/*
** 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 <inttypes.h>
#include <stdlib.h>
#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 = ('_' << 24) + ('B' << 16) + ('b' << 8) + '$';
// BlobCache::Header::mBlobCacheVersion value
static const uint32_t blobCacheVersion = 2;
// 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),
mMaxTotalSize(maxTotalSize),
mTotalSize(0) {
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
#ifdef _WIN32
srand(now);
#else
mRandState[0] = (now >> 0) & 0xFFFF;
mRandState[1] = (now >> 16) & 0xFFFF;
mRandState[2] = (now >> 32) & 0xFFFF;
#endif
ALOGV("initializing random seed using %lld", (unsigned long long)now);
}
void BlobCache::set(const void* key, size_t keySize, const void* value,
size_t valueSize) {
if (mMaxKeySize < keySize) {
ALOGV("set: not caching because the key is too large: %zu (limit: %zu)",
keySize, mMaxKeySize);
return;
}
if (mMaxValueSize < valueSize) {
ALOGV("set: not caching because the value is too large: %zu (limit: %zu)",
valueSize, mMaxValueSize);
return;
}
if (mMaxTotalSize < keySize + valueSize) {
ALOGV("set: not caching because the combined key/value size is too "
"large: %zu (limit: %zu)", keySize + valueSize, mMaxTotalSize);
return;
}
if (keySize == 0) {
ALOGW("set: not caching because keySize is 0");
return;
}
if (valueSize <= 0) {
ALOGW("set: not caching because valueSize is 0");
return;
}
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 {
ALOGV("set: not caching new key/value pair because the "
"total cache size limit would be exceeded: %zu "
"(limit: %zu)",
keySize + valueSize, mMaxTotalSize);
break;
}
}
mCacheEntries.add(CacheEntry(keyBlob, valueBlob));
mTotalSize = newTotalSize;
ALOGV("set: created new cache entry with %zu byte key and %zu 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 {
ALOGV("set: not caching new value because the total cache "
"size limit would be exceeded: %zu (limit: %zu)",
keySize + valueSize, mMaxTotalSize);
break;
}
}
mCacheEntries.editItemAt(index).setValue(valueBlob);
mTotalSize = newTotalSize;
ALOGV("set: updated existing cache entry with %zu byte key and %zu byte "
"value", keySize, valueSize);
}
break;
}
}
size_t BlobCache::get(const void* key, size_t keySize, void* value,
size_t valueSize) {
if (mMaxKeySize < keySize) {
ALOGV("get: not searching because the key is too large: %zu (limit %zu)",
keySize, mMaxKeySize);
return 0;
}
sp<Blob> dummyKey(new Blob(key, keySize, false));
CacheEntry dummyEntry(dummyKey, NULL);
ssize_t index = mCacheEntries.indexOf(dummyEntry);
if (index < 0) {
ALOGV("get: no cache entry found for key of size %zu", 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) {
ALOGV("get: copying %zu bytes to caller's buffer", valueBlobSize);
memcpy(value, valueBlob->getData(), valueBlobSize);
} else {
ALOGV("get: caller's buffer is too small for value: %zu (needs %zu)",
valueSize, valueBlobSize);
}
return valueBlobSize;
}
static inline size_t align4(size_t size) {
return (size + 3) & ~3;
}
size_t BlobCache::getFlattenedSize() const {
size_t size = 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 += align4(sizeof(EntryHeader) + keyBlob->getSize() +
valueBlob->getSize());
}
return size;
}
status_t BlobCache::flatten(void* buffer, size_t size) const {
// Write the cache header
if (size < sizeof(Header)) {
ALOGE("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;
size_t totalSize = align4(entrySize);
if (byteOffset + totalSize > size) {
ALOGE("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);
if (totalSize > entrySize) {
// We have padding bytes. Those will get written to storage, and contribute to the CRC,
// so make sure we zero-them to have reproducible results.
memset(eheader->mData + keySize + valueSize, 0, totalSize - entrySize);
}
byteOffset += totalSize;
}
return OK;
}
status_t BlobCache::unflatten(void const* buffer, size_t size) {
// All errors should result in the BlobCache being in an empty state.
mCacheEntries.clear();
// Read the cache header
if (size < sizeof(Header)) {
ALOGE("unflatten: not enough room for cache header");
return BAD_VALUE;
}
const Header* header = reinterpret_cast<const Header*>(buffer);
if (header->mMagicNumber != blobCacheMagic) {
ALOGE("unflatten: bad magic number: %" PRIu32, 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();
ALOGE("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;
size_t totalSize = align4(entrySize);
if (byteOffset + totalSize > size) {
mCacheEntries.clear();
ALOGE("unflatten: not enough room for cache entry headers");
return BAD_VALUE;
}
const uint8_t* data = eheader->mData;
set(data, keySize, data + keySize, valueSize);
byteOffset += totalSize;
}
return OK;
}
long int BlobCache::blob_random() {
#ifdef _WIN32
return rand();
#else
return nrand48(mRandState);
#endif
}
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(blob_random() % (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 (data != NULL && 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