Add base64 decoding routine

src/misc.c

@@ -1,6 +1,9 @@
 /*
  * Copyright (C) 2009 Julien BLACHE <jb@jblache.org>
  *
+ * Pieces of code adapted from mt-daapd:
+ * Copyright (C) 2003-2007 Ron Pedde (ron@pedde.com)
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -110,3 +113,94 @@ djb_hash(void *data, size_t len)
 
   return hash;
 }
+
+
+static unsigned char b64_decode_table[256];
+
+char *
+b64_decode(const char *b64)
+{
+  char *str;
+  const unsigned char *iptr;
+  unsigned char *optr;
+  unsigned char c;
+  int len;
+  int i;
+
+  if (b64_decode_table[0] == 0)
+    {
+      memset(b64_decode_table, 0xff, sizeof(b64_decode_table));
+
+      /* Base64 encoding: A-Za-z0-9+/ */
+      for (i = 0; i < 26; i++)
+	{
+	  b64_decode_table['A' + i] = i;
+	  b64_decode_table['a' + i] = i + 26;
+	}
+
+      for (i = 0; i < 10; i++)
+	b64_decode_table['0' + i] = i + 52;
+
+      b64_decode_table['+'] = 62;
+      b64_decode_table['/'] = 63;
+
+      /* Stop on '=' */
+      b64_decode_table['='] = 100; /* > 63 */
+    }
+
+  len = strlen(b64);
+
+  str = (char *)malloc(len);
+  if (!str)
+    return NULL;
+
+  memset(str, 0, len);
+
+  iptr = (const unsigned char *)b64;
+  optr = (unsigned char *)str;
+  i = 0;
+
+  while (len)
+    {
+      if (*iptr == '=')
+	break;
+
+      c = b64_decode_table[*iptr];
+      if (c > 63)
+	{
+	  iptr++;
+	  len--;
+	  continue;
+	}
+
+      switch (i)
+	{
+	  case 0:
+	    optr[0] = c << 2;
+	    break;
+	  case 1:
+	    optr[0] |= c >> 4;
+	    optr[1] = c << 4;
+	    break;
+	  case 2:
+	    optr[1] |= c >> 2;
+	    optr[2] = c << 6;
+	    break;
+	  case 3:
+	    optr[2] |= c;
+	    break;
+	}
+
+      i++;
+      if (i == 4)
+	{
+	  optr += 3;
+	  i = 0;
+	}
+
+      len--;
+      iptr++;
+    }
+
+  return str;
+}

src/misc.h

@@ -13,4 +13,7 @@ safe_atol(const char *str, long *val);
 uint32_t
 djb_hash(void *data, size_t len);
 
+char *
+b64_decode(const char *b64);
+
 #endif /* !__MISC_H__ */