--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/b64_de.c	Sat Dec 11 21:25:28 2010 +0900
@@ -0,0 +1,84 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+struct tagTT
+{
+  unsigned char buf;
+  char *cont;
+  int nlen;
+};
+
+unsigned char CtoNum( int c );
+int GetNumB64( struct tagTT *pWork );
+
+int decode(char *cont, FILE *outfile)
+{
+  int rw;
+  struct tagTT work;
+  
+  work.buf = 0;
+  work.nlen = 0;
+  work.cont = cont;
+  
+  rw = GetNumB64( &work );
+  while ( rw != -1 ) 
+    {
+      putc( rw, outfile );
+      rw = GetNumB64( &work );
+    }
+  return 0;
+}
+
+
+int GetNumB64( struct tagTT *pWork )
+{
+  int wr;
+  unsigned char w;
+  unsigned char r;
+  
+  wr = *pWork->cont;
+  pWork->cont++;
+  if ( wr == '\0' || wr == '=' )
+    return -1;
+  
+  while(wr == '\n' || wr == '\t')
+    {
+      wr = *pWork->cont;
+      pWork->cont++;
+    }
+
+  w = CtoNum( wr );
+  if ( pWork->nlen == 0 )
+    {
+      unsigned char w2;
+
+      wr = *pWork->cont;
+      pWork->cont++;
+      if ( wr != '\0' && wr != '=' )
+	w2 = CtoNum( wr );
+      else
+	w2 = 0;
+
+      pWork->buf = w << 2;
+      w = w2;
+      pWork->nlen = 6;
+    }
+
+  pWork->nlen -= 2;	
+
+  r = pWork->buf | ( w >> pWork->nlen );
+
+  pWork->buf = ( w << ( 8 - pWork->nlen ) );
+  return r;
+}
+
+unsigned char CtoNum( int c )
+{
+  if ( c >= 'A' && c <= 'Z' ) return c - 'A';
+  if ( c >= 'a' && c <= 'z' ) return ( c - 'a' ) + 26;
+  if ( c >= '0' && c <= '9' ) return ( c - '0' ) + 52;
+  if ( c == '+' ) return 62;
+  if ( c == '/' ) return 63;
+  return -1;
+}