1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
|
/*
** 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 = 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),
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 = 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;
}
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;
if (byteOffset + entrySize > 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);
byteOffset += align4(entrySize);
}
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;
if (byteOffset + entrySize > 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 += align4(entrySize);
}
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
|