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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, 2006 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: * @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: SecurityManager.current = sm; 182: } 183: 184: /** 185: * Get the current SecurityManager. If the SecurityManager has not been 186: * set yet, then this method returns null. 187: * 188: * @return the current SecurityManager, or null 189: */ 190: public static SecurityManager getSecurityManager() 191: { 192: return SecurityManager.current; 193: } 194: 195: /** 196: * Get the current time, measured in the number of milliseconds from the 197: * beginning of Jan. 1, 1970. This is gathered from the system clock, with 198: * any attendant incorrectness (it may be timezone dependent). 199: * 200: * @return the current time 201: * @see java.util.Date 202: */ 203: public static native long currentTimeMillis(); 204: 205: /** 206: * Get the current time, measured in nanoseconds. The result is as 207: * precise as possible, and is measured against a fixed epoch. 208: * However, unlike currentTimeMillis(), the epoch chosen is 209: * arbitrary and may vary by platform, etc. 210: * @since 1.5 211: */ 212: public static native long nanoTime(); 213: 214: /** 215: * Copy one array onto another from <code>src[srcStart]</code> ... 216: * <code>src[srcStart+len-1]</code> to <code>dest[destStart]</code> ... 217: * <code>dest[destStart+len-1]</code>. First, the arguments are validated: 218: * neither array may be null, they must be of compatible types, and the 219: * start and length must fit within both arrays. Then the copying starts, 220: * and proceeds through increasing slots. If src and dest are the same 221: * array, this will appear to copy the data to a temporary location first. 222: * An ArrayStoreException in the middle of copying will leave earlier 223: * elements copied, but later elements unchanged. 224: * 225: * @param src the array to copy elements from 226: * @param srcStart the starting position in src 227: * @param dest the array to copy elements to 228: * @param destStart the starting position in dest 229: * @param len the number of elements to copy 230: * @throws NullPointerException if src or dest is null 231: * @throws ArrayStoreException if src or dest is not an array, if they are 232: * not compatible array types, or if an incompatible runtime type 233: * is stored in dest 234: * @throws IndexOutOfBoundsException if len is negative, or if the start or 235: * end copy position in either array is out of bounds 236: */ 237: public static native void arraycopy(Object src, int srcStart, 238: Object dest, int destStart, int len); 239: 240: /** 241: * Get a hash code computed by the VM for the Object. This hash code will 242: * be the same as Object's hashCode() method. It is usually some 243: * convolution of the pointer to the Object internal to the VM. It 244: * follows standard hash code rules, in that it will remain the same for a 245: * given Object for the lifetime of that Object. 246: * 247: * @param o the Object to get the hash code for 248: * @return the VM-dependent hash code for this Object 249: * @since 1.1 250: */ 251: public static native int identityHashCode(Object o); 252: 253: /** 254: * Get all the system properties at once. A security check may be performed, 255: * <code>checkPropertiesAccess</code>. Note that a security manager may 256: * allow getting a single property, but not the entire group. 257: * 258: * <p>The required properties include: 259: * <dl> 260: * <dt>java.version</dt> <dd>Java version number</dd> 261: * <dt>java.vendor</dt> <dd>Java vendor specific string</dd> 262: * <dt>java.vendor.url</dt> <dd>Java vendor URL</dd> 263: * <dt>java.home</dt> <dd>Java installation directory</dd> 264: * <dt>java.vm.specification.version</dt> <dd>VM Spec version</dd> 265: * <dt>java.vm.specification.vendor</dt> <dd>VM Spec vendor</dd> 266: * <dt>java.vm.specification.name</dt> <dd>VM Spec name</dd> 267: * <dt>java.vm.version</dt> <dd>VM implementation version</dd> 268: * <dt>java.vm.vendor</dt> <dd>VM implementation vendor</dd> 269: * <dt>java.vm.name</dt> <dd>VM implementation name</dd> 270: * <dt>java.specification.version</dt> <dd>Java Runtime Environment version</dd> 271: * <dt>java.specification.vendor</dt> <dd>Java Runtime Environment vendor</dd> 272: * <dt>java.specification.name</dt> <dd>Java Runtime Environment name</dd> 273: * <dt>java.class.version</dt> <dd>Java class version number</dd> 274: * <dt>java.class.path</dt> <dd>Java classpath</dd> 275: * <dt>java.library.path</dt> <dd>Path for finding Java libraries</dd> 276: * <dt>java.io.tmpdir</dt> <dd>Default temp file path</dd> 277: * <dt>java.compiler</dt> <dd>Name of JIT to use</dd> 278: * <dt>java.ext.dirs</dt> <dd>Java extension path</dd> 279: * <dt>os.name</dt> <dd>Operating System Name</dd> 280: * <dt>os.arch</dt> <dd>Operating System Architecture</dd> 281: * <dt>os.version</dt> <dd>Operating System Version</dd> 282: * <dt>file.separator</dt> <dd>File separator ("/" on Unix)</dd> 283: * <dt>path.separator</dt> <dd>Path separator (":" on Unix)</dd> 284: * <dt>line.separator</dt> <dd>Line separator ("\n" on Unix)</dd> 285: * <dt>user.name</dt> <dd>User account name</dd> 286: * <dt>user.home</dt> <dd>User home directory</dd> 287: * <dt>user.dir</dt> <dd>User's current working directory</dd> 288: * </dl> 289: * 290: * In addition, gnu defines several other properties, where ? stands for 291: * each character in '0' through '9': 292: * <dl> 293: * <dt>gnu.classpath.home</dt> <dd>Path to the classpath libraries.</dd> 294: * <dt>gnu.classpath.version</dt> <dd>Version of the classpath libraries.</dd> 295: * <dt>gnu.classpath.vm.shortname</dt> <dd>Succinct version of the VM name; 296: * used for finding property files in file system</dd> 297: * <dt>gnu.classpath.home.url</dt> <dd> Base URL; used for finding 298: * property files in file system</dd> 299: * <dt>gnu.cpu.endian</dt> <dd>big or little</dd> 300: * <dt>gnu.java.io.encoding_scheme_alias.ISO-8859-?</dt> <dd>8859_?</dd> 301: * <dt>gnu.java.io.encoding_scheme_alias.iso-8859-?</dt> <dd>8859_?</dd> 302: * <dt>gnu.java.io.encoding_scheme_alias.iso8859_?</dt> <dd>8859_?</dd> 303: * <dt>gnu.java.io.encoding_scheme_alias.iso-latin-_?</dt> <dd>8859_?</dd> 304: * <dt>gnu.java.io.encoding_scheme_alias.latin?</dt> <dd>8859_?</dd> 305: * <dt>gnu.java.io.encoding_scheme_alias.UTF-8</dt> <dd>UTF8</dd> 306: * <dt>gnu.java.io.encoding_scheme_alias.utf-8</dt> <dd>UTF8</dd> 307: * </dl> 308: * 309: * @return the system properties, will never be null 310: * @throws SecurityException if permission is denied 311: */ 312: public static Properties getProperties() 313: { 314: SecurityManager sm = SecurityManager.current; // Be thread-safe. 315: if (sm != null) 316: sm.checkPropertiesAccess(); 317: return SystemProperties.getProperties(); 318: } 319: 320: /** 321: * Set all the system properties at once. A security check may be performed, 322: * <code>checkPropertiesAccess</code>. Note that a security manager may 323: * allow setting a single property, but not the entire group. An argument 324: * of null resets the properties to the startup default. 325: * 326: * @param properties the new set of system properties 327: * @throws SecurityException if permission is denied 328: */ 329: public static void setProperties(Properties properties) 330: { 331: SecurityManager sm = SecurityManager.current; // Be thread-safe. 332: if (sm != null) 333: sm.checkPropertiesAccess(); 334: SystemProperties.setProperties(properties); 335: } 336: 337: /** 338: * Get a single system property by name. A security check may be performed, 339: * <code>checkPropertyAccess(key)</code>. 340: * 341: * @param key the name of the system property to get 342: * @return the property, or null if not found 343: * @throws SecurityException if permission is denied 344: * @throws NullPointerException if key is null 345: * @throws IllegalArgumentException if key is "" 346: */ 347: public static String getProperty(String key) 348: { 349: SecurityManager sm = SecurityManager.current; // Be thread-safe. 350: if (sm != null) 351: sm.checkPropertyAccess(key); 352: else if (key.length() == 0) 353: throw new IllegalArgumentException("key can't be empty"); 354: return SystemProperties.getProperty(key); 355: } 356: 357: /** 358: * Get a single system property by name. A security check may be performed, 359: * <code>checkPropertyAccess(key)</code>. 360: * 361: * @param key the name of the system property to get 362: * @param def the default 363: * @return the property, or def if not found 364: * @throws SecurityException if permission is denied 365: * @throws NullPointerException if key is null 366: * @throws IllegalArgumentException if key is "" 367: */ 368: public static String getProperty(String key, String def) 369: { 370: SecurityManager sm = SecurityManager.current; // Be thread-safe. 371: if (sm != null) 372: sm.checkPropertyAccess(key); 373: return SystemProperties.getProperty(key, def); 374: } 375: 376: /** 377: * Set a single system property by name. A security check may be performed, 378: * <code>checkPropertyAccess(key, "write")</code>. 379: * 380: * @param key the name of the system property to set 381: * @param value the new value 382: * @return the previous value, or null 383: * @throws SecurityException if permission is denied 384: * @throws NullPointerException if key is null 385: * @throws IllegalArgumentException if key is "" 386: * @since 1.2 387: */ 388: public static String setProperty(String key, String value) 389: { 390: SecurityManager sm = SecurityManager.current; // Be thread-safe. 391: if (sm != null) 392: sm.checkPermission(new PropertyPermission(key, "write")); 393: return SystemProperties.setProperty(key, value); 394: } 395: 396: /** 397: * Gets the value of an environment variable. 398: * 399: * @param name the name of the environment variable 400: * @return the string value of the variable or null when the 401: * environment variable is not defined. 402: * @throws NullPointerException 403: * @throws SecurityException if permission is denied 404: * @since 1.5 405: * @specnote This method was deprecated in some JDK releases, but 406: * was restored in 1.5. 407: */ 408: public static String getenv(String name) 409: { 410: if (name == null) 411: throw new NullPointerException(); 412: SecurityManager sm = SecurityManager.current; // Be thread-safe. 413: if (sm != null) 414: sm.checkPermission(new RuntimePermission("getenv." + name)); 415: return getenv0(name); 416: } 417: 418: /** 419: * Terminate the Virtual Machine. This just calls 420: * <code>Runtime.getRuntime().exit(status)</code>, and never returns. 421: * Obviously, a security check is in order, <code>checkExit</code>. 422: * 423: * @param status the exit status; by convention non-zero is abnormal 424: * @throws SecurityException if permission is denied 425: * @see Runtime#exit(int) 426: */ 427: public static void exit(int status) 428: { 429: Runtime.getRuntime().exit(status); 430: } 431: 432: /** 433: * Calls the garbage collector. This is only a hint, and it is up to the 434: * implementation what this hint suggests, but it usually causes a 435: * best-effort attempt to reclaim unused memory from discarded objects. 436: * This calls <code>Runtime.getRuntime().gc()</code>. 437: * 438: * @see Runtime#gc() 439: */ 440: public static void gc() 441: { 442: Runtime.getRuntime().gc(); 443: } 444: 445: /** 446: * Runs object finalization on pending objects. This is only a hint, and 447: * it is up to the implementation what this hint suggests, but it usually 448: * causes a best-effort attempt to run finalizers on all objects ready 449: * to be reclaimed. This calls 450: * <code>Runtime.getRuntime().runFinalization()</code>. 451: * 452: * @see Runtime#runFinalization() 453: */ 454: public static void runFinalization() 455: { 456: Runtime.getRuntime().runFinalization(); 457: } 458: 459: /** 460: * Tell the Runtime whether to run finalization before exiting the 461: * JVM. This is inherently unsafe in multi-threaded applications, 462: * since it can force initialization on objects which are still in use 463: * by live threads, leading to deadlock; therefore this is disabled by 464: * default. There may be a security check, <code>checkExit(0)</code>. This 465: * calls <code>Runtime.getRuntime().runFinalizersOnExit()</code>. 466: * 467: * @param finalizeOnExit whether to run finalizers on exit 468: * @throws SecurityException if permission is denied 469: * @see Runtime#runFinalizersOnExit() 470: * @since 1.1 471: * @deprecated never rely on finalizers to do a clean, thread-safe, 472: * mop-up from your code 473: */ 474: public static void runFinalizersOnExit(boolean finalizeOnExit) 475: { 476: Runtime.getRuntime().runFinalizersOnExit(finalizeOnExit); 477: } 478: 479: /** 480: * Load a code file using its explicit system-dependent filename. A security 481: * check may be performed, <code>checkLink</code>. This just calls 482: * <code>Runtime.getRuntime().load(filename)</code>. 483: * 484: * <p> 485: * The library is loaded using the class loader associated with the 486: * class associated with the invoking method. 487: * 488: * @param filename the code file to load 489: * @throws SecurityException if permission is denied 490: * @throws UnsatisfiedLinkError if the file cannot be loaded 491: * @see Runtime#load(String) 492: */ 493: public static void load(String filename) 494: { 495: Runtime.getRuntime().load(filename); 496: } 497: 498: /** 499: * Load a library using its explicit system-dependent filename. A security 500: * check may be performed, <code>checkLink</code>. This just calls 501: * <code>Runtime.getRuntime().load(filename)</code>. 502: * 503: * <p> 504: * The library is loaded using the class loader associated with the 505: * class associated with the invoking method. 506: * 507: * @param libname the library file to load 508: * @throws SecurityException if permission is denied 509: * @throws UnsatisfiedLinkError if the file cannot be loaded 510: * @see Runtime#load(String) 511: */ 512: public static void loadLibrary(String libname) 513: { 514: Runtime.getRuntime().loadLibrary(libname); 515: } 516: 517: /** 518: * Convert a library name to its platform-specific variant. 519: * 520: * @param libname the library name, as used in <code>loadLibrary</code> 521: * @return the platform-specific mangling of the name 522: * @since 1.2 523: */ 524: public static String mapLibraryName(String libname) 525: { 526: // XXX Fix this!!!! 527: return Runtime.nativeGetLibname("", libname); 528: } 529: 530: /** 531: * Set {@link #in} to a new InputStream. 532: * 533: * @param in the new InputStream 534: * @see #setIn(InputStream) 535: */ 536: private static native void setIn0(InputStream in); 537: 538: /** 539: * Set {@link #out} to a new PrintStream. 540: * 541: * @param out the new PrintStream 542: * @see #setOut(PrintStream) 543: */ 544: private static native void setOut0(PrintStream out); 545: 546: /** 547: * Set {@link #err} to a new PrintStream. 548: * 549: * @param err the new PrintStream 550: * @see #setErr(PrintStream) 551: */ 552: private static native void setErr0(PrintStream err); 553: 554: /** 555: * Gets the value of an environment variable. 556: * 557: * @see #getenv(String) 558: */ 559: static native String getenv0(String name); 560: } // class System