realloc的内部实现 [英] Internal implementation of realloc

问题描述

如何在内部实施realloc？如果没有足够的内存来分配，是否在其他地方分配了新内存，并且通过指针链接的

2区域OR是复制到的旧区域

哪里有足够的内存以适应新旧区域？在

第二种情况下，如果旧的

区域很大，这种方法效率不高吗？

How is realloc implemented internally ? If there is not enough memory
in place to allocate , is new memory allocated somewhere else and the
2 regions linked via a pointer , OR , is the old region copied to a
place where there is enough memory to fit both old and new region ? In
the second case , wouldn''t this method be inefficient if the old
region was large ?

推荐答案

Kislay写道：

Kislay wrote:

如何在内部实施realloc？

How is realloc implemented internally ?

适用于早期线程''printf'的相同答案适用。


-

Ian Collins。

The same answers that were given to the earlier thread ''printf'' apply.

--
Ian Collins.

Kislay写道：

Kislay wrote:

如何在内部实施realloc？如果没有足够的内存来分配，是否在其他地方分配了新内存，并且通过指针链接的

2区域OR是复制到的旧区域

哪里有足够的内存以适应新旧区域？

How is realloc implemented internally ? If there is not enough memory
in place to allocate , is new memory allocated somewhere else and the
2 regions linked via a pointer , OR , is the old region copied to a
place where there is enough memory to fit both old and new region ?

复制。

Copied.

在第二种情况下，如果旧的话，这种方法效率不高

区域很大？

In the second case , wouldn''t this method be inefficient if the old
region was large ?

可能是。

它可以将数组扩展为N个元素，

到O（ N * N）操作。


将链表扩展到N个节点，

更可能是O（N）操作。
< br $> b $ b -

pete

It could be.
It could make expanding an array to N elements,
into an O(N*N) operation.

Expanding a linked list to N nodes,
would more likely be an O(N) operation.

--
pete

" Kislay" < ki *********** @ gmail.com在消息中写了

"Kislay" <ki***********@gmail.comwrote in message

如何在内部实施realloc？如果没有足够的内存来分配，是否在其他地方分配了新内存，并且通过指针链接的

2区域OR是复制到的旧区域

哪里有足够的内存以适应新旧区域？在

第二种情况下，如果旧的

区域很大，这种方法效率不高吗？

How is realloc implemented internally ? If there is not enough memory
in place to allocate , is new memory allocated somewhere else and the
2 regions linked via a pointer , OR , is the old region copied to a
place where there is enough memory to fit both old and new region ? In
the second case , wouldn''t this method be inefficient if the old
region was large ?

伪码


获得块大小

块后空格

if（blocksize + space< new blocksize）

调整块

其他

分配新块

复制数据

免费旧块


只需一个

getblocksize（）函数就可以实现一个效率相当低的realloc（）。如果你可以窥视malloc的内部结构（0

系统，你可以扩展块，如果可能的话，这样可以避免复制。


-

免费游戏和编程好东西。
http://www.personal.leeds.ac.uk/~bgy1mm

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