variable-pools.html

来自「ecos3.0 beta 的官方文档,html格式」· HTML 代码 · 共 364 行

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<!-- Copyright (C) 2009 Free Software Foundation, Inc.                                -->
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>Variable Size Allocation Pools</TITLE
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><H1
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NAME="VARIABLE-POOLS"
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>Variable Size Allocation Pools</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN14957"
></A
><H2
>Name</H2
>cyg_mempool_var_create, cyg_mempool_var_delete, cyg_mempool_var_alloc, cyg_mempool_var_timed_alloc, cyg_mempool_var_try_alloc, cyg_mempool_var_free, cyg_mempool_var_waiting, cyg_mempool_var_get_info&nbsp;--&nbsp;Variable Size Allocation Pools</DIV
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>Synopsis</H2
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><PRE
CLASS="FUNCSYNOPSISINFO"
>#include &lt;cyg/kernel/kapi.h&gt;
        </PRE
></TD
></TR
></TABLE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void cyg_mempool_var_create</CODE
>(void* base, cyg_uint32 size, cyg_handle_t* varpool, cyg_mempool_var* var);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void cyg_mempool_var_delete</CODE
>(cyg_handle_t varpool);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void* cyg_mempool_var_alloc</CODE
>(cyg_handle_t varpool, cyg_uint32 size);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void* cyg_mempool_var_timed_alloc</CODE
>(cyg_handle_t varpool, cyg_uint32 size, cyg_tick_count_t abstime);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void* cyg_mempool_var_try_alloc</CODE
>(cyg_handle_t varpool, cyg_uint32 size);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void cyg_mempool_var_free</CODE
>(cyg_handle_t varpool, void* p);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>cyg_bool_t cyg_mempool_var_waiting</CODE
>(cyg_handle_t varpool);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void cyg_mempool_var_get_info</CODE
>(cyg_handle_t varpool, cyg_mempool_info* info);</CODE
></P
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CLASS="REFSECT1"
><A
NAME="MEMALLOC-VARIABLE-DESCRIPTION"
></A
><H2
>Description</H2
><P
>      The variable size memory pool functions are used for allocating
      blocks of any size. Before memory can be allocated the pool must
      first be created by calling
      <CODE
CLASS="FUNCTION"
>cyg_mempool_var_create()</CODE
>. The parameter
      <CODE
CLASS="PARAMETER"
>base</CODE
> is a point to the bottom of the
      memory area to be used by the pool and
      <CODE
CLASS="PARAMETER"
>size</CODE
> is the size of the memory area in
      bytes. It also takes a pointer to a
      <CODE
CLASS="STRUCTNAME"
>cyg_mempool_var</CODE
> data structure which is
      typically statically allocated, and may be part of a larger data
      structure. It should be noted that some memory is take from the
      pool for book keeping purposes. If a memory pool is no longer
      required and there are not threads waiting to allocate memory
      from it, it can be destroyed with
      <CODE
CLASS="FUNCTION"
>cyg_mempool_var_delete()</CODE
>.  
      </P
><P
>      Memory can be allocated from the pool using a number of
      functions. They all take the
      paramters<CODE
CLASS="PARAMETER"
>varpool</CODE
>which indicates which
      pool should be used and the <CODE
CLASS="PARAMETER"
>size</CODE
>which
      indicates who big a memory area should be
      allocated. <CODE
CLASS="FUNCTION"
>cyg_mempool_var_alloc()</CODE
> will
      block until the memory becomes
      available. <CODE
CLASS="FUNCTION"
>cyg_mempool_tryalloc()</CODE
>will try
      not block if no memory is available and will return
      <TT
CLASS="LITERAL"
>NULL</TT
>. Otherwise a pointer to the allocated
      memory will be returned.
      <CODE
CLASS="FUNCTION"
>cyg_mempool_var_timed_alloc()</CODE
> will block if
      memory is not available and wait for memory to become available
      until the time<CODE
CLASS="PARAMETER"
>abstime</CODE
> is reached. It will
      then return <TT
CLASS="LITERAL"
>NULL</TT
>.
      </P
><P
>      Allocated memory can be freed using the function <CODE
CLASS="FUNCTION"
>cyg_mempool_var_free()</CODE
>.
      </P
><P
>      Lastly it is possible to query information about the pool using
      the function
      <CODE
CLASS="FUNCTION"
>cyg_mempool_var_get_info()</CODE
>. This takes a
      pointer to the structure <CODE
CLASS="STRUCTNAME"
>cyg_mempool_info</CODE
> which is:
      <TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
    cyg_int32 totalmem;
    cyg_int32 freemem;
    void      *base;
    cyg_int32 size;
    cyg_int32 blocksize;
    cyg_int32 maxfree;
} cyg_mempool_info;
      </PRE
></TD
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>
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