Frames | No Frames |
1: /* System.java -- useful methods to interface with the system 2: Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 3: Free Software Foundation, Inc. 4: 5: This file is part of GNU Classpath. 6: 7: GNU Classpath is free software; you can redistribute it and/or modify 8: it under the terms of the GNU General Public License as published by 9: the Free Software Foundation; either version 2, or (at your option) 10: any later version. 11: 12: GNU Classpath is distributed in the hope that it will be useful, but 13: WITHOUT ANY WARRANTY; without even the implied warranty of 14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15: General Public License for more details. 16: 17: You should have received a copy of the GNU General Public License 18: along with GNU Classpath; see the file COPYING. If not, write to the 19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 20: 02110-1301 USA. 21: 22: Linking this library statically or dynamically with other modules is 23: making a combined work based on this library. Thus, the terms and 24: conditions of the GNU General Public License cover the whole 25: combination. 26: 27: As a special exception, the copyright holders of this library give you 28: permission to link this library with independent modules to produce an 29: executable, regardless of the license terms of these independent 30: modules, and to copy and distribute the resulting executable under 31: terms of your choice, provided that you also meet, for each linked 32: independent module, the terms and conditions of the license of that 33: module. An independent module is a module which is not derived from 34: or based on this library. If you modify this library, you may extend 35: this exception to your version of the library, but you are not 36: obligated to do so. If you do not wish to do so, delete this 37: exception statement from your version. */ 38: 39: 40: package java.lang; 41: 42: import gnu.classpath.SystemProperties; 43: 44: import java.io.BufferedInputStream; 45: import java.io.BufferedOutputStream; 46: import java.io.FileDescriptor; 47: import java.io.FileInputStream; 48: import java.io.FileOutputStream; 49: import java.io.InputStream; 50: import java.io.PrintStream; 51: import java.util.Properties; 52: import java.util.PropertyPermission; 53: 54: /** 55: * System represents system-wide resources; things that represent the 56: * general environment. As such, all methods are static. 57: * 58: * @author John Keiser 59: * @author Eric Blake (ebb9@email.byu.edu) 60: * @since 1.0 61: * @status still missing 1.4 functionality 62: */ 63: public final class System 64: { 65: // WARNING: System is a CORE class in the bootstrap cycle. See the comments 66: // in vm/reference/java/lang/Runtime for implications of this fact. 67: 68: /** 69: * The standard InputStream. This is assigned at startup and starts its 70: * life perfectly valid. Although it is marked final, you can change it 71: * using {@link #setIn(InputStream)} through some hefty VM magic. 72: * 73: * <p>This corresponds to the C stdin and C++ cin variables, which 74: * typically input from the keyboard, but may be used to pipe input from 75: * other processes or files. That should all be transparent to you, 76: * however. 77: */ 78: public static final InputStream in 79: = new BufferedInputStream(new FileInputStream(FileDescriptor.in)); 80: /** 81: * The standard output PrintStream. This is assigned at startup and 82: * starts its life perfectly valid. Although it is marked final, you can 83: * change it using {@link #setOut(PrintStream)} through some hefty VM magic. 84: * 85: * <p>This corresponds to the C stdout and C++ cout variables, which 86: * typically output normal messages to the screen, but may be used to pipe 87: * output to other processes or files. That should all be transparent to 88: * you, however. 89: */ 90: public static final PrintStream out 91: = new PrintStream(new BufferedOutputStream(new FileOutputStream(FileDescriptor.out)), true); 92: /** 93: * The standard output PrintStream. This is assigned at startup and 94: * starts its life perfectly valid. Although it is marked final, you can 95: * change it using {@link #setErr(PrintStream)} through some hefty VM magic. 96: * 97: * <p>This corresponds to the C stderr and C++ cerr variables, which 98: * typically output error messages to the screen, but may be used to pipe 99: * output to other processes or files. That should all be transparent to 100: * you, however. 101: */ 102: public static final PrintStream err 103: = new PrintStream(new BufferedOutputStream(new FileOutputStream(FileDescriptor.err)), true); 104: 105: /** 106: * This class is uninstantiable. 107: */ 108: private System() 109: { 110: } 111: 112: /** 113: * Set {@link #in} to a new InputStream. This uses some VM magic to change 114: * a "final" variable, so naturally there is a security check, 115: * <code>RuntimePermission("setIO")</code>. 116: * 117: * @param in the new InputStream 118: * @throws SecurityException if permission is denied 119: * @since 1.1 120: */ 121: public static void setIn(InputStream in) 122: { 123: SecurityManager sm = SecurityManager.current; // Be thread-safe. 124: if (sm != null) 125: sm.checkPermission(new RuntimePermission("setIO")); 126: setIn0(in); 127: } 128: 129: /** 130: * Set {@link #out} to a new PrintStream. This uses some VM magic to change 131: * a "final" variable, so naturally there is a security check, 132: * <code>RuntimePermission("setIO")</code>. 133: * 134: * @param out the new PrintStream 135: * @throws SecurityException if permission is denied 136: * @since 1.1 137: */ 138: public static void setOut(PrintStream out) 139: { 140: SecurityManager sm = SecurityManager.current; // Be thread-safe. 141: if (sm != null) 142: sm.checkPermission(new RuntimePermission("setIO")); 143: 144: setOut0(out); 145: } 146: 147: /** 148: * Set {@link #err} to a new PrintStream. This uses some VM magic to change 149: * a "final" variable, so naturally there is a security check, 150: * <code>RuntimePermission("setIO")</code>. 151: * 152: * @param err the new PrintStream 153: * @throws SecurityException if permission is denied 154: * @since 1.1 155: */ 156: public static void setErr(PrintStream err) 157: { 158: SecurityManager sm = SecurityManager.current; // Be thread-safe. 159: if (sm != null) 160: sm.checkPermission(new RuntimePermission("setIO")); 161: setErr0(err); 162: } 163: 164: /** 165: * Set the current SecurityManager. If a security manager already exists, 166: * then <code>RuntimePermission("setSecurityManager")</code> is checked 167: * first. Since this permission is denied by the default security manager, 168: * setting the security manager is often an irreversible action. 169: * 170: * <STRONG>Spec Note:</STRONG> Don't ask me, I didn't write it. It looks 171: * pretty vulnerable; whoever gets to the gate first gets to set the policy. 172: * There is probably some way to set the original security manager as a 173: * command line argument to the VM, but I don't know it. 174: * 175: * @param sm the new SecurityManager 176: * @throws SecurityException if permission is denied 177: */ 178: public static synchronized void setSecurityManager(SecurityManager sm) 179: { 180: // Implementation note: the field lives in SecurityManager because of 181: // bootstrap initialization issues. This method is synchronized so that 182: // no other thread changes it to null before this thread makes the change. 183: if (SecurityManager.current != null) 184: SecurityManager.current.checkPermission 185: (new RuntimePermission("setSecurityManager")); 186: SecurityManager.current = sm; 187: } 188: 189: /** 190: * Get the current SecurityManager. If the SecurityManager has not been 191: * set yet, then this method returns null. 192: * 193: * @return the current SecurityManager, or null 194: */ 195: public static SecurityManager getSecurityManager() 196: { 197: return SecurityManager.current; 198: } 199: 200: /** 201: * Get the current time, measured in the number of milliseconds from the 202: * beginning of Jan. 1, 1970. This is gathered from the system clock, with 203: * any attendant incorrectness (it may be timezone dependent). 204: * 205: * @return the current time 206: * @see java.util.Date 207: */ 208: public static native long currentTimeMillis(); 209: 210: /** 211: * Copy one array onto another from <code>src[srcStart]</code> ... 212: * <code>src[srcStart+len-1]</code> to <code>dest[destStart]</code> ... 213: * <code>dest[destStart+len-1]</code>. First, the arguments are validated: 214: * neither array may be null, they must be of compatible types, and the 215: * start and length must fit within both arrays. Then the copying starts, 216: * and proceeds through increasing slots. If src and dest are the same 217: * array, this will appear to copy the data to a temporary location first. 218: * An ArrayStoreException in the middle of copying will leave earlier 219: * elements copied, but later elements unchanged. 220: * 221: * @param src the array to copy elements from 222: * @param srcStart the starting position in src 223: * @param dest the array to copy elements to 224: * @param destStart the starting position in dest 225: * @param len the number of elements to copy 226: * @throws NullPointerException if src or dest is null 227: * @throws ArrayStoreException if src or dest is not an array, if they are 228: * not compatible array types, or if an incompatible runtime type 229: * is stored in dest 230: * @throws IndexOutOfBoundsException if len is negative, or if the start or 231: * end copy position in either array is out of bounds 232: */ 233: public static native void arraycopy(Object src, int srcStart, 234: Object dest, int destStart, int len); 235: 236: /** 237: * Get a hash code computed by the VM for the Object. This hash code will 238: * be the same as Object's hashCode() method. It is usually some 239: * convolution of the pointer to the Object internal to the VM. It 240: * follows standard hash code rules, in that it will remain the same for a 241: * given Object for the lifetime of that Object. 242: * 243: * @param o the Object to get the hash code for 244: * @return the VM-dependent hash code for this Object 245: * @since 1.1 246: */ 247: public static native int identityHashCode(Object o); 248: 249: /** 250: * Get all the system properties at once. A security check may be performed, 251: * <code>checkPropertiesAccess</code>. Note that a security manager may 252: * allow getting a single property, but not the entire group. 253: * 254: * <p>The required properties include: 255: * <dl> 256: * <dt>java.version</dt> <dd>Java version number</dd> 257: * <dt>java.vendor</dt> <dd>Java vendor specific string</dd> 258: * <dt>java.vendor.url</dt> <dd>Java vendor URL</dd> 259: * <dt>java.home</dt> <dd>Java installation directory</dd> 260: * <dt>java.vm.specification.version</dt> <dd>VM Spec version</dd> 261: * <dt>java.vm.specification.vendor</dt> <dd>VM Spec vendor</dd> 262: * <dt>java.vm.specification.name</dt> <dd>VM Spec name</dd> 263: * <dt>java.vm.version</dt> <dd>VM implementation version</dd> 264: * <dt>java.vm.vendor</dt> <dd>VM implementation vendor</dd> 265: * <dt>java.vm.name</dt> <dd>VM implementation name</dd> 266: * <dt>java.specification.version</dt> <dd>Java Runtime Environment version</dd> 267: * <dt>java.specification.vendor</dt> <dd>Java Runtime Environment vendor</dd> 268: * <dt>java.specification.name</dt> <dd>Java Runtime Environment name</dd> 269: * <dt>java.class.version</dt> <dd>Java class version number</dd> 270: * <dt>java.class.path</dt> <dd>Java classpath</dd> 271: * <dt>java.library.path</dt> <dd>Path for finding Java libraries</dd> 272: * <dt>java.io.tmpdir</dt> <dd>Default temp file path</dd> 273: * <dt>java.compiler</dt> <dd>Name of JIT to use</dd> 274: * <dt>java.ext.dirs</dt> <dd>Java extension path</dd> 275: * <dt>os.name</dt> <dd>Operating System Name</dd> 276: * <dt>os.arch</dt> <dd>Operating System Architecture</dd> 277: * <dt>os.version</dt> <dd>Operating System Version</dd> 278: * <dt>file.separator</dt> <dd>File separator ("/" on Unix)</dd> 279: * <dt>path.separator</dt> <dd>Path separator (":" on Unix)</dd> 280: * <dt>line.separator</dt> <dd>Line separator ("\n" on Unix)</dd> 281: * <dt>user.name</dt> <dd>User account name</dd> 282: * <dt>user.home</dt> <dd>User home directory</dd> 283: * <dt>user.dir</dt> <dd>User's current working directory</dd> 284: * </dl> 285: * 286: * In addition, gnu defines several other properties, where ? stands for 287: * each character in '0' through '9': 288: * <dl> 289: * <dt>gnu.classpath.home</dt> <dd>Path to the classpath libraries.</dd> 290: * <dt>gnu.classpath.version</dt> <dd>Version of the classpath libraries.</dd> 291: * <dt>gnu.classpath.vm.shortname</dt> <dd>Succinct version of the VM name; 292: * used for finding property files in file system</dd> 293: * <dt>gnu.classpath.home.url</dt> <dd> Base URL; used for finding 294: * property files in file system</dd> 295: * <dt>gnu.cpu.endian</dt> <dd>big or little</dd> 296: * <dt>gnu.java.io.encoding_scheme_alias.ISO-8859-?</dt> <dd>8859_?</dd> 297: * <dt>gnu.java.io.encoding_scheme_alias.iso-8859-?</dt> <dd>8859_?</dd> 298: * <dt>gnu.java.io.encoding_scheme_alias.iso8859_?</dt> <dd>8859_?</dd> 299: * <dt>gnu.java.io.encoding_scheme_alias.iso-latin-_?</dt> <dd>8859_?</dd> 300: * <dt>gnu.java.io.encoding_scheme_alias.latin?</dt> <dd>8859_?</dd> 301: * <dt>gnu.java.io.encoding_scheme_alias.UTF-8</dt> <dd>UTF8</dd> 302: * <dt>gnu.java.io.encoding_scheme_alias.utf-8</dt> <dd>UTF8</dd> 303: * </dl> 304: * 305: * @return the system properties, will never be null 306: * @throws SecurityException if permission is denied 307: */ 308: public static Properties getProperties() 309: { 310: SecurityManager sm = SecurityManager.current; // Be thread-safe. 311: if (sm != null) 312: sm.checkPropertiesAccess(); 313: return SystemProperties.getProperties(); 314: } 315: 316: /** 317: * Set all the system properties at once. A security check may be performed, 318: * <code>checkPropertiesAccess</code>. Note that a security manager may 319: * allow setting a single property, but not the entire group. An argument 320: * of null resets the properties to the startup default. 321: * 322: * @param properties the new set of system properties 323: * @throws SecurityException if permission is denied 324: */ 325: public static void setProperties(Properties properties) 326: { 327: SecurityManager sm = SecurityManager.current; // Be thread-safe. 328: if (sm != null) 329: sm.checkPropertiesAccess(); 330: SystemProperties.setProperties(properties); 331: } 332: 333: /** 334: * Get a single system property by name. A security check may be performed, 335: * <code>checkPropertyAccess(key)</code>. 336: * 337: * @param key the name of the system property to get 338: * @return the property, or null if not found 339: * @throws SecurityException if permission is denied 340: * @throws NullPointerException if key is null 341: * @throws IllegalArgumentException if key is "" 342: */ 343: public static String getProperty(String key) 344: { 345: SecurityManager sm = SecurityManager.current; // Be thread-safe. 346: if (sm != null) 347: sm.checkPropertyAccess(key); 348: else if (key.length() == 0) 349: throw new IllegalArgumentException("key can't be empty"); 350: return SystemProperties.getProperty(key); 351: } 352: 353: /** 354: * Get a single system property by name. A security check may be performed, 355: * <code>checkPropertyAccess(key)</code>. 356: * 357: * @param key the name of the system property to get 358: * @param def the default 359: * @return the property, or def if not found 360: * @throws SecurityException if permission is denied 361: * @throws NullPointerException if key is null 362: * @throws IllegalArgumentException if key is "" 363: */ 364: public static String getProperty(String key, String def) 365: { 366: SecurityManager sm = SecurityManager.current; // Be thread-safe. 367: if (sm != null) 368: sm.checkPropertyAccess(key); 369: return SystemProperties.getProperty(key, def); 370: } 371: 372: /** 373: * Set a single system property by name. A security check may be performed, 374: * <code>checkPropertyAccess(key, "write")</code>. 375: * 376: * @param key the name of the system property to set 377: * @param value the new value 378: * @return the previous value, or null 379: * @throws SecurityException if permission is denied 380: * @throws NullPointerException if key is null 381: * @throws IllegalArgumentException if key is "" 382: * @since 1.2 383: */ 384: public static String setProperty(String key, String value) 385: { 386: SecurityManager sm = SecurityManager.current; // Be thread-safe. 387: if (sm != null) 388: sm.checkPermission(new PropertyPermission(key, "write")); 389: return SystemProperties.setProperty(key, value); 390: } 391: 392: /** 393: * Gets the value of an environment variable. 394: * 395: * @param name the name of the environment variable 396: * @return the string value of the variable or null when the 397: * environment variable is not defined. 398: * @throws NullPointerException 399: * @throws SecurityException if permission is denied 400: * @since 1.5 401: * @specnote This method was deprecated in some JDK releases, but 402: * was restored in 1.5. 403: */ 404: public static String getenv(String name) 405: { 406: if (name == null) 407: throw new NullPointerException(); 408: SecurityManager sm = SecurityManager.current; // Be thread-safe. 409: if (sm != null) 410: sm.checkPermission(new RuntimePermission("getenv." + name)); 411: return getenv0(name); 412: } 413: 414: /** 415: * Terminate the Virtual Machine. This just calls 416: * <code>Runtime.getRuntime().exit(status)</code>, and never returns. 417: * Obviously, a security check is in order, <code>checkExit</code>. 418: * 419: * @param status the exit status; by convention non-zero is abnormal 420: * @throws SecurityException if permission is denied 421: * @see Runtime#exit(int) 422: */ 423: public static void exit(int status) 424: { 425: Runtime.getRuntime().exit(status); 426: } 427: 428: /** 429: * Calls the garbage collector. This is only a hint, and it is up to the 430: * implementation what this hint suggests, but it usually causes a 431: * best-effort attempt to reclaim unused memory from discarded objects. 432: * This calls <code>Runtime.getRuntime().gc()</code>. 433: * 434: * @see Runtime#gc() 435: */ 436: public static void gc() 437: { 438: Runtime.getRuntime().gc(); 439: } 440: 441: /** 442: * Runs object finalization on pending objects. This is only a hint, and 443: * it is up to the implementation what this hint suggests, but it usually 444: * causes a best-effort attempt to run finalizers on all objects ready 445: * to be reclaimed. This calls 446: * <code>Runtime.getRuntime().runFinalization()</code>. 447: * 448: * @see Runtime#runFinalization() 449: */ 450: public static void runFinalization() 451: { 452: Runtime.getRuntime().runFinalization(); 453: } 454: 455: /** 456: * Tell the Runtime whether to run finalization before exiting the 457: * JVM. This is inherently unsafe in multi-threaded applications, 458: * since it can force initialization on objects which are still in use 459: * by live threads, leading to deadlock; therefore this is disabled by 460: * default. There may be a security check, <code>checkExit(0)</code>. This 461: * calls <code>Runtime.getRuntime().runFinalizersOnExit()</code>. 462: * 463: * @param finalizeOnExit whether to run finalizers on exit 464: * @throws SecurityException if permission is denied 465: * @see Runtime#runFinalizersOnExit() 466: * @since 1.1 467: * @deprecated never rely on finalizers to do a clean, thread-safe, 468: * mop-up from your code 469: */ 470: public static void runFinalizersOnExit(boolean finalizeOnExit) 471: { 472: Runtime.getRuntime().runFinalizersOnExit(finalizeOnExit); 473: } 474: 475: /** 476: * Load a code file using its explicit system-dependent filename. A security 477: * check may be performed, <code>checkLink</code>. This just calls 478: * <code>Runtime.getRuntime().load(filename)</code>. 479: * 480: * <p> 481: * The library is loaded using the class loader associated with the 482: * class associated with the invoking method. 483: * 484: * @param filename the code file to load 485: * @throws SecurityException if permission is denied 486: * @throws UnsatisfiedLinkError if the file cannot be loaded 487: * @see Runtime#load(String) 488: */ 489: public static void load(String filename) 490: { 491: Runtime.getRuntime().load(filename); 492: } 493: 494: /** 495: * Load a library using its explicit system-dependent filename. A security 496: * check may be performed, <code>checkLink</code>. This just calls 497: * <code>Runtime.getRuntime().load(filename)</code>. 498: * 499: * <p> 500: * The library is loaded using the class loader associated with the 501: * class associated with the invoking method. 502: * 503: * @param libname the library file to load 504: * @throws SecurityException if permission is denied 505: * @throws UnsatisfiedLinkError if the file cannot be loaded 506: * @see Runtime#load(String) 507: */ 508: public static void loadLibrary(String libname) 509: { 510: Runtime.getRuntime().loadLibrary(libname); 511: } 512: 513: /** 514: * Convert a library name to its platform-specific variant. 515: * 516: * @param libname the library name, as used in <code>loadLibrary</code> 517: * @return the platform-specific mangling of the name 518: * @since 1.2 519: */ 520: public static String mapLibraryName(String libname) 521: { 522: // XXX Fix this!!!! 523: return Runtime.nativeGetLibname("", libname); 524: } 525: 526: /** 527: * Set {@link #in} to a new InputStream. 528: * 529: * @param in the new InputStream 530: * @see #setIn(InputStream) 531: */ 532: private static native void setIn0(InputStream in); 533: 534: /** 535: * Set {@link #out} to a new PrintStream. 536: * 537: * @param out the new PrintStream 538: * @see #setOut(PrintStream) 539: */ 540: private static native void setOut0(PrintStream out); 541: 542: /** 543: * Set {@link #err} to a new PrintStream. 544: * 545: * @param err the new PrintStream 546: * @see #setErr(PrintStream) 547: */ 548: private static native void setErr0(PrintStream err); 549: 550: /** 551: * Gets the value of an environment variable. 552: * 553: * @see #getenv(String) 554: */ 555: static native String getenv0(String name); 556: } // class System