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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This is a partial implementation of Chromium's source file
// base/file/file_path.cc.
#include "base/files/file_path.h"
namespace base {
using StringType = FilePath::StringType;
using StringPieceType = FilePath::StringPieceType;
namespace {
const FilePath::CharType kStringTerminator = FILE_PATH_LITERAL('\0');
// If this FilePath contains a drive letter specification, returns the
// position of the last character of the drive letter specification,
// otherwise returns npos. This can only be true on Windows, when a pathname
// begins with a letter followed by a colon. On other platforms, this always
// returns npos.
StringPieceType::size_type FindDriveLetter(StringPieceType path) {
#if defined(FILE_PATH_USES_DRIVE_LETTERS)
// This is dependent on an ASCII-based character set, but that's a
// reasonable assumption. iswalpha can be too inclusive here.
if (path.length() >= 2 && path[1] == L':' &&
((path[0] >= L'A' && path[0] <= L'Z') ||
(path[0] >= L'a' && path[0] <= L'z'))) {
return 1;
}
#endif // FILE_PATH_USES_DRIVE_LETTERS
return StringType::npos;
}
bool IsPathAbsolute(StringPieceType path) {
#if defined(FILE_PATH_USES_DRIVE_LETTERS)
StringType::size_type letter = FindDriveLetter(path);
if (letter != StringType::npos) {
// Look for a separator right after the drive specification.
return path.length() > letter + 1 &&
FilePath::IsSeparator(path[letter + 1]);
}
// Look for a pair of leading separators.
return path.length() > 1 &&
FilePath::IsSeparator(path[0]) && FilePath::IsSeparator(path[1]);
#else // FILE_PATH_USES_DRIVE_LETTERS
// Look for a separator in the first position.
return path.length() > 0 && FilePath::IsSeparator(path[0]);
#endif // FILE_PATH_USES_DRIVE_LETTERS
}
} // namespace
FilePath::FilePath() = default;
FilePath::FilePath(const FilePath& that) = default;
FilePath::FilePath(FilePath&& that) noexcept = default;
FilePath::FilePath(StringPieceType path) : path_(path) {
StringType::size_type nul_pos = path_.find(kStringTerminator);
if (nul_pos != StringType::npos)
path_.erase(nul_pos, StringType::npos);
}
FilePath::~FilePath() = default;
FilePath& FilePath::operator=(const FilePath& that) = default;
FilePath& FilePath::operator=(FilePath&& that) = default;
// static
bool FilePath::IsSeparator(CharType character) {
for (size_t i = 0; i < kSeparatorsLength - 1; ++i) {
if (character == kSeparators[i]) {
return true;
}
}
return false;
}
// libgen's dirname and basename aren't guaranteed to be thread-safe and aren't
// guaranteed to not modify their input strings, and in fact are implemented
// differently in this regard on different platforms. Don't use them, but
// adhere to their behavior.
FilePath FilePath::DirName() const {
FilePath new_path(path_);
new_path.StripTrailingSeparatorsInternal();
// The drive letter, if any, always needs to remain in the output. If there
// is no drive letter, as will always be the case on platforms which do not
// support drive letters, letter will be npos, or -1, so the comparisons and
// resizes below using letter will still be valid.
StringType::size_type letter = FindDriveLetter(new_path.path_);
StringType::size_type last_separator =
new_path.path_.find_last_of(kSeparators, StringType::npos,
kSeparatorsLength - 1);
if (last_separator == StringType::npos) {
// path_ is in the current directory.
new_path.path_.resize(letter + 1);
} else if (last_separator == letter + 1) {
// path_ is in the root directory.
new_path.path_.resize(letter + 2);
} else if (last_separator == letter + 2 &&
IsSeparator(new_path.path_[letter + 1])) {
// path_ is in "//" (possibly with a drive letter); leave the double
// separator intact indicating alternate root.
new_path.path_.resize(letter + 3);
} else if (last_separator != 0) {
// path_ is somewhere else, trim the basename.
new_path.path_.resize(last_separator);
}
new_path.StripTrailingSeparatorsInternal();
if (!new_path.path_.length())
new_path.path_ = kCurrentDirectory;
return new_path;
}
FilePath FilePath::BaseName() const {
FilePath new_path(path_);
new_path.StripTrailingSeparatorsInternal();
// The drive letter, if any, is always stripped.
StringType::size_type letter = FindDriveLetter(new_path.path_);
if (letter != StringType::npos) {
new_path.path_.erase(0, letter + 1);
}
// Keep everything after the final separator, but if the pathname is only
// one character and it's a separator, leave it alone.
StringType::size_type last_separator =
new_path.path_.find_last_of(kSeparators, StringType::npos,
kSeparatorsLength - 1);
if (last_separator != StringType::npos &&
last_separator < new_path.path_.length() - 1) {
new_path.path_.erase(0, last_separator + 1);
}
return new_path;
}
FilePath FilePath::Append(StringPieceType component) const {
StringPieceType appended = component;
StringType without_nuls;
StringType::size_type nul_pos = component.find(kStringTerminator);
if (nul_pos != StringPieceType::npos) {
without_nuls = StringType(component.substr(0, nul_pos));
appended = StringPieceType(without_nuls);
}
DCHECK(!IsPathAbsolute(appended));
if (path_.compare(kCurrentDirectory) == 0 && !appended.empty()) {
// Append normally doesn't do any normalization, but as a special case,
// when appending to kCurrentDirectory, just return a new path for the
// component argument. Appending component to kCurrentDirectory would
// serve no purpose other than needlessly lengthening the path, and
// it's likely in practice to wind up with FilePath objects containing
// only kCurrentDirectory when calling DirName on a single relative path
// component.
return FilePath(appended);
}
FilePath new_path(path_);
new_path.StripTrailingSeparatorsInternal();
// Don't append a separator if the path is empty (indicating the current
// directory) or if the path component is empty (indicating nothing to
// append).
if (!appended.empty() && !new_path.path_.empty()) {
// Don't append a separator if the path still ends with a trailing
// separator after stripping (indicating the root directory).
if (!IsSeparator(new_path.path_.back())) {
// Don't append a separator if the path is just a drive letter.
if (FindDriveLetter(new_path.path_) + 1 != new_path.path_.length()) {
new_path.path_.append(1, kSeparators[0]);
}
}
}
new_path.path_.append(appended.data(), appended.size());
return new_path;
}
FilePath FilePath::Append(const FilePath& component) const {
return Append(component.value());
}
void FilePath::StripTrailingSeparatorsInternal() {
// If there is no drive letter, start will be 1, which will prevent stripping
// the leading separator if there is only one separator. If there is a drive
// letter, start will be set appropriately to prevent stripping the first
// separator following the drive letter, if a separator immediately follows
// the drive letter.
StringType::size_type start = FindDriveLetter(path_) + 2;
StringType::size_type last_stripped = StringType::npos;
for (StringType::size_type pos = path_.length();
pos > start && IsSeparator(path_[pos - 1]);
--pos) {
// If the string only has two separators and they're at the beginning,
// don't strip them, unless the string began with more than two separators.
if (pos != start + 1 || last_stripped == start + 2 ||
!IsSeparator(path_[start - 1])) {
path_.resize(pos - 1);
last_stripped = pos;
}
}
}
} // namespace base