RetroZilla/modules/libjar/nsZlibAllocator.h

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/* 
 * Allocator for zlib optimized for mozilla's use
 *
 */

#define NBUCKETS 6
#define BY4ALLOC_ITEMS 320

class nsZlibAllocator;
extern nsZlibAllocator *gZlibAllocator;

class nsZlibAllocator {
 public:
  struct nsMemBucket {
    void *ptr;
    PRUint32 size;

    // Is this bucket available ?
    // 1 : free
    // 0 or negative : in use
    // This is an int because we use atomic inc/dec to operate on it
    PRInt32 available;
  };

  nsMemBucket mMemBucket[NBUCKETS];

  nsZlibAllocator() {
    memset(mMemBucket, 0, sizeof(mMemBucket));
    for (PRUint32 i = 0; i < NBUCKETS; i++)
      mMemBucket[i].available = 1;
    return;
  }

  ~nsZlibAllocator() {
    for (PRUint32 i = 0; i < NBUCKETS; i++)
    {
      PRBool claimed = Claim(i);
      
      // ASSERT that we claimed the bucked. If we cannot, then the bucket is in use.
      // We dont attempt to free this ptr.
      // This will most likely cause a leak of this memory.
      PR_ASSERT(claimed);
      
      // Free bucket memory if not in use
      if (claimed && mMemBucket[i].ptr)
        free(mMemBucket[i].ptr);
    }
  }

  // zlib allocators
  void* zAlloc(PRUint32 items, PRUint32 size);
  void  zFree(void *ptr);

  // Bucket handling.
  PRBool Claim(PRUint32 i) {
    PRBool claimed = (PR_AtomicDecrement(&mMemBucket[i].available) == 0);
    // Undo the claim, if claim failed
    if (!claimed)
      Unclaim(i);

    return claimed;
  }

  void Unclaim(PRUint32 i) { PR_AtomicIncrement(&mMemBucket[i].available); }
};