/* * Copyright (C) 2015 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 "android-base/file.h" #include <errno.h> #include <fcntl.h> #include <libgen.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include <memory> #include <mutex> #include <string> #include <vector> #include "android-base/logging.h" #include "android-base/macros.h" // For TEMP_FAILURE_RETRY on Darwin. #include "android-base/unique_fd.h" #include "android-base/utf8.h" #if defined(__APPLE__) #include <mach-o/dyld.h> #endif #if defined(_WIN32) #include <windows.h> #define O_CLOEXEC O_NOINHERIT #define O_NOFOLLOW 0 #endif namespace android { namespace base { // Versions of standard library APIs that support UTF-8 strings. using namespace android::base::utf8; bool ReadFdToString(int fd, std::string* content) { content->clear(); // Although original we had small files in mind, this code gets used for // very large files too, where the std::string growth heuristics might not // be suitable. https://code.google.com/p/android/issues/detail?id=258500. struct stat sb; if (fstat(fd, &sb) != -1 && sb.st_size > 0) { content->reserve(sb.st_size); } char buf[BUFSIZ]; ssize_t n; while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], sizeof(buf)))) > 0) { content->append(buf, n); } return (n == 0) ? true : false; } bool ReadFileToString(const std::string& path, std::string* content, bool follow_symlinks) { content->clear(); int flags = O_RDONLY | O_CLOEXEC | O_BINARY | (follow_symlinks ? 0 : O_NOFOLLOW); android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), flags))); if (fd == -1) { return false; } return ReadFdToString(fd, content); } bool WriteStringToFd(const std::string& content, int fd) { const char* p = content.data(); size_t left = content.size(); while (left > 0) { ssize_t n = TEMP_FAILURE_RETRY(write(fd, p, left)); if (n == -1) { return false; } p += n; left -= n; } return true; } static bool CleanUpAfterFailedWrite(const std::string& path) { // Something went wrong. Let's not leave a corrupt file lying around. int saved_errno = errno; unlink(path.c_str()); errno = saved_errno; return false; } #if !defined(_WIN32) bool WriteStringToFile(const std::string& content, const std::string& path, mode_t mode, uid_t owner, gid_t group, bool follow_symlinks) { int flags = O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY | (follow_symlinks ? 0 : O_NOFOLLOW); android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), flags, mode))); if (fd == -1) { PLOG(ERROR) << "android::WriteStringToFile open failed"; return false; } // We do an explicit fchmod here because we assume that the caller really // meant what they said and doesn't want the umask-influenced mode. if (fchmod(fd, mode) == -1) { PLOG(ERROR) << "android::WriteStringToFile fchmod failed"; return CleanUpAfterFailedWrite(path); } if (fchown(fd, owner, group) == -1) { PLOG(ERROR) << "android::WriteStringToFile fchown failed"; return CleanUpAfterFailedWrite(path); } if (!WriteStringToFd(content, fd)) { PLOG(ERROR) << "android::WriteStringToFile write failed"; return CleanUpAfterFailedWrite(path); } return true; } #endif bool WriteStringToFile(const std::string& content, const std::string& path, bool follow_symlinks) { int flags = O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY | (follow_symlinks ? 0 : O_NOFOLLOW); android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), flags, 0666))); if (fd == -1) { return false; } return WriteStringToFd(content, fd) || CleanUpAfterFailedWrite(path); } bool ReadFully(int fd, void* data, size_t byte_count) { uint8_t* p = reinterpret_cast<uint8_t*>(data); size_t remaining = byte_count; while (remaining > 0) { ssize_t n = TEMP_FAILURE_RETRY(read(fd, p, remaining)); if (n <= 0) return false; p += n; remaining -= n; } return true; } #if defined(_WIN32) // Windows implementation of pread. Note that this DOES move the file descriptors read position, // but it does so atomically. static ssize_t pread(int fd, void* data, size_t byte_count, off64_t offset) { DWORD bytes_read; OVERLAPPED overlapped; memset(&overlapped, 0, sizeof(OVERLAPPED)); overlapped.Offset = static_cast<DWORD>(offset); overlapped.OffsetHigh = static_cast<DWORD>(offset >> 32); if (!ReadFile(reinterpret_cast<HANDLE>(_get_osfhandle(fd)), data, static_cast<DWORD>(byte_count), &bytes_read, &overlapped)) { // In case someone tries to read errno (since this is masquerading as a POSIX call) errno = EIO; return -1; } return static_cast<ssize_t>(bytes_read); } #endif bool ReadFullyAtOffset(int fd, void* data, size_t byte_count, off64_t offset) { uint8_t* p = reinterpret_cast<uint8_t*>(data); while (byte_count > 0) { ssize_t n = TEMP_FAILURE_RETRY(pread(fd, p, byte_count, offset)); if (n <= 0) return false; p += n; byte_count -= n; offset += n; } return true; } bool WriteFully(int fd, const void* data, size_t byte_count) { const uint8_t* p = reinterpret_cast<const uint8_t*>(data); size_t remaining = byte_count; while (remaining > 0) { ssize_t n = TEMP_FAILURE_RETRY(write(fd, p, remaining)); if (n == -1) return false; p += n; remaining -= n; } return true; } bool RemoveFileIfExists(const std::string& path, std::string* err) { struct stat st; #if defined(_WIN32) //TODO: Windows version can't handle symbol link correctly. int result = stat(path.c_str(), &st); bool file_type_removable = (result == 0 && S_ISREG(st.st_mode)); #else int result = lstat(path.c_str(), &st); bool file_type_removable = (result == 0 && (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode))); #endif if (result == 0) { if (!file_type_removable) { if (err != nullptr) { *err = "is not a regular or symbol link file"; } return false; } if (unlink(path.c_str()) == -1) { if (err != nullptr) { *err = strerror(errno); } return false; } } return true; } #if !defined(_WIN32) bool Readlink(const std::string& path, std::string* result) { result->clear(); // Most Linux file systems (ext2 and ext4, say) limit symbolic links to // 4095 bytes. Since we'll copy out into the string anyway, it doesn't // waste memory to just start there. We add 1 so that we can recognize // whether it actually fit (rather than being truncated to 4095). std::vector<char> buf(4095 + 1); while (true) { ssize_t size = readlink(path.c_str(), &buf[0], buf.size()); // Unrecoverable error? if (size == -1) return false; // It fit! (If size == buf.size(), it may have been truncated.) if (static_cast<size_t>(size) < buf.size()) { result->assign(&buf[0], size); return true; } // Double our buffer and try again. buf.resize(buf.size() * 2); } } #endif #if !defined(_WIN32) bool Realpath(const std::string& path, std::string* result) { result->clear(); char* realpath_buf = realpath(path.c_str(), nullptr); if (realpath_buf == nullptr) { return false; } result->assign(realpath_buf); free(realpath_buf); return true; } #endif std::string GetExecutablePath() { #if defined(__linux__) std::string path; android::base::Readlink("/proc/self/exe", &path); return path; #elif defined(__APPLE__) char path[PATH_MAX + 1]; uint32_t path_len = sizeof(path); int rc = _NSGetExecutablePath(path, &path_len); if (rc < 0) { std::unique_ptr<char> path_buf(new char[path_len]); _NSGetExecutablePath(path_buf.get(), &path_len); return path_buf.get(); } return path; #elif defined(_WIN32) char path[PATH_MAX + 1]; DWORD result = GetModuleFileName(NULL, path, sizeof(path) - 1); if (result == 0 || result == sizeof(path) - 1) return ""; path[PATH_MAX - 1] = 0; return path; #else #error unknown OS #endif } std::string GetExecutableDirectory() { return Dirname(GetExecutablePath()); } std::string Basename(const std::string& path) { // Copy path because basename may modify the string passed in. std::string result(path); #if !defined(__BIONIC__) // Use lock because basename() may write to a process global and return a // pointer to that. Note that this locking strategy only works if all other // callers to basename in the process also grab this same lock, but its // better than nothing. Bionic's basename returns a thread-local buffer. static std::mutex& basename_lock = *new std::mutex(); std::lock_guard<std::mutex> lock(basename_lock); #endif // Note that if std::string uses copy-on-write strings, &str[0] will cause // the copy to be made, so there is no chance of us accidentally writing to // the storage for 'path'. char* name = basename(&result[0]); // In case basename returned a pointer to a process global, copy that string // before leaving the lock. result.assign(name); return result; } std::string Dirname(const std::string& path) { // Copy path because dirname may modify the string passed in. std::string result(path); #if !defined(__BIONIC__) // Use lock because dirname() may write to a process global and return a // pointer to that. Note that this locking strategy only works if all other // callers to dirname in the process also grab this same lock, but its // better than nothing. Bionic's dirname returns a thread-local buffer. static std::mutex& dirname_lock = *new std::mutex(); std::lock_guard<std::mutex> lock(dirname_lock); #endif // Note that if std::string uses copy-on-write strings, &str[0] will cause // the copy to be made, so there is no chance of us accidentally writing to // the storage for 'path'. char* parent = dirname(&result[0]); // In case dirname returned a pointer to a process global, copy that string // before leaving the lock. result.assign(parent); return result; } } // namespace base } // namespace android