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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: import gnu.classpath.VMStackWalker; 44: 45: import java.io.InputStream; 46: import java.io.PrintStream; 47: import java.util.Properties; 48: import java.util.PropertyPermission; 49: 50: /** 51: * System represents system-wide resources; things that represent the 52: * general environment. As such, all methods are static. 53: * 54: * @author John Keiser 55: * @author Eric Blake (ebb9@email.byu.edu) 56: * @since 1.0 57: * @status still missing 1.4 functionality 58: */ 59: public final class System 60: { 61: // WARNING: System is a CORE class in the bootstrap cycle. See the comments 62: // in vm/reference/java/lang/Runtime for implications of this fact. 63: 64: /** 65: * The standard InputStream. This is assigned at startup and starts its 66: * life perfectly valid. Although it is marked final, you can change it 67: * using {@link #setIn(InputStream)} through some hefty VM magic. 68: * 69: * <p>This corresponds to the C stdin and C++ cin variables, which 70: * typically input from the keyboard, but may be used to pipe input from 71: * other processes or files. That should all be transparent to you, 72: * however. 73: */ 74: public static final InputStream in = VMSystem.makeStandardInputStream(); 75: 76: /** 77: * The standard output PrintStream. This is assigned at startup and 78: * starts its life perfectly valid. Although it is marked final, you can 79: * change it using {@link #setOut(PrintStream)} through some hefty VM magic. 80: * 81: * <p>This corresponds to the C stdout and C++ cout variables, which 82: * typically output normal messages to the screen, but may be used to pipe 83: * output to other processes or files. That should all be transparent to 84: * you, however. 85: */ 86: public static final PrintStream out = VMSystem.makeStandardOutputStream(); 87: 88: /** 89: * The standard output PrintStream. This is assigned at startup and 90: * starts its life perfectly valid. Although it is marked final, you can 91: * change it using {@link #setErr(PrintStream)} through some hefty VM magic. 92: * 93: * <p>This corresponds to the C stderr and C++ cerr variables, which 94: * typically output error messages to the screen, but may be used to pipe 95: * output to other processes or files. That should all be transparent to 96: * you, however. 97: */ 98: public static final PrintStream err = VMSystem.makeStandardErrorStream(); 99: 100: /** 101: * This class is uninstantiable. 102: */ 103: private System() 104: { 105: } 106: 107: /** 108: * Set {@link #in} to a new InputStream. This uses some VM magic to change 109: * a "final" variable, so naturally there is a security check, 110: * <code>RuntimePermission("setIO")</code>. 111: * 112: * @param in the new InputStream 113: * @throws SecurityException if permission is denied 114: * @since 1.1 115: */ 116: public static void setIn(InputStream in) 117: { 118: SecurityManager sm = SecurityManager.current; // Be thread-safe. 119: if (sm != null) 120: sm.checkPermission(new RuntimePermission("setIO")); 121: VMSystem.setIn(in); 122: } 123: 124: /** 125: * Set {@link #out} to a new PrintStream. This uses some VM magic to change 126: * a "final" variable, so naturally there is a security check, 127: * <code>RuntimePermission("setIO")</code>. 128: * 129: * @param out the new PrintStream 130: * @throws SecurityException if permission is denied 131: * @since 1.1 132: */ 133: public static void setOut(PrintStream out) 134: { 135: SecurityManager sm = SecurityManager.current; // Be thread-safe. 136: if (sm != null) 137: sm.checkPermission(new RuntimePermission("setIO")); 138: 139: VMSystem.setOut(out); 140: } 141: 142: /** 143: * Set {@link #err} to a new PrintStream. This uses some VM magic to change 144: * a "final" variable, so naturally there is a security check, 145: * <code>RuntimePermission("setIO")</code>. 146: * 147: * @param err the new PrintStream 148: * @throws SecurityException if permission is denied 149: * @since 1.1 150: */ 151: public static void setErr(PrintStream err) 152: { 153: SecurityManager sm = SecurityManager.current; // Be thread-safe. 154: if (sm != null) 155: sm.checkPermission(new RuntimePermission("setIO")); 156: VMSystem.setErr(err); 157: } 158: 159: /** 160: * Set the current SecurityManager. If a security manager already exists, 161: * then <code>RuntimePermission("setSecurityManager")</code> is checked 162: * first. Since this permission is denied by the default security manager, 163: * setting the security manager is often an irreversible action. 164: * 165: * <STRONG>Spec Note:</STRONG> Don't ask me, I didn't write it. It looks 166: * pretty vulnerable; whoever gets to the gate first gets to set the policy. 167: * There is probably some way to set the original security manager as a 168: * command line argument to the VM, but I don't know it. 169: * 170: * @param sm the new SecurityManager 171: * @throws SecurityException if permission is denied 172: */ 173: public static synchronized void setSecurityManager(SecurityManager sm) 174: { 175: // Implementation note: the field lives in SecurityManager because of 176: // bootstrap initialization issues. This method is synchronized so that 177: // no other thread changes it to null before this thread makes the change. 178: if (SecurityManager.current != null) 179: SecurityManager.current.checkPermission 180: (new RuntimePermission("setSecurityManager")); 181: 182: // java.security.Security's class initialiser loads and parses the 183: // policy files. If it hasn't been run already it will be run 184: // during the first permission check. That initialisation will 185: // fail if a very restrictive security manager is in force, so we 186: // preload it here. 187: if (SecurityManager.current == null) 188: { 189: try 190: { 191: Class.forName("java.security.Security"); 192: } 193: catch (ClassNotFoundException e) 194: { 195: } 196: } 197: 198: SecurityManager.current = sm; 199: } 200: 201: /** 202: * Get the current SecurityManager. If the SecurityManager has not been 203: * set yet, then this method returns null. 204: * 205: * @return the current SecurityManager, or null 206: */ 207: public static SecurityManager getSecurityManager() 208: { 209: return SecurityManager.current; 210: } 211: 212: /** 213: * Get the current time, measured in the number of milliseconds from the 214: * beginning of Jan. 1, 1970. This is gathered from the system clock, with 215: * any attendant incorrectness (it may be timezone dependent). 216: * 217: * @return the current time 218: * @see java.util.Date 219: */ 220: public static long currentTimeMillis() 221: { 222: return VMSystem.currentTimeMillis(); 223: } 224: 225: /** 226: * Copy one array onto another from <code>src[srcStart]</code> ... 227: * <code>src[srcStart+len-1]</code> to <code>dest[destStart]</code> ... 228: * <code>dest[destStart+len-1]</code>. First, the arguments are validated: 229: * neither array may be null, they must be of compatible types, and the 230: * start and length must fit within both arrays. Then the copying starts, 231: * and proceeds through increasing slots. If src and dest are the same 232: * array, this will appear to copy the data to a temporary location first. 233: * An ArrayStoreException in the middle of copying will leave earlier 234: * elements copied, but later elements unchanged. 235: * 236: * @param src the array to copy elements from 237: * @param srcStart the starting position in src 238: * @param dest the array to copy elements to 239: * @param destStart the starting position in dest 240: * @param len the number of elements to copy 241: * @throws NullPointerException if src or dest is null 242: * @throws ArrayStoreException if src or dest is not an array, if they are 243: * not compatible array types, or if an incompatible runtime type 244: * is stored in dest 245: * @throws IndexOutOfBoundsException if len is negative, or if the start or 246: * end copy position in either array is out of bounds 247: */ 248: public static void arraycopy(Object src, int srcStart, 249: Object dest, int destStart, int len) 250: { 251: VMSystem.arraycopy(src, srcStart, dest, destStart, len); 252: } 253: 254: /** 255: * Get a hash code computed by the VM for the Object. This hash code will 256: * be the same as Object's hashCode() method. It is usually some 257: * convolution of the pointer to the Object internal to the VM. It 258: * follows standard hash code rules, in that it will remain the same for a 259: * given Object for the lifetime of that Object. 260: * 261: * @param o the Object to get the hash code for 262: * @return the VM-dependent hash code for this Object 263: * @since 1.1 264: */ 265: public static int identityHashCode(Object o) 266: { 267: return VMSystem.identityHashCode(o); 268: } 269: 270: /** 271: * Get all the system properties at once. A security check may be performed, 272: * <code>checkPropertiesAccess</code>. Note that a security manager may 273: * allow getting a single property, but not the entire group. 274: * 275: * <p>The required properties include: 276: * <dl> 277: * <dt>java.version</dt> <dd>Java version number</dd> 278: * <dt>java.vendor</dt> <dd>Java vendor specific string</dd> 279: * <dt>java.vendor.url</dt> <dd>Java vendor URL</dd> 280: * <dt>java.home</dt> <dd>Java installation directory</dd> 281: * <dt>java.vm.specification.version</dt> <dd>VM Spec version</dd> 282: * <dt>java.vm.specification.vendor</dt> <dd>VM Spec vendor</dd> 283: * <dt>java.vm.specification.name</dt> <dd>VM Spec name</dd> 284: * <dt>java.vm.version</dt> <dd>VM implementation version</dd> 285: * <dt>java.vm.vendor</dt> <dd>VM implementation vendor</dd> 286: * <dt>java.vm.name</dt> <dd>VM implementation name</dd> 287: * <dt>java.specification.version</dt> <dd>Java Runtime Environment version</dd> 288: * <dt>java.specification.vendor</dt> <dd>Java Runtime Environment vendor</dd> 289: * <dt>java.specification.name</dt> <dd>Java Runtime Environment name</dd> 290: * <dt>java.class.version</dt> <dd>Java class version number</dd> 291: * <dt>java.class.path</dt> <dd>Java classpath</dd> 292: * <dt>java.library.path</dt> <dd>Path for finding Java libraries</dd> 293: * <dt>java.io.tmpdir</dt> <dd>Default temp file path</dd> 294: * <dt>java.compiler</dt> <dd>Name of JIT to use</dd> 295: * <dt>java.ext.dirs</dt> <dd>Java extension path</dd> 296: * <dt>os.name</dt> <dd>Operating System Name</dd> 297: * <dt>os.arch</dt> <dd>Operating System Architecture</dd> 298: * <dt>os.version</dt> <dd>Operating System Version</dd> 299: * <dt>file.separator</dt> <dd>File separator ("/" on Unix)</dd> 300: * <dt>path.separator</dt> <dd>Path separator (":" on Unix)</dd> 301: * <dt>line.separator</dt> <dd>Line separator ("\n" on Unix)</dd> 302: * <dt>user.name</dt> <dd>User account name</dd> 303: * <dt>user.home</dt> <dd>User home directory</dd> 304: * <dt>user.dir</dt> <dd>User's current working directory</dd> 305: * </dl> 306: * 307: * In addition, gnu defines several other properties, where ? stands for 308: * each character in '0' through '9': 309: * <dl> 310: * <dt>gnu.classpath.home</dt> <dd>Path to the classpath libraries.</dd> 311: * <dt>gnu.classpath.version</dt> <dd>Version of the classpath libraries.</dd> 312: * <dt>gnu.classpath.vm.shortname</dt> <dd>Succinct version of the VM name; 313: * used for finding property files in file system</dd> 314: * <dt>gnu.classpath.home.url</dt> <dd> Base URL; used for finding 315: * property files in file system</dd> 316: * <dt>gnu.cpu.endian</dt> <dd>big or little</dd> 317: * <dt>gnu.java.io.encoding_scheme_alias.iso-8859-?</dt> <dd>8859_?</dd> 318: * <dt>gnu.java.io.encoding_scheme_alias.iso8859_?</dt> <dd>8859_?</dd> 319: * <dt>gnu.java.io.encoding_scheme_alias.iso-latin-_?</dt> <dd>8859_?</dd> 320: * <dt>gnu.java.io.encoding_scheme_alias.latin?</dt> <dd>8859_?</dd> 321: * <dt>gnu.java.io.encoding_scheme_alias.utf-8</dt> <dd>UTF8</dd> 322: * </dl> 323: * 324: * @return the system properties, will never be null 325: * @throws SecurityException if permission is denied 326: */ 327: public static Properties getProperties() 328: { 329: SecurityManager sm = SecurityManager.current; // Be thread-safe. 330: if (sm != null) 331: sm.checkPropertiesAccess(); 332: return SystemProperties.getProperties(); 333: } 334: 335: /** 336: * Set all the system properties at once. A security check may be performed, 337: * <code>checkPropertiesAccess</code>. Note that a security manager may 338: * allow setting a single property, but not the entire group. An argument 339: * of null resets the properties to the startup default. 340: * 341: * @param properties the new set of system properties 342: * @throws SecurityException if permission is denied 343: */ 344: public static void setProperties(Properties properties) 345: { 346: SecurityManager sm = SecurityManager.current; // Be thread-safe. 347: if (sm != null) 348: sm.checkPropertiesAccess(); 349: SystemProperties.setProperties(properties); 350: } 351: 352: /** 353: * Get a single system property by name. A security check may be performed, 354: * <code>checkPropertyAccess(key)</code>. 355: * 356: * @param key the name of the system property to get 357: * @return the property, or null if not found 358: * @throws SecurityException if permission is denied 359: * @throws NullPointerException if key is null 360: * @throws IllegalArgumentException if key is "" 361: */ 362: public static String getProperty(String key) 363: { 364: SecurityManager sm = SecurityManager.current; // Be thread-safe. 365: if (sm != null) 366: sm.checkPropertyAccess(key); 367: if (key.length() == 0) 368: throw new IllegalArgumentException("key can't be empty"); 369: return SystemProperties.getProperty(key); 370: } 371: 372: /** 373: * Get a single system property by name. A security check may be performed, 374: * <code>checkPropertyAccess(key)</code>. 375: * 376: * @param key the name of the system property to get 377: * @param def the default 378: * @return the property, or def if not found 379: * @throws SecurityException if permission is denied 380: * @throws NullPointerException if key is null 381: * @throws IllegalArgumentException if key is "" 382: */ 383: public static String getProperty(String key, String def) 384: { 385: SecurityManager sm = SecurityManager.current; // Be thread-safe. 386: if (sm != null) 387: sm.checkPropertyAccess(key); 388: // This handles both the null pointer exception and the illegal 389: // argument exception. 390: if (key.length() == 0) 391: throw new IllegalArgumentException("key can't be empty"); 392: return SystemProperties.getProperty(key, def); 393: } 394: 395: /** 396: * Set a single system property by name. A security check may be performed, 397: * <code>checkPropertyAccess(key, "write")</code>. 398: * 399: * @param key the name of the system property to set 400: * @param value the new value 401: * @return the previous value, or null 402: * @throws SecurityException if permission is denied 403: * @throws NullPointerException if key is null 404: * @throws IllegalArgumentException if key is "" 405: * @since 1.2 406: */ 407: public static String setProperty(String key, String value) 408: { 409: SecurityManager sm = SecurityManager.current; // Be thread-safe. 410: if (sm != null) 411: sm.checkPermission(new PropertyPermission(key, "write")); 412: // This handles both the null pointer exception and the illegal 413: // argument exception. 414: if (key.length() == 0) 415: throw new IllegalArgumentException("key can't be empty"); 416: return SystemProperties.setProperty(key, value); 417: } 418: 419: /** 420: * Remove a single system property by name. A security check may be 421: * performed, <code>checkPropertyAccess(key, "write")</code>. 422: * 423: * @param key the name of the system property to remove 424: * @return the previous value, or null 425: * @throws SecurityException if permission is denied 426: * @throws NullPointerException if key is null 427: * @throws IllegalArgumentException if key is "" 428: * @since 1.5 429: */ 430: public static String clearProperty(String key) 431: { 432: SecurityManager sm = SecurityManager.current; // Be thread-safe. 433: if (sm != null) 434: sm.checkPermission(new PropertyPermission(key, "write")); 435: // This handles both the null pointer exception and the illegal 436: // argument exception. 437: if (key.length() == 0) 438: throw new IllegalArgumentException("key can't be empty"); 439: return SystemProperties.remove(key); 440: } 441: 442: /** 443: * Gets the value of an environment variable. 444: * 445: * @param name the name of the environment variable 446: * @return the string value of the variable or null when the 447: * environment variable is not defined. 448: * @throws NullPointerException 449: * @throws SecurityException if permission is denied 450: * @since 1.5 451: * @specnote This method was deprecated in some JDK releases, but 452: * was restored in 1.5. 453: */ 454: public static String getenv(String name) 455: { 456: if (name == null) 457: throw new NullPointerException(); 458: SecurityManager sm = SecurityManager.current; // Be thread-safe. 459: if (sm != null) 460: sm.checkPermission(new RuntimePermission("getenv." + name)); 461: return VMSystem.getenv(name); 462: } 463: 464: /** 465: * Terminate the Virtual Machine. This just calls 466: * <code>Runtime.getRuntime().exit(status)</code>, and never returns. 467: * Obviously, a security check is in order, <code>checkExit</code>. 468: * 469: * @param status the exit status; by convention non-zero is abnormal 470: * @throws SecurityException if permission is denied 471: * @see Runtime#exit(int) 472: */ 473: public static void exit(int status) 474: { 475: Runtime.getRuntime().exit(status); 476: } 477: 478: /** 479: * Calls the garbage collector. This is only a hint, and it is up to the 480: * implementation what this hint suggests, but it usually causes a 481: * best-effort attempt to reclaim unused memory from discarded objects. 482: * This calls <code>Runtime.getRuntime().gc()</code>. 483: * 484: * @see Runtime#gc() 485: */ 486: public static void gc() 487: { 488: Runtime.getRuntime().gc(); 489: } 490: 491: /** 492: * Runs object finalization on pending objects. This is only a hint, and 493: * it is up to the implementation what this hint suggests, but it usually 494: * causes a best-effort attempt to run finalizers on all objects ready 495: * to be reclaimed. This calls 496: * <code>Runtime.getRuntime().runFinalization()</code>. 497: * 498: * @see Runtime#runFinalization() 499: */ 500: public static void runFinalization() 501: { 502: Runtime.getRuntime().runFinalization(); 503: } 504: 505: /** 506: * Tell the Runtime whether to run finalization before exiting the 507: * JVM. This is inherently unsafe in multi-threaded applications, 508: * since it can force initialization on objects which are still in use 509: * by live threads, leading to deadlock; therefore this is disabled by 510: * default. There may be a security check, <code>checkExit(0)</code>. This 511: * calls <code>Runtime.runFinalizersOnExit()</code>. 512: * 513: * @param finalizeOnExit whether to run finalizers on exit 514: * @throws SecurityException if permission is denied 515: * @see Runtime#runFinalizersOnExit(boolean) 516: * @since 1.1 517: * @deprecated never rely on finalizers to do a clean, thread-safe, 518: * mop-up from your code 519: */ 520: public static void runFinalizersOnExit(boolean finalizeOnExit) 521: { 522: Runtime.runFinalizersOnExit(finalizeOnExit); 523: } 524: 525: /** 526: * Load a code file using its explicit system-dependent filename. A security 527: * check may be performed, <code>checkLink</code>. This just calls 528: * <code>Runtime.getRuntime().load(filename)</code>. 529: * 530: * <p> 531: * The library is loaded using the class loader associated with the 532: * class associated with the invoking method. 533: * 534: * @param filename the code file to load 535: * @throws SecurityException if permission is denied 536: * @throws UnsatisfiedLinkError if the file cannot be loaded 537: * @see Runtime#load(String) 538: */ 539: public static void load(String filename) 540: { 541: Runtime.getRuntime().load(filename, VMStackWalker.getCallingClassLoader()); 542: } 543: 544: /** 545: * Load a library using its explicit system-dependent filename. A security 546: * check may be performed, <code>checkLink</code>. This just calls 547: * <code>Runtime.getRuntime().load(filename)</code>. 548: * 549: * <p> 550: * The library is loaded using the class loader associated with the 551: * class associated with the invoking method. 552: * 553: * @param libname the library file to load 554: * @throws SecurityException if permission is denied 555: * @throws UnsatisfiedLinkError if the file cannot be loaded 556: * @see Runtime#load(String) 557: */ 558: public static void loadLibrary(String libname) 559: { 560: Runtime.getRuntime().loadLibrary(libname, 561: VMStackWalker.getCallingClassLoader()); 562: } 563: 564: /** 565: * Convert a library name to its platform-specific variant. 566: * 567: * @param libname the library name, as used in <code>loadLibrary</code> 568: * @return the platform-specific mangling of the name 569: * @since 1.2 570: */ 571: public static String mapLibraryName(String libname) 572: { 573: return VMRuntime.mapLibraryName(libname); 574: } 575: 576: } // class System
GNU Classpath (0.91) |