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BeefMem/gperftools/src/span.h

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+// Copyright (c) 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Author: Sanjay Ghemawat <opensource@google.com>
+//
+// A Span is a contiguous run of pages.
+
+#ifndef TCMALLOC_SPAN_H_
+#define TCMALLOC_SPAN_H_
+
+#include "tcconfig.h"
+#include "common.h"
+
+namespace tcmalloc {
+
+// Information kept for a span (a contiguous run of pages).
+struct Span {
+  PageID        start;          // Starting page number
+  Length        length;         // Number of pages in span
+  Span*         next;           // Used when in link list
+  Span*         prev;           // Used when in link list
+  void*         objects;        // Linked list of free objects
+  void*         freeingObjects; // BCF- waiting to be freed
+  void*         freeingObjectsTail;  // Note: *((intptr_t*)freeingObjectsTail) is freeingCount
+  unsigned int  refcount : 16;  // Number of non-free objects
+  unsigned int  sizeclass : 8;  // Size-class for small objects (or 0)
+  unsigned int  location : 2;   // Is the span on a freelist, and if so, which?
+  unsigned int	decommitDelay : 3;
+  unsigned int  sample : 1;     // Sampled object?
+
+#undef SPAN_HISTORY
+#ifdef SPAN_HISTORY
+  // For debugging, we can keep a log events per span
+  int nexthistory;
+  char history[64];
+  int value[64];
+#endif
+
+  // What freelist the span is on: IN_USE if on none, or normal or returned
+  enum { IN_USE, ON_NORMAL_FREELIST, ON_RETURNED_FREELIST };
+};
+
+#ifdef SPAN_HISTORY
+void Event(Span* span, char op, int v = 0);
+#else
+#define Event(s,o,v) ((void) 0)
+#endif
+
+// Allocator/deallocator for spans
+Span* NewSpan(PageID p, Length len);
+void DeleteSpan(Span* span);
+
+// -------------------------------------------------------------------------
+// Doubly linked list of spans.
+// -------------------------------------------------------------------------
+
+// Initialize *list to an empty list.
+void DLL_Init(Span* list);
+
+// Remove 'span' from the linked list in which it resides, updating the
+// pointers of adjacent Spans and setting span's next and prev to NULL.
+void DLL_Remove(Span* span);
+
+// Return true iff "list" is empty.
+inline bool DLL_IsEmpty(const Span* list) {
+  return list->next == list;
+}
+
+// Add span to the front of list.
+void DLL_Prepend(Span* list, Span* span);
+
+// Return the length of the linked list. O(n)
+int DLL_Length(const Span* list);
+
+}  // namespace tcmalloc
+
+#endif  // TCMALLOC_SPAN_H_