BASE64 de/encoding - by Edward Flick - replace John Walkers implementation with http...

[citadel.git] / libcitadel / lib / b64 / cdecode.c

diff --git a/libcitadel/lib/b64/cdecode.c b/libcitadel/lib/b64/cdecode.c
new file mode 100644 (file)
index 0000000..8f3ff94
--- /dev/null
+++ b/libcitadel/lib/b64/cdecode.c
@@ -0,0 +1,88 @@
+/*
+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 "b64/cdecode.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, char* plaintext_out, base64_decodestate* state_in)
+{
+       const char* codechar = code_in;
+       char* 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;
+}
+