//
// Created by bruno on 4/29/25.
//

#include <string.h>
#include <stdio.h>
#include <stdint-gcc.h>
#include "base.h"

// Base64 decoding table
const unsigned char dtable[256] = {
        ['A'] = 0,  ['B'] = 1,  ['C'] = 2,  ['D'] = 3,
        ['E'] = 4,  ['F'] = 5,  ['G'] = 6,  ['H'] = 7,
        ['I'] = 8,  ['J'] = 9,  ['K'] = 10, ['L'] = 11,
        ['M'] = 12, ['N'] = 13, ['O'] = 14, ['P'] = 15,
        ['Q'] = 16, ['R'] = 17, ['S'] = 18, ['T'] = 19,
        ['U'] = 20, ['V'] = 21, ['W'] = 22, ['X'] = 23,
        ['Y'] = 24, ['Z'] = 25,
        ['a'] = 26, ['b'] = 27, ['c'] = 28, ['d'] = 29,
        ['e'] = 30, ['f'] = 31, ['g'] = 32, ['h'] = 33,
        ['i'] = 34, ['j'] = 35, ['k'] = 36, ['l'] = 37,
        ['m'] = 38, ['n'] = 39, ['o'] = 40, ['p'] = 41,
        ['q'] = 42, ['r'] = 43, ['s'] = 44, ['t'] = 45,
        ['u'] = 46, ['v'] = 47, ['w'] = 48, ['x'] = 49,
        ['y'] = 50, ['z'] = 51,
        ['0'] = 52, ['1'] = 53, ['2'] = 54, ['3'] = 55,
        ['4'] = 56, ['5'] = 57, ['6'] = 58, ['7'] = 59,
        ['8'] = 60, ['9'] = 61, ['+'] = 62, ['/'] = 63,
};


int base64_decode(const char *in, unsigned char *out, size_t *out_len) {
    size_t len = strlen(in);
    size_t i, j;
    unsigned char a, b, c, d;

    if (len % 4 != 0) return -1;

    for (i = 0, j = 0; i < len; i += 4) {
        a = dtable[(unsigned char)in[i]];
        b = dtable[(unsigned char)in[i+1]];
        c = dtable[(unsigned char)in[i+2]];
        d = dtable[(unsigned char)in[i+3]];

        out[j++] = (a << 2) | (b >> 4);
        if (in[i+2] != '=') {
            out[j++] = (b << 4) | (c >> 2);
            if (in[i+3] != '=')
                out[j++] = (c << 6) | d;
        }
    }
    *out_len = j;
    return 0;
}

void hex_dump(const unsigned char *data, size_t len) {
    for (size_t i = 0; i < len; i++) {
        printf("%02X ", data[i]);
        if ((i + 1) % 16 == 0)
            printf("\n");
    }
    printf("\n");
}

static uint32_t crc32_table[256];

// Call this once before computing CRCs
void init_crc32_table(void) {
    uint32_t poly = 0xEDB88320;  // reversed polynomial of 0x04C11DB7
    for (uint32_t i = 0; i < 256; i++) {
        uint32_t crc = i;
        for (uint8_t j = 0; j < 8; j++) {
            if (crc & 1)
                crc = (crc >> 1) ^ poly;
            else
                crc >>= 1;
        }
        crc32_table[i] = crc;
    }
}

uint32_t crc32_le(uint32_t crc, const uint8_t *buf, size_t len) {
    crc = ~crc;
    while (len--) {
        crc = crc32_table[(crc ^ *buf++) & 0xFF] ^ (crc >> 8);
    }
    return ~crc;
}