text: // Copyright 2011 Google Inc. All Rights Reserved.
  //
  // 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 "disk_interface.h"
  
  #include <algorithm>
  
  #include <errno.h>
  #include <stdio.h>
  #include <string.h>
  #include <sys/stat.h>
  #include <sys/types.h>
  
  #ifdef _WIN32
  #include <sstream>
  #include <windows.h>
  #include <direct.h>  // _mkdir
  #endif
  
  #include "metrics.h"
  #include "util.h"
  
  namespace {
  
  string DirName(const string& path) {
  #ifdef _WIN32
    static const char kPathSeparators[] = "\\/";
  #else
    static const char kPathSeparators[] = "/";
  #endif
    static const char* const kEnd = kPathSeparators + sizeof(kPathSeparators) - 1;
  
    string::size_type slash_pos = path.find_last_of(kPathSeparators);
    if (slash_pos == string::npos)
      return string();  // Nothing to do.
    while (slash_pos > 0 &&
           std::find(kPathSeparators, kEnd, path[slash_pos - 1]) != kEnd)
      --slash_pos;
    return path.substr(0, slash_pos);
  }
  
  int MakeDir(const string& path) {
  #ifdef _WIN32
    return _mkdir(path.c_str());
  #else
    return mkdir(path.c_str(), 0777);
  #endif
  }
  
  #ifdef _WIN32
  TimeStamp TimeStampFromFileTime(const FILETIME& filetime) {
    // FILETIME is in 100-nanosecond increments since the Windows epoch.
    // We don't much care about epoch correctness but we do want the
    // resulting value to fit in a 64-bit integer.
    uint64_t mtime = ((uint64_t)filetime.dwHighDateTime << 32) |
      ((uint64_t)filetime.dwLowDateTime);
    // 1600 epoch -> 2000 epoch (subtract 400 years).
    return (TimeStamp)mtime - 12622770400LL * (1000000000LL / 100);
  }
  
  TimeStamp StatSingleFile(const string& path, string* err) {
    WIN32_FILE_ATTRIBUTE_DATA attrs;
    if (!GetFileAttributesExA(path.c_str(), GetFileExInfoStandard, &attrs)) {
      DWORD win_err = GetLastError();
      if (win_err == ERROR_FILE_NOT_FOUND || win_err == ERROR_PATH_NOT_FOUND)
        return 0;
      *err = "GetFileAttributesEx(" + path + "): " + GetLastErrorString();
      return -1;
    }
    return TimeStampFromFileTime(attrs.ftLastWriteTime);
  }
  
  bool IsWindows7OrLater() {
    OSVERSIONINFOEX version_info =
        { sizeof(OSVERSIONINFOEX), 6, 1, 0, 0, {0}, 0, 0, 0, 0, 0};
    DWORDLONG comparison = 0;
    VER_SET_CONDITION(comparison, VER_MAJORVERSION, VER_GREATER_EQUAL);
    VER_SET_CONDITION(comparison, VER_MINORVERSION, VER_GREATER_EQUAL);
    return VerifyVersionInfo(
        &version_info, VER_MAJORVERSION | VER_MINORVERSION, comparison);
  }
  
  bool StatAllFilesInDir(const string& dir, map<string, TimeStamp>* stamps,
                         string* err) {
    // FindExInfoBasic is 30% faster than FindExInfoStandard.
    static bool can_use_basic_info = IsWindows7OrLater();
    // This is not in earlier SDKs.
    const FINDEX_INFO_LEVELS kFindExInfoBasic =
        static_cast<FINDEX_INFO_LEVELS>(1);
    FINDEX_INFO_LEVELS level =
        can_use_basic_info ? kFindExInfoBasic : FindExInfoStandard;
    WIN32_FIND_DATAA ffd;
    HANDLE find_handle = FindFirstFileExA((dir + "\\*").c_str(), level, &ffd,
                                          FindExSearchNameMatch, NULL, 0);
  
    if (find_handle == INVALID_HANDLE_VALUE) {
      DWORD win_err = GetLastError();
      if (win_err == ERROR_FILE_NOT_FOUND || win_err == ERROR_PATH_NOT_FOUND)
        return true;
      *err = "FindFirstFileExA(" + dir + "): " + GetLastErrorString();
      return false;
    }
    do {
      string lowername = ffd.cFileName;
      if (lowername == "..") {
        // Seems to just copy the timestamp for ".." from ".", which is wrong.
        // This is the case at least on NTFS under Windows 7.
        continue;
      }
      transform(lowername.begin(), lowername.end(), lowername.begin(), ::tolower);
      stamps->insert(make_pair(lowername,
                               TimeStampFromFileTime(ffd.ftLastWriteTime)));
    } while (FindNextFileA(find_handle, &ffd));
    FindClose(find_handle);
    return true;
  }
  #endif  // _WIN32
  
  }  // namespace
  
  // DiskInterface ---------------------------------------------------------------
  
  bool DiskInterface::MakeDirs(const string& path) {
    string dir = DirName(path);
    if (dir.empty())
      return true;  // Reached root; assume it's there.
    string err;
    TimeStamp mtime = Stat(dir, &err);
    if (mtime < 0) {
      Error("%s", err.c_str());
      return false;
    }
    if (mtime > 0)
      return true;  // Exists already; we're done.
  
    // Directory doesn't exist.  Try creating its parent first.
    bool success = MakeDirs(dir);
    if (!success)
      return false;
    return MakeDir(dir);
  }
  
  // RealDiskInterface -----------------------------------------------------------
  
  TimeStamp RealDiskInterface::Stat(const string& path, string* err) const {
    METRIC_RECORD("node stat");
  #ifdef _WIN32
    // MSDN: "Naming Files, Paths, and Namespaces"
    // http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
    if (!path.empty() && path[0] != '\\' && path.size() > MAX_PATH) {
      ostringstream err_stream;
      err_stream << "Stat(" << path << "): Filename longer than " << MAX_PATH
                 << " characters";
      *err = err_stream.str();
      return -1;
    }
    if (!use_cache_)
      return StatSingleFile(path, err);
  
    string dir = DirName(path);
    string base(path.substr(dir.size() ? dir.size() + 1 : 0));
    if (base == "..") {
      // StatAllFilesInDir does not report any information for base = "..".
      base = ".";
      dir = path;
    }
  
    transform(dir.begin(), dir.end(), dir.begin(), ::tolower);
    transform(base.begin(), base.end(), base.begin(), ::tolower);
  
    Cache::iterator ci = cache_.find(dir);
    if (ci == cache_.end()) {
      ci = cache_.insert(make_pair(dir, DirCache())).first;
      if (!StatAllFilesInDir(dir.empty() ? "." : dir, &ci->second, err)) {
        cache_.erase(ci);
        return -1;
      }
    }
    DirCache::iterator di = ci->second.find(base);
    return di != ci->second.end() ? di->second : 0;
  #else
    struct stat st;
    if (stat(path.c_str(), &st) < 0) {
      if (errno == ENOENT || errno == ENOTDIR)
        return 0;
      *err = "stat(" + path + "): " + strerror(errno);
      return -1;
    }
    // Some users (Flatpak) set mtime to 0, this should be harmless
    // and avoids conflicting with our return value of 0 meaning
    // that it doesn't exist.
    if (st.st_mtime == 0)
      return 1;
  #if defined(__APPLE__) && !defined(_POSIX_C_SOURCE)
    return ((int64_t)st.st_mtimespec.tv_sec * 1000000000LL +
            st.st_mtimespec.tv_nsec);
  #elif (_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700 || defined(_BSD_SOURCE) || defined(_SVID_SOURCE) || \
         defined(__BIONIC__) || (defined (__SVR4) && defined (__sun)) || defined(__FreeBSD__))
    // For glibc, see "Timestamp files" in the Notes of http://www.kernel.org/doc/man-pages/online/pages/man2/stat.2.html
    // newlib, uClibc and musl follow the kernel (or Cygwin) headers and define the right macro values above.
    // For bsd, see https://github.com/freebsd/freebsd/blob/master/sys/sys/stat.h and similar
    // For bionic, C and POSIX API is always enabled.
    // For solaris, see https://docs.oracle.com/cd/E88353_01/html/E37841/stat-2.html.
    return (int64_t)st.st_mtim.tv_sec * 1000000000LL + st.st_mtim.tv_nsec;
  #elif defined(_AIX)
    return (int64_t)st.st_mtime * 1000000000LL + st.st_mtime_n;
  #else
    return (int64_t)st.st_mtime * 1000000000LL + st.st_mtimensec;
  #endif
  #endif
  }
  
  bool RealDiskInterface::WriteFile(const string& path, const string& contents) {
    FILE* fp = fopen(path.c_str(), "w");
    if (fp == NULL) {
      Error("WriteFile(%s): Unable to create file. %s",
            path.c_str(), strerror(errno));
      return false;
    }
  
    if (fwrite(contents.data(), 1, contents.length(), fp) < contents.length())  {
      Error("WriteFile(%s): Unable to write to the file. %s",
            path.c_str(), strerror(errno));
      fclose(fp);
      return false;
    }
  
    if (fclose(fp) == EOF) {
      Error("WriteFile(%s): Unable to close the file. %s",
            path.c_str(), strerror(errno));
      return false;
    }
  
    return true;
  }
  
  bool RealDiskInterface::MakeDir(const string& path) {
    if (::MakeDir(path) < 0) {
      if (errno == EEXIST) {
        return true;
      }
      Error("mkdir(%s): %s", path.c_str(), strerror(errno));
      return false;
    }
    return true;
  }
  
  FileReader::Status RealDiskInterface::ReadFile(const string& path,
                                                 string* contents,
                                                 string* err) {
    switch (::ReadFile(path, contents, err)) {
    case 0:       return Okay;
    case -ENOENT: return NotFound;
    default:      return OtherError;
    }
  }
  
  int RealDiskInterface::RemoveFile(const string& path) {
    if (remove(path.c_str()) < 0) {
      switch (errno) {
        case ENOENT:
          return 1;
        default:
          Error("remove(%s): %s", path.c_str(), strerror(errno));
          return -1;
      }
    } else {
      return 0;
    }
  }
  
  void RealDiskInterface::AllowStatCache(bool allow) {
  #ifdef _WIN32
    use_cache_ = allow;
    if (!use_cache_)
      cache_.clear();
  #endif
  }
  