QByteArrray invalid crc32 values - qt

I'm trying to get CRC32 hash from QByteArray. The problem is that, everytime I run program, it gives different results if using QByteArray::operator=() but right if I use QByteArray::setRawData(). could anyone explain why I'm getting these strange results? Thanks.
crc32 function:
unsigned int crc32_tab[256] = {
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};
...
unsigned int MyClass::crc32(unsigned int crc, const void *buf, unsigned int size)
{
const unsigned int *p;
p = (const unsigned int *)buf;
crc = crc ^~ 0xFFFFFFFF;
while(size--)
{
crc = this->crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
}
return crc ^~ 0xFFFFFFFF;
}
and string to be calculated.
QByteArray crcval = "abc";
MyClass mclass;
QMessageBox::information(0, 0, QString::number(mclass.crc32(0, crcval.constData(), crcval.size()))); // returns random numbers.
...
QByteArray crcval;
crcval.setRawData("abc", 3);
MyClass mclass;
QMessageBox::information(0, 0, QString::number(mclass.crc32(0, crcval.constData(), crcval.size()))); // OK.
Why?


In first case your string converted to QString. So it's byte representation will be a string in utf-16 with trailing zero (total 8 bytes).
In first case you path 4 bytes - a, b, c, \0
In second - to char[3]
What you mean by "random numbers"?

Related

Qbytearray byte to int and storing it as string value

I want to convert byte data that stored in QBytearray into string value. that string value am using it for displaying in ui window..
QByteArray array;
array.append( 0x02 );
array.append( 0xC1);
qDebug()<<( uint )array[0]<<" "<<( uint )array[1];
uint i = 0x00000000;
i |= array[1];
qDebug()<<i;
uint j = 0x00000000 | ( array[0] << 8 );
qDebug()<<j;
i |= j;
bool b = false;
QString str = QString::number( i );
qDebug()<<str;
but the str prints "4294967233"...this code works for some of the bytes like 0x1, 0x45 and for some of other..but this code not working perfectly for all bytes of data into string..please help me with this and write code for this and post it here..thanks

All values equal or bigger than 0x80 interprets in your sample as negative values, so it need cast to unsigned type before bitwise operations.
QByteArray array;
array.append( 0x02 );
array.append( 0xC1);
unsigned int value = 0;
for (int i = 0; i < array.size(); i++)
value = (value << 8) | static_cast<unsigned char>(array[i]);
QString str = QString::number(value);
qDebug() << value << str;

Converting ASCII to int in Arduino

I am trying to get user input from the serial monitor to turn a stepper motor according to the input. However my code returns the ASCII value rather than the original input.
#include <Stepper.h>
Stepper small_stepper(steps_per_motor_revolution, 8, 10, 9, 11);
void setup() {
// Put your setup code here, to run once:
Serial.begin(9600);
Serial.println("Ready");
}
void loop() {
// Put your main code here, to run repeatedly:
int Steps2Take = Serial.read();
Serial.println(Steps2Take); // Printing
if (Steps2Take == -1)
Steps2Take = 0;
else {
small_stepper.setSpeed(1000); // Setting speed
if (Steps2Take > 0)
small_stepper.step(Steps2Take * 32);
else
small_stepper.step(-Steps2Take * 32);
delay(2);
}
}

Just use the .toInt() function.
You should read the string from your serial and after that convert it to integer.
Serial.print(Serial.readString().toInt());

You could do this three ways! Notice, if the number is greater than 65535 then you have to use a long variable. With decimals use float variable.
You can use the toInt(), or toFloat() which require a String type variable. Heads up as the toFloat() is very time consuming.
// CODE:
String _int = "00254";
String _float = "002.54";
int value1 = _int.toInt();
float value2 = _float.toFloat();
Serial.println(value1);
Serial.println(value2);
// OUTPUT:
254
2.54
You could use the atoi. The function accepts a character array and then converts it to an integer.
// CODE:
// For some reason you have to have +1 your final size; if you don't you will get zeros.
char output[5] = {'1', '.', '2', '3'};
int value1 = atoi(output);
float value2 = atof(output);
Serial.print(value1);
Serial.print(value2);
// OUTPUT:
1
1.23
If you had a Character Array and and wanted to convert it to a string because you didn't know the length...like a message buffer or something, I dunno. You could use this below to change it to a string and then implement the toInt() or toFloat().
// CODE:
char _int[8];
String data = "";
for(int i = 0; i < 8; i++){
data += (char)_int[i];
}
char buf[data.length()+1];
data.toCharArray(buf, data.length()+1);

If it is just a "type-conversion" problem, you can use something like this:
int a_as_int = (int)'a';
or
#include <stdlib.h>
int num = atoi("23"); //atoi = ascii to integer
as it was point out here.
Does it solve the problem?

Difference normal cast and pointer cast

i've written a following code:
void union_bytes() {
float fnum = 1209.1996f;
union endian {
float fnum;
int inum;
unsigned char cnum[4];
}instance;
instance.fnum = fnum;
printf("Number = %f\nLittle Endian = %.2x %.2x %.2x %.2x\nHex = %x\n", instance.fnum, instance.cnum[0],
instance.cnum[1], instance.cnum[2], instance.cnum[3], instance.inum);
}
void pointer_bytes() {
float fnum = 1209.1996f;
int *ptr_inum = (int*)&fnum;;
unsigned char *cbytes = (unsigned char *)&fnum;
printf("Number = %f\nLittle Endian = %.2x %.2x %.2x %.2x\nHex = %x\n", fnum, cbytes[0], cbytes[1], cbytes[2], cbytes[3], *ptr_inum);
}
and i want to know, why i have to do such things : int *ptr_inum = (int*)&fnum; in order to get little-endian, and i cant do so like this:
int inum = (int)fnum;
i suppose, the last option forces fnum to lose some bytes, but i still dont know how such numbers are represent in memory(and which bytes are exactly to lose).
Why in this case:
unsigned char ch[4] = { 0x3b, 0x51, 0x7a, 0x24 };
float f = *(float*)ch;
When comes to casting, ch doesnt give the first nible 0x3b which is then a float, rather than it converts all the bytes in table compounding the entire float.
Thanks

why i have to do such things : int ptr_inum = (int)&fnum; in order
to get little-endian, and i cant do so like this: int inum =
(int)fnum;
There is some terminology confusion here. Little-endian is a specific order of bytes for multi-byte structures, and is usually mentioned as opposed to big-endian.
What you are getting is as a result of execution of the first statement is:
make the variable that points to integer point to a location where a floating-point number is stored, so that later its word representation can be retrieved/modifed int by int. Say, for number 1.9 in IEEE-754 compliant implementations is represented as 0x3ff33333, so on little-endian architectures if your int is 32bit you would get 0x3ff33333.
Second statement would mean: give me an integer variable, that results from a float pointing number. By standard, that means dropping of the decimal, so out of 1.9 you will get 1.

convert HEX string to Decimal in arduino

i have an Hex String like this : "0005607947" and want to convert it to Decimal number , i test it on this site and it correctly convert to decimal number and answer is : "90208583" but when i use this code i get wrong value !
where of my code is wrong or did have any one , some new code for this problem ?
long int decimal_answer = getDEC("0005607947") ;
long int getDEC(String str110) {
long int ID = 0 ;
int len = str110.length() ;
char buff[len] ;
int power = 0 ;
for(int i = 0 ; i <len ; i++) { buff[i] = str110.charAt(i); }
for(int i = (len-1) ; i >=0 ; i--) {
int num = buff[i] - '0' ;
ID = ID + num * pow(16 , power) ;
power = power + 1 ;
}
Serial.println(String(ID , DEC));
return ID ;
}
// thanks , i also use this but , get error : invalid conversion from 'void*' to 'char**' [-fpermissive]
unsigned int SiZe = sizeof(F_value) ;
char charBuf[SiZe];
F_value.toCharArray(charBuf , SiZe);
long decimal_answer = strtol(charBuf , NULL , 16);
Serial.println(decimal_answer , DEC);

Drop all that code, and just use 'strtol' from the standard library.
#include <stdlib.h>
long strtol (const char *__nptr, char **__endptr, int __base)
For your use:
long decimal_answer = strtol("0005607947", NULL, 16);

You are trying to store the value 90208583 in an int. Arduino has a 2 byte int size meaning that the largest number you can store is 2^16-1 (65535). You have a couple of options:
Use an unsigned int
min number: 0
max number: 4,294,967,295
cons: can only be used for positive numbers
Use a long int
min number: -2,147,483,648
max number: 2,147,483,647

android hexToByteArray signed to unsigned

I've got the following function to make a conversion from a Hex String to a Byte array. Then, I calculate the Checksum:
private String CalcChecksum (String message) {
/**Get string's bytes*/
//byte[] bytes = DatatypeConverter.parseHexBinary(message.replaceAll("\\s","")).getBytes();
message = message.replaceAll("\\s","");
byte[] bytes = hexToByteArray(message);
byte b_checksum = 0;
for (int byte_index = 0; byte_index < bytes.length; byte_index++) {
b_checksum += bytes[byte_index];
}
int d_checksum = b_checksum; //Convert byte to int(2 byte)
int c2_checksum = 256 - d_checksum; //Hacer complemento a 2
String hexString = Integer.toHexString(c2_checksum); //Convertir el entero (decimal) a hexadecimal
return hexString;
}
public static byte[] hexToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16));
}
return data;
}
Making some test, for example for the hex value "e0", the hexToByteArray is getting the value "-32". So the final returning value in the CalcChecksum is "17a".
What I need is to get unsigned values in the hexToByteArray function. This is because i need to send the Checksum in a hexString to a MCU where the Checksum is calculated with unsigned values, so isntead of get the "-32" value, it gets "224" and the final hex value is "7a" instead of "17a".
i think that doing some kind of conversion like when the byte result is a negative value, do something like 255 + "negative value" + 1. This will convert "-32" into "224".
The problem is that i'm trying to do it, but i'm having some errors making the conversions between bytes, int, etc...
So, how could i do?

For the moment, I think that this can be the solution.
Just including in the CalcChecksum function the next code after int d_checksum = b_checksum;:
if (d_checksum < 0) {
d_checksum = 255 + d_checksum + 1;
}

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