nanojit/Allocator.h

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  39
  40 #ifndef __nanojit_Allocator__
  41 #define __nanojit_Allocator__
  42
  43 namespace nanojit
  44 {
  45     /**
  46      * Allocator is a bump-pointer allocator with an SPI for getting more
  47      * memory from embedder-implemented allocator, such as malloc()/free().
  48      *
  49      * allocations never return NULL.  The implementation of allocChunk()
  50      * is expected to perform a longjmp or exception when an allocation can't
  51      * proceed.
  52      */
  53     class Allocator {
  54     public:
  55         Allocator();
  56         ~Allocator();
  57         void reset();
  58
  59         /** alloc memory, never return null. */
  60         void* alloc(size_t nbytes) {
  61             nbytes = (nbytes + 7) & ~7; // round up
  62             if (current_top + nbytes <= current_limit) {
  63                 void *p = current_top;
  64                 current_top += nbytes;
  65                 return p;
  66             }
  67             return allocSlow(nbytes);
  68         }
  69
  70     protected:
  71         void* allocSlow(size_t nbytes);
  72         void fill(size_t minbytes);
  73
  74         class Chunk {
  75         public:
  76             Chunk* prev;
  77             int64_t data[1]; // int64_t forces 8-byte alignment.
  78         };
  79
  80         Chunk* current_chunk;
  81         char* current_top;
  82         char* current_limit;
  83
  84         // allocator SPI
  85
  86         /** allocate another block from a host provided allocator */
  87         void* allocChunk(size_t nbytes);
  88
  89         /** free back to the same allocator */
  90         void freeChunk(void*);
  91
  92         /** hook for post-reset action. */
  93         void postReset();
  94     };
  95 }
  96
  97 /** global new overload enabling this pattern:  new (allocator) T(...) */
  98 inline void* operator new(size_t size, nanojit::Allocator &a) {
  99     return a.alloc(size);
 100 }
 101
 102 /** global new overload enabling this pattern:  new (allocator) T(...) */
 103 inline void* operator new(size_t size, nanojit::Allocator *a) {
 104     return a->alloc(size);
 105 }
 106
 107 /** global new[] overload enabling this pattern: new (allocator) T[] */
 108 inline void* operator new[](size_t size, nanojit::Allocator& a) {
 109     return a.alloc(size);
 110 }
 111
 112 /** global new[] overload enabling this pattern: new (allocator) T[] */
 113 inline void* operator new[](size_t size, nanojit::Allocator* a) {
 114     return a->alloc(size);
 115 }
 116
 117 #endif // __nanojit_Allocator__