43 行
1009 B
C
43 行
1009 B
C
#include "base32.h"
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int char_to_val(char c) {
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const char *base32_alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
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char *ptr = strchr(base32_alphabet, c);
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return ptr ? ptr - base32_alphabet : -1;
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}
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unsigned char *base32_decode(const char *encoded, size_t *out_len) {
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size_t encoded_len = strlen(encoded);
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size_t padding = 0;
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for (int i = encoded_len - 1; i >= 0 && encoded[i] == '='; --i) {
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++padding;
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}
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*out_len = (encoded_len - padding) * 5 / 8;
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if (*out_len == 0) return NULL;
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unsigned char *decoded = malloc(*out_len);
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if (!decoded) return NULL;
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int buffer = 0, bits_left = 0, count = 0;
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for (size_t i = 0; i < encoded_len - padding; ++i) {
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int val = char_to_val(encoded[i]);
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if (val < 0) {
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free(decoded);
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return NULL;
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}
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buffer <<= 5;
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buffer |= val;
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bits_left += 5;
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if (bits_left >= 8) {
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decoded[count++] = (unsigned char) (buffer >> (bits_left - 8));
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bits_left -= 8;
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}
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}
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*out_len = count;
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return decoded;
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}
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