linux.hpp

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#ifndef NDNPH_PORT_FS_LINUX_HPP
#define NDNPH_PORT_FS_LINUX_HPP
 
#include "../../core/common.hpp"
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <sys/stat.h>
#include <unistd.h>
 
namespace ndnph {
namespace port_fs_linux {
namespace detail {
 
class Mkdirp {
public:
  bool create(const char* path) {
    size_t pathLen = strlen(path);
    if (pathLen <= 1 || pathLen >= sizeof(m_path) - 1 || path[pathLen - 1] == '/') {
      return false;
    }
    return createDir(path, 0);
  }
 
private:
  bool createDir(const char* path, int up) {
    const char* dir = toDirname(path, up);
    if (::stat(dir, &m_stat) == 0) {
      return S_ISDIR(m_stat.st_mode);
    } else if (errno == ENOENT) {
      bool ok = createDir(path, up + 1);
      if (!ok) {
        return false;
      }
    }
 
    dir = toDirname(path, up);
    return ::mkdir(dir, 0700) == 0;
  }
 
  const char* toDirname(const char* path, int up) {
    strncpy(m_path, path, sizeof(m_path));
    char* dir = m_path;
    for (int i = 0; i < up; ++i) {
      dir = ::dirname(dir);
    }
    return dir;
  }
 
private:
  char m_path[PATH_MAX];
  struct stat m_stat;
};
 
class FdCloser {
public:
  explicit FdCloser(int fd = -1)
    : m_fd(fd) {}
 
  ~FdCloser() {
    close();
  }
 
  FdCloser& operator=(int fd) {
    if (fd != m_fd) {
      close();
      m_fd = fd;
    }
    return *this;
  }
 
  operator int() const {
    return m_fd;
  }
 
  void close() {
    if (m_fd >= 0) {
      ::close(m_fd);
      m_fd = -1;
    }
  }
 
private:
  int m_fd = -1;
};
 
} // namespace detail
 
class FileStore {
public:
  bool open(const char* path) {
    if (!detail::Mkdirp().create(path)) {
      return false;
    }
 
    m_dfd = ::open(path, O_RDONLY | O_DIRECTORY);
    return m_dfd >= 0;
  }
 
  int read(const char* filename, uint8_t* buffer, size_t count) {
    detail::FdCloser fd(::openat(m_dfd, filename, O_RDONLY));
    if (fd < 0) {
      if (errno == ENOENT) {
        return 0;
      }
      return -errno;
    }
 
    ssize_t nRead = ::read(fd, buffer, count);
    if (nRead < 0) {
      return -errno;
    }
    if (static_cast<size_t>(nRead) == count) {
      return ::lseek(fd, 0, SEEK_END);
    }
    return static_cast<int>(nRead);
  }
 
  bool write(const char* filename, const uint8_t* buffer, size_t count) {
    detail::FdCloser fd(::openat(m_dfd, filename, O_WRONLY | O_CREAT, 0600));
    ssize_t nWrite = ::write(fd, buffer, count);
    return static_cast<size_t>(nWrite) == count;
  }
 
  bool unlink(const char* filename) {
    int res = ::unlinkat(m_dfd, filename, 0);
    return res == 0 || errno == ENOENT;
  }
 
private:
  detail::FdCloser m_dfd;
};
 
} // namespace port_fs_linux
 
#ifdef NDNPH_PORT_FS_LINUX
namespace port {
using FileStore = port_fs_linux::FileStore;
} // namespace port
#endif
 
} // namespace ndnph
 
#endif // NDNPH_PORT_FS_LINUX_HPP