108 lines
3.8 KiB
C
108 lines
3.8 KiB
C
/*
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cdecoder.c - c source to a base64 decoding algorithm implementation
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This is part of the libb64 project, and has been placed in the public domain.
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For details, see http://sourceforge.net/projects/libb64
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*/
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#include "cdecode.h"
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#include <stdint.h>
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static int base64_decode_value_signed(int8_t value_in) {
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static const int8_t decoding[] = {62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4,
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5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1,
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26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51};
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static const int8_t decoding_size = sizeof(decoding);
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value_in -= 43;
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if (value_in < 0 || value_in >= decoding_size) {
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return -1;
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}
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return decoding[(int)value_in];
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}
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void base64_init_decodestate(base64_decodestate *state_in) {
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state_in->step = step_a;
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state_in->plainchar = 0;
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}
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static int base64_decode_block_signed(const int8_t *code_in, const int length_in, int8_t *plaintext_out, base64_decodestate *state_in) {
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const int8_t *codechar = code_in;
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int8_t *plainchar = plaintext_out;
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int8_t fragment;
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*plainchar = state_in->plainchar;
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switch (state_in->step) {
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while (1) {
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case step_a:
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do {
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if (codechar == code_in + length_in) {
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state_in->step = step_a;
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state_in->plainchar = *plainchar;
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return plainchar - plaintext_out;
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}
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fragment = (int8_t)base64_decode_value_signed(*codechar++);
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} while (fragment < 0);
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*plainchar = (fragment & 0x03f) << 2;
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// fall through
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case step_b:
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do {
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if (codechar == code_in + length_in) {
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state_in->step = step_b;
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state_in->plainchar = *plainchar;
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return plainchar - plaintext_out;
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}
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fragment = (int8_t)base64_decode_value_signed(*codechar++);
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} while (fragment < 0);
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*plainchar++ |= (fragment & 0x030) >> 4;
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*plainchar = (fragment & 0x00f) << 4;
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// fall through
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case step_c:
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do {
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if (codechar == code_in + length_in) {
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state_in->step = step_c;
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state_in->plainchar = *plainchar;
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return plainchar - plaintext_out;
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}
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fragment = (int8_t)base64_decode_value_signed(*codechar++);
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} while (fragment < 0);
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*plainchar++ |= (fragment & 0x03c) >> 2;
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*plainchar = (fragment & 0x003) << 6;
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// fall through
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case step_d:
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do {
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if (codechar == code_in + length_in) {
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state_in->step = step_d;
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state_in->plainchar = *plainchar;
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return plainchar - plaintext_out;
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}
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fragment = (int8_t)base64_decode_value_signed(*codechar++);
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} while (fragment < 0);
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*plainchar++ |= (fragment & 0x03f);
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}
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}
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/* control should not reach here */
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return plainchar - plaintext_out;
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}
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static int base64_decode_chars_signed(const int8_t *code_in, const int length_in, int8_t *plaintext_out) {
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base64_decodestate _state;
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base64_init_decodestate(&_state);
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int len = base64_decode_block_signed(code_in, length_in, plaintext_out, &_state);
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if (len > 0) {
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plaintext_out[len] = 0;
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}
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return len;
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}
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int base64_decode_value(char value_in) {
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return base64_decode_value_signed(*((int8_t *)&value_in));
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}
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int base64_decode_block(const char *code_in, const int length_in, char *plaintext_out, base64_decodestate *state_in) {
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return base64_decode_block_signed((int8_t *)code_in, length_in, (int8_t *)plaintext_out, state_in);
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}
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int base64_decode_chars(const char *code_in, const int length_in, char *plaintext_out) {
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return base64_decode_chars_signed((int8_t *)code_in, length_in, (int8_t *)plaintext_out);
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}
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