102 lines
3.1 KiB
C
102 lines
3.1 KiB
C
//
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// Created by bruno on 4/29/25.
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//
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#include <string.h>
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#include <stdio.h>
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#include <stdint-gcc.h>
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#include <malloc.h>
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#include "base.h"
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static char encoding_table[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
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'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
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'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
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'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
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'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
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'w', 'x', 'y', 'z', '0', '1', '2', '3',
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'4', '5', '6', '7', '8', '9', '+', '/'};
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static char *decoding_table = NULL;
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void build_decoding_table() {
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decoding_table = malloc(256);
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for (int i = 0; i < 64; i++)
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decoding_table[(unsigned char) encoding_table[i]] = i;
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}
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unsigned char *base64_decode(const char *data, size_t input_length, size_t *output_length) {
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if (decoding_table == NULL) build_decoding_table();
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if (input_length % 4 != 0) {
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printf("babbaba %zu\n", input_length);
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return NULL;
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}
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*output_length = input_length / 4 * 3;
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if (data[input_length - 1] == '=') (*output_length)--;
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if (data[input_length - 2] == '=') (*output_length)--;
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unsigned char *decoded_data = malloc(*output_length);
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if (decoded_data == NULL) {
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printf("fefefefeg\n");
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return NULL;
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}
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for (int i = 0, j = 0; i < input_length;) {
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uint32_t sextet_a = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
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uint32_t sextet_b = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
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uint32_t sextet_c = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
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uint32_t sextet_d = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
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uint32_t triple = (sextet_a << 3 * 6)
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+ (sextet_b << 2 * 6)
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+ (sextet_c << 1 * 6)
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+ (sextet_d << 0 * 6);
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if (j < *output_length) decoded_data[j++] = (triple >> 2 * 8) & 0xFF;
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if (j < *output_length) decoded_data[j++] = (triple >> 1 * 8) & 0xFF;
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if (j < *output_length) decoded_data[j++] = (triple >> 0 * 8) & 0xFF;
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}
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return decoded_data;
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}
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void hex_dump(const unsigned char *data, size_t len) {
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for (size_t i = 0; i < len; i++) {
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printf("%02X ", data[i]);
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if ((i + 1) % 16 == 0)
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printf("\n");
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}
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printf("\n");
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}
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static uint32_t crc32_table[256];
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// Call this once before computing CRCs
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void init_crc32_table(void) {
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uint32_t poly = 0xEDB88320; // reversed polynomial of 0x04C11DB7
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for (uint32_t i = 0; i < 256; i++) {
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uint32_t crc = i;
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for (uint8_t j = 0; j < 8; j++) {
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if (crc & 1)
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crc = (crc >> 1) ^ poly;
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else
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crc >>= 1;
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}
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crc32_table[i] = crc;
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}
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}
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uint32_t crc32_le(uint32_t crc, const uint8_t *buf, size_t len) {
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crc = ~crc;
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while (len--) {
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crc = crc32_table[(crc ^ *buf++) & 0xFF] ^ (crc >> 8);
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}
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return ~crc;
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} |