add "generic" format string based encoder and decoder (scan_asn1generic,

fmt_asn1generic, see t10.c for example usage)
add "generic" asn.1 dumper (in t10.c)
fix some read off-by-one errors, minor cleanups
add real OID support
add bitstring support

scan_asn1generic.c

@@ -0,0 +1,107 @@
+#include <stdarg.h>
+#include "asn1.h"
+
+size_t scan_asn1generic(const char* src,const char* max,const char* fmt,...) {
+  size_t curlen,seqlen;
+  const char* maxstack[100];
+  size_t curmax=0;
+  va_list args;
+  int optional=0;
+  unsigned long* application=NULL;
+  unsigned long tag;
+  enum asn1_tagclass tc;
+  enum asn1_tagtype tt;
+  const char* orig=src;
+  va_start(args,fmt);
+  maxstack[0]=max;
+  while (*fmt) {
+    switch (*fmt) {
+    case '?':		// ? = rest is optional (until end of sequence)
+      optional=1;
+      break;
+    case 'i':		// i = INTEGER
+      {
+	long* dest=va_arg(args,long*);
+	*dest=0;
+	curlen=scan_asn1int(src,maxstack[curmax],&tc,&tt,&tag,dest);
+	if (application) {
+	  if (tc!=APPLICATION) return 0;
+	  *application=tag;
+	} else {
+	  if (tc!=UNIVERSAL || tt!=PRIMITIVE || tag!=INTEGER)
+	    return 0;
+	}
+	if (!curlen) { if (optional) break; else return 0; }
+	src+=curlen;
+	application=0;
+	break;
+      }
+    case 's':		// s = STRING
+      {
+	struct string* dest=va_arg(args,struct string*);
+	dest->l=0;
+	dest->s=0;
+	curlen=scan_asn1string(src,maxstack[curmax],&tc,&tt,&tag,&dest->s,&dest->l);
+	if (!curlen) { if (optional) break; else return 0; }
+	if (application) {
+	  if (tc!=APPLICATION) return 0;
+	  *application=tag;
+	} else {
+	  if (tc!=UNIVERSAL || tt!=PRIMITIVE || tag!=OCTET_STRING)
+	    return 0;
+	}
+	src+=curlen;
+	application=0;
+	break;
+      }
+    case 'a':		// next tag class is APPLICATION instead of UNIVERSAL; write tag to unsigned long*
+      {
+	application=va_arg(args,unsigned long*);
+	break;
+      }
+    case '{':		// { = SEQUENCE
+      {
+	curlen=scan_asn1tag(src,maxstack[curmax],&tc,&tt,&tag);
+	if (!curlen) { if (optional) break; else return 0; }
+	if (application) {
+	  if (tc!=APPLICATION) return 0;
+	  *application=tag;
+	} else {
+	  if (tc!=UNIVERSAL || tt!=CONSTRUCTED || tag!=SEQUENCE_OF)
+	    return 0;
+	}
+	src+=curlen;
+	curlen=scan_asn1length(src,maxstack[curmax],&seqlen);
+	if (!curlen) return 0;
+	if (curmax>99) return 0;
+	maxstack[++curmax]=src+curlen+seqlen;
+	src+=curlen;
+	application=0;
+	break;
+      }
+    case '!':		// save current max-src into size_t
+      // useful for ldap, where you have an application sequence
+      // and the tag defines which encoding you have inside the
+      // sequence, so you can't put it in the format string.
+      // you still need to know the length so you can call this function
+      // again on the rest of the data.
+      {
+	size_t* dest=va_arg(args,size_t*);
+	*dest=maxstack[curmax]-src;
+	break;
+      }
+    case '}':		// } = end of SEQUENCE
+      {
+	optional=0;
+	if (curmax==0) return 0;
+	--curmax;
+	break;
+      }
+    default:
+      return 0;
+    }
+    ++fmt;
+  }
+  va_end(args);
+  return src-orig;
+}