IoUtils.java revision 8b15dcc5890963edad4dfcf558cc16027c7985e5 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package libcore.io;
18
19import java.io.Closeable;
20import java.io.FileDescriptor;
21import java.io.FileNotFoundException;
22import java.io.IOException;
23import java.io.RandomAccessFile;
24import java.net.Socket;
25import java.util.Arrays;
26import libcore.util.MutableInt;
27import static libcore.io.OsConstants.*;
28
29public final class IoUtils {
30    private IoUtils() {
31    }
32
33    /**
34     * Implements java.io/java.net "available" semantics.
35     */
36    public static int available(FileDescriptor fd) throws IOException {
37        try {
38            MutableInt available = new MutableInt(0);
39            int rc = Libcore.os.ioctlInt(fd, FIONREAD, available);
40            if (available.value < 0) {
41                // If the fd refers to a regular file, the result is the difference between
42                // the file size and the file position. This may be negative if the position
43                // is past the end of the file. If the fd refers to a special file masquerading
44                // as a regular file, the result may be negative because the special file
45                // may appear to have zero size and yet a previous read call may have
46                // read some amount of data and caused the file position to be advanced.
47                available.value = 0;
48            }
49            return available.value;
50        } catch (ErrnoException errnoException) {
51            if (errnoException.errno == ENOTTY) {
52                // The fd is unwilling to opine about its read buffer.
53                return 0;
54            }
55            throw errnoException.rethrowAsIOException();
56        }
57    }
58
59    /**
60     * java.io only throws FileNotFoundException when opening files, regardless of what actually
61     * went wrong. Additionally, java.io is more restrictive than POSIX when it comes to opening
62     * directories: POSIX says read-only is okay, but java.io doesn't even allow that. We also
63     * have an Android-specific hack to alter the default permissions.
64     */
65    public static FileDescriptor open(String path, int flags) throws FileNotFoundException {
66        FileDescriptor fd = null;
67        try {
68            // On Android, we don't want default permissions to allow global access.
69            int mode = ((flags & O_ACCMODE) == O_RDONLY) ? 0 : 0600;
70            fd = Libcore.os.open(path, flags, mode);
71            if (fd.valid()) {
72                // Posix open(2) fails with EISDIR only if you ask for write permission.
73                // Java disallows reading directories too.
74                boolean isDirectory = false;
75                if (S_ISDIR(Libcore.os.fstat(fd).st_mode)) {
76                    throw new ErrnoException("open", EISDIR);
77                }
78            }
79            return fd;
80        } catch (ErrnoException errnoException) {
81            try {
82                if (fd != null) {
83                    close(fd);
84                }
85            } catch (IOException ignored) {
86            }
87            FileNotFoundException ex = new FileNotFoundException(path + ": " + errnoException.getMessage());
88            ex.initCause(errnoException);
89            throw ex;
90        }
91    }
92
93    /**
94     * java.io thinks that a read at EOF is an error and should return -1, contrary to traditional
95     * Unix practice where you'd read until you got 0 bytes (and any future read would return -1).
96     */
97    public static int read(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount) throws IOException {
98        Arrays.checkOffsetAndCount(bytes.length, byteOffset, byteCount);
99        if (byteCount == 0) {
100            return 0;
101        }
102        try {
103            int readCount = Libcore.os.read(fd, bytes, byteOffset, byteCount);
104            if (readCount == 0) {
105                return -1;
106            }
107            return readCount;
108        } catch (ErrnoException errnoException) {
109            if (errnoException.errno == EAGAIN) {
110                // We return 0 rather than throw if we try to read from an empty non-blocking pipe.
111                return 0;
112            }
113            throw errnoException.rethrowAsIOException();
114        }
115    }
116
117    /**
118     * java.io always writes every byte it's asked to, or fails with an error. (That is, unlike
119     * Unix it never just writes as many bytes as happens to be convenient.)
120     */
121    public static void write(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount) throws IOException {
122        Arrays.checkOffsetAndCount(bytes.length, byteOffset, byteCount);
123        if (byteCount == 0) {
124            return;
125        }
126        try {
127            while (byteCount > 0) {
128                int bytesWritten = Libcore.os.write(fd, bytes, byteOffset, byteCount);
129                byteCount -= bytesWritten;
130                byteOffset += bytesWritten;
131            }
132        } catch (ErrnoException errnoException) {
133            throw errnoException.rethrowAsIOException();
134        }
135    }
136
137    /**
138     * Calls close(2) on 'fd'. Also resets the internal int to -1.
139     */
140    public static native void close(FileDescriptor fd) throws IOException;
141
142    /**
143     * Closes 'closeable', ignoring any exceptions. Does nothing if 'closeable' is null.
144     */
145    public static void closeQuietly(Closeable closeable) {
146        if (closeable != null) {
147            try {
148                closeable.close();
149            } catch (IOException ignored) {
150            }
151        }
152    }
153
154    /**
155     * Closes 'socket', ignoring any exceptions. Does nothing if 'socket' is null.
156     */
157    public static void closeQuietly(Socket socket) {
158        if (socket != null) {
159            try {
160                socket.close();
161            } catch (Exception ignored) {
162            }
163        }
164    }
165
166    /**
167     * Returns the int file descriptor from within the given FileDescriptor 'fd'.
168     */
169    public static native int getFd(FileDescriptor fd);
170
171    /**
172     * Sets 'fd' to be blocking or non-blocking, according to the state of 'blocking'.
173     */
174    public static void setBlocking(FileDescriptor fd, boolean blocking) throws IOException {
175        try {
176            int flags = Libcore.os.fcntlVoid(fd, F_GETFL);
177            if (!blocking) {
178                flags |= O_NONBLOCK;
179            } else {
180                flags &= ~O_NONBLOCK;
181            }
182            Libcore.os.fcntlLong(fd, F_SETFL, flags);
183        } catch (ErrnoException errnoException) {
184            throw errnoException.rethrowAsIOException();
185        }
186    }
187
188    /**
189     * Returns the contents of 'path' as a byte array.
190     */
191    public static byte[] readFileAsByteArray(String path) throws IOException {
192        RandomAccessFile f = null;
193        try {
194            f = new RandomAccessFile(path, "r");
195            byte[] buf = new byte[(int) f.length()];
196            f.readFully(buf);
197            return buf;
198        } finally {
199            IoUtils.closeQuietly(f);
200        }
201    }
202}
203