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https://github.com/sigmasternchen/libsfuid
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overflowerror
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6
Makefile
Normal file
6
Makefile
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@ -0,0 +1,6 @@
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all: F6jigYck4v
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F6jigYck4v: main.c
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gcc -lm -o $@ $<
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337
main.c
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337
main.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <unistd.h>
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typedef __uint128_t uint128_t;
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char* charset = "a-zA-Z0-9";
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unsigned int resultLength = 10;
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unsigned int offset = 5;
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bool verbose = false;
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#define verbose(...) if (verbose) printf(__VA_ARGS__);
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#define error(...) fprintf(stderr, __VA_ARGS__)
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int convertToString(char* string, unsigned long long number) {
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unsigned charsetLength = strlen(charset);
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int length = 0;
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do {
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string[length++] = charset[number % charsetLength];
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number /= charsetLength;
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} while(number > 0);
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for(; length < resultLength; length++) {
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string[length] = charset[0];
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}
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for(int i = 0; i < length / 2; i++) {
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string[i] ^= string[length - i - 1];
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string[length - i - 1] ^= string[i];
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string[i] ^= string[length - i - 1];
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}
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string[length] = '\0';
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return length;
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}
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unsigned long long convertFromString(const char* string) {
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unsigned long long result = 0;
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int stringLength = strlen(string);
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int charsetLength = strlen(charset);
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for (int i = 0; i < stringLength; i++) {
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bool found = false;
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for(int j = 0; j < charsetLength; j++) {
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if (charset[j] == string[i]) {
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found = true;
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unsigned long long val = ((unsigned long long) pow(charsetLength, stringLength - i - 1));
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//printf("position %d, digit %d, value %d\n", i, j, val);;
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result += ((unsigned long long) j) * val;
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break;
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}
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}
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if (!found) {
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error("Parsing error.\n");
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exit(3);
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}
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}
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return result;
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}
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unsigned long long primelist[] = {
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1, 1, 1, 3, 7, 13, 29, 61, 113, 251, 509, 1021, 2039, 4093, 8179, 16381,
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32749, 65521, 131063, 262139, 524269, 1048573, 2097143, 4194301,
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8388593, 16777213, 33554393, 67108859, 134217689, 268435399,
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536870909, 1073741789, 2147483629ll, 4294967291ll, 8589934583ll,
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17179869143ll, 34359738337ll, 68719476731ll, 137438953447ll,
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274877906899ll, 549755813881ll, 1099511627689ll, 2199023255531ll,
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4398046511093ll, 8796093022151ll, 17592186044399ll,
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35184372088777ll, 70368744177643ll, 140737488355213ll,
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281474976710597ll, 562949953421231ll, 1125899906842597ll,
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2251799813685119ll, 4503599627370449ll, 9007199254740881ll,
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18014398509481951ll, 36028797018963913ll, 72057594037927931ll,
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144115188075855859ll, 288230376151711717ll, 576460752303423433ll,
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1152921504606846883ll, 2305843009213693921ll // 61
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};
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int findMax(unsigned long long theoreticalMax) {
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int result = 0;
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unsigned long long tmp = 0;
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while(true) {
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if (tmp >= theoreticalMax)
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break;
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tmp = 1ll << ++result;
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}
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return result - 1;
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}
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unsigned long long findPrime(int maxBit) {
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int primelistLength = (sizeof primelist) / (sizeof (long long));
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if (maxBit >= primelistLength)
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return primelist[primelistLength - 1];
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return primelist[maxBit - 1];
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}
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unsigned long long encode(unsigned long long value, unsigned long long prime, unsigned long long maxValue) {
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uint128_t result = value;
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result *= prime;
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result &= (maxValue - 1);
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return (unsigned long long) result;
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}
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unsigned long long multiplicativeInverse(unsigned long long a, unsigned long long b) {
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/*
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* I didn't write this.
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* I got this from https://rosettacode.org/wiki/Modular_inverse#C
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* and adopted it to use long long data types.
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*/
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long long b0 = b, t, q;
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long long x0 = 0, x1 = 1;
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if (b == 1)
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return 1;
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while (a > 1) {
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q = a / b;
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t = b, b = a % b, a = t;
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t = x0, x0 = x1 - q * x0, x1 = t;
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}
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if (x1 < 0)
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x1 += b0;
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return x1;
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}
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unsigned long long decode(unsigned long long value, unsigned long long prime, unsigned long long maxValue) {
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/*
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* (x * p) mod m = v
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* (x * p) == v (mod m)
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* Def: i = multiplicative inverse of p
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* => x = v * i
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* => p * i == i (mod m)
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*/
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uint128_t tmp = value;
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tmp *= multiplicativeInverse(prime, maxValue);
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tmp &= (maxValue - 1);
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return (unsigned long long) tmp;
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}
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typedef struct settings {
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unsigned long long max;
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unsigned long long prime;
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} settings_t;
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settings_t getSettings() {
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verbose("charset length: %d\n", strlen(charset));
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double maxValueDouble = pow(strlen(charset), resultLength);
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unsigned long long maxValue;
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int maxBits;
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if (maxValueDouble > pow(2, 64)) {
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verbose("Max value %.0lf > 2^64, caping to 63 bits.\n", maxValueDouble);
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maxBits = 63;
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} else {
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maxValue = (unsigned long long) maxValueDouble;
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verbose("theoer max: %llu\n", maxValue);
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maxBits = findMax(maxValue);
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if (maxBits <= 0) {
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error("length or charset is too big.");
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exit(3);
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}
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}
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maxValue = 1ll << maxBits;
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verbose("used bits: %d\n", maxBits);
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verbose("max: %llu\n", maxValue);
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verbose("usage: %.1f%\n", (100.0 * maxValue / maxValueDouble));
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unsigned long long prime = findPrime(maxBits);
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verbose("prime: %llu\n", prime);
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return (settings_t) {.max = maxValue, .prime = prime};
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}
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void toString(char* string, unsigned long long value, settings_t settings) {
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value = encode(value, settings.prime, settings.max);
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verbose("encoded: %llu\n", value);
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convertToString(string, value);
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}
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unsigned long long fromString(const char* string, settings_t settings) {
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verbose("test\n");
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unsigned long long result = convertFromString(string);
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verbose("encoded: %llu\n", result);
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result = decode(result, settings.prime, settings.max);
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return result;
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}
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struct {
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const char* needle;
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const char* replacement;
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} shortcuts[] = {
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{
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.needle = "a-z",
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.replacement = "abcdefghijklmnopqrstuvwxyz"
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},
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{
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.needle = "A-Z",
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.replacement = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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},
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{
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.needle = "0-9",
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.replacement = "0123456789"
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}
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};
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void prepareCharset() {
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verbose("prepareing charset\n");
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int size = strlen(charset);
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char* tmp;
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for(int i = 0; i < ((sizeof shortcuts) / (sizeof shortcuts[0])); i++) {
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tmp = charset;
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while((tmp = strstr(tmp, shortcuts[i].needle)) != NULL) {
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tmp++;
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size += strlen(shortcuts[i].replacement) - strlen(shortcuts[i].needle);
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}
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}
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char* inflatedCharset = malloc(size + 1);
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strcpy(inflatedCharset, charset);
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while(true) {
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char* first = NULL;
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const char* replace;
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for (int i = 0; i < ((sizeof shortcuts) / (sizeof shortcuts[0])); i++) {
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tmp = strstr(inflatedCharset, shortcuts[i].needle);
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if ((tmp != NULL) && ((first == NULL) || (tmp < first))) {
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first = tmp;
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replace = shortcuts[i].replacement;
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}
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}
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if (first == NULL)
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break;
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memmove(first + strlen(replace), first + 3, strlen(first) + 1);
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memcpy(first, replace, strlen(replace));
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}
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//verbose("full charset: %s\n", inflatedCharset);
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charset = inflatedCharset;
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}
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int main(int argc, char** argv) {
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int opt;
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bool decodeMode = false;
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char* endptr;
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while((opt = getopt(argc, argv, "o:c:l:dv")) != -1) {
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switch(opt) {
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case 'o':
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offset = strtol(optarg, &endptr, 10);
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if (*endptr != 0) {
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error("Argument for -o has to be a number.\n");
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exit(2);
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}
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break;
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case 'l':
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resultLength = strtol(optarg, &endptr, 10);
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if (*endptr != 0) {
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error("Argument of -l has to be a number.\n");
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exit(2);
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}
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break;
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case 'c':
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charset = optarg;
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break;
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case 'd':
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decodeMode = true;
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break;
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case 'v':
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verbose = true;
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break;
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default:
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error("Unknown option.\n");
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exit(2);
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}
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}
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if (optind >= argc) {
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error("Expected data after options.\n");
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exit(2);
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}
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verbose("charset: %s\n", charset);
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verbose("length: %d\n", resultLength);
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verbose("offset: %d\n", offset);
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prepareCharset();
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settings_t settings = getSettings();
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if (decodeMode) {
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verbose("decode mode\n");
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const char* string = argv[optind];
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verbose("string: %s\n", string);
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unsigned long long value = fromString(string, settings);
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value -= offset;
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printf("%llu\n", value);
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} else {
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unsigned long long value = strtoll(argv[optind], &endptr, 10);
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if (*endptr != 0) {
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error("Value has to be a number.\n");
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exit(2);
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}
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value += offset;
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if (value > settings.max) {
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error("value is too big!\n");
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exit(1);
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}
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verbose("encode mode\n");
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verbose("value: %llu\n", value)
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char* string = malloc(resultLength);
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toString(string, value, settings);
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printf("%s\n", string);
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free(string);
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}
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}
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