36a5f8ed7f
- Replace raw slice comparison with a call to user comparator.
Added test for custom comparators.
- Fix end of namespace comments.
- Fixed bug in picking inputs for a level-0 compaction.
When finding overlapping files, the covered range may expand
as files are added to the input set. We now correctly expand
the range when this happens instead of continuing to use the
old range. For example, suppose L0 contains files with the
following ranges:
F1: a .. d
F2: c .. g
F3: f .. j
and the initial compaction target is F3. We used to search
for range f..j which yielded {F2,F3}. However we now expand
the range as soon as another file is added. In this case,
when F2 is added, we expand the range to c..j and restart the
search. That picks up file F1 as well.
This change fixes a bug related to deleted keys showing up
incorrectly after a compaction as described in Issue 44.
(Sync with upstream @25072954)
145 lines
4.3 KiB
C++
145 lines
4.3 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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// AtomicPointer provides storage for a lock-free pointer.
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// Platform-dependent implementation of AtomicPointer:
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// - If the platform provides a cheap barrier, we use it with raw pointers
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// - If cstdatomic is present (on newer versions of gcc, it is), we use
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// a cstdatomic-based AtomicPointer. However we prefer the memory
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// barrier based version, because at least on a gcc 4.4 32-bit build
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// on linux, we have encountered a buggy <cstdatomic>
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// implementation. Also, some <cstdatomic> implementations are much
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// slower than a memory-barrier based implementation (~16ns for
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// <cstdatomic> based acquire-load vs. ~1ns for a barrier based
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// acquire-load).
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// This code is based on atomicops-internals-* in Google's perftools:
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// http://code.google.com/p/google-perftools/source/browse/#svn%2Ftrunk%2Fsrc%2Fbase
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#ifndef PORT_ATOMIC_POINTER_H_
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#define PORT_ATOMIC_POINTER_H_
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#include <stdint.h>
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#ifdef LEVELDB_CSTDATOMIC_PRESENT
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#include <cstdatomic>
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#endif
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#ifdef OS_WIN
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#include <windows.h>
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#endif
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#ifdef OS_MACOSX
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#include <libkern/OSAtomic.h>
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#endif
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#if defined(_M_X64) || defined(__x86_64__)
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#define ARCH_CPU_X86_FAMILY 1
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#elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
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#define ARCH_CPU_X86_FAMILY 1
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#elif defined(__ARMEL__)
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#define ARCH_CPU_ARM_FAMILY 1
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#endif
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namespace leveldb {
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namespace port {
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// Define MemoryBarrier() if available
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// Windows on x86
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#if defined(OS_WIN) && defined(COMPILER_MSVC) && defined(ARCH_CPU_X86_FAMILY)
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// windows.h already provides a MemoryBarrier(void) macro
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// http://msdn.microsoft.com/en-us/library/ms684208(v=vs.85).aspx
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#define LEVELDB_HAVE_MEMORY_BARRIER
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// Gcc on x86
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#elif defined(ARCH_CPU_X86_FAMILY) && defined(__GNUC__)
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inline void MemoryBarrier() {
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// See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on
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// this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering.
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__asm__ __volatile__("" : : : "memory");
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}
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#define LEVELDB_HAVE_MEMORY_BARRIER
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// Sun Studio
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#elif defined(ARCH_CPU_X86_FAMILY) && defined(__SUNPRO_CC)
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inline void MemoryBarrier() {
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// See http://gcc.gnu.org/ml/gcc/2003-04/msg01180.html for a discussion on
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// this idiom. Also see http://en.wikipedia.org/wiki/Memory_ordering.
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asm volatile("" : : : "memory");
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}
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#define LEVELDB_HAVE_MEMORY_BARRIER
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// Mac OS
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#elif defined(OS_MACOSX)
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inline void MemoryBarrier() {
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OSMemoryBarrier();
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}
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#define LEVELDB_HAVE_MEMORY_BARRIER
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// ARM
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#elif defined(ARCH_CPU_ARM_FAMILY)
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typedef void (*LinuxKernelMemoryBarrierFunc)(void);
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LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
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(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
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inline void MemoryBarrier() {
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pLinuxKernelMemoryBarrier();
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}
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#define LEVELDB_HAVE_MEMORY_BARRIER
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#endif
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// AtomicPointer built using platform-specific MemoryBarrier()
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#if defined(LEVELDB_HAVE_MEMORY_BARRIER)
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class AtomicPointer {
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private:
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void* rep_;
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public:
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AtomicPointer() { }
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explicit AtomicPointer(void* p) : rep_(p) {}
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inline void* NoBarrier_Load() const { return rep_; }
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inline void NoBarrier_Store(void* v) { rep_ = v; }
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inline void* Acquire_Load() const {
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void* result = rep_;
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MemoryBarrier();
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return result;
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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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};
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// AtomicPointer based on <cstdatomic>
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#elif defined(LEVELDB_CSTDATOMIC_PRESENT)
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class AtomicPointer {
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private:
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std::atomic<void*> rep_;
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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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return rep_.load(std::memory_order_acquire);
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}
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inline void Release_Store(void* v) {
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rep_.store(v, std::memory_order_release);
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}
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inline void* NoBarrier_Load() const {
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return rep_.load(std::memory_order_relaxed);
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}
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inline void NoBarrier_Store(void* v) {
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rep_.store(v, std::memory_order_relaxed);
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}
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};
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// We have neither MemoryBarrier(), nor <cstdatomic>
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#else
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#error Please implement AtomicPointer for this platform.
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#endif
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#undef LEVELDB_HAVE_MEMORY_BARRIER
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#undef ARCH_CPU_X86_FAMILY
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#undef ARCH_CPU_ARM_FAMILY
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} // namespace port
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} // namespace leveldb
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#endif // PORT_ATOMIC_POINTER_H_
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