小内存算法中限定MIN_SIZE_ALIGNED的作用

发布于 2022-01-12 15:10:58 浏览：705 订阅该版

2 个回答

aozima 2022-01-12

调网络不抓包，调I2C等时序不上逻辑分析仪，就像电工不用万用表！多用整理的好的文字，比截图更省流量，还能在整理过程中思考。

ConorYe 2022-01-12

这家伙很懒，什么也没写！

用户名由3_15位 2024-04-10

这家伙很懒，什么也没写！

[@ConorYe](https://club.rt-thread.org/u/022c8905ccc552a7)

- 我认为在32位架构时 `12 = sizeof( pool_ptr)+sizeof(next)+sizeof(prev);`
- 但是64BIT时是 `24 = sizeof( pool_ptr)+sizeof(next)+sizeof(prev);`
- 32位时 `rt_size_t = 4位;64bitrt_size_t = 8;` 所以会是24或者12;`rt_ubase_t`也是同理

```c
#ifndef RT_USING_ARCH_DATA_TYPE
#ifdef RT_USING_LIBC
typedef int8_t                          rt_int8_t;      /**<  8bit integer type */
typedef int16_t                         rt_int16_t;     /**< 16bit integer type */
typedef int32_t                         rt_int32_t;     /**< 32bit integer type */
typedef uint8_t                         rt_uint8_t;     /**<  8bit unsigned integer type */
typedef uint16_t                        rt_uint16_t;    /**< 16bit unsigned integer type */
typedef uint32_t                        rt_uint32_t;    /**< 32bit unsigned integer type */
typedef int64_t                         rt_int64_t;     /**< 64bit integer type */
typedef uint64_t                        rt_uint64_t;    /**< 64bit unsigned integer type */
typedef size_t                          rt_size_t;      /**< Type for size number */
typedef ssize_t                         rt_ssize_t;     /**< Used for a count of bytes or an error indication */
#else
typedef signed   char                   rt_int8_t;      /**<  8bit integer type */
typedef signed   short                  rt_int16_t;     /**< 16bit integer type */
typedef signed   int                    rt_int32_t;     /**< 32bit integer type */
typedef unsigned char                   rt_uint8_t;     /**<  8bit unsigned integer type */
typedef unsigned short                  rt_uint16_t;    /**< 16bit unsigned integer type */
typedef unsigned int                    rt_uint32_t;    /**< 32bit unsigned integer type */
#ifdef ARCH_CPU_64BIT
typedef signed long                     rt_int64_t;     /**< 64bit integer type */
typedef unsigned long                   rt_uint64_t;    /**< 64bit unsigned integer type */
#else
typedef signed long long                rt_int64_t;     /**< 64bit integer type */
typedef unsigned long long              rt_uint64_t;    /**< 64bit unsigned integer type */
#endif /* ARCH_CPU_64BIT */
typedef rt_ubase_t                      rt_size_t;      /**< Type for size number */
typedef rt_base_t                       rt_ssize_t;     /**< Used for a count of bytes or an error indication */
#endif /* RT_USING_LIBC */
#endif /* RT_USING_ARCH_DATA_TYPE */

/* RT-Thread basic data type definitions */
typedef int                             rt_bool_t;      /**< boolean type */
typedef signed long                     rt_base_t;      /**< Nbit CPU related date type */
typedef unsigned long                   rt_ubase_t;     /**< Nbit unsigned CPU related data type */

/**
  * memory item on the small mem
  */
struct rt_small_mem_item
{
    rt_ubase_t              pool_ptr;         /**< small memory object addr */
#ifdef ARCH_CPU_64BIT
    rt_uint32_t             resv;
#endif /* ARCH_CPU_64BIT */
    rt_size_t               next;             /**< next free item */
    rt_size_t               prev;             /**< prev free item */
#ifdef RT_USING_MEMTRACE
#ifdef ARCH_CPU_64BIT
    rt_uint8_t              thread[8];       /**< thread name */
#else
    rt_uint8_t              thread[4];       /**< thread name */
#endif /* ARCH_CPU_64BIT */
#endif /* RT_USING_MEMTRACE */
};

#ifdef ARCH_CPU_64BIT
#define MIN_SIZE 24
#else
#define MIN_SIZE 12
#endif /* ARCH_CPU_64BIT */
```