common/libs/utils/files.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "common/libs/utils/files.h"

#include <android-base/logging.h>

#include <array>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <libgen.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>
#include <vector>

#include "common/libs/fs/shared_fd.h"

namespace cuttlefish {

bool FileExists(const std::string& path) {
  struct stat st;
  return stat(path.c_str(), &st) == 0;
}

bool FileHasContent(const std::string& path) {
  return FileSize(path) > 0;
}

std::vector<std::string> DirectoryContents(const std::string& path) {
  std::vector<std::string> ret;
  std::unique_ptr<DIR, int(*)(DIR*)> dir(opendir(path.c_str()), closedir);
  CHECK(dir != nullptr) << "Could not read from dir \"" << path << "\"";
  if (dir) {
    struct dirent *ent;
    while ((ent = readdir(dir.get()))) {
      ret.push_back(ent->d_name);
    }
  }
  return ret;
}

bool DirectoryExists(const std::string& path) {
  struct stat st;
  if (stat(path.c_str(), &st) == -1) {
    return false;
  }
  if ((st.st_mode & S_IFMT) != S_IFDIR) {
    return false;
  }
  return true;
}

bool IsDirectoryEmpty(const std::string& path) {
  auto direc = ::opendir(path.c_str());
  if (!direc) {
    LOG(ERROR) << "IsDirectoryEmpty test failed with " << path
               << " as it failed to be open" << std::endl;
    return false;
  }

  decltype(::readdir(direc)) sub = nullptr;
  int cnt {0};
  while ( (sub = ::readdir(direc)) ) {
    cnt++;
    if (cnt > 2) {
    LOG(ERROR) << "IsDirectoryEmpty test failed with " << path
               << " as it exists but not empty" << std::endl;
      return false;
    }
  }
  return true;
}

std::string AbsolutePath(const std::string& path) {
  if (path.empty()) {
    return {};
  }
  if (path[0] == '/') {
    return path;
  }
  if (path[0] == '~') {
    LOG(WARNING) << "Tilde expansion in path " << path <<" is not supported";
    return {};
  }

  std::array<char, PATH_MAX> buffer{};
  if (!realpath(".", buffer.data())) {
    LOG(WARNING) << "Could not get real path for current directory \".\""
                 << ": " << strerror(errno);
    return {};
  }
  return std::string{buffer.data()} + "/" + path;
}

off_t FileSize(const std::string& path) {
  struct stat st;
  if (stat(path.c_str(), &st) == -1) {
    return 0;
  }
  return st.st_size;
}

// TODO(schuffelen): Use std::filesystem::last_write_time when on C++17
std::chrono::system_clock::time_point FileModificationTime(const std::string& path) {
  struct stat st;
  if (stat(path.c_str(), &st) == -1) {
    return std::chrono::system_clock::time_point();
  }
  std::chrono::seconds seconds(st.st_mtim.tv_sec);
  return std::chrono::system_clock::time_point(seconds);
}

bool RenameFile(const std::string& old_name, const std::string& new_name) {
  LOG(DEBUG) << "Renaming " << old_name << " to " << new_name;
  if(rename(old_name.c_str(), new_name.c_str())) {
    LOG(ERROR) << "File rename failed due to " << strerror(errno);
    return false;
  }

  return true;
}

bool RemoveFile(const std::string& file) {
  LOG(DEBUG) << "Removing " << file;
  return remove(file.c_str()) == 0;
}


std::string ReadFile(const std::string& file) {
  std::string contents;
  std::ifstream in(file, std::ios::in | std::ios::binary);
  in.seekg(0, std::ios::end);
  contents.resize(in.tellg());
  in.seekg(0, std::ios::beg);
  in.read(&contents[0], contents.size());
  in.close();
  return(contents);
}

std::string CurrentDirectory() {
  char* path = getcwd(nullptr, 0);
  std::string ret(path);
  free(path);
  return ret;
}

FileSizes SparseFileSizes(const std::string& path) {
  auto fd = SharedFD::Open(path, O_RDONLY);
  if (!fd->IsOpen()) {
    LOG(ERROR) << "Could not open \"" << path << "\": " << fd->StrError();
    return {};
  }
  off_t farthest_seek = fd->LSeek(0, SEEK_END);
  LOG(VERBOSE) << "Farthest seek: " << farthest_seek;
  if (farthest_seek == -1) {
    LOG(ERROR) << "Could not lseek in \"" << path << "\": " << fd->StrError();
    return {};
  }
  off_t data_bytes = 0;
  off_t offset = 0;
  while (offset < farthest_seek) {
    off_t new_offset = fd->LSeek(offset, SEEK_HOLE);
    if (new_offset == -1) {
      // ENXIO is returned when there are no more blocks of this type coming.
      if (fd->GetErrno() == ENXIO) {
        break;
      } else {
        LOG(ERROR) << "Could not lseek in \"" << path << "\": " << fd->StrError();
        return {};
      }
    } else {
      data_bytes += new_offset - offset;
      offset = new_offset;
    }
    if (offset >= farthest_seek) {
      break;
    }
    new_offset = fd->LSeek(offset, SEEK_DATA);
    if (new_offset == -1) {
      // ENXIO is returned when there are no more blocks of this type coming.
      if (fd->GetErrno() == ENXIO) {
        break;
      } else {
        LOG(ERROR) << "Could not lseek in \"" << path << "\": " << fd->StrError();
        return {};
      }
    } else {
      offset = new_offset;
    }
  }
  return (FileSizes) { .sparse_size = farthest_seek, .disk_size = data_bytes };
}

std::string cpp_basename(const std::string& str) {
  char* copy = strdup(str.c_str()); // basename may modify its argument
  std::string ret(basename(copy));
  free(copy);
  return ret;
}

std::string cpp_dirname(const std::string& str) {
  char* copy = strdup(str.c_str()); // dirname may modify its argument
  std::string ret(dirname(copy));
  free(copy);
  return ret;
}

}  // namespace cuttlefish