| /* |
| * cdecoder.c - c source to a base64 decoding algorithm implementation |
| * |
| * This is part of the libb64 project, and has been placed in the public domain. |
| * For details, see http://sourceforge.net/projects/libb64 |
| */ |
| |
| #include <libzrtpcpp/zrtpB64Decode.h> |
| |
| int base64_decode_value(char value_in) |
| { |
| static const char decoding[] = {62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51}; |
| static const char decoding_size = sizeof(decoding); |
| value_in -= 43; |
| if (value_in < 0 || value_in > decoding_size) return -1; |
| return decoding[(int)value_in]; |
| } |
| |
| void base64_init_decodestate(base64_decodestate* state_in) |
| { |
| state_in->step = step_a; |
| state_in->plainchar = 0; |
| } |
| |
| int base64_decode_block(const char* code_in, const int length_in, uint8_t *plaintext_out, base64_decodestate* state_in) |
| { |
| const char* codechar = code_in; |
| uint8_t *plainchar = plaintext_out; |
| char fragment; |
| |
| *plainchar = state_in->plainchar; |
| |
| switch (state_in->step) |
| { |
| while (1) |
| { |
| case step_a: |
| do { |
| if (codechar == code_in+length_in) |
| { |
| state_in->step = step_a; |
| state_in->plainchar = *plainchar; |
| return plainchar - plaintext_out; |
| } |
| fragment = (char)base64_decode_value(*codechar++); |
| } while (fragment < 0); |
| *plainchar = (fragment & 0x03f) << 2; |
| case step_b: |
| do { |
| if (codechar == code_in+length_in) |
| { |
| state_in->step = step_b; |
| state_in->plainchar = *plainchar; |
| return plainchar - plaintext_out; |
| } |
| fragment = (char)base64_decode_value(*codechar++); |
| } while (fragment < 0); |
| *plainchar++ |= (fragment & 0x030) >> 4; |
| *plainchar = (fragment & 0x00f) << 4; |
| case step_c: |
| do { |
| if (codechar == code_in+length_in) |
| { |
| state_in->step = step_c; |
| state_in->plainchar = *plainchar; |
| return plainchar - plaintext_out; |
| } |
| fragment = (char)base64_decode_value(*codechar++); |
| } while (fragment < 0); |
| *plainchar++ |= (fragment & 0x03c) >> 2; |
| *plainchar = (fragment & 0x003) << 6; |
| case step_d: |
| do { |
| if (codechar == code_in+length_in) |
| { |
| state_in->step = step_d; |
| state_in->plainchar = *plainchar; |
| return plainchar - plaintext_out; |
| } |
| fragment = (char)base64_decode_value(*codechar++); |
| } while (fragment < 0); |
| *plainchar++ |= (fragment & 0x03f); |
| } |
| } |
| /* control should not reach here */ |
| return plainchar - plaintext_out; |
| } |
| |