319 lines
9.3 KiB
C++
319 lines
9.3 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "android-base/file.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <libgen.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <memory>
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#include <mutex>
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#include <string>
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#include <vector>
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#include "android-base/macros.h" // For TEMP_FAILURE_RETRY on Darwin.
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#include "android-base/logging.h"
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#include "android-base/utf8.h"
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#include "utils/Compat.h"
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#if defined(__APPLE__)
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#include <mach-o/dyld.h>
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#endif
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#if defined(_WIN32)
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#include <windows.h>
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#endif
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namespace android {
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namespace base {
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// Versions of standard library APIs that support UTF-8 strings.
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using namespace android::base::utf8;
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bool ReadFdToString(int fd, std::string* content) {
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content->clear();
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// Although original we had small files in mind, this code gets used for
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// very large files too, where the std::string growth heuristics might not
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// be suitable. https://code.google.com/p/android/issues/detail?id=258500.
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struct stat sb;
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if (fstat(fd, &sb) != -1 && sb.st_size > 0) {
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content->reserve(sb.st_size);
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}
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char buf[BUFSIZ];
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ssize_t n;
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while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], sizeof(buf)))) > 0) {
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content->append(buf, n);
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}
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return (n == 0) ? true : false;
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}
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bool ReadFileToString(const std::string& path, std::string* content, bool follow_symlinks) {
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content->clear();
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int flags = O_RDONLY | O_CLOEXEC | O_BINARY | (follow_symlinks ? 0 : O_NOFOLLOW);
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int fd = TEMP_FAILURE_RETRY(open(path.c_str(), flags));
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if (fd == -1) {
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return false;
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}
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bool result = ReadFdToString(fd, content);
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close(fd);
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return result;
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}
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bool WriteStringToFd(const std::string& content, int fd) {
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const char* p = content.data();
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size_t left = content.size();
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while (left > 0) {
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ssize_t n = TEMP_FAILURE_RETRY(write(fd, p, left));
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if (n == -1) {
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return false;
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}
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p += n;
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left -= n;
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}
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return true;
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}
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static bool CleanUpAfterFailedWrite(const std::string& path) {
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// Something went wrong. Let's not leave a corrupt file lying around.
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int saved_errno = errno;
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unlink(path.c_str());
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errno = saved_errno;
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return false;
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}
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#if !defined(_WIN32)
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bool WriteStringToFile(const std::string& content, const std::string& path,
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mode_t mode, uid_t owner, gid_t group,
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bool follow_symlinks) {
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int flags = O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY |
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(follow_symlinks ? 0 : O_NOFOLLOW);
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int fd = TEMP_FAILURE_RETRY(open(path.c_str(), flags, mode));
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if (fd == -1) {
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PLOG(ERROR) << "android::WriteStringToFile open failed";
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return false;
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}
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// We do an explicit fchmod here because we assume that the caller really
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// meant what they said and doesn't want the umask-influenced mode.
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if (fchmod(fd, mode) == -1) {
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PLOG(ERROR) << "android::WriteStringToFile fchmod failed";
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return CleanUpAfterFailedWrite(path);
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}
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if (fchown(fd, owner, group) == -1) {
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PLOG(ERROR) << "android::WriteStringToFile fchown failed";
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return CleanUpAfterFailedWrite(path);
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}
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if (!WriteStringToFd(content, fd)) {
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PLOG(ERROR) << "android::WriteStringToFile write failed";
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return CleanUpAfterFailedWrite(path);
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}
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close(fd);
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return true;
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}
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#endif
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bool WriteStringToFile(const std::string& content, const std::string& path,
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bool follow_symlinks) {
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int flags = O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY |
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(follow_symlinks ? 0 : O_NOFOLLOW);
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int fd = TEMP_FAILURE_RETRY(open(path.c_str(), flags, DEFFILEMODE));
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if (fd == -1) {
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return false;
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}
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bool result = WriteStringToFd(content, fd);
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close(fd);
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return result || CleanUpAfterFailedWrite(path);
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}
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bool ReadFully(int fd, void* data, size_t byte_count) {
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uint8_t* p = reinterpret_cast<uint8_t*>(data);
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size_t remaining = byte_count;
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while (remaining > 0) {
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ssize_t n = TEMP_FAILURE_RETRY(read(fd, p, remaining));
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if (n <= 0) return false;
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p += n;
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remaining -= n;
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}
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return true;
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}
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bool WriteFully(int fd, const void* data, size_t byte_count) {
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const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
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size_t remaining = byte_count;
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while (remaining > 0) {
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ssize_t n = TEMP_FAILURE_RETRY(write(fd, p, remaining));
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if (n == -1) return false;
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p += n;
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remaining -= n;
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}
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return true;
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}
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bool RemoveFileIfExists(const std::string& path, std::string* err) {
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struct stat st;
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#if defined(_WIN32)
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//TODO: Windows version can't handle symbol link correctly.
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int result = stat(path.c_str(), &st);
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bool file_type_removable = (result == 0 && S_ISREG(st.st_mode));
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#else
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int result = lstat(path.c_str(), &st);
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bool file_type_removable = (result == 0 && (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)));
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#endif
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if (result == 0) {
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if (!file_type_removable) {
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if (err != nullptr) {
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*err = "is not a regular or symbol link file";
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}
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return false;
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}
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if (unlink(path.c_str()) == -1) {
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if (err != nullptr) {
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*err = strerror(errno);
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}
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return false;
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}
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}
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return true;
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}
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#if !defined(_WIN32)
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bool Readlink(const std::string& path, std::string* result) {
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result->clear();
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// Most Linux file systems (ext2 and ext4, say) limit symbolic links to
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// 4095 bytes. Since we'll copy out into the string anyway, it doesn't
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// waste memory to just start there. We add 1 so that we can recognize
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// whether it actually fit (rather than being truncated to 4095).
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std::vector<char> buf(4095 + 1);
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while (true) {
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ssize_t size = readlink(path.c_str(), &buf[0], buf.size());
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// Unrecoverable error?
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if (size == -1) return false;
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// It fit! (If size == buf.size(), it may have been truncated.)
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if (static_cast<size_t>(size) < buf.size()) {
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result->assign(&buf[0], size);
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return true;
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}
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// Double our buffer and try again.
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buf.resize(buf.size() * 2);
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}
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}
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#endif
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#if !defined(_WIN32)
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bool Realpath(const std::string& path, std::string* result) {
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result->clear();
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char* realpath_buf = realpath(path.c_str(), nullptr);
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if (realpath_buf == nullptr) {
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return false;
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}
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result->assign(realpath_buf);
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free(realpath_buf);
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return true;
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}
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#endif
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std::string GetExecutablePath() {
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#if defined(__linux__)
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std::string path;
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android::base::Readlink("/proc/self/exe", &path);
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return path;
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#elif defined(__APPLE__)
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char path[PATH_MAX + 1];
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uint32_t path_len = sizeof(path);
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int rc = _NSGetExecutablePath(path, &path_len);
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if (rc < 0) {
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std::unique_ptr<char> path_buf(new char[path_len]);
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_NSGetExecutablePath(path_buf.get(), &path_len);
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return path_buf.get();
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}
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return path;
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#elif defined(_WIN32)
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char path[PATH_MAX + 1];
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DWORD result = GetModuleFileName(NULL, path, sizeof(path) - 1);
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if (result == 0 || result == sizeof(path) - 1) return "";
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path[PATH_MAX - 1] = 0;
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return path;
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#else
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#error unknown OS
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#endif
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}
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std::string GetExecutableDirectory() {
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return Dirname(GetExecutablePath());
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}
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std::string Basename(const std::string& path) {
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// Copy path because basename may modify the string passed in.
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std::string result(path);
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#if !defined(__BIONIC__)
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// Use lock because basename() may write to a process global and return a
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// pointer to that. Note that this locking strategy only works if all other
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// callers to basename in the process also grab this same lock, but its
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// better than nothing. Bionic's basename returns a thread-local buffer.
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static std::mutex& basename_lock = *new std::mutex();
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std::lock_guard<std::mutex> lock(basename_lock);
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#endif
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// Note that if std::string uses copy-on-write strings, &str[0] will cause
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// the copy to be made, so there is no chance of us accidentally writing to
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// the storage for 'path'.
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char* name = basename(&result[0]);
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// In case basename returned a pointer to a process global, copy that string
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// before leaving the lock.
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result.assign(name);
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return result;
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}
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std::string Dirname(const std::string& path) {
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// Copy path because dirname may modify the string passed in.
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std::string result(path);
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#if !defined(__BIONIC__)
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// Use lock because dirname() may write to a process global and return a
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// pointer to that. Note that this locking strategy only works if all other
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// callers to dirname in the process also grab this same lock, but its
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// better than nothing. Bionic's dirname returns a thread-local buffer.
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static std::mutex& dirname_lock = *new std::mutex();
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std::lock_guard<std::mutex> lock(dirname_lock);
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#endif
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// Note that if std::string uses copy-on-write strings, &str[0] will cause
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// the copy to be made, so there is no chance of us accidentally writing to
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// the storage for 'path'.
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char* parent = dirname(&result[0]);
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// In case dirname returned a pointer to a process global, copy that string
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// before leaving the lock.
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result.assign(parent);
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return result;
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}
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} // namespace base
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} // namespace android
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