How to use

open

method

in

libcore.io.Os

public FileDescriptor open(String path, int flags, int mode) throws ErrnoException { return os.open(path, flags, mode); }
public FileDescriptor[] pipe() throws ErrnoException { return os.pipe(); }

/**
 * Do not use. This is for System.loadLibrary use only.
 *
 * Checks whether {@code path} can be opened read-only. Similar to File.exists, but doesn't
 * require read permission on the parent, so it'll work in more cases, and allow you to
 * remove read permission from more directories. Everyone else should just open(2) and then
 * use the fd, but the loadLibrary API is broken by its need to ask ClassLoaders where to
 * find a .so rather than just calling dlopen(3).
 */
public static boolean canOpenReadOnly(String path) {
  try {
    // Use open(2) rather than stat(2) so we require fewer permissions. http://b/6485312.
    FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
    Libcore.os.close(fd);
    return true;
  } catch (ErrnoException errnoException) {
    return false;
  }
}

try {
  fd = Libcore.os.open(path, O_RDWR | O_CREAT | O_EXCL, 0600);
  return true;
} catch (ErrnoException errnoException) {

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

fd = Libcore.os.open(path, flags, mode);
if (fd.valid()) {

public FileDescriptor open(String path, int flags, int mode) throws ErrnoException { return os.open(path, flags, mode); }
public FileDescriptor[] pipe() throws ErrnoException { return os.pipe(); }

public FileDescriptor open(String path, int flags, int mode) throws ErrnoException { return os.open(path, flags, mode); }
public FileDescriptor[] pipe() throws ErrnoException { return os.pipe(); }

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

/**
 * Use this to mmap the whole file read-only.
 */
public static MemoryMappedFile mmapRO(String path) throws ErrnoException {
  FileDescriptor fd = Libcore.os.open(path, O_RDONLY, 0);
  long size = Libcore.os.fstat(fd).st_size;
  long address = Libcore.os.mmap(0L, size, PROT_READ, MAP_SHARED, fd, 0);
  Libcore.os.close(fd);
  return new MemoryMappedFile(address, size);
}

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}

@Override public FileDescriptor open(String path, int flags, int mode) throws ErrnoException {
  BlockGuard.getThreadPolicy().onReadFromDisk();
  if ((mode & O_ACCMODE) != O_RDONLY) {
    BlockGuard.getThreadPolicy().onWriteToDisk();
  }
  return os.open(path, flags, mode);
}