--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/asn1/der/utctime/der_decode_utctime.c	Wed Mar 08 13:23:58 2006 +0000
@@ -0,0 +1,120 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file der_decode_utctime.c
+  ASN.1 DER, decode a  UTCTIME, Tom St Denis
+*/
+
+#ifdef LTC_DER
+
+static int char_to_int(unsigned char x)
+{
+   switch (x)  {
+      case '0': return 0;
+      case '1': return 1;
+      case '2': return 2;
+      case '3': return 3;
+      case '4': return 4;
+      case '5': return 5;
+      case '6': return 6;
+      case '7': return 7;
+      case '8': return 8;
+      case '9': return 9;
+   }
+   return 100;
+}
+
+#define DECODE_V(y, max) \
+   y  = char_to_int(buf[x])*10 + char_to_int(buf[x+1]); \
+   if (y >= max) return CRYPT_INVALID_PACKET;           \
+   x += 2;
+
+int der_decode_utctime(const unsigned char *in, unsigned long *inlen,
+                             ltc_utctime   *out)
+{
+   unsigned char buf[32];
+   unsigned long x;
+   int           y;
+
+   LTC_ARGCHK(in    != NULL);
+   LTC_ARGCHK(inlen != NULL);
+   LTC_ARGCHK(out   != NULL);
+
+   /* check header */
+   if (*inlen < 2UL || (in[1] >= sizeof(buf)) || ((in[1] + 2UL) > *inlen)) {
+      return CRYPT_INVALID_PACKET;
+   }
+
+   /* decode the string */
+   for (x = 0; x < in[1]; x++) {
+       y = der_ia5_value_decode(in[x+2]);
+       if (y == -1) {
+          return CRYPT_INVALID_PACKET;
+       }
+       buf[x] = y;
+   }
+   *inlen = 2 + x;
+
+
+   /* possible encodings are 
+YYMMDDhhmmZ
+YYMMDDhhmm+hh'mm'
+YYMMDDhhmm-hh'mm'
+YYMMDDhhmmssZ
+YYMMDDhhmmss+hh'mm'
+YYMMDDhhmmss-hh'mm'
+
+    So let's do a trivial decode upto [including] mm 
+   */
+
+    x = 0;
+    DECODE_V(out->YY, 100);
+    DECODE_V(out->MM, 13);
+    DECODE_V(out->DD, 32);
+    DECODE_V(out->hh, 24);
+    DECODE_V(out->mm, 60);
+
+    /* clear timezone and seconds info */
+    out->off_dir = out->off_hh = out->off_mm = out->ss = 0;
+
+    /* now is it Z, +, - or 0-9 */
+    if (buf[x] == 'Z') {
+       return CRYPT_OK;
+    } else if (buf[x] == '+' || buf[x] == '-') {
+       out->off_dir = (buf[x++] == '+') ? 0 : 1;
+       DECODE_V(out->off_hh, 24);
+       DECODE_V(out->off_mm, 60);
+       return CRYPT_OK;
+    }
+
+    /* decode seconds */
+    DECODE_V(out->ss, 60);
+
+    /* now is it Z, +, - */
+    if (buf[x] == 'Z') {
+       return CRYPT_OK;
+    } else if (buf[x] == '+' || buf[x] == '-') {
+       out->off_dir = (buf[x++] == '+') ? 0 : 1;
+       DECODE_V(out->off_hh, 24);
+       DECODE_V(out->off_mm, 60);
+       return CRYPT_OK;
+    } else {
+       return CRYPT_INVALID_PACKET;
+    }
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/utctime/der_decode_utctime.c,v $ */
+/* $Revision: 1.6 $ */
+/* $Date: 2005/06/19 12:07:00 $ */