Mercurial > projects > dwt2
annotate java/src/java/nonstandard/WeakRef.d @ 21:9b96950f2c3c
the 'java' tree compiles on both D1-Tango and D2-Phobos
author | Frank Benoit <benoit@tionex.de> |
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date | Thu, 19 Mar 2009 20:38:55 +0100 |
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1 /*========================================================================== |
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2 * weakref.d |
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3 * Written in the D Programming Language (http://www.digitalmars.com/d) |
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4 */ |
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5 /*************************************************************************** |
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6 * Creates a weak reference to a class instance. |
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7 * |
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8 * A weak reference lets you hold onto a pointer to an object without |
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9 * preventing the garbage collector from collecting it. |
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10 * If the garbage collector collects the object then the weak pointer will |
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11 * become 'null'. Thus one should always check a weak pointer for null |
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12 * before doing anything that depends upon it having a value. |
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13 * |
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14 * Tested with: |
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15 * DMD 1.025 / Phobos 1.025 |
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16 * DMD 1.025 / Tango 0.99.4 |
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17 * |
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18 * Usage example: |
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19 --- |
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20 class Something {} |
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21 |
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22 auto a = new Something(); |
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23 auto wa = new WeakRef!(Something)(a); |
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24 std.gc.fullCollect(); |
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25 |
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26 // Reference 'a' prevents collection so wa.ptr is non-null |
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27 assert(wa.ptr is a); |
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28 |
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29 delete a; |
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30 |
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31 // 'a' is gone now, so wa.ptr magically becomes null |
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32 assert(wa.ptr is null); |
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33 --- |
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34 * |
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35 * |
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36 * Author: William V. Baxter III |
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37 * Contributors: |
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38 * Date: 21 Jan 2008 |
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39 * Copyright: (C) 2008 William Baxter |
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40 * License: Public Domain where allowed by law, ZLIB/PNG otherwise. |
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41 */ |
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42 //=========================================================================== |
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43 |
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44 module java.nonstandard.WeakRef; |
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45 |
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46 private { |
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47 alias void delegate(Object) DisposeEvt; |
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48 extern (C) void rt_attachDisposeEvent( Object obj, DisposeEvt evt ); |
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49 extern (C) void rt_detachDisposeEvent( Object obj, DisposeEvt evt ); |
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50 } |
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51 |
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52 class WeakRef(T : Object) { |
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53 private: |
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54 size_t cast_ptr_; |
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55 void unhook(Object o) { |
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56 if (cast(size_t)cast(void*)o == cast_ptr_) { |
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57 rt_detachDisposeEvent(o, &unhook); |
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58 cast_ptr_ = 0; |
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59 } |
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60 } |
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61 public: |
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62 |
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63 this(T tptr) { |
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64 cast_ptr_ = cast(size_t)cast(void*)tptr; |
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65 rt_attachDisposeEvent(tptr, &unhook); |
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66 } |
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67 ~this() { |
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68 T p = ptr(); |
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69 if (p) { |
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70 rt_detachDisposeEvent(p, &unhook); |
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71 } |
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72 } |
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73 T ptr() { |
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74 return cast(T)cast(void*)cast_ptr_; |
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75 } |
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76 WeakRef dup() { |
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77 return new WeakRef(ptr()); |
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78 } |
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79 equals_t opEquals( Object o ){ |
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80 if( auto other = cast( WeakRef!(T) )o ){ |
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81 return other.cast_ptr_ is cast_ptr_; |
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82 } |
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83 return false; |
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84 } |
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85 hash_t toHash(){ |
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86 return cast_ptr_; |
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87 } |
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88 } |