一、Android系统里面自带的文件操作工具类（FileUtils）android.os.FileUtils，读写文件的时候可以调用。
二、下面读节点实例
三、大概看一下这个类 frameworks\base\core\java\android\os\FileUtils.java ，里面有readTextFile、stringToFile等使用的函数。
/*
* Copyright (C) 2006 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.
*/
package android.os;
import static android.os.ParcelFileDescriptor.MODE_APPEND;
import static android.os.ParcelFileDescriptor.MODE_CREATE;
import static android.os.ParcelFileDescriptor.MODE_READ_ONLY;
import static android.os.ParcelFileDescriptor.MODE_READ_WRITE;
import static android.os.ParcelFileDescriptor.MODE_TRUNCATE;
import static android.os.ParcelFileDescriptor.MODE_WRITE_ONLY;
import static android.system.OsConstants.F_OK;
import static android.system.OsConstants.O_ACCMODE;
import static android.system.OsConstants.O_APPEND;
import static android.system.OsConstants.O_CREAT;
import static android.system.OsConstants.O_RDONLY;
import static android.system.OsConstants.O_RDWR;
import static android.system.OsConstants.O_TRUNC;
import static android.system.OsConstants.O_WRONLY;
import static android.system.OsConstants.R_OK;
import static android.system.OsConstants.SPLICE_F_MORE;
import static android.system.OsConstants.SPLICE_F_MOVE;
import static android.system.OsConstants.S_ISFIFO;
import static android.system.OsConstants.S_ISREG;
import static android.system.OsConstants.W_OK;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.TestApi;
import android.compat.annotation.UnsupportedAppUsage;
import android.content.ContentResolver;
import android.provider.DocumentsContract.Document;
import android.system.ErrnoException;
import android.system.Os;
import android.system.StructStat;
import android.text.TextUtils;
import android.util.Log;
import android.util.Slog;
import android.webkit.MimeTypeMap;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.ArrayUtils;
import com.android.internal.util.SizedInputStream;
import libcore.io.IoUtils;
import libcore.util.EmptyArray;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.Objects;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.regex.Pattern;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;
/**
* Utility methods useful for working with files.
*/
public final class FileUtils {
private static final String TAG = "FileUtils";
/** {@hide} */ public static final int S_IRWXU = 00700;
/** {@hide} */ public static final int S_IRUSR = 00400;
/** {@hide} */ public static final int S_IWUSR = 00200;
/** {@hide} */ public static final int S_IXUSR = 00100;
/** {@hide} */ public static final int S_IRWXG = 00070;
/** {@hide} */ public static final int S_IRGRP = 00040;
/** {@hide} */ public static final int S_IWGRP = 00020;
/** {@hide} */ public static final int S_IXGRP = 00010;
/** {@hide} */ public static final int S_IRWXO = 00007;
/** {@hide} */ public static final int S_IROTH = 00004;
/** {@hide} */ public static final int S_IWOTH = 00002;
/** {@hide} */ public static final int S_IXOTH = 00001;
@UnsupportedAppUsage
private FileUtils() {
}
/** Regular expression for safe filenames: no spaces or metacharacters.
*
* Use a preload holder so that FileUtils can be compile-time initialized.
*/
private static class NoImagePreloadHolder {
public static final Pattern SAFE_FILENAME_PATTERN = Pattern.compile("[\\w%+,./=_-]+");
}
// non-final so it can be toggled by Robolectric's ShadowFileUtils
private static boolean sEnableCopyOptimizations = true;
private static final long COPY_CHECKPOINT_BYTES = 524288;
/**
* Listener that is called periodically as progress is made.
*/
public interface ProgressListener {
public void onProgress(long progress);
}
/**
* Set owner and mode of of given {@link File}.
*
* @param mode to apply through {@code chmod}
* @param uid to apply through {@code chown}, or -1 to leave unchanged
* @param gid to apply through {@code chown}, or -1 to leave unchanged
* @return 0 on success, otherwise errno.
* @hide
*/
@UnsupportedAppUsage
public static int setPermissions(File path, int mode, int uid, int gid) {
return setPermissions(path.getAbsolutePath(), mode, uid, gid);
}
/**
* Set owner and mode of of given path.
*
* @param mode to apply through {@code chmod}
* @param uid to apply through {@code chown}, or -1 to leave unchanged
* @param gid to apply through {@code chown}, or -1 to leave unchanged
* @return 0 on success, otherwise errno.
* @hide
*/
@UnsupportedAppUsage
public static int setPermissions(String path, int mode, int uid, int gid) {
try {
Os.chmod(path, mode);
} catch (ErrnoException e) {
Slog.w(TAG, "Failed to chmod(" + path + "): " + e);
return e.errno;
}
if (uid >= 0 || gid >= 0) {
try {
Os.chown(path, uid, gid);
} catch (ErrnoException e) {
Slog.w(TAG, "Failed to chown(" + path + "): " + e);
return e.errno;
}
}
return 0;
}
/**
* Set owner and mode of of given {@link FileDescriptor}.
*
* @param mode to apply through {@code chmod}
* @param uid to apply through {@code chown}, or -1 to leave unchanged
* @param gid to apply through {@code chown}, or -1 to leave unchanged
* @return 0 on success, otherwise errno.
* @hide
*/
@UnsupportedAppUsage
public static int setPermissions(FileDescriptor fd, int mode, int uid, int gid) {
try {
Os.fchmod(fd, mode);
} catch (ErrnoException e) {
Slog.w(TAG, "Failed to fchmod(): " + e);
return e.errno;
}
if (uid >= 0 || gid >= 0) {
try {
Os.fchown(fd, uid, gid);
} catch (ErrnoException e) {
Slog.w(TAG, "Failed to fchown(): " + e);
return e.errno;
}
}
return 0;
}
/**
* Copy the owner UID, owner GID, and mode bits from one file to another.
*
* @param from File where attributes should be copied from.
* @param to File where attributes should be copied to.
* @hide
*/
public static void copyPermissions(@NonNull File from, @NonNull File to) throws IOException {
try {
final StructStat stat = Os.stat(from.getAbsolutePath());
Os.chmod(to.getAbsolutePath(), stat.st_mode);
Os.chown(to.getAbsolutePath(), stat.st_uid, stat.st_gid);
} catch (ErrnoException e) {
throw e.rethrowAsIOException();
}
}
/**
* @deprecated use {@link Os#stat(String)} instead.
* @hide
*/
@Deprecated
public static int getUid(String path) {
try {
return Os.stat(path).st_uid;
} catch (ErrnoException e) {
return -1;
}
}
/**
* Perform an fsync on the given FileOutputStream. The stream at this
* point must be flushed but not yet closed.
*
* @hide
*/
@UnsupportedAppUsage
public static boolean sync(FileOutputStream stream) {
try {
if (stream != null) {
stream.getFD().sync();
}
return true;
} catch (IOException e) {
}
return false;
}
/**
* @deprecated use {@link #copy(File, File)} instead.
* @hide
*/
@UnsupportedAppUsage
@Deprecated
public static boolean copyFile(File srcFile, File destFile) {
try {
copyFileOrThrow(srcFile, destFile);
return true;
} catch (IOException e) {
return false;
}
}
/**
* @deprecated use {@link #copy(File, File)} instead.
* @hide
*/
@Deprecated
public static void copyFileOrThrow(File srcFile, File destFile) throws IOException {
try (InputStream in = new FileInputStream(srcFile)) {
copyToFileOrThrow(in, destFile);
}
}
/**
* @deprecated use {@link #copy(InputStream, OutputStream)} instead.
* @hide
*/
@UnsupportedAppUsage
@Deprecated
public static boolean copyToFile(InputStream inputStream, File destFile) {
try {
copyToFileOrThrow(inputStream, destFile);
return true;
} catch (IOException e) {
return false;
}
}
/**
* @deprecated use {@link #copy(InputStream, OutputStream)} instead.
* @hide
*/
@Deprecated
public static void copyToFileOrThrow(InputStream in, File destFile) throws IOException {
if (destFile.exists()) {
destFile.delete();
}
try (FileOutputStream out = new FileOutputStream(destFile)) {
copy(in, out);
try {
Os.fsync(out.getFD());
} catch (ErrnoException e) {
throw e.rethrowAsIOException();
}
}
}
/**
* Copy the contents of one file to another, replacing any existing content.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @return number of bytes copied.
* @hide
*/
public static long copy(@NonNull File from, @NonNull File to) throws IOException {
return copy(from, to, null, null, null);
}
/**
* Copy the contents of one file to another, replacing any existing content.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @param signal to signal if the copy should be cancelled early.
* @param executor that listener events should be delivered via.
* @param listener to be periodically notified as the copy progresses.
* @return number of bytes copied.
* @hide
*/
public static long copy(@NonNull File from, @NonNull File to,
@Nullable CancellationSignal signal, @Nullable Executor executor,
@Nullable ProgressListener listener) throws IOException {
try (FileInputStream in = new FileInputStream(from);
FileOutputStream out = new FileOutputStream(to)) {
return copy(in, out, signal, executor, listener);
}
}
/**
* Copy the contents of one stream to another.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @return number of bytes copied.
*/
public static long copy(@NonNull InputStream in, @NonNull OutputStream out) throws IOException {
return copy(in, out, null, null, null);
}
/**
* Copy the contents of one stream to another.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @param signal to signal if the copy should be cancelled early.
* @param executor that listener events should be delivered via.
* @param listener to be periodically notified as the copy progresses.
* @return number of bytes copied.
*/
public static long copy(@NonNull InputStream in, @NonNull OutputStream out,
@Nullable CancellationSignal signal, @Nullable Executor executor,
@Nullable ProgressListener listener) throws IOException {
if (sEnableCopyOptimizations) {
if (in instanceof FileInputStream && out instanceof FileOutputStream) {
return copy(((FileInputStream) in).getFD(), ((FileOutputStream) out).getFD(),
signal, executor, listener);
}
}
// Worse case fallback to userspace
return copyInternalUserspace(in, out, signal, executor, listener);
}
/**
* Copy the contents of one FD to another.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @return number of bytes copied.
*/
public static long copy(@NonNull FileDescriptor in, @NonNull FileDescriptor out)
throws IOException {
return copy(in, out, null, null, null);
}
/**
* Copy the contents of one FD to another.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @param signal to signal if the copy should be cancelled early.
* @param executor that listener events should be delivered via.
* @param listener to be periodically notified as the copy progresses.
* @return number of bytes copied.
*/
public static long copy(@NonNull FileDescriptor in, @NonNull FileDescriptor out,
@Nullable CancellationSignal signal, @Nullable Executor executor,
@Nullable ProgressListener listener) throws IOException {
return copy(in, out, Long.MAX_VALUE, signal, executor, listener);
}
/**
* Copy the contents of one FD to another.
* <p>
* Attempts to use several optimization strategies to copy the data in the
* kernel before falling back to a userspace copy as a last resort.
*
* @param count the number of bytes to copy.
* @param signal to signal if the copy should be cancelled early.
* @param executor that listener events should be delivered via.
* @param listener to be periodically notified as the copy progresses.
* @return number of bytes copied.
* @hide
*/
public static long copy(@NonNull FileDescriptor in, @NonNull FileDescriptor out, long count,
@Nullable CancellationSignal signal, @Nullable Executor executor,
@Nullable ProgressListener listener) throws IOException {
if (sEnableCopyOptimizations) {
try {
final StructStat st_in = Os.fstat(in);
final StructStat st_out = Os.fstat(out);
if (S_ISREG(st_in.st_mode) && S_ISREG(st_out.st_mode)) {
return copyInternalSendfile(in, out, count, signal, executor, listener);
} else if (S_ISFIFO(st_in.st_mode) || S_ISFIFO(st_out.st_mode)) {
return copyInternalSplice(in, out, count, signal, executor, listener);
}
} catch (ErrnoException e) {
throw e.rethrowAsIOException();
}
}
// Worse case fallback to userspace
return copyInternalUserspace(in, out, count, signal, executor, listener);
}
/**
* Requires one of input or output to be a pipe.
*
* @hide
*/
@VisibleForTesting
public static long copyInternalSplice(FileDescriptor in, FileDescriptor out, long count,
CancellationSignal signal, Executor executor, ProgressListener listener)
throws ErrnoException {
long progress = 0;
long checkpoint = 0;
long t;
while ((t = Os.splice(in, null, out, null, Math.min(count, COPY_CHECKPOINT_BYTES),
SPLICE_F_MOVE | SPLICE_F_MORE)) != 0) {
progress += t;
checkpoint += t;
count -= t;
if (checkpoint >= COPY_CHECKPOINT_BYTES) {
if (signal != null) {
signal.throwIfCanceled();
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
checkpoint = 0;
}
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
return progress;
}
/**
* Requires both input and output to be a regular file.
*
* @hide
*/
@VisibleForTesting
public static long copyInternalSendfile(FileDescriptor in, FileDescriptor out, long count,
CancellationSignal signal, Executor executor, ProgressListener listener)
throws ErrnoException {
long progress = 0;
long checkpoint = 0;
long t;
while ((t = Os.sendfile(out, in, null, Math.min(count, COPY_CHECKPOINT_BYTES))) != 0) {
progress += t;
checkpoint += t;
count -= t;
if (checkpoint >= COPY_CHECKPOINT_BYTES) {
if (signal != null) {
signal.throwIfCanceled();
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
checkpoint = 0;
}
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
return progress;
}
/** {@hide} */
@Deprecated
@VisibleForTesting
public static long copyInternalUserspace(FileDescriptor in, FileDescriptor out,
ProgressListener listener, CancellationSignal signal, long count)
throws IOException {
return copyInternalUserspace(in, out, count, signal, Runnable::run, listener);
}
/** {@hide} */
@VisibleForTesting
public static long copyInternalUserspace(FileDescriptor in, FileDescriptor out, long count,
CancellationSignal signal, Executor executor, ProgressListener listener)
throws IOException {
if (count != Long.MAX_VALUE) {
return copyInternalUserspace(new SizedInputStream(new FileInputStream(in), count),
new FileOutputStream(out), signal, executor, listener);
} else {
return copyInternalUserspace(new FileInputStream(in),
new FileOutputStream(out), signal, executor, listener);
}
}
/** {@hide} */
@VisibleForTesting
public static long copyInternalUserspace(InputStream in, OutputStream out,
CancellationSignal signal, Executor executor, ProgressListener listener)
throws IOException {
long progress = 0;
long checkpoint = 0;
byte[] buffer = new byte[8192];
int t;
while ((t = in.read(buffer)) != -1) {
out.write(buffer, 0, t);
progress += t;
checkpoint += t;
if (checkpoint >= COPY_CHECKPOINT_BYTES) {
if (signal != null) {
signal.throwIfCanceled();
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
checkpoint = 0;
}
}
if (executor != null && listener != null) {
final long progressSnapshot = progress;
executor.execute(() -> {
listener.onProgress(progressSnapshot);
});
}
return progress;
}
/**
* Check if a filename is "safe" (no metacharacters or spaces).
* @param file The file to check
* @hide
*/
@UnsupportedAppUsage
public static boolean isFilenameSafe(File file) {
// Note, we check whether it matches what's known to be safe,
// rather than what's known to be unsafe. Non-ASCII, control
// characters, etc. are all unsafe by default.
return NoImagePreloadHolder.SAFE_FILENAME_PATTERN.matcher(file.getPath()).matches();
}
/**
* Read a text file into a String, optionally limiting the length.
* @param file to read (will not seek, so things like /proc files are OK)
* @param max length (positive for head, negative of tail, 0 for no limit)
* @param ellipsis to add of the file was truncated (can be null)
* @return the contents of the file, possibly truncated
* @throws IOException if something goes wrong reading the file
* @hide
*/
@UnsupportedAppUsage
public static String readTextFile(File file, int max, String ellipsis) throws IOException {
InputStream input = new FileInputStream(file);
// wrapping a BufferedInputStream around it because when reading /proc with unbuffered
// input stream, bytes read not equal to buffer size is not necessarily the correct
// indication for EOF; but it is true for BufferedInputStream due to its implementation.
BufferedInputStream bis = new BufferedInputStream(input);
try {
long size = file.length();
if (max > 0 || (size > 0 && max == 0)) { // "head" mode: read the first N bytes
if (size > 0 && (max == 0 || size < max)) max = (int) size;
byte[] data = new byte[max + 1];
int length = bis.read(data);
if (length <= 0) return "";
if (length <= max) return new String(data, 0, length);
if (ellipsis == null) return new String(data, 0, max);
return new String(data, 0, max) + ellipsis;
} else if (max < 0) { // "tail" mode: keep the last N
int len;
boolean rolled = false;
byte[] last = null;
byte[] data = null;
do {
if (last != null) rolled = true;
byte[] tmp = last; last = data; data = tmp;
if (data == null) data = new byte[-max];
len = bis.read(data);
} while (len == data.length);
if (last == null && len <= 0) return "";
if (last == null) return new String(data, 0, len);
if (len > 0) {
rolled = true;
System.arraycopy(last, len, last, 0, last.length - len);
System.arraycopy(data, 0, last, last.length - len, len);
}
if (ellipsis == null || !rolled) return new String(last);
return ellipsis + new String(last);
} else { // "cat" mode: size unknown, read it all in streaming fashion
ByteArrayOutputStream contents = new ByteArrayOutputStream();
int len;
byte[] data = new byte[1024];
do {
len = bis.read(data);
if (len > 0) contents.write(data, 0, len);
} while (len == data.length);
return contents.toString();
}
} finally {
bis.close();
input.close();
}
}
/** {@hide} */
@UnsupportedAppUsage
public static void stringToFile(File file, String string) throws IOException {
stringToFile(file.getAbsolutePath(), string);
}
/**
* Writes the bytes given in {@code content} to the file whose absolute path
* is {@code filename}.
*
* @hide
*/
public static void bytesToFile(String filename, byte[] content) throws IOException {
if (filename.startsWith("/proc/")) {
final int oldMask = StrictMode.allowThreadDiskWritesMask();
try (FileOutputStream fos = new FileOutputStream(filename)) {
fos.write(content);
} finally {
StrictMode.setThreadPolicyMask(oldMask);
}
} else {
try (FileOutputStream fos = new FileOutputStream(filename)) {
fos.write(content);
}
}
}
/**
* Writes string to file. Basically same as "echo -n $string > $filename"
*
* @param filename
* @param string
* @throws IOException
* @hide
*/
@UnsupportedAppUsage
public static void stringToFile(String filename, String string) throws IOException {
bytesToFile(filename, string.getBytes(StandardCharsets.UTF_8));
}
/**
* Computes the checksum of a file using the CRC32 checksum routine. The
* value of the checksum is returned.
*
* @param file the file to checksum, must not be null
* @return the checksum value or an exception is thrown.
* @deprecated this is a weak hashing algorithm, and should not be used due
* to its potential for collision.
* @hide
*/
@UnsupportedAppUsage
@Deprecated
public static long checksumCrc32(File file) throws FileNotFoundException, IOException {
CRC32 checkSummer = new CRC32();
CheckedInputStream cis = null;
try {
cis = new CheckedInputStream( new FileInputStream(file), checkSummer);
byte[] buf = new byte[128];
while(cis.read(buf) >= 0) {
// Just read for checksum to get calculated.
}
return checkSummer.getValue();
} finally {
if (cis != null) {
try {
cis.close();
} catch (IOException e) {
}
}
}
}
/**
* Compute the digest of the given file using the requested algorithm.
*
* @param algorithm Any valid algorithm accepted by
* {@link MessageDigest#getInstance(String)}.
* @hide
*/
@TestApi
@NonNull
public static byte[] digest(@NonNull File file, @NonNull String algorithm)
throws IOException, NoSuchAlgorithmException {
try (FileInputStream in = new FileInputStream(file)) {
return digest(in, algorithm);
}
}
/**
* Compute the digest of the given file using the requested algorithm.
*
* @param algorithm Any valid algorithm accepted by
* {@link MessageDigest#getInstance(String)}.
* @hide
*/
@TestApi
@NonNull
public static byte[] digest(@NonNull InputStream in, @NonNull String algorithm)
throws IOException, NoSuchAlgorithmException {
// TODO: implement kernel optimizations
return digestInternalUserspace(in, algorithm);
}
/**
* Compute the digest of the given file using the requested algorithm.
*
* @param algorithm Any valid algorithm accepted by
* {@link MessageDigest#getInstance(String)}.
* @hide
*/
public static byte[] digest(FileDescriptor fd, String algorithm)
throws IOException, NoSuchAlgorithmException {
// TODO: implement kernel optimizations
return digestInternalUserspace(new FileInputStream(fd), algorithm);
}
private static byte[] digestInternalUserspace(InputStream in, String algorithm)
throws IOException, NoSuchAlgorithmException {
final MessageDigest digest = MessageDigest.getInstance(algorithm);
try (DigestInputStream digestStream = new DigestInputStream(in, digest)) {
final byte[] buffer = new byte[8192];
while (digestStream.read(buffer) != -1) {
}
}
return digest.digest();
}
/**
* Delete older files in a directory until only those matching the given
* constraints remain.
*
* @param minCount Always keep at least this many files.
* @param minAgeMs Always keep files younger than this age, in milliseconds.
* @return if any files were deleted.
* @hide
*/
@UnsupportedAppUsage
public static boolean deleteOlderFiles(File dir, int minCount, long minAgeMs) {
if (minCount < 0 || minAgeMs < 0) {
throw new IllegalArgumentException("Constraints must be positive or 0");
}
final File[] files = dir.listFiles();
if (files == null) return false;
// Sort with newest files first
Arrays.sort(files, new Comparator<File>() {
@Override
public int compare(File lhs, File rhs) {
return Long.compare(rhs.lastModified(), lhs.lastModified());
}
});
// Keep at least minCount files
boolean deleted = false;
for (int i = minCount; i < files.length; i++) {
final File file = files[i];
// Keep files newer than minAgeMs
final long age = System.currentTimeMillis() - file.lastModified();
if (age > minAgeMs) {
if (file.delete()) {
Log.d(TAG, "Deleted old file " + file);
deleted = true;
}
}
}
return deleted;
}
/**
* Test if a file lives under the given directory, either as a direct child
* or a distant grandchild.
* <p>
* Both files <em>must</em> have been resolved using
* {@link File#getCanonicalFile()} to avoid symlink or path traversal
* attacks.
*
* @hide
*/
public static boolean contains(File[] dirs, File file) {
for (File dir : dirs) {
if (contains(dir, file)) {
return true;
}
}
return false;
}
/** {@hide} */
public static boolean contains(Collection<File> dirs, File file) {
for (File dir : dirs) {
if (contains(dir, file)) {
return true;
}
}
return false;
}
/**
* Test if a file lives under the given directory, either as a direct child
* or a distant grandchild.
* <p>
* Both files <em>must</em> have been resolved using
* {@link File#getCanonicalFile()} to avoid symlink or path traversal
* attacks.
*
* @hide
*/
@TestApi
public static boolean contains(File dir, File file) {
if (dir == null || file == null) return false;
return contains(dir.getAbsolutePath(), file.getAbsolutePath());
}
/**
* Test if a file lives under the given directory, either as a direct child
* or a distant grandchild.
* <p>
* Both files <em>must</em> have been resolved using
* {@link File#getCanonicalFile()} to avoid symlink or path traversal
* attacks.
*
* @hide
*/
public static boolean contains(String dirPath, String filePath) {
if (dirPath.equals(filePath)) {
return true;
}
if (!dirPath.endsWith("/")) {
dirPath += "/";
}
return filePath.startsWith(dirPath);
}
/** {@hide} */
public static boolean deleteContentsAndDir(File dir) {
if (deleteContents(dir)) {
return dir.delete();
} else {
return false;
}
}
/** {@hide} */
@UnsupportedAppUsage
public static boolean deleteContents(File dir) {
File[] files = dir.listFiles();
boolean success = true;
if (files != null) {
for (File file : files) {
if (file.isDirectory()) {
success &= deleteContents(file);
}
if (!file.delete()) {
Log.w(TAG, "Failed to delete " + file);
success = false;
}
}
}
return success;
}
private static boolean isValidExtFilenameChar(char c) {
switch (c) {
case '\0':
case '/':
return false;
default:
return true;
}
}
/**
* Check if given filename is valid for an ext4 filesystem.
*
* @hide
*/
public static boolean isValidExtFilename(String name) {
return (name != null) && name.equals(buildValidExtFilename(name));
}
/**
* Mutate the given filename to make it valid for an ext4 filesystem,
* replacing any invalid characters with "_".
*
* @hide
*/
public static String buildValidExtFilename(String name) {
if (TextUtils.isEmpty(name) || ".".equals(name) || "..".equals(name)) {
return "(invalid)";
}
final StringBuilder res = new StringBuilder(name.length());
for (int i = 0; i < name.length(); i++) {
final char c = name.charAt(i);
if (isValidExtFilenameChar(c)) {
res.append(c);
} else {
res.append('_');
}
}
trimFilename(res, 255);
return res.toString();
}
private static boolean isValidFatFilenameChar(char c) {
if ((0x00 <= c && c <= 0x1f)) {
return false;
}
switch (c) {
case '"':
case '*':
case '/':
case ':':
case '<':
case '>':
case '?':
case '\\':
case '|':
case 0x7F:
return false;
default:
return true;
}
}
/**
* Check if given filename is valid for a FAT filesystem.
*
* @hide
*/
public static boolean isValidFatFilename(String name) {
return (name != null) && name.equals(buildValidFatFilename(name));
}
/**
* Mutate the given filename to make it valid for a FAT filesystem,
* replacing any invalid characters with "_".
*
* @hide
*/
public static String buildValidFatFilename(String name) {
if (TextUtils.isEmpty(name) || ".".equals(name) || "..".equals(name)) {
return "(invalid)";
}
final StringBuilder res = new StringBuilder(name.length());
for (int i = 0; i < name.length(); i++) {
final char c = name.charAt(i);
if (isValidFatFilenameChar(c)) {
res.append(c);
} else {
res.append('_');
}
}
// Even though vfat allows 255 UCS-2 chars, we might eventually write to
// ext4 through a FUSE layer, so use that limit.
trimFilename(res, 255);
return res.toString();
}
/** {@hide} */
@VisibleForTesting
public static String trimFilename(String str, int maxBytes) {
final StringBuilder res = new StringBuilder(str);
trimFilename(res, maxBytes);
return res.toString();
}
/** {@hide} */
private static void trimFilename(StringBuilder res, int maxBytes) {
byte[] raw = res.toString().getBytes(StandardCharsets.UTF_8);
if (raw.length > maxBytes) {
maxBytes -= 3;
while (raw.length > maxBytes) {
res.deleteCharAt(res.length() / 2);
raw = res.toString().getBytes(StandardCharsets.UTF_8);
}
res.insert(res.length() / 2, "...");
}
}
/** {@hide} */
public static String rewriteAfterRename(File beforeDir, File afterDir, String path) {
if (path == null) return null;
final File result = rewriteAfterRename(beforeDir, afterDir, new File(path));
return (result != null) ? result.getAbsolutePath() : null;
}
/** {@hide} */
public static String[] rewriteAfterRename(File beforeDir, File afterDir, String[] paths) {
if (paths == null) return null;
final String[] result = new String[paths.length];
for (int i = 0; i < paths.length; i++) {
result[i] = rewriteAfterRename(beforeDir, afterDir, paths[i]);
}
return result;
}
/**
* Given a path under the "before" directory, rewrite it to live under the
* "after" directory. For example, {@code /before/foo/bar.txt} would become
* {@code /after/foo/bar.txt}.
*
* @hide
*/
public static File rewriteAfterRename(File beforeDir, File afterDir, File file) {
if (file == null || beforeDir == null || afterDir == null) return null;
if (contains(beforeDir, file)) {
final String splice = file.getAbsolutePath().substring(
beforeDir.getAbsolutePath().length());
return new File(afterDir, splice);
}
return null;
}
/** {@hide} */
private static File buildUniqueFileWithExtension(File parent, String name, String ext)
throws FileNotFoundException {
File file = buildFile(parent, name, ext);
// If conflicting file, try adding counter suffix
int n = 0;
while (file.exists()) {
if (n++ >= 32) {
throw new FileNotFoundException("Failed to create unique file");
}
file = buildFile(parent, name + " (" + n + ")", ext);
}
return file;
}
/**
* Generates a unique file name under the given parent directory. If the display name doesn't
* have an extension that matches the requested MIME type, the default extension for that MIME
* type is appended. If a file already exists, the name is appended with a numerical value to
* make it unique.
*
* For example, the display name 'example' with 'text/plain' MIME might produce
* 'example.txt' or 'example (1).txt', etc.
*
* @throws FileNotFoundException
* @hide
*/
public static File buildUniqueFile(File parent, String mimeType, String displayName)
throws FileNotFoundException {
final String[] parts = splitFileName(mimeType, displayName);
return buildUniqueFileWithExtension(parent, parts[0], parts[1]);
}
/** {@hide} */
public static File buildNonUniqueFile(File parent, String mimeType, String displayName) {
final String[] parts = splitFileName(mimeType, displayName);
return buildFile(parent, parts[0], parts[1]);
}
/**
* Generates a unique file name under the given parent directory, keeping
* any extension intact.
*
* @hide
*/
public static File buildUniqueFile(File parent, String displayName)
throws FileNotFoundException {
final String name;
final String ext;
// Extract requested extension from display name
final int lastDot = displayName.lastIndexOf('.');
if (lastDot >= 0) {
name = displayName.substring(0, lastDot);
ext = displayName.substring(lastDot + 1);
} else {
name = displayName;
ext = null;
}
return buildUniqueFileWithExtension(parent, name, ext);
}
/**
* Splits file name into base name and extension.
* If the display name doesn't have an extension that matches the requested MIME type, the
* extension is regarded as a part of filename and default extension for that MIME type is
* appended.
*
* @hide
*/
public static String[] splitFileName(String mimeType, String displayName) {
String name;
String ext;
if (Document.MIME_TYPE_DIR.equals(mimeType)) {
name = displayName;
ext = null;
} else {
String mimeTypeFromExt;
// Extract requested extension from display name
final int lastDot = displayName.lastIndexOf('.');
if (lastDot >= 0) {
name = displayName.substring(0, lastDot);
ext = displayName.substring(lastDot + 1);
mimeTypeFromExt = MimeTypeMap.getSingleton().getMimeTypeFromExtension(
ext.toLowerCase());
} else {
name = displayName;
ext = null;
mimeTypeFromExt = null;
}
if (mimeTypeFromExt == null) {
mimeTypeFromExt = ContentResolver.MIME_TYPE_DEFAULT;
}
final String extFromMimeType;
if (ContentResolver.MIME_TYPE_DEFAULT.equals(mimeType)) {
extFromMimeType = null;
} else {
extFromMimeType = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType);
}
if (Objects.equals(mimeType, mimeTypeFromExt) || Objects.equals(ext, extFromMimeType)) {
// Extension maps back to requested MIME type; allow it
} else {
// No match; insist that create file matches requested MIME
name = displayName;
ext = extFromMimeType;
}
}
if (ext == null) {
ext = "";
}
return new String[] { name, ext };
}
/** {@hide} */
private static File buildFile(File parent, String name, String ext) {
if (TextUtils.isEmpty(ext)) {
return new File(parent, name);
} else {
return new File(parent, name + "." + ext);
}
}
/** {@hide} */
public static @NonNull String[] listOrEmpty(@Nullable File dir) {
return (dir != null) ? ArrayUtils.defeatNullable(dir.list())
: EmptyArray.STRING;
}
/** {@hide} */
public static @NonNull File[] listFilesOrEmpty(@Nullable File dir) {
return (dir != null) ? ArrayUtils.defeatNullable(dir.listFiles())
: ArrayUtils.EMPTY_FILE;
}
/** {@hide} */
public static @NonNull File[] listFilesOrEmpty(@Nullable File dir, FilenameFilter filter) {
return (dir != null) ? ArrayUtils.defeatNullable(dir.listFiles(filter))
: ArrayUtils.EMPTY_FILE;
}
/** {@hide} */
public static @Nullable File newFileOrNull(@Nullable String path) {
return (path != null) ? new File(path) : null;
}
/**
* Creates a directory with name {@code name} under an existing directory {@code baseDir}.
* Returns a {@code File} object representing the directory on success, {@code null} on
* failure.
*
* @hide
*/
public static @Nullable File createDir(File baseDir, String name) {
final File dir = new File(baseDir, name);
return createDir(dir) ? dir : null;
}
/** @hide */
public static boolean createDir(File dir) {
if (dir.exists()) {
return dir.isDirectory();
}
return dir.mkdir();
}
/**
* Round the given size of a storage device to a nice round power-of-two
* value, such as 256MB or 32GB. This avoids showing weird values like
* "29.5GB" in UI.
*
* @hide
*/
public static long roundStorageSize(long size) {
long val = 1;
long pow = 1;
while ((val * pow) < size) {
val <<= 1;
if (val > 512) {
val = 1;
pow *= 1000;
}
}
return val * pow;
}
/**
* Closes the given object quietly, ignoring any checked exceptions. Does
* nothing if the given object is {@code null}.
*
* @deprecated This method may suppress potentially significant exceptions, particularly when
* closing writable resources. With a writable resource, a failure thrown from {@code close()}
* should be considered as significant as a failure thrown from a write method because it may
* indicate a failure to flush bytes to the underlying resource.
*/
@Deprecated
public static void closeQuietly(@Nullable AutoCloseable closeable) {
IoUtils.closeQuietly(closeable);
}
/**
* Closes the given object quietly, ignoring any checked exceptions. Does
* nothing if the given object is {@code null}.
*
* @deprecated This method may suppress potentially significant exceptions, particularly when
* closing writable resources. With a writable resource, a failure thrown from {@code close()}
* should be considered as significant as a failure thrown from a write method because it may
* indicate a failure to flush bytes to the underlying resource.
*/
@Deprecated
public static void closeQuietly(@Nullable FileDescriptor fd) {
IoUtils.closeQuietly(fd);
}
/** {@hide} */
public static int translateModeStringToPosix(String mode) {
// Sanity check for invalid chars
for (int i = 0; i < mode.length(); i++) {
switch (mode.charAt(i)) {
case 'r':
case 'w':
case 't':
case 'a':
break;
default:
throw new IllegalArgumentException("Bad mode: " + mode);
}
}
int res = 0;
if (mode.startsWith("rw")) {
res = O_RDWR | O_CREAT;
} else if (mode.startsWith("w")) {
res = O_WRONLY | O_CREAT;
} else if (mode.startsWith("r")) {
res = O_RDONLY;
} else {
throw new IllegalArgumentException("Bad mode: " + mode);
}
if (mode.indexOf('t') != -1) {
res |= O_TRUNC;
}
if (mode.indexOf('a') != -1) {
res |= O_APPEND;
}
return res;
}
/** {@hide} */
public static String translateModePosixToString(int mode) {
String res = "";
if ((mode & O_ACCMODE) == O_RDWR) {
res = "rw";
} else if ((mode & O_ACCMODE) == O_WRONLY) {
res = "w";
} else if ((mode & O_ACCMODE) == O_RDONLY) {
res = "r";
} else {
throw new IllegalArgumentException("Bad mode: " + mode);
}
if ((mode & O_TRUNC) == O_TRUNC) {
res += "t";
}
if ((mode & O_APPEND) == O_APPEND) {
res += "a";
}
return res;
}
/** {@hide} */
public static int translateModePosixToPfd(int mode) {
int res = 0;
if ((mode & O_ACCMODE) == O_RDWR) {
res = MODE_READ_WRITE;
} else if ((mode & O_ACCMODE) == O_WRONLY) {
res = MODE_WRITE_ONLY;
} else if ((mode & O_ACCMODE) == O_RDONLY) {
res = MODE_READ_ONLY;
} else {
throw new IllegalArgumentException("Bad mode: " + mode);
}
if ((mode & O_CREAT) == O_CREAT) {
res |= MODE_CREATE;
}
if ((mode & O_TRUNC) == O_TRUNC) {
res |= MODE_TRUNCATE;
}
if ((mode & O_APPEND) == O_APPEND) {
res |= MODE_APPEND;
}
return res;
}
/** {@hide} */
public static int translateModePfdToPosix(int mode) {
int res = 0;
if ((mode & MODE_READ_WRITE) == MODE_READ_WRITE) {
res = O_RDWR;
} else if ((mode & MODE_WRITE_ONLY) == MODE_WRITE_ONLY) {
res = O_WRONLY;
} else if ((mode & MODE_READ_ONLY) == MODE_READ_ONLY) {
res = O_RDONLY;
} else {
throw new IllegalArgumentException("Bad mode: " + mode);
}
if ((mode & MODE_CREATE) == MODE_CREATE) {
res |= O_CREAT;
}
if ((mode & MODE_TRUNCATE) == MODE_TRUNCATE) {
res |= O_TRUNC;
}
if ((mode & MODE_APPEND) == MODE_APPEND) {
res |= O_APPEND;
}
return res;
}
/** {@hide} */
public static int translateModeAccessToPosix(int mode) {
if (mode == F_OK) {
// There's not an exact mapping, so we attempt a read-only open to
// determine if a file exists
return O_RDONLY;
} else if ((mode & (R_OK | W_OK)) == (R_OK | W_OK)) {
return O_RDWR;
} else if ((mode & R_OK) == R_OK) {
return O_RDONLY;
} else if ((mode & W_OK) == W_OK) {
return O_WRONLY;
} else {
throw new IllegalArgumentException("Bad mode: " + mode);
}
}
/** {@hide} */
@VisibleForTesting
public static class MemoryPipe extends Thread implements AutoCloseable {
private final FileDescriptor[] pipe;
private final byte[] data;
private final boolean sink;
private MemoryPipe(byte[] data, boolean sink) throws IOException {
try {
this.pipe = Os.pipe();
} catch (ErrnoException e) {
throw e.rethrowAsIOException();
}
this.data = data;
this.sink = sink;
}
private MemoryPipe startInternal() {
super.start();
return this;
}
public static MemoryPipe createSource(byte[] data) throws IOException {
return new MemoryPipe(data, false).startInternal();
}
public static MemoryPipe createSink(byte[] data) throws IOException {
return new MemoryPipe(data, true).startInternal();
}
public FileDescriptor getFD() {
return sink ? pipe[1] : pipe[0];
}
public FileDescriptor getInternalFD() {
return sink ? pipe[0] : pipe[1];
}
@Override
public void run() {
final FileDescriptor fd = getInternalFD();
try {
int i = 0;
while (i < data.length) {
if (sink) {
i += Os.read(fd, data, i, data.length - i);
} else {
i += Os.write(fd, data, i, data.length - i);
}
}
} catch (IOException | ErrnoException e) {
// Ignored
} finally {
if (sink) {
SystemClock.sleep(TimeUnit.SECONDS.toMillis(1));
}
IoUtils.closeQuietly(fd);
}
}
@Override
public void close() throws Exception {
IoUtils.closeQuietly(getFD());
}
}
}