cache/nnCache/nnCache.cpp

/*
 ** 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.
 */

#include "nnCache.h"

#include <inttypes.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include <thread>

#include <log/log.h>

// Cache file header
static const char* cacheFileMagic = "nn$$";
static const size_t cacheFileHeaderSize = 8;

// The time in seconds to wait before saving newly inserted cache entries.
static const unsigned int deferredSaveDelay = 4;

// ----------------------------------------------------------------------------
namespace android {
// ----------------------------------------------------------------------------

//
// NNCache definition
//
NNCache::NNCache()
    : mInitialized(false),
      mMaxKeySize(0),
      mMaxValueSize(0),
      mMaxTotalSize(0),
      mPolicy(defaultPolicy()),
      mSavePending(false) {}

NNCache::~NNCache() {}

NNCache NNCache::sCache;

NNCache* NNCache::get() {
    return &sCache;
}

void NNCache::initialize(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize,
                         Policy policy) {
    std::lock_guard<std::mutex> lock(mMutex);
    mInitialized = true;
    mMaxKeySize = maxKeySize;
    mMaxValueSize = maxValueSize;
    mMaxTotalSize = maxTotalSize;
    mPolicy = policy;
}

void NNCache::terminate() {
    std::lock_guard<std::mutex> lock(mMutex);
    saveBlobCacheLocked();
    mBlobCache = NULL;
    mInitialized = false;
}

void NNCache::setBlob(const void* key, ssize_t keySize, const void* value, ssize_t valueSize) {
    std::lock_guard<std::mutex> lock(mMutex);

    if (keySize < 0 || valueSize < 0) {
        ALOGW("nnCache::setBlob: negative sizes are not allowed");
        return;
    }

    if (mInitialized) {
        BlobCache* bc = getBlobCacheLocked();
        bc->set(key, keySize, value, valueSize);

        if (!mSavePending) {
            mSavePending = true;
            std::thread deferredSaveThread([this]() {
                sleep(deferredSaveDelay);
                std::lock_guard<std::mutex> lock(mMutex);
                if (mInitialized) {
                    saveBlobCacheLocked();
                }
                mSavePending = false;
            });
            deferredSaveThread.detach();
        }
    }
}

ssize_t NNCache::getBlob(const void* key, ssize_t keySize, void* value, ssize_t valueSize) {
    std::lock_guard<std::mutex> lock(mMutex);

    if (keySize < 0 || valueSize < 0) {
        ALOGW("nnCache::getBlob: negative sizes are not allowed");
        return 0;
    }

    if (mInitialized) {
        BlobCache* bc = getBlobCacheLocked();
        return bc->get(key, keySize, value, valueSize);
    }
    return 0;
}

ssize_t NNCache::getBlob(const void* key, ssize_t keySize, void** value,
                         std::function<void*(size_t)> alloc) {
    std::lock_guard<std::mutex> lock(mMutex);

    if (keySize < 0) {
        ALOGW("nnCache::getBlob: negative sizes are not allowed");
        return 0;
    }

    if (mInitialized) {
        BlobCache* bc = getBlobCacheLocked();
        return bc->get(key, keySize, value, alloc);
    }
    return 0;
}

void NNCache::setCacheFilename(const char* filename) {
    std::lock_guard<std::mutex> lock(mMutex);
    mFilename = filename;
}

BlobCache* NNCache::getBlobCacheLocked() {
    if (mBlobCache == nullptr) {
        mBlobCache.reset(new BlobCache(mMaxKeySize, mMaxValueSize, mMaxTotalSize, mPolicy));
        loadBlobCacheLocked();
    }
    return mBlobCache.get();
}

static uint32_t crc32c(const uint8_t* buf, size_t len) {
    const uint32_t polyBits = 0x82F63B78;
    uint32_t r = 0;
    for (size_t i = 0; i < len; i++) {
        r ^= buf[i];
        for (int j = 0; j < 8; j++) {
            if (r & 1) {
                r = (r >> 1) ^ polyBits;
            } else {
                r >>= 1;
            }
        }
    }
    return r;
}

void NNCache::saveBlobCacheLocked() {
    if (mFilename.length() > 0 && mBlobCache != NULL) {
        size_t cacheSize = mBlobCache->getFlattenedSize();
        size_t headerSize = cacheFileHeaderSize;
        const char* fname = mFilename.c_str();

        // Try to create the file with no permissions so we can write it
        // without anyone trying to read it.
        int fd = open(fname, O_CREAT | O_EXCL | O_RDWR, 0);
        if (fd == -1) {
            if (errno == EEXIST) {
                // The file exists, delete it and try again.
                if (unlink(fname) == -1) {
                    // No point in retrying if the unlink failed.
                    ALOGE("error unlinking cache file %s: %s (%d)", fname, strerror(errno), errno);
                    return;
                }
                // Retry now that we've unlinked the file.
                fd = open(fname, O_CREAT | O_EXCL | O_RDWR, 0);
            }
            if (fd == -1) {
                ALOGE("error creating cache file %s: %s (%d)", fname, strerror(errno), errno);
                return;
            }
        }

        size_t fileSize = headerSize + cacheSize;

        uint8_t* buf = new uint8_t[fileSize];
        if (!buf) {
            ALOGE("error allocating buffer for cache contents: %s (%d)", strerror(errno), errno);
            close(fd);
            unlink(fname);
            return;
        }

        int err = mBlobCache->flatten(buf + headerSize, cacheSize);
        if (err < 0) {
            ALOGE("error writing cache contents: %s (%d)", strerror(-err), -err);
            delete[] buf;
            close(fd);
            unlink(fname);
            return;
        }

        // Write the file magic and CRC
        memcpy(buf, cacheFileMagic, 4);
        uint32_t* crc = reinterpret_cast<uint32_t*>(buf + 4);
        *crc = crc32c(buf + headerSize, cacheSize);

        if (write(fd, buf, fileSize) == -1) {
            ALOGE("error writing cache file: %s (%d)", strerror(errno), errno);
            delete[] buf;
            close(fd);
            unlink(fname);
            return;
        }

        delete[] buf;
        fchmod(fd, S_IRUSR);
        close(fd);
    }
}

void NNCache::loadBlobCacheLocked() {
    if (mFilename.length() > 0) {
        size_t headerSize = cacheFileHeaderSize;

        int fd = open(mFilename.c_str(), O_RDONLY, 0);
        if (fd == -1) {
            if (errno != ENOENT) {
                ALOGE("error opening cache file %s: %s (%d)", mFilename.c_str(), strerror(errno),
                      errno);
            }
            return;
        }

        struct stat statBuf;
        if (fstat(fd, &statBuf) == -1) {
            ALOGE("error stat'ing cache file: %s (%d)", strerror(errno), errno);
            close(fd);
            return;
        }

        // Sanity check the size before trying to mmap it.
        size_t fileSize = statBuf.st_size;
        if (fileSize > mMaxTotalSize * 2) {
            ALOGE("cache file is too large: %#" PRIx64, static_cast<off64_t>(statBuf.st_size));
            close(fd);
            return;
        }

        uint8_t* buf =
                reinterpret_cast<uint8_t*>(mmap(NULL, fileSize, PROT_READ, MAP_PRIVATE, fd, 0));
        if (buf == MAP_FAILED) {
            ALOGE("error mmaping cache file: %s (%d)", strerror(errno), errno);
            close(fd);
            return;
        }

        // Check the file magic and CRC
        size_t cacheSize = fileSize - headerSize;
        if (memcmp(buf, cacheFileMagic, 4) != 0) {
            ALOGE("cache file has bad mojo");
            close(fd);
            return;
        }
        uint32_t* crc = reinterpret_cast<uint32_t*>(buf + 4);
        if (crc32c(buf + headerSize, cacheSize) != *crc) {
            ALOGE("cache file failed CRC check");
            close(fd);
            return;
        }

        int err = mBlobCache->unflatten(buf + headerSize, cacheSize);
        if (err < 0) {
            ALOGE("error reading cache contents: %s (%d)", strerror(-err), -err);
            munmap(buf, fileSize);
            close(fd);
            return;
        }

        munmap(buf, fileSize);
        close(fd);
    }
}

// ----------------------------------------------------------------------------
};  // namespace android
// ----------------------------------------------------------------------------