAL;
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}
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EntryHeader* eheader = reinterpret_cast<EntryHeader*>(&byteBuffer[byteOffset]);
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eheader->mKeySize = keySize;
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eheader->mValueSize = valueSize;
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memcpy(eheader->mData, keyBlob->getData(), keySize);
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memcpy(eheader->mData + keySize, valueBlob->getData(), valueSize);
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if (totalSize > entrySize) {
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// We have padding bytes. Those will get written to storage, and contribute to the CRC,
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// so make sure we zero-them to have reproducible results.
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memset(eheader->mData + keySize + valueSize, 0, totalSize - entrySize);
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}
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byteOffset += totalSize;
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}
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return 0;
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}
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int BlobCache::unflatten(void const* buffer, size_t size) {
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// All errors should result in the BlobCache being in an empty state.
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mCacheEntries.clear();
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// Read the cache header
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if (size < sizeof(Header)) {
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ALOGE("unflatten: not enough room for cache header");
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return -EINVAL;
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}
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const Header* header = reinterpret_cast<const Header*>(buffer);
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if (header->mMagicNumber != blobCacheMagic) {
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ALOGE("unflatten: bad magic number: %" PRIu32, header->mMagicNumber);
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return -EINVAL;
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}
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auto buildId = base::GetProperty("ro.build.id", "");
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if (header->mBlobCacheVersion != blobCacheVersion ||
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header->mDeviceVersion != blobCacheDeviceVersion ||
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buildId.size() != header->mBuildIdLength ||
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strncmp(buildId.c_str(), header->mBuildId, buildId.size())) {
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// We treat version mismatches as an empty cache.
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return 0;
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}
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// Read cache entries
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const uint8_t* byteBuffer = reinterpret_cast<const uint8_t*>(buffer);
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off_t byteOffset = align4(sizeof(Header) + header->mBuildIdLength);
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size_t numEntries = header->mNumEntries;
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for (size_t i = 0; i < numEntries; i++) {
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if (byteOffset + sizeof(EntryHeader) > size) {
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mCacheEntries.clear();
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ALOGE("unflatten: not enough room for cache entry headers");
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return -EINVAL;
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}
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const EntryHeader* eheader = reinterpret_cast<const EntryHeader*>(&byteBuffer[byteOffset]);
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size_t keySize = eheader->mKeySize;
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size_t valueSize = eheader->mValueSize;
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size_t entrySize = sizeof(EntryHeader) + keySize + valueSize;
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size_t totalSize = align4(entrySize);
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if (byteOffset + totalSize > size) {
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mCacheEntries.clear();
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ALOGE("unflatten: not enough room for cache entry headers");
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return -EINVAL;
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}
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const uint8_t* data = eheader->mData;
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set(data, keySize, data + keySize, valueSize);
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byteOffset += totalSize;
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}
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return 0;
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}
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long int BlobCache::blob_random() {
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#ifdef _WIN32
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return rand();
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#else
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return nrand48(mRandState);
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#endif
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}
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void BlobCache::clean() {
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// Remove a random cache entry until the total cache size gets below half
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// the maximum total cache size.
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while (mTotalSize > mMaxTotalSize / 2) {
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size_t i = size_t(blob_random() % (mCacheEntries.size()));
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const CacheEntry& entry(mCacheEntries[i]);
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mTotalSize -= entry.getKey()->getSize() + entry.getValue()->getSize();
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mCacheEntries.erase(mCacheEntries.begin() + i);
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}
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}
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bool BlobCache::isCleanable() const {
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return mTotalSize > mMaxTotalSize / 2;
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}
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BlobCache::Blob::Blob(const void* data, size_t size, bool copyData)
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: mData(copyData ? malloc(size) : data), mSize(size), mOwnsData(copyData) {
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if (data != nullptr && copyData) {
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memcpy(const_cast<void*>(mData), data, size);
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}
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}
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BlobCache::Blob::~Blob() {
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if (mOwnsData) {
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free(const_cast<void*>(mData));
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}
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}
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bool BlobCache::Blob::operator<(const Blob& rhs) const {
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if (mSize == rhs.mSize) {
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return memcmp(mData, rhs.mData, mSize) < 0;
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} else {
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return mSize < rhs.mSize;
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}
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}
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const void* BlobCache::Blob::getData() const {
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return mData;
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}
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size_t BlobCache::Blob::getSize() const {
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return mSize;
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}
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BlobCache::CacheEntry::CacheEntry() {}
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BlobCache::CacheEntry::CacheEntry(const std::shared_ptr<Blob>& key,
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const std::shared_ptr<Blob>& value)
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: mKey(key), mValue(value) {}
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BlobCache::CacheEntry::CacheEntry(const CacheEntry& ce) : mKey(ce.mKey), mValue(ce.mValue) {}
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bool BlobCache::CacheEntry::operator<(const CacheEntry& rhs) const {
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return *mKey < *rhs.mKey;
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}
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const BlobCache::CacheEntry& BlobCache::CacheEntry::operator=(const CacheEntry& rhs) {
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mKey = rhs.mKey;
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mValue = rhs.mValue;
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return *this;
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}
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std::shared_ptr<BlobCache::Blob> BlobCache::CacheEntry::getKey() const {
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|
return mKey;
|
||
|
|
}
|
||
|
|
|
||
|
|
std::shared_ptr<BlobCache::Blob> BlobCache::CacheEntry::getValue() const {
|
||
|
|
return mValue;
|
||
|
|
}
|
||
|
|
|
||
|
|
void BlobCache::CacheEntry::setValue(const std::shared_ptr<Blob>& value) {
|
||
|
|
mValue = value;
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace android
|