how to read bitwise operation, what it actually does

i need to be certain about some bitwise operation in memory. This C code is too low level for me, but i need to understand and then improve it. decalage bit Its from an algorithm called feistel structure, using a key and "XOR" with 32bits data block. its bit shifting ..

These are the lines that i don't get really even if i know most of the C operators.

char *pkey;

int64_t keym;

while(*pkey)                                                                   {                                                                            
      keym = keym*16 + (*pkey <= 57 && *pkey >= 48 ? *pkey - 48 : *pkey - 55);
   pkey++;                                                                    }   


char *tmp;

  tmp |= (keym&254L << 8*i) >> i + 1; 

int64_t k;
define MYBIT _|_

k = k << 4 | z(k << 4, 56) & (MYBIT << 24);



int64_t a, b, lb

if(y&8)                                                                         |
        return bl;                                                                    |
      a = bl >> 32&((1L << 32)-1);                                                    |
      b = (bl&(1L << 32) -1);                                                         |
      a = a^b^rotate(keym, y);  

                                                  |
  bl = y < 7 ? (b << 32) + a : (a << 32) + b;

Thanks for any explanation, as clear as possible for me to re-use this code.