如何获取结构数组中某些结构成员的地址 [英] How to get address of some struct member in array of structures

问题描述

我尝试获取结构数组中某些struct成员的地址，但我不想使用该成员的名称.

应该是这样的:

typedef struct{               
  unsigned char MrChar;
  unsigned short MrShort;
  unsigned long MrLong;
  unsigned char MrArray[5];
}tModule;

static tModule taModulesArray[MODULES_AMOUNT] = {  // MODULES_AMOUNT = 2
  {0x22, 0x3298, 0x92324583, "djsoe"}, // Module 1
  {0x33, 0x1843, 0x65644113, "gskwc"}, // Module 2  
};

unsigned long usGetMemberAddr(unsigned long ulModule, unsigned long ulMember){
  unsigned long Address;
  Address = abs(taModulesArray_BaseAddress - taModulesArray[ulModule].[ulMember]);
  return Address;
}

我需要它来快速修改结构不同的配置(在EEPROM中).因此，我尝试做一个函数，该函数采用模块号和模块成员之一的索引，并返回适当成员的偏移量.

返回之前是否有可能出现类似该行的内容?

解决方案

我们还可以使用以下逻辑找到结构中每个成员的偏移量，然后将其直接添加到特定实例的基础地址中结构变量.

#define OFFSET(type, member)   ( (int) (& ( ((type *)(0))->member ) ) )

int find_offset(unsigned long ulMember)
{
    unsigned long off = 0;

    switch(ulMember)
    {
         case 1:
             off = OFFSET(tModule, MrChar);
             break;
         case 2:
             off = OFFSET(tModule, MrShorc);
             break;
         case 3:
             off = OFFSET(tModule, MrLong);
             break;
         case 4:
             off = OFFSET(tModule, MrArray);
             break;
    }

    return off;
}

unsigned long usGetMemberAddr(unsigned long ulModule, unsigned long ulMember)
{   
    unsigned long Address;   

    Address = (unsigned long)&taModulesArray[ulModule] + find_offset(ulMember);

    return Address; 
} 

I try to get the address of some struct member in array of structures but i don't want to use name of that member.

It should be something like this:

typedef struct{               
  unsigned char MrChar;
  unsigned short MrShort;
  unsigned long MrLong;
  unsigned char MrArray[5];
}tModule;

static tModule taModulesArray[MODULES_AMOUNT] = {  // MODULES_AMOUNT = 2
  {0x22, 0x3298, 0x92324583, "djsoe"}, // Module 1
  {0x33, 0x1843, 0x65644113, "gskwc"}, // Module 2  
};

unsigned long usGetMemberAddr(unsigned long ulModule, unsigned long ulMember){
  unsigned long Address;
  Address = abs(taModulesArray_BaseAddress - taModulesArray[ulModule].[ulMember]);
  return Address;
}

I need that for quick modification of configuration (in EEPROM) which is in different structs. So I try to do function which takes number of module and index of one of the module member and returns offset of for proper member.

If there is any possibility for something like that line before return?

解决方案

We can use the below logic also to find the offset of each memebers of a structure and then we can directly add it to the base addres of the particular instance of the structure variable.

#define OFFSET(type, member)   ( (int) (& ( ((type *)(0))->member ) ) )

int find_offset(unsigned long ulMember)
{
    unsigned long off = 0;

    switch(ulMember)
    {
         case 1:
             off = OFFSET(tModule, MrChar);
             break;
         case 2:
             off = OFFSET(tModule, MrShorc);
             break;
         case 3:
             off = OFFSET(tModule, MrLong);
             break;
         case 4:
             off = OFFSET(tModule, MrArray);
             break;
    }

    return off;
}

unsigned long usGetMemberAddr(unsigned long ulModule, unsigned long ulMember)
{   
    unsigned long Address;   

    Address = (unsigned long)&taModulesArray[ulModule] + find_offset(ulMember);

    return Address; 
} 

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