Thread: Substitution problem...

Ok thanks!

Aha, I know why. It's because strings hold chars, not unsigned chars.

From the lookup table:

Code:

27, 144, 241, 223, 244, 24, 1

Since char is signed on my platform and yours, 241, 223, and anything above 127 cannot be stored properly. It's stored, but comes out as a negative number, and in dSubstitution you end up accessing a negative array index.

This works:

Code:

#include <iostream>
#include <string>

using std::string;

void eSubstitution(unsigned char *text)
{
	int subTable[256] = {27, 144, 241, 223, 244, 24, 1, 60, 149, 154, 50, 174, 70, 132, 
167, 86, 38, 188, 3, 233, 128, 130, 39, 118, 175, 22, 46, 84, 191, 42, 19, 113, 153, 225, 227, 
110, 114, 254, 25, 230, 181, 185, 207, 2, 226, 243, 150, 236, 187, 14, 77, 116, 249, 137, 182, 
133, 125, 17, 152, 197, 143, 105, 208, 57, 168, 119, 36, 224, 120, 189, 146, 90, 166, 101, 210
, 201, 11, 82, 196, 23, 56, 43, 44, 159, 12, 157, 123, 5, 156, 96, 97, 160, 242, 9, 171, 121, 220
, 95, 85, 41, 212, 237, 69, 139, 20, 228, 194, 59, 253, 195, 203, 161, 7, 200, 192, 169, 115, 21
, 204, 91, 30, 75, 164, 252, 172, 117, 88, 13, 89, 247, 32, 108, 206, 178, 65, 81, 198, 145, 147
, 170, 190, 209, 54, 67, 0, 179, 79, 6, 26, 4, 64, 124, 98, 62, 29, 193, 127, 104, 45, 140, 74, 
218, 93, 134, 176, 232, 28, 202, 221, 234, 49, 35, 235, 155, 68, 217, 102, 33, 142, 251, 58, 
231, 131, 135, 63, 163, 205, 87, 112, 165, 222, 245, 40, 72, 141, 246, 186, 92, 238, 255, 173, 
37, 111, 240, 15, 76, 126, 248, 199, 122, 148, 213, 16, 48, 34, 78, 103, 47, 158, 219, 52, 73, 
18, 106, 94, 183, 99, 53, 214, 83, 177, 107, 100, 211, 61, 66, 51, 138, 239, 31, 80, 8, 250, 71, 
55, 109, 184, 229, 215, 10, 162, 151, 216, 180, 129, 136};
	//substitute
	for(int i=0; i<4; i++)
	{
		text[i] = ((char)subTable[((int)text[i])]);
	}
}

void dSubstitution(unsigned char *text)
{
	int subTable[256] = {144, 6, 43, 18, 149, 87, 147, 112, 241, 93, 249, 76, 84, 127, 
49, 204, 212, 57, 222, 30, 104, 117, 25, 79, 5, 38, 148, 0, 166, 154, 120, 239, 130, 177, 214,
 171, 66, 201, 16, 22, 192, 99, 29, 81, 82, 158, 26, 217, 213, 170, 10, 236, 220, 227, 142, 244
, 80, 63, 180, 107, 7, 234, 153, 184, 150, 134, 235, 143, 174, 102, 12, 243, 193, 221, 160, 121
, 205, 50, 215, 146, 240, 135, 77, 229, 27, 98, 15, 187, 126, 128, 71, 119, 197, 162, 224, 97, 
89, 90, 152, 226, 232, 73, 176, 216, 157, 61, 223, 231, 131, 245, 35, 202, 188, 31, 36, 116, 51
, 125, 23, 65, 68, 95, 209, 86, 151, 56, 206, 156, 20, 254, 21, 182, 13, 55, 163, 183, 255, 53, 
237, 103, 159, 194, 178, 60, 1, 137, 70, 138, 210, 8, 46, 251, 58, 32, 9, 173, 88, 85, 218, 83, 
91, 111, 250, 185, 122, 189, 72, 14, 64, 115, 139, 94, 124, 200, 11, 24, 164, 230, 133, 145, 
253, 40, 54, 225, 246, 41, 196, 48, 17, 69, 140, 28, 114, 155, 106, 109, 78, 59, 136, 208, 113, 
75, 167, 110, 118, 186, 132, 42, 62, 141, 74, 233, 100, 211, 228, 248, 252, 175, 161, 219, 96, 
168, 190, 3, 67, 33, 44, 34, 105, 247, 39, 181, 165, 19, 169, 172, 47, 101, 198, 238, 203, 2, 92
, 45, 4, 191, 195, 129, 207, 52, 242, 179, 123, 108, 37, 199};
	//substitute
	for(int i=0; i<4; i++)
	{
		text[i] = (subTable[((int)text[i])]);
	}
}

int main() {
    unsigned char from1[] = "abcd", from2[] = "john", from3[] = "zueq";
    
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    eSubstitution(from1);
    eSubstitution(from2);
    eSubstitution(from3);
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    dSubstitution(from1);
    dSubstitution(from2);
    dSubstitution(from3);
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    //std::cout << (int)from2.at(1);
    
    std::cin.get();
    return 0;
}

But if you get rid of all instances of the word "unsigned", it doesn't.

What you did using d then esubstitution, for me the last 3 worked with the regular way, e then d, but the opposite was very messed up. Only one char came out right.

There's no way to do it with strings? Cause my whole algorithm uses strings in every single other part of it. Maybe convert the string to a char array temporarily then convert it back?

Yes, you can do it with strings, you just have to create a lookup table from 0-127. Then you can use isprint() to make sure that each character is within that range.

Unless you need to process unsigned char values, then you wouldn't be able to use a string.

[edit] And I still think that a lookup table is a bad idea. [/edit]

You could always do it like this.

Code:

#include <climits>

void eSubstitution(string &text)
{
    /* snip */
	//substitute
	for(int i=0; i<4; i++)
	{
		text.at(i) = ((char)subTable[((int)text.at(i))-CHAR_MIN]) + CHAR_MIN;
	}
}

void dSubstitution(string &text)
{
    /* snip */
	//substitute
	for(int i=0; i<4; i++)
	{
		text.at(i) = ((char)subTable[((int)text.at(i))-CHAR_MIN]) + CHAR_MIN;
	}
}

I've tested it, and that works, I think.

[edit] No, it doesn't really. Give me a minute. [/edit]

[edit=2] Yes, it does work! Whew!

Code:

#include <iostream>
#include <string>
#include <climits>

using std::string;

void eSubstitution(string &text)
{
	int subTable[256] = {27, 144, 241, 223, 244, 24, 1, 60, 149, 154, 50, 174, 70, 132, 
167, 86, 38, 188, 3, 233, 128, 130, 39, 118, 175, 22, 46, 84, 191, 42, 19, 113, 153, 225, 227, 
110, 114, 254, 25, 230, 181, 185, 207, 2, 226, 243, 150, 236, 187, 14, 77, 116, 249, 137, 182, 
133, 125, 17, 152, 197, 143, 105, 208, 57, 168, 119, 36, 224, 120, 189, 146, 90, 166, 101, 210
, 201, 11, 82, 196, 23, 56, 43, 44, 159, 12, 157, 123, 5, 156, 96, 97, 160, 242, 9, 171, 121, 220
, 95, 85, 41, 212, 237, 69, 139, 20, 228, 194, 59, 253, 195, 203, 161, 7, 200, 192, 169, 115, 21
, 204, 91, 30, 75, 164, 252, 172, 117, 88, 13, 89, 247, 32, 108, 206, 178, 65, 81, 198, 145, 147
, 170, 190, 209, 54, 67, 0, 179, 79, 6, 26, 4, 64, 124, 98, 62, 29, 193, 127, 104, 45, 140, 74, 
218, 93, 134, 176, 232, 28, 202, 221, 234, 49, 35, 235, 155, 68, 217, 102, 33, 142, 251, 58, 
231, 131, 135, 63, 163, 205, 87, 112, 165, 222, 245, 40, 72, 141, 246, 186, 92, 238, 255, 173, 
37, 111, 240, 15, 76, 126, 248, 199, 122, 148, 213, 16, 48, 34, 78, 103, 47, 158, 219, 52, 73, 
18, 106, 94, 183, 99, 53, 214, 83, 177, 107, 100, 211, 61, 66, 51, 138, 239, 31, 80, 8, 250, 71, 
55, 109, 184, 229, 215, 10, 162, 151, 216, 180, 129, 136};
	//substitute
	for(int i=0; i<4; i++)
	{
        std::cout << '[' << (int)text[i];
		text[i] = ((char)subTable[((int)text[i])-CHAR_MIN])+CHAR_MIN;
		std::cout << ',' << (int)text[i] << ']';
	}
	
	std::cout << std::endl;
}

void dSubstitution(string &text)
{
	int subTable[256] = {144, 6, 43, 18, 149, 87, 147, 112, 241, 93, 249, 76, 84, 127, 
49, 204, 212, 57, 222, 30, 104, 117, 25, 79, 5, 38, 148, 0, 166, 154, 120, 239, 130, 177, 214,
 171, 66, 201, 16, 22, 192, 99, 29, 81, 82, 158, 26, 217, 213, 170, 10, 236, 220, 227, 142, 244
, 80, 63, 180, 107, 7, 234, 153, 184, 150, 134, 235, 143, 174, 102, 12, 243, 193, 221, 160, 121
, 205, 50, 215, 146, 240, 135, 77, 229, 27, 98, 15, 187, 126, 128, 71, 119, 197, 162, 224, 97, 
89, 90, 152, 226, 232, 73, 176, 216, 157, 61, 223, 231, 131, 245, 35, 202, 188, 31, 36, 116, 51
, 125, 23, 65, 68, 95, 209, 86, 151, 56, 206, 156, 20, 254, 21, 182, 13, 55, 163, 183, 255, 53, 
237, 103, 159, 194, 178, 60, 1, 137, 70, 138, 210, 8, 46, 251, 58, 32, 9, 173, 88, 85, 218, 83, 
91, 111, 250, 185, 122, 189, 72, 14, 64, 115, 139, 94, 124, 200, 11, 24, 164, 230, 133, 145, 
253, 40, 54, 225, 246, 41, 196, 48, 17, 69, 140, 28, 114, 155, 106, 109, 78, 59, 136, 208, 113, 
75, 167, 110, 118, 186, 132, 42, 62, 141, 74, 233, 100, 211, 228, 248, 252, 175, 161, 219, 96, 
168, 190, 3, 67, 33, 44, 34, 105, 247, 39, 181, 165, 19, 169, 172, 47, 101, 198, 238, 203, 2, 92
, 45, 4, 191, 195, 129, 207, 52, 242, 179, 123, 108, 37, 199};
	//substitute
	for(int i=0; i<4; i++)
	{
        std::cout << '[' << (int)text[i];
		text[i] = (subTable[((int)text[i])-CHAR_MIN])+CHAR_MIN;
		std::cout << ',' << (int)text[i] << ']';
	}
	
	std::cout << std::endl;
}

int main() {
    string from1 = "abcd", from2 = "john", from3 = "zueq";
    
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    eSubstitution(from1);
    eSubstitution(from2);
    eSubstitution(from3);
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    dSubstitution(from1);
    dSubstitution(from2);
    dSubstitution(from3);
    std::cout << from1 << ", " << from2 << ", " << from3 << std::endl;
    //std::cout << (int)from2.at(1);
    
    std::cin.get();
    return 0;
}

Enjoy. [/edit]

i did it a bit simpler (the conversion bit) and it works great.

Thanks so much DWKS, as always, you're a great help!