内存映射查询表(LUT)

Question

我正在编写一个闪存驱动程序，我有一个函数可以根据地址检索内存扇区，另一个函数可以根据扇区找到扇区大小。

如何使用查找表而不是if条件？

我目前的实现：

hal_status_t flashGetSector(uint32_t address, uint32_t* sectorResult) {
  hal_status_t status = HAL_STATUS_SUCCESS;

  /*BANK1 start*/
  if((address < 0x08003FFF) && (address >= 0x08000000)) {
    *sectorResult = FLASH_SECTOR_0;
    return status;
  }
  if((address < 0x08007FFF) && (address >= 0x08004000)) {
    *sectorResult = FLASH_SECTOR_1;
    return status;
  }

/*more sectors...*/

  if((address < 0x081FFFFF) && (address >= 0x081E0000)) {
    *sectorResult = FLASH_SECTOR_23;
    return status;
  }

  return HAL_STATUS_ILLEGAL;
}

hal_status_t flashGetSectorSize(uint32_t sector, uint32_t* sectorSize) {
  if((sector == FLASH_SECTOR_0) || (sector == FLASH_SECTOR_1) || (sector == FLASH_SECTOR_2) ||  (sector == FLASH_SECTOR_3)
     || (sector == FLASH_SECTOR_12) || (sector == FLASH_SECTOR_13) || (sector == FLASH_SECTOR_14) || (sector == FLASH_SECTOR_15)) {
    *sectorSize = 16 * 1024;
    return HAL_STATUS_SUCCESS;
  }

  if((sector == FLASH_SECTOR_4) || (sector == FLASH_SECTOR_16)) {
    *sectorSize = 64 * 1024;
    return HAL_STATUS_SUCCESS;
  }

  if ((sector >= FLASH_SECTOR_5 && sector <= FLASH_SECTOR_11) || (sector >= FLASH_SECTOR_17 && sector <= FLASH_SECTOR_23) ) {
    *sectorSize = 128 * 1024;
    return HAL_STATUS_SUCCESS;
  }

  return HAL_STATUS_ILLEGAL;
}

Answer 1

你可以做一些事情：

typedef uint32_t sector_t;
typedef uint32_t address_t;
#define ARRAY_SIZE(x)  sizeof(x)/sizeof(*x)

static const sector_t _idx_to_sector[] = {
    FLASH_SECTOR_0,
    FLASH_SECTOR_1,
    FLASH_SECTOR_2,
    ...
};

size_t sector_to_idx(sector_t sector) {
    for (size_t i = 0; i < ARRAY_SIZE(_idx_to_sector); ++i) {
         if (_idx_to_sector[i] == sector) {
              return i;
         }
     }
     return -1;
}

#define SMALL_SECTOR_SIZE   (16 * 1024)
#define MEDIUM_SECTOR_SIZE  (64 * 1024)
static const address_t _sector_sizes[] = {
    [0] = SMALL_SECTOR_SIZE,
    [1] = SMALL_SECTOR_SIZE,
    ...
    [4] = MEDIUM_SECTOR_SIZE,
    [5] = SMALL_SECTOR_SIZE,
    [6] = MEDIUM_SECTOR_SIZE,
    ...
};

hal_status_t flashGetSectorSize(sector_t sector, address_t *sectorSize) {
      const size_t idx = sector_to_idx(sector);
      if (idx == (size_t)-1) return FAILURE;
      *sectorSize = _sector_sizes[idx];
      return SUCCESS;
}

hal_status_t flashGetSector(address_t address, sector_t *seectorResult) {
     const address_t startaddress = 0x08000000;
     if (address < startaddress) return FAILURE;
     address -= startaddress; // 0...0x1FFFFF
     for (size_t i = 0; i < ARRAY_SIZE(_idx_to_sector); ++i) {
         const address_t sectorsize = _sector_sizes[i];
         // check for each in range - move to the next
         if (address < sectorsize) {
                *seectorResult = _idx_to_sector[i];
                return SUCCESS;
         }
         address -= sectorsize;
     }
     return FAILURE;
}

多个数组可能很难管理-你可以考虑做一个结构，将你所有的“扇区描述”保存在一个地方。