SolarBT_iOS/SolarBT/Classes/BLE/NSString+WithCRCModbus.m

//
//  NSString+WithCRCModbus.m
//  iOS-CRC
//
//  Created by leon on 2017/3/7.
//
//

/**
 * CRC在线检验网址:https://www.lammertbies.nl/comm/info/crc-calculation.html
 * http://stackoverflow.com/questions/33794878/when-converting-nsdata-to-unsigned-char-i-get-the-wrong-result
 * http://stackoverflow.com/questions/10214990/how-to-convert-nsdata-to-char-array-containing-hexa-values
 * http://stackoverflow.com/questions/12971117/how-to-convert-nsdata-to-char
 */

#import "NSString+WithCRCModbus.h"

@implementation NSString (WithCRCModbus)


- (NSString*)withCrc16CCITT{
    if(self.length%2!=0){
        return nil;
    }
    return [self stringByAppendingString:[self getCrcString2]];
}


uint16_t xmodem_crc16_ccitt_2(const uint8_t *pbBuf, uint32_t dwLen)
{
    uint16_t wCRC = 0;
    uint16_t  bCycle;
    
    while (dwLen-- > 0)
    {
        wCRC ^= (unsigned short) *pbBuf++ << 8;
        for (bCycle = 0; bCycle < 8; bCycle++)
        {
            if (wCRC & 0x8000)
            {
                wCRC = wCRC << 1 ^ 0x1021;
            }
            else
            {
                wCRC <<= 1;
            }
        }
    }
    return wCRC;
}

- (NSString*)getCrcString2{
    NSData *nsdataString = [self toNSData];
    unsigned char *chars = (unsigned char *)[nsdataString bytes];
  //  unsigned short result = [self CRC16:chars length:nsdataString.length];
    unsigned short result = xmodem_crc16_ccitt_2(chars, nsdataString.length);
    //下面这种方式方可，直接用dataWithBytes传short的地址可能导致字节反序
    // 参考：http://www.jianshu.com/p/0d8cf741584a
    Byte b1=result & 0xff;
    Byte b2=(result>>8) & 0xff;
    Byte byte[] = {b1, b2};
    NSData *data = [NSData dataWithBytes:byte length:sizeof(byte)];
    return [self toNSString:data];
}

- (NSString*)withCrc16Modbus{
    if(self.length%2!=0){
        return nil;
    }
    return [self stringByAppendingString:[self getCrcString]];
}


- (NSString*)getCrcString{
    NSData *nsdataString = [self toNSData];
    unsigned char *chars = (unsigned char *)[nsdataString bytes];
    unsigned short result = [self CRC16:chars length:nsdataString.length];
    
    //下面这种方式方可，直接用dataWithBytes传short的地址可能导致字节反序
    // 参考：http://www.jianshu.com/p/0d8cf741584a
    Byte b1=result & 0xff;
    Byte b2=(result>>8) & 0xff;
    Byte byte[] = {b1, b2};
    NSData *data = [NSData dataWithBytes:byte length:sizeof(byte)];
    return [self toNSString:data];
}

// http://liumh.com/2015/06/06/convert-between-nsdata-and-hexstr/
- (NSData *)toNSData{
    if (!self || [self length] == 0) {
        return nil;
    }
    
    NSMutableData *hexData = [[NSMutableData alloc] initWithCapacity:8];
    NSRange range;
    if ([self length] % 2 == 0) {
        range = NSMakeRange(0, 2);
    } else {
        range = NSMakeRange(0, 1);
    }
    for (NSInteger i = range.location; i < [self length]; i += 2) {
        unsigned int anInt;
        NSString *hexCharStr = [self substringWithRange:range];
        NSScanner *scanner = [[NSScanner alloc] initWithString:hexCharStr];
        
        [scanner scanHexInt:&anInt];
        NSData *entity = [[NSData alloc] initWithBytes:&anInt length:1];
        [hexData appendData:entity];
        
        range.location += range.length;
        range.length = 2;
    }
    return hexData;
}



// http://liumh.com/2015/06/06/convert-between-nsdata-and-hexstr/
- (NSString *)toNSString:(NSData*)data{
    if (!self || [self length] == 0) {
        return @"";
    }
    NSMutableString *string = [[NSMutableString alloc] initWithCapacity:[self length]];
    
    [data enumerateByteRangesUsingBlock:^(const void *bytes, NSRange byteRange, BOOL *stop) {
        unsigned char *dataBytes = (unsigned char*)bytes;
        for (NSInteger i = 0; i < byteRange.length; i++) {
            NSString *hexStr = [NSString stringWithFormat:@"%x", (dataBytes[i]) & 0xff];
            if ([hexStr length] == 2) {
                [string appendString:hexStr];
            } else {
                [string appendFormat:@"0%@", hexStr];
            }
        }
    }];
    
    return string;
}

const char chCRCHTalbe[]={
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40
};
const char chCRCLTalbe[] =
{
    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
    0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
    0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
    0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
    0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
    0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38,
    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
    0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
    0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB,
    0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
    0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
    0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
    0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
    0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
    0x41, 0x81, 0x80, 0x40
};

/*
 *decription:  计算CRC校验码
 *input:       无符号进制字符串数组
 *output:      CRC检验码
 */
-(unsigned short)CRC16:(unsigned char *)puchMsg length:(unsigned int) usDataLen
{
    unsigned char chCRCHi = 0xFF; // 高CRC字节初始化
    unsigned char  chCRCLo = 0xFF; // 低CRC字节初始化
    unsigned short  wIndex;
    while(usDataLen--)
    {
        wIndex = chCRCLo ^ *puchMsg++ ;
        chCRCLo = chCRCHi ^ chCRCHTalbe[wIndex];
        chCRCHi = chCRCLTalbe[wIndex] ;
    }
    return ((chCRCHi << 8) | chCRCLo) ;
}

@end