Fixed a snappy compression wrapper bug (passing wrong variable).
Change atomic_pointer.h to prefer a memory barrier based
implementation over a <cstdatomic> based implementation for
the following reasons:
(1) On a x86-32-bit gcc-4.4 build, <ctdatomic> was corrupting
the AtomicPointer.
(2) On a x86-64-bit gcc build, a <ctstdatomic> based acquire-load
takes ~15ns as opposed to the ~1ns for a memory-barrier
based implementation.
Fixes issue 9 (corruption_test fails)
http://code.google.com/p/leveldb/issues/detail?id=9
Fixes issue 16 (CorruptionTest.MissingDescriptor fails)
http://code.google.com/p/leveldb/issues/detail?id=16
git-svn-id: https://leveldb.googlecode.com/svn/trunk@36 62dab493-f737-651d-591e-8d6aee1b9529
This commit is contained in:
gabor@google.com
parent
85f0ab1975
commit
ed154f6dc4
@ -4,30 +4,101 @@
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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
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// - If it is not, we define processor-dependent AtomicWord operations,
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// and then use them to build AtomicPointer
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//
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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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#ifdef LEVELDB_CSTDATOMIC_PRESENT
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///////////////////////////////////////////////////////////////////////////////
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// WE HAVE <cstdatomic>
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// Use a <cstdatomic>-based AtomicPointer
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#include <cstdatomic>
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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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// Storage for a lock-free pointer
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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(__GNUC__) && defined(ARCH_CPU_X86_FAMILY)
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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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@ -48,166 +119,17 @@ class AtomicPointer {
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}
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};
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} // namespace leveldb::port
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} // namespace leveldb
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// We have neither MemoryBarrier(), nor <cstdatomic>
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#else
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///////////////////////////////////////////////////////////////////////////////
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// NO <cstdatomic>
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// The entire rest of this file covers that case
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#error Please implement AtomicPointer for this platform.
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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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#else
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#warning Please add support for your architecture in atomicpointer.h
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#endif
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namespace leveldb {
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namespace port {
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namespace internal {
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// AtomicWord is a machine-sized pointer.
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typedef intptr_t AtomicWord;
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} // namespace leveldb::port::internal
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} // namespace leveldb::port
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} // namespace leveldb
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// Include our platform specific implementation.
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///////////////////////////////////////////////////////////////////////////////
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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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// void MemoryBarrier(void) macro is defined in windows.h:
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// http://msdn.microsoft.com/en-us/library/ms684208(v=vs.85).aspx
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// Including windows.h here; MemoryBarrier() gets used below.
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#include <windows.h>
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///////////////////////////////////////////////////////////////////////////////
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// Mac OS on x86
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#elif defined(OS_MACOSX) && defined(ARCH_CPU_X86_FAMILY)
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#include <libkern/OSAtomic.h>
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namespace leveldb {
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namespace port {
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namespace internal {
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inline void MemoryBarrier() {
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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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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#else
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OSMemoryBarrier();
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#endif
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}
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} // namespace leveldb::port::internal
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} // namespace leveldb::port
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} // namespace leveldb
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///////////////////////////////////////////////////////////////////////////////
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// Any x86 CPU
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#elif defined(ARCH_CPU_X86_FAMILY)
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namespace leveldb {
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namespace port {
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namespace internal {
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inline void MemoryBarrier() {
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__asm__ __volatile__("" : : : "memory");
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}
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} // namespace leveldb::port::internal
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} // namespace leveldb::port
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} // namespace leveldb
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#undef ATOMICOPS_COMPILER_BARRIER
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///////////////////////////////////////////////////////////////////////////////
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// ARM
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#elif defined(ARCH_CPU_ARM_FAMILY)
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namespace leveldb {
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namespace port {
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namespace internal {
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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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} // namespace leveldb::port::internal
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} // namespace leveldb::port
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} // namespace leveldb
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#else
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#error "Atomic operations are not supported on your platform"
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#endif
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///////////////////////////////////////////////////////////////////////////////
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// Implementation of AtomicPointer based on MemoryBarriers above
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namespace leveldb {
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namespace port {
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namespace internal {
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// Atomic operations using per-system MemoryBarrier()s
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inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {
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AtomicWord value = *ptr;
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MemoryBarrier();
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return value;
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}
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inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {
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MemoryBarrier();
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*ptr = value;
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}
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inline AtomicWord NoBarrier_Load(volatile const AtomicWord* ptr) {
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return *ptr;
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}
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inline void NoBarrier_Store(volatile AtomicWord* ptr, AtomicWord value) {
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*ptr = value;
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}
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} // namespace leveldb::port::internal
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// AtomicPointer definition for systems without <cstdatomic>.
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class AtomicPointer {
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private:
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typedef internal::AtomicWord Rep;
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Rep rep_;
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public:
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AtomicPointer() { }
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explicit AtomicPointer(void* p) : rep_(reinterpret_cast<Rep>(p)) {}
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inline void* Acquire_Load() const {
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return reinterpret_cast<void*>(internal::Acquire_Load(&rep_));
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}
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inline void Release_Store(void* v) {
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internal::Release_Store(&rep_, reinterpret_cast<Rep>(v));
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}
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inline void* NoBarrier_Load() const {
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return reinterpret_cast<void*>(internal::NoBarrier_Load(&rep_));
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}
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inline void NoBarrier_Store(void* v) {
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internal::NoBarrier_Store(&rep_, reinterpret_cast<Rep>(v));
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}
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};
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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 leveldb::port
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} // namespace leveldb
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#endif // LEVELDB_CSTDATOMIC_PRESENT
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#endif // PORT_ATOMIC_POINTER_H_
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@ -97,7 +97,7 @@ inline bool Snappy_Uncompress(const char* input_data, size_t input_length,
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::std::string* output) {
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#ifdef SNAPPY
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size_t ulength;
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if (!snappy::GetUncompressedLength(input_data, ulength, &ulength)) {
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if (!snappy::GetUncompressedLength(input_data, input_length, &ulength)) {
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return false;
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}
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output->resize(ulength);
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