stl_alloc.h

STL完整源码,实现STL文件的读写和三维体的重建及其分析

  static char *end_free;
  static size_t heap_size;

# ifdef __STL_SGI_THREADS
    static volatile unsigned long __node_allocator_lock;
    static void __lock(volatile unsigned long *); 
    static inline void __unlock(volatile unsigned long *);
# endif

# ifdef __STL_PTHREADS
    static pthread_mutex_t __node_allocator_lock;
# endif

# ifdef __STL_WIN32THREADS
    static CRITICAL_SECTION __node_allocator_lock;
    static bool __node_allocator_lock_initialized;

  public:
    __default_alloc_template() {
	// This assumes the first constructor is called before threads
	// are started.
        if (!__node_allocator_lock_initialized) {
            InitializeCriticalSection(&__node_allocator_lock);
            __node_allocator_lock_initialized = true;
        }
    }
  private:
# endif

    class lock {
        public:
            lock() { __NODE_ALLOCATOR_LOCK; }
            ~lock() { __NODE_ALLOCATOR_UNLOCK; }
    };
    friend class lock;

public:

  /* n must be > 0      */
  static void * allocate(size_t n)
  {
    obj * __VOLATILE * my_free_list;
    obj * __RESTRICT result;

    if (n > (size_t) __MAX_BYTES) {
        return(malloc_alloc::allocate(n));
    }
    my_free_list = free_list + FREELIST_INDEX(n);
    // Acquire the lock here with a constructor call.
    // This ensures that it is released in exit or during stack
    // unwinding.
#       ifndef _NOTHREADS
        /*REFERENCED*/
        lock lock_instance;
#       endif
    result = *my_free_list;
    if (result == 0) {
        void *r = refill(ROUND_UP(n));
        return r;
    }
    *my_free_list = result -> free_list_link;
    return (result);
  };

  /* p may not be 0 */
  static void deallocate(void *p, size_t n)
  {
    obj *q = (obj *)p;
    obj * __VOLATILE * my_free_list;

    if (n > (size_t) __MAX_BYTES) {
        malloc_alloc::deallocate(p, n);
        return;
    }
    my_free_list = free_list + FREELIST_INDEX(n);
    // acquire lock
#       ifndef _NOTHREADS
        /*REFERENCED*/
        lock lock_instance;
#       endif /* _NOTHREADS */
    q -> free_list_link = *my_free_list;
    *my_free_list = q;
    // lock is released here
  }

  static void * reallocate(void *p, size_t old_sz, size_t new_sz);

} ;

typedef __default_alloc_template<__NODE_ALLOCATOR_THREADS, 0> alloc;
typedef __default_alloc_template<false, 0> single_client_alloc;



/* We allocate memory in large chunks in order to avoid fragmenting     */
/* the malloc heap too much.                                            */
/* We assume that size is properly aligned.                             */
/* We hold the allocation lock.                                         */
template <bool threads, int inst>
char*
__default_alloc_template<threads, inst>::chunk_alloc(size_t size, int& nobjs)
{
    char * result;
    size_t total_bytes = size * nobjs;
    size_t bytes_left = end_free - start_free;

    if (bytes_left >= total_bytes) {
        result = start_free;
        start_free += total_bytes;
        return(result);
    } else if (bytes_left >= size) {
        nobjs = bytes_left/size;
        total_bytes = size * nobjs;
        result = start_free;
        start_free += total_bytes;
        return(result);
    } else {
        size_t bytes_to_get = 2 * total_bytes + ROUND_UP(heap_size >> 4);
        // Try to make use of the left-over piece.
        if (bytes_left > 0) {
            obj * __VOLATILE * my_free_list =
                        free_list + FREELIST_INDEX(bytes_left);

            ((obj *)start_free) -> free_list_link = *my_free_list;
            *my_free_list = (obj *)start_free;
        }
        start_free = (char *)malloc(bytes_to_get);
        if (0 == start_free) {
            int i;
            obj * __VOLATILE * my_free_list, *p;
            // Try to make do with what we have.  That can't
            // hurt.  We do not try smaller requests, since that tends
            // to result in disaster on multi-process machines.
            for (i = size; i <= __MAX_BYTES; i += __ALIGN) {
                my_free_list = free_list + FREELIST_INDEX(i);
                p = *my_free_list;
                if (0 != p) {
                    *my_free_list = p -> free_list_link;
                    start_free = (char *)p;
                    end_free = start_free + i;
                    return(chunk_alloc(size, nobjs));
                    // Any leftover piece will eventually make it to the
                    // right free list.
                }
            }
	    end_free = 0;	// In case of exception.
            start_free = (char *)malloc_alloc::allocate(bytes_to_get);
            // This should either throw an
            // exception or remedy the situation.  Thus we assume it
            // succeeded.
        }
        heap_size += bytes_to_get;
        end_free = start_free + bytes_to_get;
        return(chunk_alloc(size, nobjs));
    }
}


/* Returns an object of size n, and optionally adds to size n free list.*/
/* We assume that n is properly aligned.                                */
/* We hold the allocation lock.                                         */
template <bool threads, int inst>
void* __default_alloc_template<threads, inst>::refill(size_t n)
{
    int nobjs = 20;
    char * chunk = chunk_alloc(n, nobjs);
    obj * __VOLATILE * my_free_list;
    obj * result;
    obj * current_obj, * next_obj;
    int i;

    if (1 == nobjs) return(chunk);
    my_free_list = free_list + FREELIST_INDEX(n);

    /* Build free list in chunk */
      result = (obj *)chunk;
      *my_free_list = next_obj = (obj *)(chunk + n);
      for (i = 1; ; i++) {
        current_obj = next_obj;
        next_obj = (obj *)((char *)next_obj + n);
        if (nobjs - 1 == i) {
            current_obj -> free_list_link = 0;
            break;
        } else {
            current_obj -> free_list_link = next_obj;
        }
      }
    return(result);
}

template <bool threads, int inst>
void*
__default_alloc_template<threads, inst>::reallocate(void *p,
                                                    size_t old_sz,
                                                    size_t new_sz)
{
    void * result;
    size_t copy_sz;

    if (old_sz > (size_t) __MAX_BYTES && new_sz > (size_t) __MAX_BYTES) {
        return(realloc(p, new_sz));
    }
    if (ROUND_UP(old_sz) == ROUND_UP(new_sz)) return(p);
    result = allocate(new_sz);
    copy_sz = new_sz > old_sz? old_sz : new_sz;
    memcpy(result, p, copy_sz);
    deallocate(p, old_sz);
    return(result);
}

#ifdef __STL_PTHREADS
    template <bool threads, int inst>
    pthread_mutex_t
    __default_alloc_template<threads, inst>::__node_allocator_lock
        = PTHREAD_MUTEX_INITIALIZER;
#endif

#ifdef __STL_WIN32THREADS
    template <bool threads, int inst> CRITICAL_SECTION
    __default_alloc_template<threads, inst>::__node_allocator_lock;

    template <bool threads, int inst> bool
    __default_alloc_template<threads, inst>::__node_allocator_lock_initialized
	= false;
#endif

#ifdef __STL_SGI_THREADS
__STL_END_NAMESPACE
#include <mutex.h>
#include <time.h>
__STL_BEGIN_NAMESPACE
// Somewhat generic lock implementations.  We need only test-and-set
// and some way to sleep.  These should work with both SGI pthreads
// and sproc threads.  They may be useful on other systems.
template <bool threads, int inst>
volatile unsigned long
__default_alloc_template<threads, inst>::__node_allocator_lock = 0;

#if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64)) || defined(__GNUC__)
#   define __test_and_set(l,v) test_and_set(l,v)
#endif

template <bool threads, int inst>
void 
__default_alloc_template<threads, inst>::__lock(volatile unsigned long *lock)
{
    const unsigned low_spin_max = 30;  // spin cycles if we suspect uniprocessor
    const unsigned high_spin_max = 1000; // spin cycles for multiprocessor
    static unsigned spin_max = low_spin_max;
    unsigned my_spin_max;
    static unsigned last_spins = 0;
    unsigned my_last_spins;
    static struct timespec ts = {0, 1000};
    unsigned junk;
#   define __ALLOC_PAUSE junk *= junk; junk *= junk; junk *= junk; junk *= junk
    int i;

    if (!__test_and_set((unsigned long *)lock, 1)) {
        return;
    }
    my_spin_max = spin_max;
    my_last_spins = last_spins;
    for (i = 0; i < my_spin_max; i++) {
        if (i < my_last_spins/2 || *lock) {
            __ALLOC_PAUSE;
            continue;
        }
        if (!__test_and_set((unsigned long *)lock, 1)) {
            // got it!
            // Spinning worked.  Thus we're probably not being scheduled
            // against the other process with which we were contending.
            // Thus it makes sense to spin longer the next time.
            last_spins = i;
            spin_max = high_spin_max;
            return;
        }
    }
    // We are probably being scheduled against the other process.  Sleep.
    spin_max = low_spin_max;
    for (;;) {
        if (!__test_and_set((unsigned long *)lock, 1)) {
            return;
        }
        nanosleep(&ts, 0);
    }
}

template <bool threads, int inst>
inline void
__default_alloc_template<threads, inst>::__unlock(volatile unsigned long *lock)
{
#   if defined(__GNUC__) && __mips >= 3
        asm("sync");
        *lock = 0;
#   elif __mips >= 3 && (defined (_ABIN32) || defined(_ABI64))
        __lock_release(lock);
#   else 
        *lock = 0;
        // This is not sufficient on many multiprocessors, since
        // writes to protected variables and the lock may be reordered.
#   endif
}
#endif

template <bool threads, int inst>
char *__default_alloc_template<threads, inst>::start_free = 0;

template <bool threads, int inst>
char *__default_alloc_template<threads, inst>::end_free = 0;

template <bool threads, int inst>
size_t __default_alloc_template<threads, inst>::heap_size = 0;

template <bool threads, int inst>
__default_alloc_template<threads, inst>::obj * __VOLATILE
__default_alloc_template<threads, inst> ::free_list[
# ifdef __SUNPRO_CC
    __NFREELISTS
# else
    __default_alloc_template<threads, inst>::__NFREELISTS
# endif
] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, };
// The 16 zeros are necessary to make version 4.1 of the SunPro
// compiler happy.  Otherwise it appears to allocate too little
// space for the array.

# ifdef __STL_WIN32THREADS
  // Create one to get critical section initialized.
  // We do this onece per file, but only the first constructor
  // does anything.
  static alloc __node_allocator_dummy_instance;
# endif

#endif /* ! __USE_MALLOC */

#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma reset woff 1174
#endif

__STL_END_NAMESPACE

#undef __PRIVATE

#endif /* __SGI_STL_INTERNAL_ALLOC_H */

// Local Variables:
// mode:C++
// End: