runtime.java

linux下建立JAVA虚拟机的源码KAFFE

   * @throws SecurityException if permission is denied
   * @see #exit(int)
   * @see #gc()
   * @since 1.1
   * @deprecated never rely on finalizers to do a clean, thread-safe,
   *             mop-up from your code
   */
  public static void runFinalizersOnExit(boolean finalizeOnExit)
  {
    SecurityManager sm = SecurityManager.current; // Be thread-safe!
    if (sm != null)
      sm.checkExit(0);
    VMRuntime.runFinalizersOnExit(finalizeOnExit);
  }

  /**
   * Create a new subprocess with the specified command line. Calls
   * <code>exec(cmdline, null, null)</code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null
   * @throws IndexOutOfBoundsException if cmdline is ""
   */
  public Process exec(String cmdline) throws IOException
  {
    return exec(cmdline, null, null);
  }

  /**
   * Create a new subprocess with the specified command line and environment.
   * If the environment is null, the process inherits the environment of
   * this process. Calls <code>exec(cmdline, env, null)</code>. A security
   * check is performed, <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @param env the environment to use, in the format name=value
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null, or env has null entries
   * @throws IndexOutOfBoundsException if cmdline is ""
   */
  public Process exec(String cmdline, String[] env) throws IOException
  {
    return exec(cmdline, env, null);
  }

  /**
   * Create a new subprocess with the specified command line, environment, and
   * working directory. If the environment is null, the process inherits the
   * environment of this process. If the directory is null, the process uses
   * the current working directory. This splits cmdline into an array, using
   * the default StringTokenizer, then calls
   * <code>exec(cmdArray, env, dir)</code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmdline the command to call
   * @param env the environment to use, in the format name=value
   * @param dir the working directory to use
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmdline is null, or env has null entries
   * @throws IndexOutOfBoundsException if cmdline is ""
   * @since 1.3
   */
  public Process exec(String cmdline, String[] env, File dir)
    throws IOException
  {
    StringTokenizer t = new StringTokenizer(cmdline);
    String[] cmd = new String[t.countTokens()];
    for (int i = 0; i < cmd.length; i++)
      cmd[i] = t.nextToken();
    return exec(cmd, env, dir);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized. Calls <code>exec(cmd, null, null)</code>. A security check
   * is performed, <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or has null entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   */
  public Process exec(String[] cmd) throws IOException
  {
    return exec(cmd, null, null);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized, and specified environment. If the environment is null, the
   * process inherits the environment of this process. Calls
   * <code>exec(cmd, env, null)</code>. A security check is performed,
   * <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @param env the environment to use, in the format name=value
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or cmd or env has null
   *         entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   */
  public Process exec(String[] cmd, String[] env) throws IOException
  {
    return exec(cmd, env, null);
  }

  /**
   * Create a new subprocess with the specified command line, already
   * tokenized, and the specified environment and working directory. If the
   * environment is null, the process inherits the environment of this
   * process. If the directory is null, the process uses the current working
   * directory. A security check is performed, <code>checkExec</code>.
   *
   * @param cmd the command to call
   * @param env the environment to use, in the format name=value
   * @param dir the working directory to use
   * @return the Process object
   * @throws SecurityException if permission is denied
   * @throws IOException if an I/O error occurs
   * @throws NullPointerException if cmd is null, or cmd or env has null
   *         entries
   * @throws IndexOutOfBoundsException if cmd is length 0
   * @since 1.3
   */
  public Process exec(String[] cmd, String[] env, File dir)
    throws IOException
  {
    SecurityManager sm = SecurityManager.current; // Be thread-safe!
    if (sm != null)
      sm.checkExec(cmd[0]);
    return VMRuntime.exec(cmd, env, dir);
  }

  /**
   * Returns the number of available processors currently available to the
   * virtual machine. This number may change over time; so a multi-processor
   * program want to poll this to determine maximal resource usage.
   *
   * @return the number of processors available, at least 1
   */
  public int availableProcessors()
  {
    return VMRuntime.availableProcessors();
  }

  /**
   * Find out how much memory is still free for allocating Objects on the heap.
   *
   * @return the number of bytes of free memory for more Objects
   */
  public long freeMemory()
  {
    return VMRuntime.freeMemory();
  }

  /**
   * Find out how much memory total is available on the heap for allocating
   * Objects.
   *
   * @return the total number of bytes of memory for Objects
   */
  public long totalMemory()
  {
    return VMRuntime.totalMemory();
  }

  /**
   * Returns the maximum amount of memory the virtual machine can attempt to
   * use. This may be <code>Long.MAX_VALUE</code> if there is no inherent
   * limit (or if you really do have a 8 exabyte memory!).
   *
   * @return the maximum number of bytes the virtual machine will attempt
   *         to allocate
   */
  public long maxMemory()
  {
    return VMRuntime.maxMemory();
  }

  /**
   * Run the garbage collector. This method is more of a suggestion than
   * anything. All this method guarantees is that the garbage collector will
   * have "done its best" by the time it returns. Notice that garbage
   * collection takes place even without calling this method.
   */
  public void gc()
  {
    VMRuntime.gc();
  }

  /**
   * Run finalization on all Objects that are waiting to be finalized. Again,
   * a suggestion, though a stronger one than {@link #gc()}. This calls the
   * <code>finalize</code> method of all objects waiting to be collected.
   *
   * @see #finalize()
   */
  public void runFinalization()
  {
    VMRuntime.runFinalization();
  }

  /**
   * Tell the VM to trace every bytecode instruction that executes (print out
   * a trace of it).  No guarantees are made as to where it will be printed,
   * and the VM is allowed to ignore this request.
   *
   * @param on whether to turn instruction tracing on
   */
  public void traceInstructions(boolean on)
  {
    VMRuntime.traceInstructions(on);
  }

  /**
   * Tell the VM to trace every method call that executes (print out a trace
   * of it).  No guarantees are made as to where it will be printed, and the
   * VM is allowed to ignore this request.
   *
   * @param on whether to turn method tracing on
   */
  public void traceMethodCalls(boolean on)
  {
    VMRuntime.traceMethodCalls(on);
  }

  /**
   * Load a native library using the system-dependent filename. This is similar
   * to loadLibrary, except the only name mangling done is inserting "_g"
   * before the final ".so" if the VM was invoked by the name "java_g". There
   * may be a security check, of <code>checkLink</code>.
   *
   * <p>
   * The library is loaded using the class loader associated with the
   * class associated with the invoking method.
   *
   * @param filename the file to load
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   */
  public void load(String filename)
  {
    load(filename, VMStackWalker.getCallingClassLoader());
  }

  /**
   * Same as <code>load(String)</code> but using the given loader.
   *
   * @param filename the file to load
   * @param loader class loader, or <code>null</code> for the boot loader
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   */
  void load(String filename, ClassLoader loader)
  {
    SecurityManager sm = SecurityManager.current; // Be thread-safe!
    if (sm != null)
      sm.checkLink(filename);
    if (loadLib(filename, loader) == 0)
      throw new UnsatisfiedLinkError("Could not load library " + filename);
  }

  /**
   * Do a security check on the filename and then load the native library.
   *
   * @param filename the file to load
   * @param loader class loader, or <code>null</code> for the boot loader
   * @return 0 on failure, nonzero on success
   * @throws SecurityException if file read permission is denied
   */
  private static int loadLib(String filename, ClassLoader loader)
  {
    SecurityManager sm = SecurityManager.current; // Be thread-safe!
    if (sm != null)
      sm.checkRead(filename);
    return VMRuntime.nativeLoad(filename, loader);
  }

  /**
   * Load a native library using a system-independent "short name" for the
   * library.  It will be transformed to a correct filename in a
   * system-dependent manner (for example, in Windows, "mylib" will be turned
   * into "mylib.dll").  This is done as follows: if the context that called
   * load has a ClassLoader cl, then <code>cl.findLibrary(libpath)</code> is
   * used to convert the name. If that result was null, or there was no class
   * loader, this searches each directory of the system property
   * <code>java.library.path</code> for a file named
   * <code>System.mapLibraryName(libname)</code>. There may be a security
   * check, of <code>checkLink</code>.
   *
   * <p>Note: Besides <code>java.library.path</code> a VM may chose to search
   * for native libraries in a path that is specified by the
   * <code>gnu.classpath.boot.library.path</code> system property. However
   * this is for internal usage or development of GNU Classpath only.
   * <b>A Java application must not load a non-system library by changing
   * this property otherwise it will break compatibility.</b></p>
   *
   * <p>
   * The library is loaded using the class loader associated with the
   * class associated with the invoking method.
   *
   * @param libname the library to load
   *
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   *
   * @see System#mapLibraryName(String)
   * @see ClassLoader#findLibrary(String)
   */
  public void loadLibrary(String libname)
  {
    loadLibrary(libname, VMStackWalker.getCallingClassLoader());
  }

  /**
   * Same as <code>loadLibrary(String)</code> but using the given loader.
   *
   * @param libname the library to load
   * @param loader class loader, or <code>null</code> for the boot loader
   * @throws SecurityException if permission is denied
   * @throws UnsatisfiedLinkError if the library is not found
   */
  void loadLibrary(String libname, ClassLoader loader)
  {
    SecurityManager sm = SecurityManager.current; // Be thread-safe!
    if (sm != null)
      sm.checkLink(libname);
    String filename;
    if (loader != null && (filename = loader.findLibrary(libname)) != null)
      {
	if (loadLib(filename, loader) != 0)
	  return;
      }
    else
      {
	filename = VMRuntime.mapLibraryName(libname);
	for (int i = 0; i < libpath.length; i++)
	  if (loadLib(libpath[i] + filename, loader) != 0)
	    return;

	// OK. That did not work. Let's be creative and try different
	// prefix-suffix combinations.
	// NB: Yes, this is a wasteful implementation.

	String [] prefixes = {"lib",
			      "cyg", 
			      "" };
	String [] suffixes = {".so",
			      ".dll", 
			      ".la",
			      ".a",
			      ".dylib", 
			      ".jnilib",
			      ".dll.a"};
	for (int j = 0; j < prefixes.length; j++)
	    for (int k = 0; k < suffixes.length; k++)
		for (int i = 0; i < libpath.length; i++)
		    if (loadLib(libpath[i] + prefixes[j] + libname + suffixes[k], loader) != 0)
			return;
      }
    throw new UnsatisfiedLinkError("Native library `" + libname
      + "' not found (as file `" + filename 
      + "' in class loader " + loader
      + ") in gnu.classpath.boot.library.path and java.library.path `"
      + Arrays.asList(libpath) + "'");
  }

  /**
   * Return a localized version of this InputStream, meaning all characters
   * are localized before they come out the other end.
   *
   * @param in the stream to localize
   * @return the localized stream
   * @deprecated <code>InputStreamReader</code> is the preferred way to read
   *             local encodings
   * @XXX This implementation does not localize, yet.
   */
  public InputStream getLocalizedInputStream(InputStream in)
  {
    return in;
  }

  /**
   * Return a localized version of this OutputStream, meaning all characters
   * are localized before they are sent to the other end.
   *
   * @param out the stream to localize
   * @return the localized stream
   * @deprecated <code>OutputStreamWriter</code> is the preferred way to write
   *             local encodings
   * @XXX This implementation does not localize, yet.
   */
  public OutputStream getLocalizedOutputStream(OutputStream out)
  {
    return out;
  }
} // class Runtime