Arduino CRC32C与CRC32对比

zc0qhyus  于 2022-12-17  发布在  其他
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我正在尝试为我的Arduino编写一个函数，它接受一个十六进制char *并返回其十六进制校验和。我已经能够解析和迭代我的char *，但我还没有得到正确的校验和返回。有人能帮我找到我的bug或更好的计算方法吗？
所以最初我尝试按照this tutorial的CRC32和修改它为CRC32C。然后我看到这个代码，并认为这是更容易理解，这是我目前的代码的基础。
下面是我目前的代码：

static unsigned long crc_table[256] = {
  0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
  0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
  0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
  0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
  0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
  0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
  0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
  0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
  0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
  0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
  0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
  0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7, 
  0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 
  0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 
  0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6, 
  0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829, 
  0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 
  0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c, 
  0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc, 
  0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 
  0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d, 
  0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982, 
  0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 
  0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed, 
  0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f, 
  0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
  0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540, 
  0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 
  0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 
  0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e, 
  0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 
  0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351 
};

unsigned long crc_string(char *s)
{
  unsigned long crc = 0xffffffff; 
  while (*s){
    crc = crc_table[(crc ^ ((uint8_t) hex2int(*s++))) & 0xff] ^ (crc >> 8);
  }
  crc = ~crc;
  
  return crc;
}

int hex2int(char ch)
{
    if (ch >= '0' && ch <= '9')
        return ch - '0';
    if (ch >= 'A' && ch <= 'F')
        return ch - 'A' + 10;
    if (ch >= 'a' && ch <= 'f')
        return ch - 'a' + 10;
    return -1;
}

我正在使用的数据包示例如下：

B100880000000000C840C000160C0E0E2400CD19921979194B00004B00004A00004B00004B00004A00004A00004B00004B00004B00004A00004A00004B00004A00004A00004B00004A00004B00004A00004B00004B00004B00004A00004A00004A00004B00004A00004B00004A00004A00004B00004B00004A00004B00004B00004A00004B00004B0D66BC1B0D0A

其中校验和为：0D66BC1B
函数的校验和是：348BA995
进入crc_string的数据为：

00000000C840C000160C0E0E2400CD19921979194B00004B00004A00004B00004B00004A00004A00004B00004B00004B00004A00004A00004B00004A00004A00004B00004A00004B00004A00004B00004B00004B00004A00004A00004A00004B00004A00004B00004A00004A00004B00004B00004A00004B00004B00004A00004B00004B

其他信息：
数据最初是以字节数组接收的，为了方便阅读，字节数组改为十六进制的String，具体见以下函数：

void array_to_string(byte array[], unsigned int len, char buffer[]) {
  for (unsigned int i = 0; i < len; i++) {  // make this len*2 ? to avoid buffer overflow
    byte nib1 = (array[i] >> 4) & 0x0F;
    byte nib2 = (array[i] >> 0) & 0x0F;
    buffer[i * 2 + 0] = nib1 < 0xA ? '0' + nib1 : 'A' + nib1 - 0xA;
    buffer[i * 2 + 1] = nib2 < 0xA ? '0' + nib2 : 'A' + nib2 - 0xA;
  }
  buffer[len * 2] = '\0';
}

下面是我正在使用的文件的一大部分。currentDataString的一个例子等同于上面列出的“数据包的例子”。

void array_to_string(byte array[], unsigned int len, char buffer[]) {
  for (unsigned int i = 0; i < len; i++) {  // make this len*2 ? to avoid buffer overflow
    byte nib1 = (array[i] >> 4) & 0x0F;
    byte nib2 = (array[i] >> 0) & 0x0F;
    buffer[i * 2 + 0] = nib1 < 0xA ? '0' + nib1 : 'A' + nib1 - 0xA;
    buffer[i * 2 + 1] = nib2 < 0xA ? '0' + nib2 : 'A' + nib2 - 0xA;
  }
  buffer[len * 2] = '\0';
}

static void notifyCallback(BLERemoteCharacteristic *pBLERemoteCharacteristic, byte pData[], size_t length, bool isNotify) {
  array_to_string(pData, length, currentData);
  Serial.print(F("Clean data: "));
  Serial.println(currentData);
  String currentDataString(currentData);
  else if(currentDataString.indexOf("B100")!= -1){ 
    Serial.println("b100 Data");
    if(checkCRC(currentDataString)){
      Serial.println("Good Data");
    }
  }
}

boolean checkCRC(String currentDataString){
  int len = currentDataString.length(); 
  String newCRC = currentDataString.substring(8,len - 12 );
  char buf[len- 8 - 12];
  newCRC.toCharArray(buf, len-8-12);
  unsigned long newFunction = crc_string(buf);
  Serial.println(crc_string(buf), HEX);
  Serial.print(F("newCRC: "));
  Serial.println(newCRC);

  String GivenCRC = currentDataString.substring(len - 4 - 8 ,len - 4 ); 
  Serial.print(F("GivenCRC: "));
  Serial.println(GivenCRC);
  return newCRC == GivenCRC;
}
c

2条答案

按热度按时间
agxfikkp

agxfikkp1#

如果您发送的是原始字节，这应该可以正常工作：
编辑：对不起，原来的解决方案只关注生成crc的内容，我也加了一个len参数。

unsigned long crc_string(char *s, int len)
{
  unsigned long crc = 0xffffffff; 
  int i = 0;
  for (; i < len; ++i){
    crc = crc_table[((crc << 8) ^ *s++) & 0xff] ^ (crc >> 8);
  }
  crc = ~crc;
  
  return crc;
}

另一种方法是发送一个seed参数，这样可以更好地动态执行crc。

unsigned long crc_string(char *s, int len, unsigned long seed)

然后，开始将crc设置为seed，而不是0xffffffff。
如果你有这样的东西，你所拥有的东西就会起作用：

const char* s = "ab0c135a";
crc_string(s);

如果你真的得到了十六进制字符串，我会很惊讶。

赞(0）分享  回复(0）举报  2022-12-17
woobm2wo

woobm2wo2#

最好的解决方案是在将字节数组转换为十六进制字符串之前计算CRC。在问题中添加minimal reproducible example以获得详细的解决方案。
如果十六进制字符串表示仅用于调试/打印，则可能存在不需要转换整个字节数组的替代方法。
CRC表设计用于8位输入值，而函数hex2int转换仅代表4位的单个字符。
这意味着您在CRC计算中输入了错误的数据。
这可以通过将十六进制字符串输入的两个字符转换为一个字节并送入CRC计算来解决。

int hex2nibble(char ch)
{
    if (ch >= '0' && ch <= '9')
        return ch - '0';
    if (ch >= 'A' && ch <= 'F')
        return ch - 'A' + 10;
    if (ch >= 'a' && ch <= 'f')
        return ch - 'a' + 10;
    return -1;
}

int hex2byte(const char *p)
{
    int byte = hex2nibble(*p++);
    /* If the 1st character was invalid we want to keep the -1. */
    if(byte >= 0)
    {
        /* Cast to unsigned because bit operations on signed data might be implementation defined. */
        unsigned int val = (unsigned int)byte;
        val <<= 4;
        val |= (unsigned int)hex2nibble(*p);
        byte = (int)val;
    }
    return byte;
}

/* I suggest to replace unsigned int with uint32_t for portable code.*/
unsigned int crc_string(const char *s)
{
    unsigned int crc = 0xffffffff; 
    while (*s){
        /* note: missing error handling for return value -1 */
        crc = crc_table[(crc ^ ((uint8_t) hex2byte(s))) & 0xff] ^ (crc >> 8);
        s += 2;
    }
    crc = ~crc;
  
    return crc;
}

我无法在Arduino上测试建议的代码。
测试的标准C++版本代码：

#include <iostream>
#include <cstdint>

using namespace std;

static uint32_t crc_table[256] = {
  0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
  0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
  0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
  0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
  0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
  0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
  0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
  0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
  0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
  0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
  0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
  0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7, 
  0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 
  0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 
  0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6, 
  0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829, 
  0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 
  0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c, 
  0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc, 
  0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 
  0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d, 
  0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982, 
  0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 
  0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed, 
  0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f, 
  0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
  0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540, 
  0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 
  0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 
  0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e, 
  0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 
  0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351 
};

int hex2nibble(char ch)
{
    if (ch >= '0' && ch <= '9')
        return ch - '0';
    if (ch >= 'A' && ch <= 'F')
        return ch - 'A' + 10;
    if (ch >= 'a' && ch <= 'f')
        return ch - 'a' + 10;
    return -1;
}

int hex2byte(const char *p)
{
    int byte = hex2nibble(*p++);
    /* If the 1st character was invalid we want to keep the -1. */
    if(byte >= 0)
    {
        /* Cast to unsigned because bit operations on signed data might be implementation defined. */
        unsigned int val = (unsigned int)byte;
        val <<= 4;
        val |= (unsigned int)hex2nibble(*p);
        byte = (int)val;
    }
    return byte;
}

/* Replaced unsigned int with uint32_t for portable code. */
uint32_t crc_string(const char *s)
{
    uint32_t crc = 0xffffffff; 
    while (*s){
        /* note: missing error handling for return value -1 */
        crc = crc_table[(crc ^ ((uint8_t) hex2byte(s))) & 0xff] ^ (crc >> 8);
        s += 2;
    }
    crc = ~crc;
  
    return crc;
}

int main()
{
    string currentDataString = "B100880000000000C840C000160C0E101E00B219761954194C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004CDC49F5C30D0A";

    cout << "input:      " << currentDataString << endl;
  
    int len = currentDataString.length();
    string newCRC = currentDataString.substr(8, len - 12 -8 );
  
    const char *buf = newCRC.c_str();
  
    cout << "newCRCFrom: " << "        " << newCRC << endl;
    cout << "newCRC:     " << hex << crc_string(buf) << endl;
  
    string GivenCRC = currentDataString.substr(len - 4 - 8, 8); // TODO we only need to put the CRC to a string not the whole packet
    cout << "GivenCRC:   " << GivenCRC << endl;

    cout << "Valid:      " << (newCRC == GivenCRC) << endl;
    
    return 0;
}

输出：

input:      B100880000000000C840C000160C0E101E00B219761954194C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004CDC49F5C30D0A
newCRCFrom:         00000000C840C000160C0E101E00B219761954194C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004C00004D00004C00004C
newCRC:     c3f549dc
GivenCRC:   DC49F5C3
Valid:      0

如您所见，计算得出的CRC基本相同，但数据字符串以小端字节顺序包含CRC，而计算得出的CRC字符串以正常字节顺序显示4字节数的十六进制表示。
问题中缺少CRC以little-endian字节顺序存储的信息。（这应该是我在注解中要求的规范的一部分。）
链接的Arduino example中的表用于4位输入，crc_update将8位输入拆分为两个4位值。如果您想将4位值输入CRC计算，可以使用此表。Arduino解决方案将低半字节首先输入CRC计算。下面未经测试的提议将先输入高半字节，因此此计算可能是错误的。

static PROGMEM prog_uint32_t crc_table[16] = {
    0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
    0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
    0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
    0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
};

unsigned long crc_string(char *s)
{
    unsigned long crc = 0xffffffff; 
    while (*s){
        crc = pgm_read_dword_near(crc_table + ((uint8_t) hex2int(*s++) & 0x0f))
            ^ (crc >> 4);
    }
    crc = ~crc;
  
    return crc;
}
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