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Commit 52671a78 authored by Nick Kralevich's avatar Nick Kralevich
Browse files

FileUtils.java: Don't treat open access modes as flags 

O_RDONLY, O_WRONLY, and O_RDWR are not flags. Rather, they are the
integer values 0, 1, and 2, respectively.

  #define O_RDONLY 00000000
  #define O_WRONLY 00000001
  #define O_RDWR 00000002

Quoting "man 2 open"

  * File access mode *

  Unlike  the  other  values  that  can  be  specified in flags,
  the access mode values O_RDONLY, O_WRONLY, and O_RDWR do not
  specify individual bits.  Rather, they define the low order
  two bits of flags, and are defined respectively as 0, 1, and
  2. In other words, the combination O_RDONLY | O_WRONLY is a
  logical error, and certainly does not have the same meaning
  as O_RDWR.

  Linux reserves the special, nonstandard access mode 3
  (binary 11) in flags to mean: check for read and write
  permission on the file and return a file descriptor that
  can't be used for reading or writing. This nonstandard access
  mode is used by some Linux drivers to return a file
  descriptor that is to be used only for device-specific
  ioctl(2) operations.

Rather than treat these values like flags, use O_ACCMODE to extract the
values and then perform the comparisons.

Introduced in 63280e06.

Test: android compiles and boots.
Change-Id: I4d3185e835615ffba3a7854d3d58351e124599d0
parent f98c2c41

core/java/android/os/FileUtils.java

+19 −19
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 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;
@@ -1259,11 +1260,11 @@ public class FileUtils { 


        int res = 0;

        if (mode.startsWith("rw")) {

            res |= O_RDWR | O_CREAT;

            res = O_RDWR | O_CREAT;

        } else if (mode.startsWith("w")) {

            res |= O_WRONLY | O_CREAT;

            res = O_WRONLY | O_CREAT;

        } else if (mode.startsWith("r")) {

            res |= O_RDONLY;

            res = O_RDONLY;

        } else {

            throw new IllegalArgumentException("Bad mode: " + mode);

        }
@@ -1279,12 +1280,12 @@ public class FileUtils { 
    /** {@hide} */

    public static String translateModePosixToString(int mode) {

        String res = "";

        if ((mode & O_RDWR) == O_RDWR) {

            res += "rw";

        } else if ((mode & O_WRONLY) == O_WRONLY) {

            res += "w";

        } else if ((mode & O_RDONLY) == O_RDONLY) {

            res += "r";

        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);

        }
@@ -1300,12 +1301,12 @@ public class FileUtils { 
    /** {@hide} */

    public static int translateModePosixToPfd(int mode) {

        int res = 0;

        if ((mode & O_RDWR) == O_RDWR) {

            res |= MODE_READ_WRITE;

        } else if ((mode & O_WRONLY) == O_WRONLY) {

            res |= MODE_WRITE_ONLY;

        } else if ((mode & O_RDONLY) == O_RDONLY) {

            res |= MODE_READ_ONLY;

        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);

        }
@@ -1325,11 +1326,11 @@ public class FileUtils { 
    public static int translateModePfdToPosix(int mode) {

        int res = 0;

        if ((mode & MODE_READ_WRITE) == MODE_READ_WRITE) {

            res |= O_RDWR;

            res = O_RDWR;

        } else if ((mode & MODE_WRITE_ONLY) == MODE_WRITE_ONLY) {

            res |= O_WRONLY;

            res = O_WRONLY;

        } else if ((mode & MODE_READ_ONLY) == MODE_READ_ONLY) {

            res |= O_RDONLY;

            res = O_RDONLY;

        } else {

            throw new IllegalArgumentException("Bad mode: " + mode);

        }
@@ -1428,4 +1429,3 @@ public class FileUtils { 
        }

    }

}

core/tests/coretests/src/android/os/FileUtilsTest.java

+22 −0
Original line number Diff line number Diff line
@@ -516,6 +516,28 @@ public class FileUtilsTest { 
                MODE_WRITE_ONLY | MODE_CREATE | MODE_APPEND);

    }



    @Test

    public void testMalformedTransate_int() throws Exception {

        try {

            // The non-standard Linux access mode 3 should throw

            // an IllegalArgumentException.

            translateModePosixToPfd(O_RDWR | O_WRONLY);

            fail();

        } catch (IllegalArgumentException expected) {

        }

    }



    @Test

    public void testMalformedTransate_string() throws Exception {

        try {

            // The non-standard Linux access mode 3 should throw

            // an IllegalArgumentException.

            translateModePosixToString(O_RDWR | O_WRONLY);

            fail();

        } catch (IllegalArgumentException expected) {

        }

    }



    @Test

    public void testTranslateMode_Invalid() throws Exception {

        try {