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// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// 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 <config.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
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 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_
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