own_malloc.h

GPRS模块设计资料包

/*
  Default header file for malloc-2.7.2, written by Doug Lea
  and released to the public domain.  Use, modify, and redistribute
  this code without permission or acknowledgement in any way you wish.
  Send questions, comments, complaints, performance data, etc to
  [e-mail].
 
  last update: Sun Feb 25 18:38:11 2001  Doug Lea  (dl at gee)

  This header is for ANSI C/C++ only.  You can set either of
  the following #defines before including:

  * If USE_DL_PREFIX is defined, it is assumed that malloc.c 
    was also compiled with this option, so all routines
    have names starting with "dl".

  * If HAVE_USR_INCLUDE_MALLOC_H is defined, it is assumed that this
    file will be #included AFTER <malloc.h>. This is needed only if
    your system defines a struct mallinfo that is incompatible with the
    standard one declared here.  Otherwise, you can include this file
    INSTEAD of your system system <malloc.h>.  At least on ANSI, all
    declarations should be compatible with system versions
*/

#ifndef MALLOC_270_H
#define MALLOC_270_H

#ifdef __cplusplus
extern "C" {
#endif

#include <stddef.h>   /* for size_t */

/*
  malloc(size_t n)
  Returns a pointer to a newly allocated chunk of at least n bytes, or
  null if no space is available. Additionally, on failure, errno is
  set to ENOMEM on ANSI C systems.

  If n is zero, malloc returns a minimum-sized chunk. The minimum size
  is 16 bytes on most 32bit systems, and either 24 or 32 bytes on
  64bit systems, depending on internal size and alignment restrictions.

  On most systems, size_t is an unsigned type.  Calls with values of n
  that appear "negative" when signed are interpreted as requests for
  huge amounts of space, which will most often fail.

  The maximum allowed value of n differs across systems, but is in all
  cases less (typically by 8K) than the maximum representable value of
  a size_t. Requests greater than this value result in failure.
*/

#ifndef USE_DL_PREFIX
void*  malloc(size_t);
#else
void*  dlmalloc(size_t);
#endif

/*
  free(void* p)
  Releases the chunk of memory pointed to by p, that had been previously
  allocated using malloc or a related routine such as realloc.
  It has no effect if p is null. It can have arbitrary (and bad!)
  effects if p has already been freed or was not obtained via malloc.

  Unless disabled using mallopt, freeing very large spaces will,
  when possible, automatically trigger operations that give
  back unused memory to the system, thus reducing program footprint.
*/
#ifndef USE_DL_PREFIX
void     free(void*);
#else
void     dlfree(void*);
#endif

/*
  calloc(size_t n_elements, size_t element_size);
  Returns a pointer to n_elements * element_size bytes, with all locations
  set to zero.
*/
#ifndef USE_DL_PREFIX
void*  calloc(size_t, size_t);
#else
void*  dlcalloc(size_t, size_t);
#endif

/*
  realloc(void* p, size_t n)
  Returns a pointer to a chunk of size n that contains the same data
  as does chunk p up to the minimum of (n, p's size) bytes.

  The returned pointer may or may not be the same as p. The algorithm
  prefers extending p when possible, otherwise it employs the
  equivalent of a malloc-copy-free sequence.

  If p is null, realloc is equivalent to malloc.  

  If space is not available, realloc returns null, errno is set (if on
  ANSI) and p is NOT freed.

  if n is for fewer bytes than already held by p, the newly unused
  space is lopped off and freed if possible.  Unless the #define
  REALLOC_ZERO_BYTES_FREES is set, realloc with a size argument of
  zero (re)allocates a minimum-sized chunk.

  Large chunks that were internally obtained via mmap will always
  be reallocated using malloc-copy-free sequences unless
  the system supports MREMAP (currently only linux).

  The old unix realloc convention of allowing the last-free'd chunk
  to be used as an argument to realloc is not supported.
*/

#ifndef USE_DL_PREFIX
void*  realloc(void*, size_t);
#else
void*  dlrealloc(void*, size_t);
#endif

/*
  memalign(size_t alignment, size_t n);
  Returns a pointer to a newly allocated chunk of n bytes, aligned
  in accord with the alignment argument.

  The alignment argument should be a power of two. If the argument is
  not a power of two, the nearest greater power is used.
  8-byte alignment is guaranteed by normal malloc calls, so don't
  bother calling memalign with an argument of 8 or less.

  Overreliance on memalign is a sure way to fragment space.
*/

#ifndef USE_DL_PREFIX
void*  memalign(size_t, size_t);
#else
void*  dlmemalign(size_t, size_t);
#endif


/*
  valloc(size_t n);
  Allocates a page-aligned chunk of at least n bytes.
  Equivalent to memalign(pagesize, n), where pagesize is the page
  size of the system. If the pagesize is unknown, 4096 is used.
*/

#ifndef USE_DL_PREFIX
void*  valloc(size_t);
#else
void*  dlvalloc(size_t);
#endif

#if 0

/*
  independent_calloc(size_t n_elements, size_t element_size, void* chunks[]);

  independent_calloc is similar to calloc, but instead of returning a
  single cleared space, it returns an array of pointers to n_elements
  independent elements, each of which can hold contents of size
  elem_size.  Each element starts out cleared, and can be
  independently freed, realloc'ed etc. The elements are guaranteed to
  be adjacently allocated (this is not guaranteed to occur with
  multiple callocs or mallocs), which may also improve cache locality
  in some applications.

  The "chunks" argument is optional (i.e., may be null, which is
  probably the most typical usage). If it is null, the returned array
  is itself dynamically allocated and should also be freed when it is
  no longer needed. Otherwise, the chunks array must be of at least
  n_elements in length. It is filled in with the pointers to the
  chunks.

  In either case, independent_calloc returns this pointer array, or
  null if the allocation failed.  If n_elements is zero and "chunks"
  is null, it returns a chunk representing an array with zero elements
  (which should be freed if not wanted).

  Each element must be individually freed when it is no longer
  needed. If you'd like to instead be able to free all at once, you
  should instead use regular calloc and assign pointers into this
  space to represent elements.  (In this case though, you cannot
  independently free elements.)
  
  independent_calloc simplifies and speeds up implementations of many
  kinds of pools.  It may also be useful when constructing large data
  structures that initially have a fixed number of fixed-sized nodes,
  but the number is not known at compile time, and some of the nodes
  may later need to be freed. For example:

  struct Node { int item; struct Node* next; };
  
  struct Node* build_list() {
    struct Node** pool;
    int n = read_number_of_nodes_needed();
    if (n <= 0) return 0;
    pool = (struct Node**)(independent_calloc(n, sizeof(struct Node), 0);
    if (pool == 0) return 0; // failure
    // organize into a linked list... 
    struct Node* first = pool[0];
    for (i = 0; i < n-1; ++i) 
      pool[i]->next = pool[i+1];
    free(pool);     // Can now free the array (or not, if it is needed later)
    return first;
  }
*/

#ifndef USE_DL_PREFIX
void** independent_calloc(size_t, size_t, void**);
#else
void** dlindependent_calloc(size_t, size_t, void**);
#endif

/*
  independent_comalloc(size_t n_elements, size_t sizes[], void* chunks[]);

  independent_comalloc allocates, all at once, a set of n_elements
  chunks with sizes indicated in the "sizes" array.    It returns
  an array of pointers to these elements, each of which can be
  independently freed, realloc'ed etc. The elements are guaranteed to
  be adjacently allocated (this is not guaranteed to occur with
  multiple callocs or mallocs), which may also improve cache locality
  in some applications.

  The "chunks" argument is optional (i.e., may be null). If it is null
  the returned array is itself dynamically allocated and should also
  be freed when it is no longer needed. Otherwise, the chunks array
  must be of at least n_elements in length. It is filled in with the
  pointers to the chunks.

  In either case, independent_comalloc returns this pointer array, or
  null if the allocation failed.  If n_elements is zero and chunks is
  null, it returns a chunk representing an array with zero elements
  (which should be freed if not wanted).
  
  Each element must be individually freed when it is no longer
  needed. If you'd like to instead be able to free all at once, you
  should instead use a single regular malloc, and assign pointers at
  particular offsets in the aggregate space. (In this case though, you 
  cannot independently free elements.)

  independent_comallac differs from independent_calloc in that each
  element may have a different size, and also that it does not
  automatically clear elements.

  independent_comalloc can be used to speed up allocation in cases
  where several structs or objects must always be allocated at the
  same time.  For example:

  struct Head { ... }
  struct Foot { ... }

  void send_message(char* msg) {
    int msglen = strlen(msg);
    size_t sizes[3] = { sizeof(struct Head), msglen, sizeof(struct Foot) };
    void* chunks[3];
    if (independent_comalloc(3, sizes, chunks) == 0)
      die();
    struct Head* head = (struct Head*)(chunks[0]);
    char*        body = (char*)(chunks[1]);
    struct Foot* foot = (struct Foot*)(chunks[2]);
    // ...
  }

  In general though, independent_comalloc is worth using only for
  larger values of n_elements. For small values, you probably won't
  detect enough difference from series of malloc calls to bother.

  Overuse of independent_comalloc can increase overall memory usage,
  since it cannot reuse existing noncontiguous small chunks that
  might be available for some of the elements.
*/

#ifndef USE_DL_PREFIX
void** independent_comalloc(size_t, size_t*, void**);
#else
void** dlindependent_comalloc(size_t, size_t*, void**);
#endif


/*
  pvalloc(size_t n);
  Equivalent to valloc(minimum-page-that-holds(n)), that is,
  round up n to nearest pagesize.
 */

#ifndef USE_DL_PREFIX
void*  pvalloc(size_t);
#else
void*  dlpvalloc(size_t);
#endif

/*
  cfree(void* p);
  Equivalent to free(p).

  cfree is needed/defined on some systems that pair it with calloc,
  for odd historical reasons (such as: cfree is used in example 
  code in the first edition of K&R).
*/

#ifndef USE_DL_PREFIX
void     cfree(void*);
#else
void     dlcfree(void*);
#endif


/*
  malloc_trim(size_t pad);

  If possible, gives memory back to the system (via negative
  arguments to sbrk) if there is unused memory at the `high' end of
  the malloc pool. You can call this after freeing large blocks of
  memory to potentially reduce the system-level memory requirements
  of a program. However, it cannot guarantee to reduce memory. Under
  some allocation patterns, some large free blocks of memory will be
  locked between two used chunks, so they cannot be given back to
  the system.
  
  The `pad' argument to malloc_trim represents the amount of free
  trailing space to leave untrimmed. If this argument is zero,
  only the minimum amount of memory to maintain internal data
  structures will be left (one page or less). Non-zero arguments
  can be supplied to maintain enough trailing space to service
  future expected allocations without having to re-obtain memory
  from the system.
  
  Malloc_trim returns 1 if it actually released any memory, else 0.
  On systems that do not support "negative sbrks", it will always
  return 0.
*/

#ifndef USE_DL_PREFIX
int      malloc_trim(size_t);
#else
int      dlmalloc_trim(size_t);
#endif


/*
  malloc_usable_size(void* p);