85584d497e
In particular, we add a new FilterPolicy class. An instance of this class can be supplied in Options when opening a database. If supplied, the instance is used to generate summaries of keys (e.g., a bloom filter) which are placed in sstables. These summaries are consulted by DB::Get() so we can avoid reading sstable blocks that are guaranteed to not contain the key we are looking for. This change provides one implementation of FilterPolicy based on bloom filters. Other changes: - Updated version number to 1.4. - Some build tweaks. - C binding for CompactRange. - A few more benchmarks: deleteseq, deleterandom, readmissing, seekrandom. - Minor .gitignore update.
160 lines
3.8 KiB
C++
160 lines
3.8 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// See port_example.h for documentation for the following types/functions.
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#ifndef STORAGE_LEVELDB_PORT_PORT_ANDROID_H_
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#define STORAGE_LEVELDB_PORT_PORT_ANDROID_H_
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#include <endian.h>
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#include <pthread.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <string>
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#include <cctype>
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// Collapse the plethora of ARM flavors available to an easier to manage set
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// Defs reference is at https://wiki.edubuntu.org/ARM/Thumb2PortingHowto
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#if defined(__ARM_ARCH_6__) || \
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defined(__ARM_ARCH_6J__) || \
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defined(__ARM_ARCH_6K__) || \
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defined(__ARM_ARCH_6Z__) || \
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defined(__ARM_ARCH_6T2__) || \
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defined(__ARM_ARCH_6ZK__) || \
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defined(__ARM_ARCH_7__) || \
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defined(__ARM_ARCH_7R__) || \
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defined(__ARM_ARCH_7A__)
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#define ARMV6_OR_7 1
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#endif
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extern "C" {
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size_t fread_unlocked(void *a, size_t b, size_t c, FILE *d);
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size_t fwrite_unlocked(const void *a, size_t b, size_t c, FILE *d);
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int fflush_unlocked(FILE *f);
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int fdatasync (int fd);
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}
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namespace leveldb {
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namespace port {
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static const bool kLittleEndian = __BYTE_ORDER == __LITTLE_ENDIAN;
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class CondVar;
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class Mutex {
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public:
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Mutex();
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~Mutex();
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void Lock();
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void Unlock();
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void AssertHeld() {
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//TODO(gabor): How can I implement this?
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}
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private:
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friend class CondVar;
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pthread_mutex_t mu_;
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// No copying
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Mutex(const Mutex&);
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void operator=(const Mutex&);
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};
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class CondVar {
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public:
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explicit CondVar(Mutex* mu);
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~CondVar();
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void Wait();
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void Signal();
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void SignalAll();
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private:
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Mutex* mu_;
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pthread_cond_t cv_;
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};
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#ifndef ARMV6_OR_7
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// On ARM chipsets <V6, 0xffff0fa0 is the hard coded address of a
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// memory barrier function provided by the kernel.
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typedef void (*LinuxKernelMemoryBarrierFunc)(void);
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// TODO(user): ATTRIBUTE_WEAK is undefined, so this fails to build on
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// non-ARMV6_OR_7. We may be able to replace it with __attribute__((weak)) for
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// older ARM builds, but x86 builds will require a different memory barrier.
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LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier ATTRIBUTE_WEAK =
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(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
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#endif
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// Storage for a lock-free pointer
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class AtomicPointer {
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private:
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void* rep_;
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inline void MemoryBarrier() const {
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// TODO(gabor): This only works on Android instruction sets >= V6
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#ifdef ARMV6_OR_7
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__asm__ __volatile__("dmb" : : : "memory");
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#else
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pLinuxKernelMemoryBarrier();
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#endif
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}
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public:
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AtomicPointer() { }
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explicit AtomicPointer(void* v) : rep_(v) { }
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inline void* Acquire_Load() const {
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void* r = rep_;
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MemoryBarrier();
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return r;
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}
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inline void Release_Store(void* v) {
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MemoryBarrier();
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rep_ = v;
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}
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inline void* NoBarrier_Load() const {
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void* r = rep_;
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return r;
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}
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inline void NoBarrier_Store(void* v) {
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rep_ = v;
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}
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};
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// TODO(gabor): Implement compress
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inline bool Snappy_Compress(
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const char* input,
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size_t input_length,
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std::string* output) {
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return false;
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}
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// TODO(gabor): Implement uncompress
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inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
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size_t* result) {
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return false;
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}
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// TODO(gabor): Implement uncompress
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inline bool Snappy_Uncompress(
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const char* input_data,
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size_t input_length,
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char* output) {
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return false;
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}
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inline uint64_t ThreadIdentifier() {
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pthread_t tid = pthread_self();
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uint64_t r = 0;
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memcpy(&r, &tid, sizeof(r) < sizeof(tid) ? sizeof(r) : sizeof(tid));
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return r;
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}
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inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
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return false;
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}
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} // namespace port
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_PORT_PORT_ANDROID_H_
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