libcitadel/lib/b64/cencode.c

   1 /*
   2 cencoder.c - c source to a base64 encoding algorithm implementation
   3
   4 This is part of the libb64 project, and has been placed in the public domain.
   5 For details, see http://sourceforge.net/projects/libb64
   6 */
   7
   8 #include "b64/cencode.h"
   9
  10 void base64_init_encodestate(base64_encodestate* state_in)
  11 {
  12         state_in->step = step_A;
  13         state_in->result = 0;
  14 }
  15
  16 char base64_encode_value(char value_in)
  17 {
  18         static const char* encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  19         if (value_in > 63) return '=';
  20         return encoding[(int)value_in];
  21 }
  22
  23 int base64_encode_block(const char* plaintext_in, int length_in, char* code_out, base64_encodestate* state_in)
  24 {
  25         const char* plainchar = plaintext_in;
  26         const char* const plaintextend = plaintext_in + length_in;
  27         char* codechar = code_out;
  28         char result;
  29         char fragment;
  30
  31         result = state_in->result;
  32
  33         switch (state_in->step)
  34         {
  35                 while (1)
  36                 {
  37         case step_A:
  38                         if (plainchar == plaintextend)
  39                         {
  40                                 state_in->result = result;
  41                                 state_in->step = step_A;
  42                                 return codechar - code_out;
  43                         }
  44                         fragment = *plainchar++;
  45                         result = (fragment & 0x0fc) >> 2;
  46                         *codechar++ = base64_encode_value(result);
  47                         result = (fragment & 0x003) << 4;
  48         case step_B:
  49                         if (plainchar == plaintextend)
  50                         {
  51                                 state_in->result = result;
  52                                 state_in->step = step_B;
  53                                 return codechar - code_out;
  54                         }
  55                         fragment = *plainchar++;
  56                         result |= (fragment & 0x0f0) >> 4;
  57                         *codechar++ = base64_encode_value(result);
  58                         result = (fragment & 0x00f) << 2;
  59         case step_C:
  60                         if (plainchar == plaintextend)
  61                         {
  62                                 state_in->result = result;
  63                                 state_in->step = step_C;
  64                                 return codechar - code_out;
  65                         }
  66                         fragment = *plainchar++;
  67                         result |= (fragment & 0x0c0) >> 6;
  68                         *codechar++ = base64_encode_value(result);
  69                         result  = (fragment & 0x03f) >> 0;
  70                         *codechar++ = base64_encode_value(result);
  71                 }
  72         }
  73         /* control should not reach here */
  74         return codechar - code_out;
  75 }
  76
  77 int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
  78 {
  79         char* codechar = code_out;
  80
  81         switch (state_in->step)
  82         {
  83         case step_B:
  84                 *codechar++ = base64_encode_value(state_in->result);
  85                 *codechar++ = '=';
  86                 *codechar++ = '=';
  87                 break;
  88         case step_C:
  89                 *codechar++ = base64_encode_value(state_in->result);
  90                 *codechar++ = '=';
  91                 break;
  92         case step_A:
  93                 break;
  94         }
  95         *codechar++ = '\n';
  96
  97         return codechar - code_out;
  98 }
  99