source/Utility/FileSpec.cpp

//===-- FileSpec.cpp --------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "lldb/Utility/FileSpec.h"
#include "lldb/Utility/RegularExpression.h"
#include "lldb/Utility/Stream.h"
#include "lldb/Utility/TildeExpressionResolver.h"

#include "llvm/ADT/SmallString.h" // for SmallString
#include "llvm/ADT/SmallVector.h" // for SmallVectorTemplat...
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"         // for Triple
#include "llvm/ADT/Twine.h"          // for Twine
#include "llvm/Support/ErrorOr.h"    // for ErrorOr
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/raw_ostream.h" // for raw_ostream, fs

#include <algorithm>    // for replace, min, unique
#include <system_error> // for error_code
#include <vector>       // for vector

#include <assert.h> // for assert
#include <stdio.h>  // for size_t, NULL, snpr...
#include <string.h> // for strcmp

using namespace lldb;
using namespace lldb_private;

namespace {

static constexpr FileSpec::PathSyntax GetNativeSyntax() {
#if defined(_WIN32)
  return FileSpec::ePathSyntaxWindows;
#else
  return FileSpec::ePathSyntaxPosix;
#endif
}

bool PathSyntaxIsPosix(FileSpec::PathSyntax syntax) {
  return (syntax == FileSpec::ePathSyntaxPosix ||
          (syntax == FileSpec::ePathSyntaxHostNative &&
           GetNativeSyntax() == FileSpec::ePathSyntaxPosix));
}

const char *GetPathSeparators(FileSpec::PathSyntax syntax) {
  return PathSyntaxIsPosix(syntax) ? "/" : "\\/";
}

char GetPreferredPathSeparator(FileSpec::PathSyntax syntax) {
  return GetPathSeparators(syntax)[0];
}

bool IsPathSeparator(char value, FileSpec::PathSyntax syntax) {
  return value == '/' || (!PathSyntaxIsPosix(syntax) && value == '\\');
}

inline llvm::sys::path::Style
LLVMPathSyntax(FileSpec::PathSyntax lldb_syntax) {
  switch (lldb_syntax) {
    case FileSpec::ePathSyntaxPosix:
      return llvm::sys::path::Style::posix;
    case FileSpec::ePathSyntaxWindows:
      return llvm::sys::path::Style::windows;
    case FileSpec::ePathSyntaxHostNative:
      return llvm::sys::path::Style::native;
  };
  return llvm::sys::path::Style::native;
}

void Denormalize(llvm::SmallVectorImpl<char> &path,
                 FileSpec::PathSyntax syntax) {
  if (PathSyntaxIsPosix(syntax))
    return;

  std::replace(path.begin(), path.end(), '/', '\\');
}

size_t FilenamePos(llvm::StringRef str, FileSpec::PathSyntax syntax) {
  if (str.size() == 2 && IsPathSeparator(str[0], syntax) && str[0] == str[1])
    return 0;

  if (str.size() > 0 && IsPathSeparator(str.back(), syntax))
    return str.size() - 1;

  size_t pos = str.find_last_of(GetPathSeparators(syntax), str.size() - 1);

  if (!PathSyntaxIsPosix(syntax) && pos == llvm::StringRef::npos)
    pos = str.find_last_of(':', str.size() - 2);

  if (pos == llvm::StringRef::npos ||
      (pos == 1 && IsPathSeparator(str[0], syntax)))
    return 0;

  return pos + 1;
}

size_t RootDirStart(llvm::StringRef str, FileSpec::PathSyntax syntax) {
  // case "c:/"
  if (!PathSyntaxIsPosix(syntax) &&
      (str.size() > 2 && str[1] == ':' && IsPathSeparator(str[2], syntax)))
    return 2;

  // case "//"
  if (str.size() == 2 && IsPathSeparator(str[0], syntax) && str[0] == str[1])
    return llvm::StringRef::npos;

  // case "//net"
  if (str.size() > 3 && IsPathSeparator(str[0], syntax) && str[0] == str[1] &&
      !IsPathSeparator(str[2], syntax))
    return str.find_first_of(GetPathSeparators(syntax), 2);

  // case "/"
  if (str.size() > 0 && IsPathSeparator(str[0], syntax))
    return 0;

  return llvm::StringRef::npos;
}

size_t ParentPathEnd(llvm::StringRef path, FileSpec::PathSyntax syntax) {
  size_t end_pos = FilenamePos(path, syntax);

  bool filename_was_sep =
      path.size() > 0 && IsPathSeparator(path[end_pos], syntax);

  // Skip separators except for root dir.
  size_t root_dir_pos = RootDirStart(path.substr(0, end_pos), syntax);

  while (end_pos > 0 && (end_pos - 1) != root_dir_pos &&
         IsPathSeparator(path[end_pos - 1], syntax))
    --end_pos;

  if (end_pos == 1 && root_dir_pos == 0 && filename_was_sep)
    return llvm::StringRef::npos;

  return end_pos;
}

} // end anonymous namespace

void FileSpec::Resolve(llvm::SmallVectorImpl<char> &path) {
  if (path.empty())
    return;

  llvm::SmallString<32> Source(path.begin(), path.end());
  StandardTildeExpressionResolver Resolver;
  Resolver.ResolveFullPath(Source, path);

  // Save a copy of the original path that's passed in
  llvm::SmallString<128> original_path(path.begin(), path.end());

  llvm::sys::fs::make_absolute(path);
  if (!llvm::sys::fs::exists(path)) {
    path.clear();
    path.append(original_path.begin(), original_path.end());
  }
}

FileSpec::FileSpec() : m_syntax(GetNativeSyntax()) {}

//------------------------------------------------------------------
// Default constructor that can take an optional full path to a file on disk.
//------------------------------------------------------------------
FileSpec::FileSpec(llvm::StringRef path, bool resolve_path, PathSyntax syntax)
    : m_syntax(syntax) {
  SetFile(path, resolve_path, syntax);
}

FileSpec::FileSpec(llvm::StringRef path, bool resolve_path,
                   const llvm::Triple &Triple)
    : FileSpec{path, resolve_path,
               Triple.isOSWindows() ? ePathSyntaxWindows : ePathSyntaxPosix} {}

//------------------------------------------------------------------
// Copy constructor
//------------------------------------------------------------------
FileSpec::FileSpec(const FileSpec &rhs)
    : m_directory(rhs.m_directory), m_filename(rhs.m_filename),
      m_is_resolved(rhs.m_is_resolved), m_syntax(rhs.m_syntax) {}

//------------------------------------------------------------------
// Copy constructor
//------------------------------------------------------------------
FileSpec::FileSpec(const FileSpec *rhs) : m_directory(), m_filename() {
  if (rhs)
    *this = *rhs;
}

//------------------------------------------------------------------
// Virtual destructor in case anyone inherits from this class.
//------------------------------------------------------------------
FileSpec::~FileSpec() {}

namespace {
//------------------------------------------------------------------
/// Safely get a character at the specified index.
///
/// @param[in] path
///     A full, partial, or relative path to a file.
///
/// @param[in] i
///     An index into path which may or may not be valid.
///
/// @return
///   The character at index \a i if the index is valid, or 0 if
///   the index is not valid.
//------------------------------------------------------------------
inline char safeCharAtIndex(const llvm::StringRef &path, size_t i) {
  if (i < path.size())
    return path[i];
  return 0;
}

//------------------------------------------------------------------
/// Check if a path needs to be normalized.
///
/// Check if a path needs to be normalized. We currently consider a
/// path to need normalization if any of the following are true
///  - path contains "/./"
///  - path contains "/../"
///  - path contains "//"
///  - path ends with "/"
/// Paths that start with "./" or with "../" are not considered to
/// need normalization since we aren't trying to resolve the path,
/// we are just trying to remove redundant things from the path.
///
/// @param[in] path
///     A full, partial, or relative path to a file.
///
/// @return
///   Returns \b true if the path needs to be normalized.
//------------------------------------------------------------------
bool needsNormalization(const llvm::StringRef &path) {
  if (path.empty())
    return false;
  // We strip off leading "." values so these paths need to be normalized
  if (path[0] == '.')
    return true;
  for (auto i = path.find_first_of("\\/"); i != llvm::StringRef::npos;
       i = path.find_first_of("\\/", i + 1)) {
    const auto next = safeCharAtIndex(path, i+1);
    switch (next) {
      case 0:
        // path separator char at the end of the string which should be
        // stripped unless it is the one and only character
        return i > 0;
      case '/':
      case '\\':
        // two path separator chars in the middle of a path needs to be
        // normalized
        if (i > 0)
          return true;
        ++i;
        break;

      case '.': {
          const auto next_next = safeCharAtIndex(path, i+2);
          switch (next_next) {
            default: break;
            case 0: return true; // ends with "/."
            case '/':
            case '\\':
              return true; // contains "/./"
            case '.': {
              const auto next_next_next = safeCharAtIndex(path, i+3);
              switch (next_next_next) {
                default: break;
                case 0: return true; // ends with "/.."
                case '/':
                case '\\':
                  return true; // contains "/../"
              }
              break;
            }
          }
        }
        break;

      default:
        break;
    }
  }
  return false;
}


}
//------------------------------------------------------------------
// Assignment operator.
//------------------------------------------------------------------
const FileSpec &FileSpec::operator=(const FileSpec &rhs) {
  if (this != &rhs) {
    m_directory = rhs.m_directory;
    m_filename = rhs.m_filename;
    m_is_resolved = rhs.m_is_resolved;
    m_syntax = rhs.m_syntax;
  }
  return *this;
}

//------------------------------------------------------------------
// Update the contents of this object with a new path. The path will be split
// up into a directory and filename and stored as uniqued string values for
// quick comparison and efficient memory usage.
//------------------------------------------------------------------
void FileSpec::SetFile(llvm::StringRef pathname, bool resolve,
                       PathSyntax syntax) {
  // CLEANUP: Use StringRef for string handling.  This function is kind of a
  // mess and the unclear semantics of RootDirStart and ParentPathEnd make it
  // very difficult to understand this function.  There's no reason this
  // function should be particularly complicated or difficult to understand.
  m_filename.Clear();
  m_directory.Clear();
  m_is_resolved = false;
  m_syntax = (syntax == ePathSyntaxHostNative) ? GetNativeSyntax() : syntax;

  if (pathname.empty())
    return;

  llvm::SmallString<64> resolved(pathname);

  if (resolve) {
    FileSpec::Resolve(resolved);
    m_is_resolved = true;
  }

  // Normalize the path by removing ".", ".." and other redundant components.
  if (needsNormalization(resolved))
    llvm::sys::path::remove_dots(resolved, true, LLVMPathSyntax(m_syntax));

  // Normalize back slashes to forward slashes
  if (m_syntax == FileSpec::ePathSyntaxWindows)
    std::replace(resolved.begin(), resolved.end(), '\\', '/');

  llvm::StringRef resolve_path_ref(resolved.c_str());
  size_t dir_end = ParentPathEnd(resolve_path_ref, m_syntax);
  if (dir_end == 0) {
    m_filename.SetString(resolve_path_ref);
    return;
  }

  m_directory.SetString(resolve_path_ref.substr(0, dir_end));

  size_t filename_begin = dir_end;
  size_t root_dir_start = RootDirStart(resolve_path_ref, m_syntax);
  while (filename_begin != llvm::StringRef::npos &&
         filename_begin < resolve_path_ref.size() &&
         filename_begin != root_dir_start &&
         IsPathSeparator(resolve_path_ref[filename_begin], m_syntax))
    ++filename_begin;
  m_filename.SetString((filename_begin == llvm::StringRef::npos ||
                        filename_begin >= resolve_path_ref.size())
                           ? "."
                           : resolve_path_ref.substr(filename_begin));
}

void FileSpec::SetFile(llvm::StringRef path, bool resolve,
                       const llvm::Triple &Triple) {
  return SetFile(path, resolve,
                 Triple.isOSWindows() ? ePathSyntaxWindows : ePathSyntaxPosix);
}

//----------------------------------------------------------------------
// Convert to pointer operator. This allows code to check any FileSpec objects
// to see if they contain anything valid using code such as:
//
//  if (file_spec)
//  {}
//----------------------------------------------------------------------
FileSpec::operator bool() const { return m_filename || m_directory; }

//----------------------------------------------------------------------
// Logical NOT operator. This allows code to check any FileSpec objects to see
// if they are invalid using code such as:
//
//  if (!file_spec)
//  {}
//----------------------------------------------------------------------
bool FileSpec::operator!() const { return !m_directory && !m_filename; }

bool FileSpec::DirectoryEquals(const FileSpec &rhs) const {
  const bool case_sensitive = IsCaseSensitive() || rhs.IsCaseSensitive();
  return ConstString::Equals(m_directory, rhs.m_directory, case_sensitive);
}

bool FileSpec::FileEquals(const FileSpec &rhs) const {
  const bool case_sensitive = IsCaseSensitive() || rhs.IsCaseSensitive();
  return ConstString::Equals(m_filename, rhs.m_filename, case_sensitive);
}

//------------------------------------------------------------------
// Equal to operator
//------------------------------------------------------------------
bool FileSpec::operator==(const FileSpec &rhs) const {
  if (!FileEquals(rhs))
    return false;
  if (DirectoryEquals(rhs))
    return true;

  // TODO: determine if we want to keep this code in here.
  // The code below was added to handle a case where we were trying to set a
  // file and line breakpoint and one path was resolved, and the other not and
  // the directory was in a mount point that resolved to a more complete path:
  // "/tmp/a.c" == "/private/tmp/a.c". I might end up pulling this out...
  if (IsResolved() && rhs.IsResolved()) {
    // Both paths are resolved, no need to look further...
    return false;
  }

  FileSpec resolved_lhs(*this);

  // If "this" isn't resolved, resolve it
  if (!IsResolved()) {
    if (resolved_lhs.ResolvePath()) {
      // This path wasn't resolved but now it is. Check if the resolved
      // directory is the same as our unresolved directory, and if so, we can
      // mark this object as resolved to avoid more future resolves
      m_is_resolved = (m_directory == resolved_lhs.m_directory);
    } else
      return false;
  }

  FileSpec resolved_rhs(rhs);
  if (!rhs.IsResolved()) {
    if (resolved_rhs.ResolvePath()) {
      // rhs's path wasn't resolved but now it is. Check if the resolved
      // directory is the same as rhs's unresolved directory, and if so, we can
      // mark this object as resolved to avoid more future resolves
      rhs.m_is_resolved = (rhs.m_directory == resolved_rhs.m_directory);
    } else
      return false;
  }

  // If we reach this point in the code we were able to resolve both paths and
  // since we only resolve the paths if the basenames are equal, then we can
  // just check if both directories are equal...
  return DirectoryEquals(rhs);
}

//------------------------------------------------------------------
// Not equal to operator
//------------------------------------------------------------------
bool FileSpec::operator!=(const FileSpec &rhs) const { return !(*this == rhs); }

//------------------------------------------------------------------
// Less than operator
//------------------------------------------------------------------
bool FileSpec::operator<(const FileSpec &rhs) const {
  return FileSpec::Compare(*this, rhs, true) < 0;
}

//------------------------------------------------------------------
// Dump a FileSpec object to a stream
//------------------------------------------------------------------
Stream &lldb_private::operator<<(Stream &s, const FileSpec &f) {
  f.Dump(&s);
  return s;
}

//------------------------------------------------------------------
// Clear this object by releasing both the directory and filename string values
// and making them both the empty string.
//------------------------------------------------------------------
void FileSpec::Clear() {
  m_directory.Clear();
  m_filename.Clear();
}

//------------------------------------------------------------------
// Compare two FileSpec objects. If "full" is true, then both the directory and
// the filename must match. If "full" is false, then the directory names for
// "a" and "b" are only compared if they are both non-empty. This allows a
// FileSpec object to only contain a filename and it can match FileSpec objects
// that have matching filenames with different paths.
//
// Return -1 if the "a" is less than "b", 0 if "a" is equal to "b" and "1" if
// "a" is greater than "b".
//------------------------------------------------------------------
int FileSpec::Compare(const FileSpec &a, const FileSpec &b, bool full) {
  int result = 0;

  // case sensitivity of compare
  const bool case_sensitive = a.IsCaseSensitive() || b.IsCaseSensitive();

  // If full is true, then we must compare both the directory and filename.

  // If full is false, then if either directory is empty, then we match on the
  // basename only, and if both directories have valid values, we still do a
  // full compare. This allows for matching when we just have a filename in one
  // of the FileSpec objects.

  if (full || (a.m_directory && b.m_directory)) {
    result = ConstString::Compare(a.m_directory, b.m_directory, case_sensitive);
    if (result)
      return result;
  }
  return ConstString::Compare(a.m_filename, b.m_filename, case_sensitive);
}

bool FileSpec::Equal(const FileSpec &a, const FileSpec &b, bool full) {

  // case sensitivity of equality test
  const bool case_sensitive = a.IsCaseSensitive() || b.IsCaseSensitive();

  const bool filenames_equal = ConstString::Equals(a.m_filename,
                                                   b.m_filename,
                                                   case_sensitive);

  if (!filenames_equal)
      return false;

  if (!full && (a.GetDirectory().IsEmpty() || b.GetDirectory().IsEmpty()))
    return filenames_equal;

  return a == b;
}

//------------------------------------------------------------------
// Dump the object to the supplied stream. If the object contains a valid
// directory name, it will be displayed followed by a directory delimiter, and
// the filename.
//------------------------------------------------------------------
void FileSpec::Dump(Stream *s) const {
  if (s) {
    std::string path{GetPath(true)};
    s->PutCString(path);
    char path_separator = GetPreferredPathSeparator(m_syntax);
    if (!m_filename && !path.empty() && path.back() != path_separator)
      s->PutChar(path_separator);
  }
}

//------------------------------------------------------------------
// Returns true if the file exists.
//------------------------------------------------------------------
bool FileSpec::Exists() const { return llvm::sys::fs::exists(GetPath()); }

bool FileSpec::Readable() const {
  return GetPermissions() & llvm::sys::fs::perms::all_read;
}

bool FileSpec::ResolveExecutableLocation() {
  // CLEANUP: Use StringRef for string handling.
  if (!m_directory) {
    const char *file_cstr = m_filename.GetCString();
    if (file_cstr) {
      const std::string file_str(file_cstr);
      llvm::ErrorOr<std::string> error_or_path =
          llvm::sys::findProgramByName(file_str);
      if (!error_or_path)
        return false;
      std::string path = error_or_path.get();
      llvm::StringRef dir_ref = llvm::sys::path::parent_path(path);
      if (!dir_ref.empty()) {
        // FindProgramByName returns "." if it can't find the file.
        if (strcmp(".", dir_ref.data()) == 0)
          return false;

        m_directory.SetCString(dir_ref.data());
        if (Exists())
          return true;
        else {
          // If FindProgramByName found the file, it returns the directory +
          // filename in its return results. We need to separate them.
          FileSpec tmp_file(dir_ref.data(), false);
          if (tmp_file.Exists()) {
            m_directory = tmp_file.m_directory;
            return true;
          }
        }
      }
    }
  }

  return false;
}

bool FileSpec::ResolvePath() {
  if (m_is_resolved)
    return true; // We have already resolved this path

  // SetFile(...) will set m_is_resolved correctly if it can resolve the path
  SetFile(GetPath(false), true);
  return m_is_resolved;
}

uint64_t FileSpec::GetByteSize() const {
  uint64_t Size = 0;
  if (llvm::sys::fs::file_size(GetPath(), Size))
    return 0;
  return Size;
}

FileSpec::PathSyntax FileSpec::GetPathSyntax() const { return m_syntax; }

uint32_t FileSpec::GetPermissions() const {
  namespace fs = llvm::sys::fs;
  fs::file_status st;
  if (fs::status(GetPath(), st, false))
    return fs::perms::perms_not_known;

  return st.permissions();
}

//------------------------------------------------------------------
// Directory string get accessor.
//------------------------------------------------------------------
ConstString &FileSpec::GetDirectory() { return m_directory; }

//------------------------------------------------------------------
// Directory string const get accessor.
//------------------------------------------------------------------
const ConstString &FileSpec::GetDirectory() const { return m_directory; }

//------------------------------------------------------------------
// Filename string get accessor.
//------------------------------------------------------------------
ConstString &FileSpec::GetFilename() { return m_filename; }

//------------------------------------------------------------------
// Filename string const get accessor.
//------------------------------------------------------------------
const ConstString &FileSpec::GetFilename() const { return m_filename; }

//------------------------------------------------------------------
// Extract the directory and path into a fixed buffer. This is needed as the
// directory and path are stored in separate string values.
//------------------------------------------------------------------
size_t FileSpec::GetPath(char *path, size_t path_max_len,
                         bool denormalize) const {
  if (!path)
    return 0;

  std::string result = GetPath(denormalize);
  ::snprintf(path, path_max_len, "%s", result.c_str());
  return std::min(path_max_len - 1, result.length());
}

std::string FileSpec::GetPath(bool denormalize) const {
  llvm::SmallString<64> result;
  GetPath(result, denormalize);
  return std::string(result.begin(), result.end());
}

const char *FileSpec::GetCString(bool denormalize) const {
  return ConstString{GetPath(denormalize)}.AsCString(NULL);
}

void FileSpec::GetPath(llvm::SmallVectorImpl<char> &path,
                       bool denormalize) const {
  path.append(m_directory.GetStringRef().begin(),
              m_directory.GetStringRef().end());
  // Since the path was normalized and all paths use '/' when stored in these
  // objects, we don't need to look for the actual syntax specific path
  // separator, we just look for and insert '/'.
  if (m_directory && m_filename && m_directory.GetStringRef().back() != '/' &&
      m_filename.GetStringRef().back() != '/')
    path.insert(path.end(), '/');
  path.append(m_filename.GetStringRef().begin(),
              m_filename.GetStringRef().end());
  if (denormalize && !path.empty())
    Denormalize(path, m_syntax);
}

ConstString FileSpec::GetFileNameExtension() const {
  if (m_filename) {
    const char *filename = m_filename.GetCString();
    const char *dot_pos = strrchr(filename, '.');
    if (dot_pos && dot_pos[1] != '\0')
      return ConstString(dot_pos + 1);
  }
  return ConstString();
}

ConstString FileSpec::GetFileNameStrippingExtension() const {
  const char *filename = m_filename.GetCString();
  if (filename == NULL)
    return ConstString();

  const char *dot_pos = strrchr(filename, '.');
  if (dot_pos == NULL)
    return m_filename;

  return ConstString(filename, dot_pos - filename);
}

//------------------------------------------------------------------
// Return the size in bytes that this object takes in memory. This returns the
// size in bytes of this object, not any shared string values it may refer to.
//------------------------------------------------------------------
size_t FileSpec::MemorySize() const {
  return m_filename.MemorySize() + m_directory.MemorySize();
}

void FileSpec::EnumerateDirectory(llvm::StringRef dir_path,
                                  bool find_directories, bool find_files,
                                  bool find_other,
                                  EnumerateDirectoryCallbackType callback,
                                  void *callback_baton) {
  namespace fs = llvm::sys::fs;
  std::error_code EC;
  fs::recursive_directory_iterator Iter(dir_path, EC);
  fs::recursive_directory_iterator End;
  for (; Iter != End && !EC; Iter.increment(EC)) {
    const auto &Item = *Iter;
    llvm::ErrorOr<fs::basic_file_status> Status = Item.status();
    if (!Status)
      break;
    if (!find_files && fs::is_regular_file(*Status))
      continue;
    if (!find_directories && fs::is_directory(*Status))
      continue;
    if (!find_other && fs::is_other(*Status))
      continue;

    FileSpec Spec(Item.path(), false);
    auto Result = callback(callback_baton, Status->type(), Spec);
    if (Result == eEnumerateDirectoryResultQuit)
      return;
    if (Result == eEnumerateDirectoryResultNext) {
      // Default behavior is to recurse.  Opt out if the callback doesn't want
      // this behavior.
      Iter.no_push();
    }
  }
}

FileSpec
FileSpec::CopyByAppendingPathComponent(llvm::StringRef component) const {
  FileSpec ret = *this;
  ret.AppendPathComponent(component);
  return ret;
}

FileSpec FileSpec::CopyByRemovingLastPathComponent() const {
  // CLEANUP: Use StringRef for string handling.
  const bool resolve = false;
  if (m_filename.IsEmpty() && m_directory.IsEmpty())
    return FileSpec("", resolve);
  if (m_directory.IsEmpty())
    return FileSpec("", resolve);
  if (m_filename.IsEmpty()) {
    const char *dir_cstr = m_directory.GetCString();
    const char *last_slash_ptr = ::strrchr(dir_cstr, '/');

    // check for obvious cases before doing the full thing
    if (!last_slash_ptr)
      return FileSpec("", resolve);
    if (last_slash_ptr == dir_cstr)
      return FileSpec("/", resolve);

    size_t last_slash_pos = last_slash_ptr - dir_cstr + 1;
    ConstString new_path(dir_cstr, last_slash_pos);
    return FileSpec(new_path.GetCString(), resolve);
  } else
    return FileSpec(m_directory.GetCString(), resolve);
}

ConstString FileSpec::GetLastPathComponent() const {
  // CLEANUP: Use StringRef for string handling.
  if (m_filename)
    return m_filename;
  if (m_directory) {
    const char *dir_cstr = m_directory.GetCString();
    const char *last_slash_ptr = ::strrchr(dir_cstr, '/');
    if (last_slash_ptr == NULL)
      return m_directory;
    if (last_slash_ptr == dir_cstr) {
      if (last_slash_ptr[1] == 0)
        return ConstString(last_slash_ptr);
      else
        return ConstString(last_slash_ptr + 1);
    }
    if (last_slash_ptr[1] != 0)
      return ConstString(last_slash_ptr + 1);
    const char *penultimate_slash_ptr = last_slash_ptr;
    while (*penultimate_slash_ptr) {
      --penultimate_slash_ptr;
      if (penultimate_slash_ptr == dir_cstr)
        break;
      if (*penultimate_slash_ptr == '/')
        break;
    }
    ConstString result(penultimate_slash_ptr + 1,
                       last_slash_ptr - penultimate_slash_ptr);
    return result;
  }
  return ConstString();
}

static std::string
join_path_components(FileSpec::PathSyntax syntax,
                     const std::vector<llvm::StringRef> components) {
  std::string result;
  for (size_t i = 0; i < components.size(); ++i) {
    if (components[i].empty())
      continue;
    result += components[i];
    if (i != components.size() - 1 &&
        !IsPathSeparator(components[i].back(), syntax))
      result += GetPreferredPathSeparator(syntax);
  }

  return result;
}

void FileSpec::PrependPathComponent(llvm::StringRef component) {
  if (component.empty())
    return;

  const bool resolve = false;
  if (m_filename.IsEmpty() && m_directory.IsEmpty()) {
    SetFile(component, resolve);
    return;
  }

  std::string result =
      join_path_components(m_syntax, {component, m_directory.GetStringRef(),
                                      m_filename.GetStringRef()});
  SetFile(result, resolve, m_syntax);
}

void FileSpec::PrependPathComponent(const FileSpec &new_path) {
  return PrependPathComponent(new_path.GetPath(false));
}

void FileSpec::AppendPathComponent(llvm::StringRef component) {
  if (component.empty())
    return;

  component = component.drop_while(
      [this](char c) { return IsPathSeparator(c, m_syntax); });

  std::string result =
      join_path_components(m_syntax, {m_directory.GetStringRef(),
                                      m_filename.GetStringRef(), component});

  SetFile(result, false, m_syntax);
}

void FileSpec::AppendPathComponent(const FileSpec &new_path) {
  return AppendPathComponent(new_path.GetPath(false));
}

void FileSpec::RemoveLastPathComponent() {
  // CLEANUP: Use StringRef for string handling.

  const bool resolve = false;
  if (m_filename.IsEmpty() && m_directory.IsEmpty()) {
    SetFile("", resolve);
    return;
  }
  if (m_directory.IsEmpty()) {
    SetFile("", resolve);
    return;
  }
  if (m_filename.IsEmpty()) {
    const char *dir_cstr = m_directory.GetCString();
    const char *last_slash_ptr = ::strrchr(dir_cstr, '/');

    // check for obvious cases before doing the full thing
    if (!last_slash_ptr) {
      SetFile("", resolve);
      return;
    }
    if (last_slash_ptr == dir_cstr) {
      SetFile("/", resolve);
      return;
    }
    size_t last_slash_pos = last_slash_ptr - dir_cstr + 1;
    ConstString new_path(dir_cstr, last_slash_pos);
    SetFile(new_path.GetCString(), resolve);
  } else
    SetFile(m_directory.GetCString(), resolve);
}
//------------------------------------------------------------------
/// Returns true if the filespec represents an implementation source
/// file (files with a ".c", ".cpp", ".m", ".mm" (many more)
/// extension).
///
/// @return
///     \b true if the filespec represents an implementation source
///     file, \b false otherwise.
//------------------------------------------------------------------
bool FileSpec::IsSourceImplementationFile() const {
  ConstString extension(GetFileNameExtension());
  if (!extension)
    return false;

  static RegularExpression g_source_file_regex(llvm::StringRef(
      "^([cC]|[mM]|[mM][mM]|[cC][pP][pP]|[cC]\\+\\+|[cC][xX][xX]|[cC][cC]|["
      "cC][pP]|[sS]|[aA][sS][mM]|[fF]|[fF]77|[fF]90|[fF]95|[fF]03|[fF][oO]["
      "rR]|[fF][tT][nN]|[fF][pP][pP]|[aA][dD][aA]|[aA][dD][bB]|[aA][dD][sS])"
      "$"));
  return g_source_file_regex.Execute(extension.GetStringRef());
}

bool FileSpec::IsRelative() const {
  const char *dir = m_directory.GetCString();
  llvm::StringRef directory(dir ? dir : "");

  if (directory.size() > 0) {
    if (PathSyntaxIsPosix(m_syntax)) {
      // If the path doesn't start with '/' or '~', return true
      switch (directory[0]) {
      case '/':
      case '~':
        return false;
      default:
        return true;
      }
    } else {
      if (directory.size() >= 2 && directory[1] == ':')
        return false;
      if (directory[0] == '/')
        return false;
      return true;
    }
  } else if (m_filename) {
    // No directory, just a basename, return true
    return true;
  }
  return false;
}

bool FileSpec::IsAbsolute() const { return !FileSpec::IsRelative(); }

void llvm::format_provider<FileSpec>::format(const FileSpec &F,
                                             raw_ostream &Stream,
                                             StringRef Style) {
  assert(
      (Style.empty() || Style.equals_lower("F") || Style.equals_lower("D")) &&
      "Invalid FileSpec style!");

  StringRef dir = F.GetDirectory().GetStringRef();
  StringRef file = F.GetFilename().GetStringRef();

  if (dir.empty() && file.empty()) {
    Stream << "(empty)";
    return;
  }

  if (Style.equals_lower("F")) {
    Stream << (file.empty() ? "(empty)" : file);
    return;
  }

  // Style is either D or empty, either way we need to print the directory.
  if (!dir.empty()) {
    // Directory is stored in normalized form, which might be different than
    // preferred form.  In order to handle this, we need to cut off the
    // filename, then denormalize, then write the entire denorm'ed directory.
    llvm::SmallString<64> denormalized_dir = dir;
    Denormalize(denormalized_dir, F.GetPathSyntax());
    Stream << denormalized_dir;
    Stream << GetPreferredPathSeparator(F.GetPathSyntax());
  }

  if (Style.equals_lower("D")) {
    // We only want to print the directory, so now just exit.
    if (dir.empty())
      Stream << "(empty)";
    return;
  }

  if (!file.empty())
    Stream << file;
}