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