學(xué)習(xí)Tips

• ios中將16進(jìn)制轉(zhuǎn)換為浮點(diǎn)型

NSString *temp = [NSString stringWithFormat:@"%@%@",@"0x",[[[temp0 stringByAppendingString:temp1] stringByAppendingString:temp2] stringByAppendingString:temp3]];
            
const char *str = NULL;
 if ([temp canBeConvertedToEncoding:NSUTF8StringEncoding]) {
      str = [temp cStringUsingEncoding:NSUTF8StringEncoding];
}
uint32_t num;
float f;
sscanf(str, "%x", &num);  // assuming you checked input
f = *((float*)&num);
printf("the hexadecimal 0x%08x becomes %.3f as a float\n", num, f);

• CRC16-MODBUS校驗(OC版本代碼)

+ (NSString *)getCrc16_MODBUSWithString:(NSString *)str{
    
    NSArray *array = [[NSArray alloc]initWithArray:[self seperateStr:str byLength:2]];
    unsigned short tmp = 0xffff;
    unsigned short ret1 = 0;
    Byte buff[10240] = {};
    
    for (int i = 0; i < array.count; i++) {
        buff[i] = [[self decimalStringFromHexString:array[i]] intValue];//  這個是10進(jìn)制轉(zhuǎn)換成16進(jìn)制
    }
  
    for(int n = 0; n < array.count; n++){
        tmp = buff[n] ^ tmp;
        for(int i = 0;i < 8;i++){  /*此處的8 -- 指每一個char類型又8bit，每bit都要處理*/
            if(tmp & 0x01){
                tmp = tmp >> 1;
                tmp = tmp ^ 0xa001;
            }
            else{
                tmp = tmp >> 1;
            }
        }
    }
    /*CRC校驗后的值*/
    printf("校驗后的值%X\n",tmp);
    /*將CRC校驗的高低位對換位置*/
    ret1 = tmp >> 8;
    ret1 = ret1 | (tmp << 8);
    printf("高低位對換后的值ret: %X\n",ret1);
    
    NSString *returnStr = [NSString stringWithFormat:@"%X",ret1];
    return returnStr;
}

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