sandboxed-api/sandboxed_api/sandbox2/util/path.cc

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// Copyright 2019 Google LLC. 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 "sandboxed_api/sandbox2/util/path.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/strip.h"
namespace sandbox2 {
namespace file {
namespace internal {
constexpr char kPathSeparator[] = "/";
std::string JoinPathImpl(std::initializer_list<absl::string_view> paths) {
std::string result;
for (const auto& path : paths) {
if (path.empty()) {
continue;
}
if (result.empty()) {
absl::StrAppend(&result, path);
continue;
}
const auto comp = absl::StripPrefix(path, kPathSeparator);
if (absl::EndsWith(result, kPathSeparator)) {
absl::StrAppend(&result, comp);
} else {
absl::StrAppend(&result, kPathSeparator, comp);
}
}
return result;
}
} // namespace internal
bool IsAbsolutePath(absl::string_view path) {
return !path.empty() && path[0] == '/';
}
std::pair<absl::string_view, absl::string_view> SplitPath(
absl::string_view path) {
const auto pos = path.find_last_of('/');
// Handle the case with no '/' in 'path'.
if (pos == absl::string_view::npos) {
return {path.substr(0, 0), path};
}
// Handle the case with a single leading '/' in 'path'.
if (pos == 0) {
return {path.substr(0, 1), absl::ClippedSubstr(path, 1)};
}
return {path.substr(0, pos), absl::ClippedSubstr(path, pos + 1)};
}
std::string CleanPath(const absl::string_view unclean_path) {
auto path = std::string(unclean_path);
const char* src = path.c_str();
std::string::iterator dst = path.begin();
// Check for absolute path and determine initial backtrack limit.
const bool is_absolute_path = *src == '/';
if (is_absolute_path) {
*dst++ = *src++;
while (*src == '/') {
++src;
}
}
std::string::const_iterator backtrack_limit = dst;
// Process all parts
while (*src) {
bool parsed = false;
if (src[0] == '.') {
// 1dot ".<whateverisnext>", check for END or SEP.
if (src[1] == '/' || !src[1]) {
if (*++src) {
++src;
}
parsed = true;
} else if (src[1] == '.' && (src[2] == '/' || !src[2])) {
// 2dot END or SEP (".." | "../<whateverisnext>").
src += 2;
if (dst != backtrack_limit) {
// We can backtrack the previous part
for (--dst; dst != backtrack_limit && dst[-1] != '/'; --dst) {
// Empty.
}
} else if (!is_absolute_path) {
// Failed to backtrack and we can't skip it either. Rewind and copy.
src -= 2;
*dst++ = *src++;
*dst++ = *src++;
if (*src) {
*dst++ = *src;
}
// We can never backtrack over a copied "../" part so set new limit.
backtrack_limit = dst;
}
if (*src) {
++src;
}
parsed = true;
}
}
// If not parsed, copy entire part until the next SEP or EOS.
if (!parsed) {
while (*src && *src != '/') {
*dst++ = *src++;
}
if (*src) {
*dst++ = *src++;
}
}
// Skip consecutive SEP occurrences.
while (*src == '/') {
++src;
}
}
// Calculate and check the length of the cleaned path.
int path_length = dst - path.begin();
if (path_length != 0) {
// Remove trailing '/' except if it is root path ("/" ==> path_length := 1).
if (path_length > 1 && path[path_length - 1] == '/') {
--path_length;
}
path.resize(path_length);
} else {
// The cleaned path is empty; assign "." as per the spec.
path.assign(1, '.');
}
return path;
}
} // namespace file
} // namespace sandbox2