third_party/tcmalloc/chromium/src/free_list.h

// Copyright (c) 2011, Google Inc.
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//
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//
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// --- 
// Author: Rebecca Shapiro <bxx@google.com>
//
// This file contains declarations of functions that implement doubly
// linked lists and definitions of functions that implement singly
// linked lists.  It also contains macros to tell the SizeMap class
// how much space a node in the freelist needs so that SizeMap can
// create large enough size classes.

#ifndef TCMALLOC_FREE_LIST_H_
#define TCMALLOC_FREE_LIST_H_

#include <stddef.h>
#include "internal_logging.h"
#include "linked_list.h"
#include "system-alloc.h"

// Remove to enable singly linked lists (the default for open source tcmalloc).
#define TCMALLOC_USE_DOUBLYLINKED_FREELIST

namespace tcmalloc {

#if defined(TCMALLOC_USE_DOUBLYLINKED_FREELIST)

// size class information for common.h.
static const bool kSupportsDoublyLinkedList = true;

void FL_PopRange(void **head, int n, void **start, void **end);
void FL_PushRange(void **head, void *start, void *end);
size_t FL_Size(void *head);

template <typename T> inline void FL_EqualityCheck(const T& v0,
                                                   const T& v1,
                                                   const char* file,
                                                   int line) {
  if (v0 != v1) Log(kCrash, file, line, "Memory corruption detected.");
}

inline void EnsureNonLoop(void* node, void* next) {
  // We only have time to do minimal checking.  We don't traverse the list, but
  // only look for an immediate loop (cycle back to ourself).
  if (node != next) return;
  Log(kCrash, __FILE__, __LINE__, "Circular loop in list detected: ", next);
}

inline void* MaskPtr(void* p) {
  // Maximize ASLR entropy and guarantee the result is an invalid address.
  const uintptr_t mask = ~(reinterpret_cast<uintptr_t>(TCMalloc_SystemAlloc)
                           >> 13);
  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(p) ^ mask);
}

inline void* UnmaskPtr(void* p) {
  return MaskPtr(p);
}

// Returns value of the |previous| pointer w/out running a sanity
// check.
inline void *FL_Previous_No_Check(void *t) {
  return UnmaskPtr(reinterpret_cast<void**>(t)[1]);
}

// Returns value of the |next| pointer w/out running a sanity check.
inline void *FL_Next_No_Check(void *t) {
  return UnmaskPtr(reinterpret_cast<void**>(t)[0]);
}

inline void *FL_Previous(void *t) {
  void *previous = FL_Previous_No_Check(t);
  if (previous) {
    FL_EqualityCheck(FL_Next_No_Check(previous), t, __FILE__, __LINE__);
  }
  return previous;
}

inline void FL_SetPrevious(void *t, void *n) {
  EnsureNonLoop(t, n);
  reinterpret_cast<void**>(t)[1] = MaskPtr(n);
}

inline void FL_SetNext(void *t, void *n) {
  EnsureNonLoop(t, n);
  reinterpret_cast<void**>(t)[0] = MaskPtr(n);
}

inline void *FL_Next(void *t) {
  void *next = FL_Next_No_Check(t);
  if (next) {
    FL_EqualityCheck(FL_Previous_No_Check(next), t, __FILE__, __LINE__);
  }
  return next;
}

// Pops the top element off the linked list whose first element is at
// |*list|, and updates |*list| to point to the next element in the
// list.  Returns the address of the element that was removed from the
// linked list.  |list| must not be NULL.
inline void *FL_Pop(void **list) {
  void *result = *list;
  ASSERT(FL_Previous_No_Check(result) == NULL);
  *list = FL_Next(result);
  if (*list != NULL) {
    FL_SetPrevious(*list, NULL);
  }
  return result;
}

// Makes the element at |t| a singleton doubly linked list.
inline void FL_Init(void *t) {
  FL_SetPrevious(t, NULL);
  FL_SetNext(t, NULL);
}

// Pushes element to a linked list whose first element is at
// |*list|. When this call returns, |list| will point to the new head
// of the linked list.
inline void FL_Push(void **list, void *element) {
  void *old = *list;
  if (old == NULL) { // Builds singleton list.
    FL_Init(element);
  } else {
    ASSERT(FL_Previous_No_Check(old) == NULL);
    FL_SetNext(element, old);
    FL_SetPrevious(old, element);
    FL_SetPrevious(element, NULL);
  }
  *list = element;
}

#else // TCMALLOC_USE_DOUBLYLINKED_FREELIST not defined
static const bool kSupportsDoublyLinkedList = false;

inline void *FL_Next(void *t) {
  return SLL_Next(t);
}

inline void FL_Init(void *t) {
  SLL_SetNext(t, NULL);
}

inline void FL_Push(void **list, void *element) {
  if(*list != element) {
    SLL_Push(list,element);
    return;
  }
  Log(kCrash, __FILE__, __LINE__, "Double Free of %p detected", element);
}

inline void *FL_Pop(void **list) {
  return SLL_Pop(list);
}

// Removes |N| elements from a linked list to which |head| points.
// |head| will be modified to point to the new |head|.  |start| and
// |end| will point to the first and last nodes of the range.  Note
// that |end| will point to NULL after this function is called.
inline void FL_PopRange(void **head, int n, void **start, void **end) {
  SLL_PopRange(head, n, start, end);
}

inline void FL_PushRange(void **head, void *start, void *end) {
  SLL_PushRange(head,start,end);
}

inline size_t FL_Size(void *head) {
  return SLL_Size(head);
}

#endif // TCMALLOC_USE_DOUBLYLINKED_FREELIST

} // namespace tcmalloc

#endif // TCMALLOC_FREE_LIST_H_