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// 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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#include <sys/types.h>
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#if defined(LEVELDB_PLATFORM_ANDROID)
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#include "leveldb/env.h"
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#include "leveldb/slice.h"
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#include "port/port.h"
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#include "util/logging.h"
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#include "util/posix_logger.h"
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static Status IOError(const std::string& context, int err_number) {
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return Status::IOError(context, strerror(err_number));
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class PosixSequentialFile: public SequentialFile {
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std::string filename_;
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PosixSequentialFile(const std::string& fname, FILE* f)
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: filename_(fname), file_(f) { }
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virtual ~PosixSequentialFile() { fclose(file_); }
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virtual Status Read(size_t n, Slice* result, char* scratch) {
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size_t r = fread_unlocked(scratch, 1, n, file_);
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*result = Slice(scratch, r);
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// We leave status as ok if we hit the end of the file
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// A partial read with an error: return a non-ok status
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s = IOError(filename_, errno);
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virtual Status Skip(uint64_t n) {
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if (fseek(file_, n, SEEK_CUR)) {
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return IOError(filename_, errno);
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class PosixRandomAccessFile: public RandomAccessFile {
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std::string filename_;
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PosixRandomAccessFile(const std::string& fname, int fd)
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: filename_(fname), fd_(fd) { }
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virtual ~PosixRandomAccessFile() { close(fd_); }
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virtual Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const {
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ssize_t r = pread(fd_, scratch, n, static_cast<off_t>(offset));
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*result = Slice(scratch, (r < 0) ? 0 : r);
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// An error: return a non-ok status
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s = IOError(filename_, errno);
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// We preallocate up to an extra megabyte and use memcpy to append new
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// data to the file. This is safe since we either properly close the
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// file before reading from it, or for log files, the reading code
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// knows enough to skip zero suffixes.
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class PosixMmapFile : public WritableFile {
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std::string filename_;
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size_t map_size_; // How much extra memory to map at a time
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char* base_; // The mapped region
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char* limit_; // Limit of the mapped region
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char* dst_; // Where to write next (in range [base_,limit_])
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char* last_sync_; // Where have we synced up to
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uint64_t file_offset_; // Offset of base_ in file
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// Have we done an munmap of unsynced data?
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// Roundup x to a multiple of y
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static size_t Roundup(size_t x, size_t y) {
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return ((x + y - 1) / y) * y;
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size_t TruncateToPageBoundary(size_t s) {
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s -= (s & (page_size_ - 1));
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assert((s % page_size_) == 0);
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bool UnmapCurrentRegion() {
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if (last_sync_ < limit_) {
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// Defer syncing this data until next Sync() call, if any
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pending_sync_ = true;
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if (munmap(base_, limit_ - base_) != 0) {
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file_offset_ += limit_ - base_;
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// Increase the amount we map the next time, but capped at 1MB
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if (map_size_ < (1<<20)) {
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bool MapNewRegion() {
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assert(base_ == NULL);
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if (ftruncate(fd_, file_offset_ + map_size_) < 0) {
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void* ptr = mmap(NULL, map_size_, PROT_READ | PROT_WRITE, MAP_SHARED,
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if (ptr == MAP_FAILED) {
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base_ = reinterpret_cast<char*>(ptr);
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limit_ = base_ + map_size_;
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PosixMmapFile(const std::string& fname, int fd, size_t page_size)
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page_size_(page_size),
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map_size_(Roundup(65536, page_size)),
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pending_sync_(false) {
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assert((page_size & (page_size - 1)) == 0);
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PosixMmapFile::Close();
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virtual Status Append(const Slice& data) {
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const char* src = data.data();
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size_t left = data.size();
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assert(base_ <= dst_);
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assert(dst_ <= limit_);
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size_t avail = limit_ - dst_;
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if (!UnmapCurrentRegion() ||
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return IOError(filename_, errno);
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size_t n = (left <= avail) ? left : avail;
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memcpy(dst_, src, n);
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virtual Status Close() {
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size_t unused = limit_ - dst_;
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if (!UnmapCurrentRegion()) {
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s = IOError(filename_, errno);
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} else if (unused > 0) {
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// Trim the extra space at the end of the file
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if (ftruncate(fd_, file_offset_ - unused) < 0) {
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s = IOError(filename_, errno);
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if (close(fd_) < 0) {
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s = IOError(filename_, errno);
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virtual Status Flush() {
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virtual Status Sync() {
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// Some unmapped data was not synced
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pending_sync_ = false;
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if (fdatasync(fd_) < 0) {
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s = IOError(filename_, errno);
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if (dst_ > last_sync_) {
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// Find the beginnings of the pages that contain the first and last
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// bytes to be synced.
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size_t p1 = TruncateToPageBoundary(last_sync_ - base_);
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size_t p2 = TruncateToPageBoundary(dst_ - base_ - 1);
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if (msync(base_ + p1, p2 - p1 + page_size_, MS_SYNC) < 0) {
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s = IOError(filename_, errno);
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static int LockOrUnlock(int fd, bool lock) {
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memset(&f, 0, sizeof(f));
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f.l_type = (lock ? F_WRLCK : F_UNLCK);
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f.l_whence = SEEK_SET;
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f.l_len = 0; // Lock/unlock entire file
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return fcntl(fd, F_SETLK, &f);
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class PosixFileLock : public FileLock {
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class PosixEnv : public Env {
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virtual ~PosixEnv() {
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fprintf(stderr, "Destroying Env::Default()\n");
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virtual Status NewSequentialFile(const std::string& fname,
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SequentialFile** result) {
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FILE* f = fopen(fname.c_str(), "r");
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return IOError(fname, errno);
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*result = new PosixSequentialFile(fname, f);
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virtual Status NewRandomAccessFile(const std::string& fname,
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RandomAccessFile** result) {
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int fd = open(fname.c_str(), O_RDONLY);
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return IOError(fname, errno);
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*result = new PosixRandomAccessFile(fname, fd);
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virtual Status NewWritableFile(const std::string& fname,
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WritableFile** result) {
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const int fd = open(fname.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
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s = IOError(fname, errno);
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*result = new PosixMmapFile(fname, fd, page_size_);
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virtual bool FileExists(const std::string& fname) {
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return access(fname.c_str(), F_OK) == 0;
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virtual Status GetChildren(const std::string& dir,
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std::vector<std::string>* result) {
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DIR* d = opendir(dir.c_str());
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return IOError(dir, errno);
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struct dirent* entry;
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while ((entry = readdir(d)) != NULL) {
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result->push_back(entry->d_name);
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virtual Status DeleteFile(const std::string& fname) {
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if (unlink(fname.c_str()) != 0) {
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result = IOError(fname, errno);
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virtual Status CreateDir(const std::string& name) {
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if (mkdir(name.c_str(), 0755) != 0) {
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result = IOError(name, errno);
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virtual Status DeleteDir(const std::string& name) {
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if (rmdir(name.c_str()) != 0) {
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result = IOError(name, errno);
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virtual Status GetFileSize(const std::string& fname, uint64_t* size) {
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if (stat(fname.c_str(), &sbuf) != 0) {
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s = IOError(fname, errno);
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*size = sbuf.st_size;
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virtual Status RenameFile(const std::string& src, const std::string& target) {
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if (rename(src.c_str(), target.c_str()) != 0) {
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result = IOError(src, errno);
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virtual Status LockFile(const std::string& fname, FileLock** lock) {
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int fd = open(fname.c_str(), O_RDWR | O_CREAT, 0644);
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result = IOError(fname, errno);
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} else if (LockOrUnlock(fd, true) == -1) {
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result = IOError("lock " + fname, errno);
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PosixFileLock* my_lock = new PosixFileLock;
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virtual Status UnlockFile(FileLock* lock) {
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PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
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if (LockOrUnlock(my_lock->fd_, false) == -1) {
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result = IOError("unlock", errno);
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virtual void Schedule(void (*function)(void*), void* arg);
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virtual void StartThread(void (*function)(void* arg), void* arg);
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virtual Status GetTestDirectory(std::string* result) {
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const char* env = getenv("TEST_TMPDIR");
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if (env && env[0] != '\0') {
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snprintf(buf, sizeof(buf), "/tmp/leveldbtest-%d", int(geteuid()));
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// Directory may already exist
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static uint64_t gettid() {
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pthread_t tid = pthread_self();
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uint64_t thread_id = 0;
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memcpy(&thread_id, &tid, std::min(sizeof(thread_id), sizeof(tid)));
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virtual Status NewLogger(const std::string& fname, Logger** result) {
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FILE* f = fopen(fname.c_str(), "w");
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return IOError(fname, errno);
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*result = new PosixLogger(f, &PosixEnv::gettid);
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virtual uint64_t NowMicros() {
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gettimeofday(&tv, NULL);
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return static_cast<uint64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
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virtual void SleepForMicroseconds(int micros) {
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void PthreadCall(const char* label, int result) {
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fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
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// BGThread() is the body of the background thread
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static void* BGThreadWrapper(void* arg) {
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reinterpret_cast<PosixEnv*>(arg)->BGThread();
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pthread_cond_t bgsignal_;
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bool started_bgthread_;
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// Entry per Schedule() call
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struct BGItem { void* arg; void (*function)(void*); };
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typedef std::deque<BGItem> BGQueue;
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PosixEnv::PosixEnv() : page_size_(getpagesize()),
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started_bgthread_(false) {
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PthreadCall("mutex_init", pthread_mutex_init(&mu_, NULL));
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PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, NULL));
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void PosixEnv::Schedule(void (*function)(void*), void* arg) {
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PthreadCall("lock", pthread_mutex_lock(&mu_));
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// Start background thread if necessary
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if (!started_bgthread_) {
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started_bgthread_ = true;
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pthread_create(&bgthread_, NULL, &PosixEnv::BGThreadWrapper, this));
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// If the queue is currently empty, the background thread may currently be
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if (queue_.empty()) {
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PthreadCall("signal", pthread_cond_signal(&bgsignal_));
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// Add to priority queue
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queue_.push_back(BGItem());
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queue_.back().function = function;
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queue_.back().arg = arg;
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PthreadCall("unlock", pthread_mutex_unlock(&mu_));
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void PosixEnv::BGThread() {
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// Wait until there is an item that is ready to run
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PthreadCall("lock", pthread_mutex_lock(&mu_));
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while (queue_.empty()) {
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PthreadCall("wait", pthread_cond_wait(&bgsignal_, &mu_));
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void (*function)(void*) = queue_.front().function;
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void* arg = queue_.front().arg;
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PthreadCall("unlock", pthread_mutex_unlock(&mu_));
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struct StartThreadState {
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void (*user_function)(void*);
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static void* StartThreadWrapper(void* arg) {
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StartThreadState* state = reinterpret_cast<StartThreadState*>(arg);
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state->user_function(state->arg);
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void PosixEnv::StartThread(void (*function)(void* arg), void* arg) {
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StartThreadState* state = new StartThreadState;
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state->user_function = function;
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PthreadCall("start thread",
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pthread_create(&t, NULL, &StartThreadWrapper, state));
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static pthread_once_t once = PTHREAD_ONCE_INIT;
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static Env* default_env;
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static void InitDefaultEnv() { default_env = new PosixEnv; }
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Env* Env::Default() {
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pthread_once(&once, InitDefaultEnv);
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} // namespace leveldb
added
removed
src/leveldb/util/env_posix.cc
