mapped_file.cc

//
// Copyright RIME Developers
// Distributed under the BSD License
//
// register components
//
// 2011-06-30 GONG Chen <chen.sst@gmail.com>
//
#include <fstream>
#define BOOST_NO_CXX11_SCOPED_ENUMS
#include <boost/filesystem.hpp>
#undef BOOST_NO_CXX11_SCOPED_ENUMS
//#include <boost/filesystem.hpp>
#include <boost/interprocess/file_mapping.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include "mapped_file.h"

#ifdef BOOST_RESIZE_FILE

#define RESIZE_FILE boost::filesystem::resize_file

#else

#ifdef _WIN32
#include <windows.h>
#define RESIZE_FILE(P,SZ) (resize_file_api(P, SZ) != 0)
static BOOL resize_file_api(const char* p, boost::uintmax_t size) {
  HANDLE handle = CreateFileA(p, GENERIC_WRITE, 0, 0, OPEN_EXISTING,
                              FILE_ATTRIBUTE_NORMAL, 0);
  LARGE_INTEGER sz;
  sz.QuadPart = size;
  return handle != INVALID_HANDLE_VALUE
    && ::SetFilePointerEx(handle, sz, 0, FILE_BEGIN)
    && ::SetEndOfFile(handle)
    && ::CloseHandle(handle);
}
#else
#include <unistd.h>
#define RESIZE_FILE(P,SZ) (::truncate(P, SZ) == 0)
#endif  // _WIN32

#endif  // BOOST_RESIZE_FILE

namespace rime {

class MappedFileImpl {
 public:
  enum OpenMode {
    kOpenReadOnly,
    kOpenReadWrite,
  };

  MappedFileImpl(const string& file_name, OpenMode mode) {
    boost::interprocess::mode_t file_mapping_mode =
        (mode == kOpenReadOnly) ? boost::interprocess::read_only
                                : boost::interprocess::read_write;
    file_.reset(new boost::interprocess::file_mapping(file_name.c_str(), file_mapping_mode));
    region_.reset(new boost::interprocess::mapped_region(*file_, file_mapping_mode));
  }
  ~MappedFileImpl() {
    region_.reset();
    file_.reset();
  }
  bool Flush() {
    return region_->flush();
  }
  void* get_address() const {
    return region_->get_address();
  }
  size_t get_size() const {
    return region_->get_size();
  }

 private:
  the<boost::interprocess::file_mapping> file_;
  the<boost::interprocess::mapped_region> region_;

};

MappedFile::MappedFile(const string& file_name)
    : file_name_(file_name) {
}

MappedFile::~MappedFile() {
  if (file_) {
    file_.reset();
  }
}

bool MappedFile::Create(size_t capacity) {
  if (Exists()) {
    LOG(INFO) << "overwriting file '" << file_name_ << "'.";
    Resize(capacity);
  }
  else {
    LOG(INFO) << "creating file '" << file_name_ << "'.";
    std::filebuf fbuf;
    fbuf.open(file_name_.c_str(),
              std::ios_base::in | std::ios_base::out |
              std::ios_base::trunc | std::ios_base::binary);
    if (capacity > 0) {
      fbuf.pubseekoff(capacity - 1, std::ios_base::beg);
      fbuf.sputc(0);
    }
    fbuf.close();
  }
  LOG(INFO) << "opening file for read/write access.";
  file_.reset(new MappedFileImpl(file_name_, MappedFileImpl::kOpenReadWrite));
  size_ = 0;
  return bool(file_);
}

bool MappedFile::OpenReadOnly() {
  if (!Exists()) {
    LOG(ERROR) << "attempt to open non-existent file '" << file_name_ << "'.";
    return false;
  }
  file_.reset(new MappedFileImpl(file_name_, MappedFileImpl::kOpenReadOnly));
  size_ = file_->get_size();
  return bool(file_);
}

bool MappedFile::OpenReadWrite() {
  if (!Exists()) {
    LOG(ERROR) << "attempt to open non-existent file '" << file_name_ << "'.";
    return false;
  }
  file_.reset(new MappedFileImpl(file_name_, MappedFileImpl::kOpenReadWrite));
  size_ = 0;
  return bool(file_);
}

void MappedFile::Close() {
  if (file_) {
    file_.reset();
    size_ = 0;
  }
}

bool MappedFile::Exists() const {
  return boost::filesystem::exists(file_name_);
}

bool MappedFile::IsOpen() const {
  return bool(file_);
}

bool MappedFile::Flush() {
  if (!file_)
    return false;
  return file_->Flush();
}

bool MappedFile::ShrinkToFit() {
  LOG(INFO) << "shrinking file to fit data size. capacity: " << capacity();
  return Resize(size_);
}

bool MappedFile::Remove() {
  if (IsOpen())
    Close();
  return boost::interprocess::file_mapping::remove(file_name_.c_str());
}

bool MappedFile::Resize(size_t capacity) {
  LOG(INFO) << "resize file to: " << capacity;
  if (IsOpen())
    Close();
  try {
    RESIZE_FILE(file_name_.c_str(), capacity);
  }
  catch (...) {
    return false;
  }
  return true;
}

String* MappedFile::CreateString(const string& str) {
  String* ret = Allocate<String>();
  if (ret && !str.empty()) {
    CopyString(str, ret);
  }
  return ret;
}

bool MappedFile::CopyString(const string& src, String* dest) {
  if (!dest)
    return false;
  size_t size = src.length() + 1;
  char* ptr = Allocate<char>(size);
  if (!ptr)
    return false;
  std::strncpy(ptr, src.c_str(), size);
  dest->data = ptr;
  return true;
}

size_t MappedFile::capacity() const {
  return file_->get_size();
}

char* MappedFile::address() const {
  return reinterpret_cast<char*>(file_->get_address());
}

}  // namespace rime