libcod/cracking.cpp at master · damage99/libcod · GitHub

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#include"cracking.hpp"

voidcracking_hook_function(int from, int to)
{
int relative = to - (from+5); // +5 is the position of next opcode
memset((void *)from, 0xE9, 1); // JMP-OPCODE
memcpy((void *)(from+1), &relative, 4); // set relative address with endian
}

voidcracking_hook_call(int from, int to)
{
int relative = to - (from+5); // +5 is the position of next opcode
memcpy((void *)(from+1), &relative, 4); // set relative address with endian
}

intsingleHexToNumber(char hexchar)
{
switch (hexchar)
	{
case'0':
return0;

case'1':
return1;

case'2':
return2;

case'3':
return3;

case'4':
return4;

case'5':
return5;

case'6':
return6;

case'7':
return7;

case'8':
return8;

case'9':
return9;

case'a':
case'A':
return10;

case'b':
case'B':
return11;

case'c':
case'C':
return12;

case'd':
case'D':
return13;

case'e':
case'E':
return14;

case'f':
case'F':
return15;

default:
return -1;
	}
}

inthexToBuffer(char *hex, char *buffer, int bufferLen)
{
int len, neededBytes, i, padding, first, pos, leftPart, rightPart;
	len = strlen(hex); // every byte of hex is taking 4 bits. F=1111
	padding = 0; // just for "a", "abc" etc... "a" = 0x0a, "abc" = 0x0abc
// we dont handle 4-bits for one hex-number, so round up to bytes...
// three bytes will not take 12 bits, they will use 16 bits = 2 bytes
if (len % 2 != 0)
	{
 padding = 1;
 len++;
	}
	neededBytes = len >> 1; // its like dividing by 2
	first = 1;
	pos = 0;
for (i=0; i<neededBytes; i++)
	{
char twochars[2] = {'0', '0'};
if (first)
 {
if (padding)
 {
 twochars[1] = hex[0];
 pos++;
 }
else
 {
 twochars[0] = hex[0];
 twochars[1] = hex[1];
 pos += 2;
 }
 first = 0;
 }
else
 {
 twochars[0] = hex[pos];
 twochars[1] = hex[pos+1];
 pos += 2;
 }
 leftPart = singleHexToNumber(twochars[0]);
 rightPart = singleHexToNumber(twochars[1]);
if (leftPart == -1 || rightPart == -1)
return i;
 buffer[i] = (leftPart << 4) + rightPart;
// buffer end:
if (i == bufferLen)
return i;
	}
return neededBytes;
}

intcracking_write_hex(int address, char *hex)
{
unsignedchar *ptr = (unsignedchar *)address;
char buffer[128] = {0};
int bytes;
int i;
	bytes = hexToBuffer(hex, buffer, 128);


for (i=0; i<bytes; i++)
 ptr[i] = buffer[i];

return bytes;
}

cHook::cHook(int from, int to)
{
this->from = from;
this->to = to;
}

voidcHook::hook()
{
memcpy((void *)oldCode, (void *)from, 5);
cracking_hook_function(from, to);
}

voidcHook::unhook()
{
memcpy((void *)from, (void *)oldCode, 5);
}