Introducing errors by flipping bits

I have a character array in C i开发者_如何学运维nto which I want to introduce errors by flipping some bits.

How can I flip bits and introduce errors?

You can flip bits using the xor operator:

x = x ^ mask;
x ^= mask; // Same functionality as above.

For example, if mask is 1, the least significant bit is flipped. You can create any desired mask by bit-shifting the 1: mask = 1 << k; where k is the number of bits to shift.

For distributing the errors, use a random number generator. rand() / srand() should suffice if this is for test purposes.

To flip a bit you can use the bit shifting and bitwise xor operators.

unsigned char flip(unsigned char c, int bit) {
    return c ^ (1 << bit);
}

You can also flip more than one bit by using a bitmask other than (1 << bit), which has just one bit set:

unsigned char flip(unsigned char c, unsigned char mask) {
    return c ^ (1 << mask);
}

// flip bits 0 and 3 (00001001 = 0x09)
flip(c, 0x09);